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POLITECNICO DI MILANO
Building and Architectural Engineering
Track - Building Engineering
STRATEGIES FOR ENERGY RETROFITTING OF EXISTING
SCHOOL BUILDING IN THE CENTRAL EUROPE AREA:
Analysis of two case studies located in Czech Republic and Italy Supervisors:
prof. Giuliana Iannaccone
Co-Supervisors:
prof. Jan Růžička of the České Vysoké Učení Technické
Author
Paolo Lo Conte
852448
Academic Year 2016-2017
Thesis Report | Paolo Lo Conte
Thesis Report | Paolo Lo Conte
TABLE OF CONTENTS
1 Regulation Framework .................................................................................................................... 1
1.1 Energy Savings Policy in the European Union ......................................................................... 1
1.1.1 The role of the public building ............................................................................................ 2
1.1.2 Potential savings from school buildings .......................................................................... 6
1.2 Analysis of two case studies: Italy and Czech Republic ........................................................... 8
1.2.1 Italian Regulation............................................................................................................. 8
1.2.2 Regional Legislation ....................................................................................................... 10
1.2.3 Czech Regulation ........................................................................................................... 13
2 Description: Case study “Lecco” .................................................................................................... 17
2.1 Geographical and historical overlook .................................................................................... 17
2.2 Architectural construction..................................................................................................... 20
2.3 Energy data collection ........................................................................................................... 21
2.3.1 Envelope Characteristics ............................................................................................... 22
2.3.2 Internal Conditions ........................................................................................................ 30
2.3.3 Technological Plant ....................................................................................................... 32
2.3.4 Energy classification ...................................................................................................... 38
3 Description: Case study “Buštěhrad” ............................................................................................ 41
3.1 Geographical and historical overlook .................................................................................... 41
3.2 Architectural construction..................................................................................................... 43
3.3 Energy data collection ........................................................................................................... 45
3.3.1 Envelope Characteristics ............................................................................................... 45
3.3.2 Internal Conditions ........................................................................................................ 50
3.3.3 Technological Plant ....................................................................................................... 51
3.3.4 Energy Classification ...................................................................................................... 55
4 Climatic analysis ............................................................................................................................ 57
4.1 Geographical framework ....................................................................................................... 57
4.2 Outdoor dry-bulb temperature ............................................................................................. 58
4.3 External relative humidity ..................................................................................................... 59
4.4 Horizontal radiation .............................................................................................................. 60
4.5 Wind exposure ...................................................................................................................... 61
4.6 Rainfall precipitation analysis ................................................................................................ 62
4.7 Snow precipitation ................................................................................................................ 63
Thesis Report | Paolo Lo Conte
4.8 Seismic activity ...................................................................................................................... 63
4.8.1 Lecco .............................................................................................................................. 63
4.8.2 Buštěhrad ...................................................................................................................... 64
5 Energy Diagnosis: Case study “Lecco” ........................................................................................... 67
5.1 Energy Performance of the Building ..................................................................................... 67
5.1.1 Energy Consumption ..................................................................................................... 67
5.1.2 Economic and Environmental Impact ........................................................................... 68
5.1.3 Heating Consumption .................................................................................................... 70
5.1.4 Heat Gains ..................................................................................................................... 71
5.1.5 Heat Losses .................................................................................................................... 72
5.1.6 Solar Energy Analysis ..................................................................................................... 74
5.2 Internal Comfort .................................................................................................................... 76
5.2.1 Thermal Comfort ........................................................................................................... 78
5.2.2 Adaptive Thermal Comfort Model ................................................................................ 80
5.2.3 Indoor air quality ........................................................................................................... 83
5.2.4 Daylight Analysis ............................................................................................................ 85
6 Energy Diagnosis: Case study “Buštěhrad” ................................................................................... 89
6.1 Energy Performance of the Building ..................................................................................... 89
6.1.1 Energy Consumption ..................................................................................................... 89
6.1.2 Economic and Environmental Impact ........................................................................... 90
6.1.3 Heating Consumptions .................................................................................................. 92
6.1.4 Heat gains ...................................................................................................................... 93
6.1.5 Heat Losses .................................................................................................................... 94
6.1.6 Solar energy analysis ..................................................................................................... 96
6.2 Internal Comfort .................................................................................................................... 98
6.2.1 Thermal Comfort ........................................................................................................... 98
6.2.2 Adaptive thermal comfort criteria ................................................................................ 99
6.2.3 Indoor air quality ......................................................................................................... 100
6.2.4 Daylight Analysis .......................................................................................................... 101
7 Envelope Optimization ................................................................................................................ 105
7.1 Design philosophy ............................................................................................................... 105
7.1.1 Technical Analysis ........................................................................................................ 107
Thesis Report | Paolo Lo Conte
7.1.2 Economic Analysis ....................................................................................................... 108
7.1.3 Environmental analysis ................................................................................................ 109
7.2 Case study “Lecco” .............................................................................................................. 110
7.2.1 External thermal insulating coating ............................................................................ 110
7.2.2 Internal thermal insulation .......................................................................................... 114
7.2.3 Attic Insulation ............................................................................................................ 120
7.2.4 Roof insulation ............................................................................................................ 123
7.2.5 Basement Insulation .................................................................................................... 127
7.2.6 Ground-contact element insulation ............................................................................ 129
7.2.7 Glazing optimization .................................................................................................... 132
7.2.8 Envelope retrofit: Proposed intervention ................................................................... 141
7.3 Case study “Bustehrad” ....................................................................................................... 145
7.3.1 External thermal insulation coating ............................................................................ 145
7.3.2 Internal thermal insulation .......................................................................................... 148
7.3.3 Attic Insulation ............................................................................................................ 153
7.3.4 Roof insulation ............................................................................................................ 155
7.3.5 Basement insulation .................................................................................................... 158
7.3.6 Ground-contact element insulation ............................................................................ 158
7.3.7 Glazing optimization .................................................................................................... 160
7.3.8 Envelope retrofit: Proposed intervention ................................................................... 165
8 Plant Optimization ....................................................................................................................... 169
8.1 Photovoltaic system ............................................................................................................ 169
8.1.1 Parametric solar radiation analysis ............................................................................. 169
8.2 Stand-Alone plant refurbishment ....................................................................................... 172
8.2.1 Case study “Lecco” ...................................................................................................... 173
8.2.2 Case study “Bustehrad” ............................................................................................... 175
8.3 Heat pump technology ........................................................................................................ 178
8.3.1 Design choice ............................................................................................................... 179
8.3.2 Case study “Lecco” ...................................................................................................... 180
8.3.3 Case study “Bustehrad” ............................................................................................... 182
Conclusions
Bibliography
Appendices
Thesis Report | Paolo Lo Conte
Thesis Report | Paolo Lo Conte
INDEX OF FIGURES
Figure 1-1: Share of non-residential buildings in UE [5] ....................................................................... 2
Figure 1-2: Annual thermal energy consumption per country of CE .................................................... 3
Figure 1-3: Benchmarks for energy consumption in secondary schools ............................................... 3
Figure 1-4: Average energy use school profile [6] ................................................................................. 4
Figure 1-5: Flowchart of Energy Consumption ..................................................................................... 5
Figure 1-6: Distribution of schools in the Italian and age [5] ................................................................. 6
Figure 1-7: Consumption reduction potential by 2020 from complete renovation of schools starting [6]
................................................................................................................................................................. 7
Figure 2-1: Territorial overview of the case study building ................................................................. 17
Figure 2-2: School “Giosuè Carducci”, 1909 ....................................................................................... 18
Figure 2-3: School “Giosuè Carducci”, 2016 ........................................................................................ 18
Figure 2-4: Capture of the 3D representation of the case study area (21 September 12:00). ............... 19
Figure 2-5: Ground floor plan of the case study building ..................................................................... 20
Figure 2-6: Stone masonry wall ............................................................................................................ 23
Figure 2-7: Hollow clay planks slab ..................................................................................................... 24
Figure 2-8: Brick vault slab .................................................................................................................. 25
Figure 2-9: Basement crawl-space slab. ............................................................................................... 25
Figure 2-10: Wood beam structure roof ............................................................................................... 25
Figure 2-11: Single glazed wooden window ........................................................................................ 26
Figure 2-12: Double layer brick wall .................................................................................................... 27
Figure 2-13: Brick internal partition ..................................................................................................... 27
Figure 2-14: Concrete bearing wall ...................................................................................................... 28
Figure 2-15: Hollow core concrete slab ................................................................................................ 28
Figure 2-16: Single glazed metal window ............................................................................................ 29
Figure 2-17: School building boiler ...................................................................................................... 33
Figure 2-18: Lateral and front view of the gas air heater installed onto the gym's external wall ......... 34
Figure 2-19: Table C.1 - GHG global warming potentials, EN ISO 14064. ........................................ 35
Figure 2-20: Existing cast-iron radiators. ............................................................................................. 36
Figure 2-21: Existing air heater. ........................................................................................................... 36
Figure 2-22: On the left the supposed scheme of the distribution system: Prospectus 22 of the EN ISO
11300-2. On the right the installed circulation pumps. ......................................................................... 37
Figure 2-23: Reference Building definition. ......................................................................................... 38
Figure 2-24: Energy Performance Certification "APE". ....................................................................... 39
Thesis Report | Paolo Lo Conte
Figure 3-1: Central Bohemia region, CZ .............................................................................................. 41
Figure 3-2: Territorial overview of the case study building .................................................................. 41
Figure 3-3: Oty Pavla school in the 1900-1920 on the left, and Oty Pavla school nowadays on the right.
............................................................................................................................................................... 42
Figure 3-4: Capture of the 3D representation of the case study area (21 May 12:00). ......................... 42
Figure 3-5: Internal facades of the building (on the left), roof structure (on the right). ....................... 43
Figure 3-6: Wood beam slab structure .................................................................................................. 47
Figure 3-7: Wood beam ceiling ............................................................................................................ 48
Figure 3-8: Slab made of vault in steel beams ...................................................................................... 48
Figure 3-9: Stone ground slab ............................................................................................................... 49
Figure 3-10: Wood beam structure roof ............................................................................................... 49
Figure 3-11: Boiler system used as heating system .............................................................................. 52
Figure 3-12: DHW boiler...................................................................................................................... 52
Figure 3-13: Cast iron radiator ............................................................................................................. 54
Figure 3-14: Distribution scheme ......................................................................................................... 54
Figure 3-15: Energy classes [kWh/m2y] for different building types.................................................... 55
Figure 4-1: Primary Energy consumption ............................................................................................. 68
Figure 4-2: Trendline of the economic-environmental impact of the school building per year ........... 69
Figure 4-3: Economic and Environmental Impact -%- of different energy-class building. ................. 69
Figure 4-4: Annual PE consumption for Heating Demand ................................................................... 70
Figure 4-5: Monthly PE consumption for Heating Demand [kWh/(m2y)] ........................................... 70
Figure 4-6: Heat Gains in terms of kWh/(m2y) and %. ........................................................................ 71
Figure 4-7: Contribution in terms of % of the elements of the old part (left) and the recent part (right)
of the building to the global Heat Losses of the case study. ................................................................. 72
Figure 4-8: Daily average incident solar radiation [Wh/m2] calculated on the 4 different orientation.74
Figure 4-9: Solar analysis radiation on SW, NW, NE, SE oriented wall (from left to right) ............... 75
Figure 4-10: Diversification of the classrooms by window’s orientation ............................................. 77
Figure 4-11: Discomfort hours % of the classrooms, dived by glazing’s orientation, during the cooling
season. ................................................................................................................................................... 79
Figure 4-12: Adaptive Thermal Comfort check of the classrooms divided by orientation, according to
TM52 ..................................................................................................................................................... 83
Figure 4-13: Distribution in percentage of the CO2 level present in the classroom, divided by orientation.
............................................................................................................................................................... 84
Figure 4-14: UDI -%- of the classrooms, divided by orientation. ........................................................ 86
Figure 5-1: Primary Energy Consumption............................................................................................ 89
Thesis Report | Paolo Lo Conte
Figure 5-2: Trendline of the economic-environmental impact of the school building per year. .......... 91
Figure 5-3: Economic and Environmental Impact -%- of different energy-class building. ................. 91
Figure 5-4: Annual PE consumption for Heating Demand. .................................................................. 92
Figure 5-5: Monthly PE consumption for Heating Demand [kWh/(m2y)] ........................................... 93
Figure 5-6: Heat Gains in terms of kWh/(m2y) and %. ........................................................................ 93
Figure 5-7: Contribution in terms of % of the elements of the building to the global Heat Losses of the
case study. ............................................................................................................................................. 94
Figure 5-8: Daily average incident solar radiation [Wh/m2] calculated on the 4 different orientation.96
Figure 5-9: Solar analysis radiation on S, E, N, W oriented wall (from left to right) .......................... 97
Figure 5-10: Discomfort hours % of the classrooms, dived by glazing’s orientation, during the cooling
season. ................................................................................................................................................... 99
Figure 5-11: Distribution in percentage of the CO2 level present in the classroom, divided by orientation.
............................................................................................................................................................. 100
Figure 5-12: UDI -%- of the classrooms, divided by orientation. ...................................................... 103
Figure 6-1:Displacement and attenuation of a thermal wave ............................................................. 108
Figure 6-2: NW facade of the old part of the school building ............................................................ 110
Figure 6-3: Representation of the payback time -x axis- and of the economic benefit -y axis- of each of
the case scenarios chosen for the external thermal insulation, Lecco ................................................. 113
Figure 6-4: Representation of the return year -x axis- and of the emission benefit -y axis- of each of the
case scenarios chosen for the external thermal insulation, Lecco ....................................................... 114
Figure 6-5: NW facade of the old part of the school building ............................................................ 115
Figure 6-6: Calcium silicate insulation panels .................................................................................... 115
Figure 6-7: Representation of the return year -x axis- and of the emission benefit -y axis- of each of the
case scenarios chosen for the internal thermal insulation.................................................................... 119
Figure 6-8: Attic in the old part of the building .................................................................................. 120
Figure 6-9: Roll insulation of the attic ................................................................................................ 121
Figure 6-10: Rigid panel attic insulation............................................................................................. 121
Figure 6-11: Representation of the return year -x axis- and of the economic benefit -y axis- of each of
the case scenarios chosen for the attic insulation ................................................................................ 123
Figure 6-12: Google earth capture of the roof of the two parts of the case study school building ..... 123
Figure 6-13: Representation of the return year -x axis- and of the economic benefit -y axis- of each of
the case scenarios chosen for the roof insulation ................................................................................ 127
Figure 6-14: Basement of the old part of the building ........................................................................ 127
Figure 6-15: Vault aluminum structure ............................................................................................... 128
Figure 6-16: Aerogel horizontal insulation ......................................................................................... 129
Thesis Report | Paolo Lo Conte
Figure 6-17: Representation of the return year -x axis- and of the economic benefit -y axis- of the work
representing the insulation of the gym ................................................................................................ 132
Figure 6-18: Chosen PVC glazing ...................................................................................................... 133
Figure 6-19: VMC's heat recovery scheme ......................................................................................... 135
Figure 6-20: Adaptive Thermal Comfort criteria check of the classrooms divided by orientation,
considering the installation of a CMV system. The verification has been done according to TM52.. 138
Figure 6-21: Distribution in percentage of the CO2 level present in the classroom, divided by orientation
and considering the installation of a CMV system, Lecco .................................................................. 139
Figure 6-22: Representation of the payback year -x axis- and of the economic benefit -y axis- of the
work representing the refurbishment of the glazing area of Lecco’s school ....................................... 140
Figure 6-23: Different case scenarios analyzed for the energy retrofit of Lecco’s school building ... 142
Figure 6-24: Analysis of the heating energy demand reduction % – x axis- and the cost of the investment
[k€] - y axis- of the different case scenarios considered for the for the energy retrofit of Lecco’s school
building................................................................................................................................................ 144
Figure 6-25:SE facade of the old part of the school building ............................................................. 145
Figure 6-26: Representation of the payback time -x axis- and of the economic benefit -y axis- of each
of the case scenarios chosen for the external thermal insulation, Buštěhrad ...................................... 148
Figure 6-27: Representation of the return year -x axis- and of the emission benefit -y axis- of each of
the case scenarios chosen for the internal thermal insulation, Buštěhrad ........................................... 152
Figure 6-28: Roof structure of Bustehrad’s school ............................................................................. 153
Figure 6-29: Representation of the return year -x axis- and of the economic benefit -y axis- of each of
the case scenarios chosen for the attic insulation in Buštěhrad ........................................................... 155
Figure 6-30: Bustherad's roof structure ............................................................................................... 155
Figure 6-31: Representation of the return year -x axis- and of the economic benefit -y axis- of each of
the case scenarios chosen for the roof insulation in Buštěhrad ........................................................... 158
Figure 6-32: Representation of the return year -x axis- and of the economic benefit -y axis- of each of
the case scenarios chosen for the ground floor insulation in Buštěhrad .............................................. 160
Figure 6-33: Discomfort hours % of the classrooms, dived by glazing’s orientation, during the cooling
season. ................................................................................................................................................. 163
Figure 6-34: Distribution in percentage of the CO2 level present in the classroom, divided by orientation
and considering the installation of a CMV system, Buštěhrad............................................................ 164
Figure 6-35: Representation of the payback year -x axis- and of the economic benefit -y axis- of the
work representing the refurbishment of the glazing area of Bustehrad’s school ................................ 165
Figure 6-36: Different case scenarios analyzed for the energy retrofit of Lecco’s school building ... 166
Figure 6-37: Analysis of the heating energy demand reduction % – x axis- and the cost of the investment
Thesis Report | Paolo Lo Conte
[k€] - y axis- of the different case scenarios considered for the for the energy retrofit of Bustehrad’s
school building .................................................................................................................................... 168
Figure 7-1: Solar radiation analysis on the PV panels placed in the starting position on the roof of
Lecco’s school ..................................................................................................................................... 170
Figure 7-2: Solar radiation analysis on the PV panels placed in the starting position of Bustehrad’s
school .................................................................................................................................................. 171
Figure 7-3: Representation of the payback time -x axis- and of the economic benefit -y axis- of each of
the case scenarios chosen for the plant refurbishment, Lecco ............................................................. 175
Figure 7-4: Representation of the payback time -x axis- and of the economic benefit -y axis- of each of
the case scenarios chosen for the plant refurbishment, Bustehrad ...................................................... 177
Thesis Report | Paolo Lo Conte
Thesis Report | Paolo Lo Conte
INDEX OF TABLES
Table 1.1: Representation of the numerical data representing the building ......................................... 21
Table 1.2: Parameters recreating users’ activity ................................................................................... 30
Table 1.3: Lighting and machinery profile ............................................................................................ 30
Table 1.4:Infiltration rate values[ach] ................................................................................................... 31
Table 1.5: Natural ventilation [l/(sm2)] for internal school spaces ....................................................... 31
Table 1.6: Mechanical exhaust ventilation ............................................................................................ 32
Table 1.7: Activation periods of the technological plants ..................................................................... 32
Table 1.8: Efficiency value for a class C boiler .................................................................................... 33
Table 1.9: Energy classes of the energy certification ............................................................................ 39
Table 2.1: Parameters representing the building ................................................................................... 44
Table 2.2: Parameters recreating users’ activity .................................................................................... 50
Table 2.3: Light system and machinery profile ..................................................................................... 50
Table 2.4: Infiltration rate ..................................................................................................................... 51
Table 2.5: Ventilation rate for each heated space inside the building ................................................... 51
Table 2.6: Activation profile of the technological plant ........................................................................ 52
Table 3.1: Natural philosophy’s parameters to maintain comfort conditions and improve learning
performances. ........................................................................................................................................ 76
Table 3.2: DLF and Illuminance values for each class. ........................................................................ 86
Table 4.1: DLF and Illuminance values for each class ....................................................................... 102
Table 5.1: Thermal transmittance U limitations in Italy and in CZ, defined by national regulations . 106
Table 5.2: Correction factor btr,U from EN ISO 12831:2006 ............................................................... 106
Table 5.3: Glazing’s thermal transmittance limitations in Italy and in CZ, defined by national regulations
[21] [40] ............................................................................................................................................... 107
Table 5.4: Thermal coating scenario considered for the retrofit intervention located in Lecco.......... 111
Table 5.5: Environmental and economic analysis of the different scenarios ...................................... 111
Table 5.6: Dynamic properties of the different case scenarios Table 5.7: Limit values set by standard
[21] ...................................................................................................................................................... 112
Table 5.8: Heating reductions obtained with the external thermal coating ......................................... 113
Table 5.9: Internal thermal insulation scenario considered for the retrofit, Lecco ............................. 115
Table 5.10: Dynamic properties of the case scenario Table 5.11: Limit values set by standard [21]
............................................................................................................................................................. 117
Table 5.12: Cost of thermal bridge intervention ................................................................................. 117
Table 5.13: Heating reductions obtained with the internal thermal coating, Lecco ............................ 118
Thesis Report | Paolo Lo Conte
Table 5.14: Cost of thermal bridge intervention ................................................................................. 118
Table 5.15: Cost of the different case scenarios intervention .............................................................. 118
Table 5.16: Different combination case scenarios .............................................................................. 119
Table 5.17: Case scenarios of attic retrofit in the old part of the building .......................................... 121
Table 5.18:Case scenarios of attic retrofit in the recent part of the building....................................... 121
Table 5.19: Heating reductions obtained with the attic thermal insulation ......................................... 122
Table 5.20: Case scenarios of the roof insulation intervention in Lecco ............................................ 125
Table 5.21: Dynamic properties of the different case scenarios Table 5.22: Limit values set by
standard [21] ........................................................................................................................................ 125
Table 5.23: Performances of the old part roof .................................................................................... 126
Table 5.24: Heating reductions obtained with the attic thermal insulation in Lecco .......................... 126
Table 5.25: Component solutions for each of the presented energy retrofit interventions ................. 130
Table 5.26: Heating reductions obtained with the thermal insulation of the gym .............................. 131
Table 5.27: Glazing’s component thermal properties. Thermal transmittance of the proposed windows
............................................................................................................................................................. 133
Table 5.28: Case scenarios considered for the retrofit of the glazing areas of the case study building in
Lecco ................................................................................................................................................... 136
Table 5.29: Heating reductions with the complete refurbishment of the glazing area and CMV combined,
Lecco ................................................................................................................................................... 139
Table 5.30: Thermal coating scenario considered for the retrofit of the case study located in Buštěhrad
............................................................................................................................................................. 146
Table 5.31: Dynamic properties of the scenarios Table 5.32: Limit values set by standard [21] 146
Table 5.33: Heating reductions obtained with the external thermal coating applied onto the case study
Buštěhrad ............................................................................................................................................. 147
Table 5.34: Internal thermal insulation scenario considered for the retrofit, Buštěhrad ..................... 149
Table 5.35: Dynamic properties of the scenario, Bustehrad Table 5.36: Limit values set by standard
[21] ...................................................................................................................................................... 150
Table 5.37: Cost of the intervention, CZ ............................................................................................. 151
Table 5.38: Heating reductions obtained with the internal thermal coating, Buštěhrad ..................... 151
Table 5.39: Case scenario combination, Buštěhrad ............................................................................. 152
Table 5.40: Case scenarios of attic retrofit for the school building of Bustehrad ............................... 153
Table 5.41: Heating reductions obtained with the attic thermal insulation applied onto the case study
Buštěhrad ............................................................................................................................................. 154
Table 5.42: Case scenarios of the roof insulation intervention in Bustehrad ...................................... 156
Table 5.43: Dynamic properties of the scenario, Bustehrad Table 5.44: Limit values set by standard
Thesis Report | Paolo Lo Conte
[21] ...................................................................................................................................................... 156
Table 5.45: Performances of the old part roof .................................................................................... 157
Table 5.46: Heating reductions obtained with the attic thermal insulation in Bustehrad .................... 157
Table 5.47: Case scenarios for the ground floor insulation in Bustehrad ........................................... 159
Table 5.48: Heating reductions obtained with the ground floor thermal insulation in Bustehrad ...... 159
Table 5.49: Glazing’s component thermal properties. Thermal transmittance of the proposed windows
............................................................................................................................................................. 161
Table 5.50: Case scenarios considered for the retrofit of the glazing areas of the case study building in
Bustherad ............................................................................................................................................. 162
Table 5.51: Heating reductions with the complete refurbishment of the glazing area and CMV combined,
Buštěhrad ............................................................................................................................................. 164
Table 6.1: PV panels dimension, Lecco .............................................................................................. 171
Table 6.2: Solar radiation optimization of the PV panels positioning, Lecco ..................................... 171
Table 6.3: PV panels dimension, Buštěhrad ........................................................................................ 172
Table 6.4: Solar radiation optimization of the PV panels positioning, Buštěhrad .............................. 172
Table 6.5: Plant 1 costs, Lecco ............................................................................................................ 173
Table 6.6: Reduction of the electric and thermal energy consumption of the school building of Lecco
............................................................................................................................................................. 174
Table 6.7: Plant 1 costs, Bustehrad ..................................................................................................... 176
Table 6.8: Reduction of the electric and thermal energy consumption of the school in Bustehrad .... 176
Thesis Report | Paolo Lo Conte
Thesis Report | Paolo Lo Conte
INDEX OF APPENDICES
Appendix I - Validation of the energy models
Appendix II – Thermal analysis of the window
Appendix III – Economic index of the case scenarios
Appendix IV – Dimensioning verification of radiators served by an air/water heat pump
INDEX OF THE GRAPHIC TABLES
Elementary school G.Carducci, Lecco – Plans
Elementary school G.Carducci, Lecco – Elevations
Elementary school Bustehrad – Plans
Elementary school Bustehrad – Elevations
Thesis Report | Paolo Lo Conte
Thesis Report | Paolo Lo Conte
ABSTRACT
Nel valutare il dispendio energetico dell’Europa non è possibile trascurare il contributo relativo al
comparto delle costruzioni, ed in special modo le istituzioni pubbliche. I dati dimostrano che è proprio
questo settore, in particolar modo il patrimonio edilizio esistente, a poter garantire il più grande
potenziale di risparmio di energia. Per promuovere corrette misure di efficientamento energetico è
necessario avvalersi di metodi di calcolo e strumenti che permettano di prevedere, con buona
attendibilità, il reale consumo energetico degli edifici esistenti, cosicché, di conseguenza, sia possibile
stabilire scenari di riqualificazione appropriati, sia da un punto di vista tecnologico che economico, e
determinare con esattezza i risparmi conseguibili a seguito degli interventi stessi.
Il presente lavoro di tesi si sviluppa proprio all’interno di questo contesto, ovvero, definisce il consumo
energetico di due edifici scolastici situati in due città diverse della regione dell’Europa Centrale, quali
Lecco (IT) e Bustehrad (CZ), e si pone quindi l’obiettivo di valutare le opportunità di risparmio
energetico e soprattutto la possibilità di stabilire interventi di efficientamento energetico applicabili, con
risultati positivi ed omogenei tra loro, ad una vasta gamma di edifici scolastici presenti nel patrimonio
centro europeo. Il lavoro si struttura principalmente in tre fasi.
La prima fase ha l’obiettivo di definire e raccogliere i dati riguardanti le caratteristiche degli edifici in
analisi, considerandone in particolare, i requisisti relativi l’ambito urbanistico, architettonico,
impiantistico e gestionale. Simultaneamente avviene l’inserimento dei dati raccolti all’interno di un
software di simulazione energetica in regime dinamico (IES VE), allo scopo di definire e validare un
modello energetico rappresentativo delle condizioni reali degli edifici presi in esame. Nella seconda fase
si è proceduto con la scelta delle soluzioni di miglioramento delle prestazioni dell’involucro e degli
impianti dei due edifici presi in esame, per raggiungere l’obiettivo previsto dall’attuale normativa
europea riguardo gli edifici riqualificati. La terza fase, sviluppata in simultanea con la seconda,
rappresenta lo studio dell’ impatto energetico ed economico che le stesse soluzioni di miglioramento
delle prestazione prima citate, hanno sui due edifici presi come casi studio.
PAROLE CHIAVE
Simulazione energetica in regime dinamico, ottimizzazione energetica, riqualificazione energetica,
risparmio energetico, analisi energetica, analisi del comfort termico interno, impatto economico e
ambientale, costo dell’investimento, tempo di ammortamento, edifici scolastici nell’Europa centrale
Thesis Report | Paolo Lo Conte
Thesis Report | Paolo Lo Conte
ABSTRACT
In assessing Europe’s energy consumptions, it is not possible to neglect the contribution related to the
construction sector, and especially public institutions. The data show that it is precisely this sector, in
particular the existing building stock, that can guarantee the greatest potential for energy savings. In
order to promote correct energy efficiency measures, it is necessary to use calculation methods and tools
that make it possible to predict, with good reliability, the real energy consumption of existing buildings,
so that it is therefore possible to establish appropriate redevelopment scenarios, both from a point
technological and economic view, and determine exactly the savings achievable as a result of the
interventions themselves.
This thesis work develops within this context, as it defines the energy consumption of two school
buildings located in two different cities of the Central European region, such as Lecco (IT) and
Buštěhrad (CZ), and it therefore sets the goal of evaluating energy saving opportunities and in particular
the possibility of establishing energy efficiency measures that can be applied, with positive and
homogeneous results, to a wide range of school buildings present in the central European heritage. The
work is structured mainly in three phases.
The first phase aims to define and collect data concerning the characteristics of the analyzed buildings,
considering in particular the requisites concerning the urban, architectural, plant and management areas.
Simultaneously, the data collected is inserted in a dynamic energy simulation software (IES VE) in order
to define and validate an energy model that is representative of the real conditions of the buildings
examined. In the second phase, it has been analyzed the choice of solutions, to improve the performances
of the envelope and the systems of the two buildings, in order to achieve the requirements set by the
current European legislation, regarding retrofitted buildings. The third phase, developed simultaneously
with the second, represents the study of the energy and economic impact that the same performance
improvement solutions mentioned above, have on the two case study school buildings.
KEYWORDS
Dynamic energy simulation, energy optimization, energy retrofit, energy saving, energy analysis, indoor
thermal comfort analysis, economic and environmental impact, investment cost, payback time, school
building in Central Europe
Thesis Report | Paolo Lo Conte
Thesis Report | Paolo Lo Conte
INTRODUCTION
Educational buildings account for 17% of the total European floor space of non-residential building
stock. With an average specific energy consumption estimated at 280kWh/m2, it is at least 40% higher
than the equivalent value for the residential sector. Central Europe Regions vary greatly in their policy
frameworks and have a wide disparity in their current performance and targets, but as a general trend,
most are at risk of missing their targets for energy consumptions. The share of renewables in gross final
consumption of energy (20%) is one of the headline indicators of the Europe 2020 strategy. The
frontrunners in Central Europe were Austria and Slovenia with a share of 32.6% and 21.5% in 2013.
Croatia, Italy, Germany and Czech Republic rank in the middle with a share between 18% and 12.4%
and Hungary is at the back of the pack at 9.1%. Although some strategic and action plans were made,
the main obstacle for speeding up the process is the lack of public funding and low awareness about
possibilities. The project, through the organization of existing knowledge in an integrated methodology,
wants to develop an effective communication strategy addressing the necessary development of skills
for public owners of educational buildings in the Central Europe area in order to support their decision-
making processes and increase their potential to access to financial support.
This thesis work addresses the necessary implementation of an integrated strategy promoting a large-
scale energy retrofitting of the public educational building stock in the CE area. The innovativeness of
the approach is based on the statement that public educational buildings need specific measures that are
not covered by the existing regulatory frameworks, tools or methodologies. This work develops tailored
planning for these buildings so to address the long-term objective of deep retrofitting promoting a
technologically logical step-by-step approach that can be managed with affordable budgets and
profitable investments and without interrupting the operation of the school during the year. The goals
are increasing energy efficiency and implementing renewables in existing public infrastructure through
the development and the demonstration of integrated strategies for the effective and sustainable energy
retrofitting of public educational buildings. This work supports the overall program goal of reducing
carbon emission in the cities of Central Europe, creating an enabling framework to promote large scale
energy retrofit of existing public educational buildings.
Thesis Report | Paolo Lo Conte
Thesis Report | Paolo Lo Conte
1
CHAPTER 1
1 Regulation Framework
It will be analyzed the European regulations framework seen as European Union and as single Member
State. Starting from the standard at European level to the implementation done by each of the Member
State considered for the analysis, which are Italy and Czech Republic.
1.1 Energy Savings Policy in the European Union
In Europe, over the last few years, energy issues have been the focus of many directives and action
plans, with the aim of raising awareness among the governments of the State Members.
Buildings are a strategic focus of European policies aiming to achieve a sustainable and competitive
low-carbon economy by 2020. The European Commission encourages Member States (MS) to decrease
energy consumption in buildings and convert national building stocks from energy consumers to energy
producers through retrofit measures and renewable energy sources (RES).
EU Directives require that public authorities should adopt exemplary actions to achieve this target.
The main policy that governments are trying to implement is the Energy Climate Package 20-20-20 [1],
a set of measures planned by the European Union (EU) for the period following the end of the Kyoto
Protocol [2]. The package, part of an Action Plan approved in 2007, came into force in June 2009 and
will be valid from January 2013 to 2020. The EU, over this period, has committed itself to reaching
three goals: reduction of 20% of the emission of CO2 compared to 1990; 20% of the energy, on the basis
of consumption, coming from renewables; saving 20% of primary energy consumption to 2020
compared to a reference scenario.
The EU’s “2020 Europe Strategy” [1] for employment and smart and sustainable growth includes among
its main objectives the energy efficiency, which is always emphasized in the European political program
as a means of addressing the threefold challenge of the economic crisis, energy dependence and climate
change.
NEEAPs (National Energy Efficiency Action Plans) have the task of showing estimates of state
consumption, measures already implemented and energy efficiency forecasts and improvements that
individual countries expect to achieve. The NEEAPs submitted by the State Members during the
reporting period under Directive 2006/32/EC on Energy Services Directive (ESD) have suggested that
the efforts implemented so far are not in line with the target set for 20 % of energy efficiency by 2020.
To address this problem, it was established in the November 2012 the Directive 2012/27UE “Energy
Efficiency Directive” [3] (EED), which explains to MS how to work to achieve the 20% efficiency
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target set by the Climate-Energy Package . In addition, this directive requires each MS to set its own
national consumption reduction target, which will be monitored by the European Commission with the
prerogative of intervention where necessary with binding measures and adjustments for the countries at
risk.
The EED adopted by the European Parliament has become the central instrument for the UE’s energy
policies. It intensifies MS’ efforts to manage energy more efficiently at all stages of the energy chain,
from transformation to distribution for the final consumption. The key measures in the Directive are:
- Renovation of some public buildings, and public procurement of energy-efficient materials
(Articles 4 and 5).
- Energy efficiency obligation schemes, which require utility companies to help their customers
save energy (an annual final energy reduction of 1.5 per cent has been set as a goal) (Article 6).
- Energy audits to be compulsory for large companies. These will be carried out every three years
(Article 7).
- More information to be provided for metering and billing (Article 8).
For many MS, the 2014 Action Plan, under the EED, was the third, following the 2007 and 2011 ESD
requirements. To ensure continuity between the different action plans, they were written based on
information on efficiency measures contained in previous NEEAPs. The deadline for submitting the
NEEAPs was 30 April 2014 and will then be submitted every three years.
1.1.1 The role of the public building
The EU database classifies buildings in residential and non-residential buildings, and based on the type
of the building it shows data about the stock of the selected type and also energy data linked to the
building characteristics.
Non-residential buildings represent around the
10 % of the European building stock, there are
over 15 million of buildings located in the
European territory classified as Non-residential
building [4]. The European territory is wide and
various, therefore there are different scenarios
regarding energy consumption in the, above
mentioned, buildings classification. In
particular, there more than 800,000 buildings
entirely or partly used as schools. With regard to their location 40 % of school building are concentrated
Figure 1-1: Share of non-residential buildings in UE [4]
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in the Central part of Europe, such as Germany, Italy, Austria, Czech Republic, Hungary, Croatia, and
more than 20 % are located in the Northern part of Europe [4]. Furthermore, about 29% of schools are
located in very small municipalities (up to 5000 inhabitants), and roughly the same percentage are in
medium sized municipalities.
Educational building are classified as
non-residential buildings, the average
annual values of thermal energy show
the comparison between the
consumption for non-residential
buildings and educational between
different states of the Central Europe.
From the graph it’s clear that for most
of the countries the average for the non-
residential buildings is really close to
the one of the educational, this is reasonable since, as said, the education buildings represents around
7% of non-residential buildings throughout the European territory [4]. The stats regarding the
educational buildings show that the consumption per country are close one to each other, this means that
even if the European territory is very diversified, the starting point for school’s energy optimization is
similar in every country. This sets some benchmarks in order to understand the average condition of a
school in Europe and, as said before, in order to be able to set the starting point of the retrofit strategy.
Another important benchmark is highlighted by the table here represented, it’s possible to see an
approximation of expense for each child, based on the data collected by the Energy Consumption Guide.
Good practice benchmarks represents the energy performance of the top 25% of schools, while Typical
benchmarks are the average energy performance of all schools [4].
The table shows the price for each student school, it was done in order to have a simple and fats way to
calculate how much a school with a fixed number of students will consume by fossil fuel and electricity
and have an easy way to understand the energy cost of old buildings such as schools in this case.
The majority of existing school buildings present inefficient systems and technologies. They often use
Good
practiceTypical
Good
practiceTypical
Good
practiceTypical
Good
practiceTypical
136 174 11.07 15.26 24 30 15.53 19.56
Secondary schools
Fossil Fuel
€/pupils
Electricity
kWh/m2 €/pupilskWh/m2
0 50 100 150 200 250 300
Austria
Croatia
Czechia
Germany
Hungary
Italy
Slovakia
Slovenia
kWh/m2
Non-residential
Educational
Figure 1-2: Annual thermal energy consumption per country of CE
Figure 1-3: Benchmarks for energy consumption in secondary schools
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traditional heating systems, in particular radiators for heat distribution and gas/oil-fired boilers for
generation . Space heating is still the main end-use with more than 40% of heating needs met using
natural gas in 2012 [5].
The major cause of high energy consumption is
represented by the Space heating of the classrooms. Most
schools present outdated thermal energy plant, with old
boilers with a low efficiency(sometimes lower than 50
%), really far behind from the values achievable with the
new technology used in the NZEB buildings (i.e.
condensing boilers). The lack of maintenance and proper
know-how is another key aspect on why the energy
consumption are so high for schools, they may lead to
high involuntary leakage of the plants and even lower
values of efficiency due to the possible unknown
presence of damages and dirt throughout the thermal
plant and the distribution system. The overall efficiency of the plant is given also by the specific
efficiency of the emission system present in the school, in particular in the classrooms. The most
common emission terminals are the cast iron radiators, the major feature of this system is its high thermal
inertia, this term means the ability to retain heat for a long time even after the heat source has gone out,
a characteristic that is typical of cast iron due to the physical structure of this alloy, but also its great
disadvantage when igniting. To heat the cast iron heaters it is necessary water at a temperature of 65-80
°C , which is very high (certainly not an energy-saving temperature!) and the time to warm an
environment is much slower, in addition the thermal yield is lower, this means that for the same heat
transfer, cast iron heaters will be larger than other types [5].
The disadvantages due to inefficient plant are combined with the high thermal losses due to the opaque
and transparent envelope, they create a sort of cause and effect relationship since the presence of a
permeable envelope increases the losses of the envelope therefore increasing the energy needed from
the plant in order to guarantee comfort, this obviously overstresses the plant, which in case the plant is
already inefficient will only mean more involuntary losses from the system and higher consumption
due to the higher energy demand of the thermal plant, basically that’s what it’s possible to see from the
figure below. The starting point are the two major influencer the “Envelope” and the “Plant”, depending
on the performances of the two it’s possible to understand whether they have a positive or a negative
impact on the energy consumption of the building, depending on the properties of the envelope we can
define the losses and calculate the energy demand, needed to guarantee internal comfort, in the same
way the efficiency is defined by the plant. The energy consumption of the building is represented as
Figure 1-4: Average energy use school profile [5]
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“Energy need x Efficiency”, this is because in this case it’s relevant the individual and combine effect
of the characteristic of the envelope and the plant. The flowchart intention is to highlight the combined
effect of low performance envelope and plant, in this case the envelope will increase the energy needed
to guarantee the project fixed temperatures, this means that not only the consumption will be high
because of the low efficiency of the plant but it will be even higher since the inefficient plant will have
to generate more energy in order to compensate the losses of the envelope.
he high consumption and the inefficiency of the building’s component is obviously due to the age of
construction of those buildings. School all over Europe have been classified as “old” or “long-standing”
this is showed by the various European surveys in which it’s possible to identify the average construction
year.
The diagram shows the share of School buildings
located in the European territory based on the
construction period. It’s easy to understand that
the period in which more school can be located is
the one between 1961 and 1980, been WWII over
at the end of 1945, it’s reasonable to see that the
period 1946-1960 represents an introduction to
the massive reconstruction and improvement of
the ’60. Less than 25% of the school present in
the territory was built before the European Union was found, therefore before any European energy plan
Figure 1-5: Flowchart of Energy Consumption
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was even in the minds of the State Members, in this particular case, relevant importance is taken by
National energy legislations that were passed before any of the EEP. An important example of national
legislation is the Italian Parliament’s ordinary law n 373/76 [6] which contains the standards for the
containment of energy consumption for thermal uses in buildings.
The 75% of Italian schools dates before
energy laws and the distribution in the
territory from north to south does not
change. The 33% of the school buildings
dates before law n° 373/76 and about the
50% has been realized after the law
nonetheless, the energy quality did not
improve dramatically [7] .
The 25% of the school building dates after
‘80s and thus towards the “Law 10” [8] , in
which it was finally showed a complex National Energy Plan, with the addition of studies on the
renewable energies.
Moreover, the progressive ageing of the schools means a crucial need of improvement and performance
to accomplish current standards and EU Directives. The school building stock counts over 62,000
schools of which about 45,000 public, largely overtake the public housing sector with about 1 million
TEP of energy consumption per year of which 70% of heating and 30% of electricity. The potential of
reduction, with effects on energy, environment and social aspects is impressive. A first step towards
energy efficiency can be implemented by promoting energy behavioral awareness with low cost actions
and a 20% of estimated effectiveness.
1.1.2 Potential savings from school buildings
Energy saving that can be derived from improvements to existing school buildings are potentially large
because of their typical high energy consumption linked to inefficient systems and poor thermal
insulation thickness. With the aim of improving energy efficiency in public buildings (e.g., offices,
schools, health facilities, infrastructures), energy services companies “ESCOs” are being more common
nationally.
A study has been carried out on the potential savings deriving from energy retrofit in schools in
compliance with the EED [9] . Potential savings refer to the saving achievable if, in the period 2014–
2020, energy efficiency actions would be put into practice with a cost-optimal approach to achieve
saving of 60% in the public sector and 40% in the private sector. To assess these potential savings, the
Figure 1-6: Distribution of schools in the Italian and age [4]
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Italian school building stock has been analyzed. The floor area of public and private schools that can be
renovated each year has been estimated at 6 million m2 (about 3800 buildings). This total includes about
1 million m2 private schools and 5 million m2 public schools.
For this stock, the study considers actions differentiated by climatic zone and applicability. Among them
there are: thermal insulation of roof and heat-dispersing external walls, thermal insulation of floors or
floors/ceilings bordering on unheated spaces, replacement of existing windows with high-energy
performance windows, upgrading heating/cooling control systems, replacement of heat generators, use
of high-efficiency heat recovery systems, installation of automation systems or a building energy
management system (BEMS), replacement of lighting and external solar screens.
Specifically, the total energy savings achievable from schools by 2020 are estimated as follows: 617
GWh/y for private schools and 5821 GWh/y for public schools. The difference in energy saving
percentages between public and private sectors stems from the fact that public buildings are mainly
constructed prior to 1980 and their starting energy performance is poorer. The estimated investments
for these retrofit projects amount to around 6.54 billion €/y, and should yield potential energy savings
of 6.438 GWh/y by 2020. At European level, the added value deriving from specialized construction
activities that include renovation work and energy retrofits has been estimated as 283 billion € in 2011,
66% of this value is linked to the EU building sector. In particular, specialized construction activities
supported 7.84 million jobs in the EU building sector, and 1.55 million in Italy. In more detail, activities
linked to building envelope (e.g., roofing, walls and floor covering, glazing) have been quantified at 166
billion in the same year [10] .
Energy saving measures focusing on
envelope and thermal plants can
decrease strongly the consumption
with additional costs however about
40% of the school buildings are in
need of maintenance and the retrofit
measures could be included inside this
cost item. The cost percentage of
energy retrofit measures in school
buildings show that the control and upgrading of lighting and thermal systems have low costs in
Figure 1-7: Consumption reduction potential by 2020 from complete renovation of schools starting [5]
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comparison with envelope solutions such as insulation of the vertical and horizontal opaque portions or
thermal enhancement of transparent surfaces. The cost of measures focusing on the envelope can affect
by 10% to 46% the refurbishment interventions [11]. Furthermore, the age of the school building stock,
defines the typologies of envelope and the associated thermal plant. In fact the 70% of the national
school buildings is realized with reinforced concrete frame structure with brick infill walls and it is
equipped with a gas boiler heating system [11]. In any case, for buildings realized after the 1976 a thin
insulation layer in the opaque envelope can be expected. The average heating energy consumption for
public schools is about 180 kWh/m2year whereas the requirement for new construction is about 30-40
kWh/m2year. Thus, it is not appropriate supplement with an additional cooling need this amount of
energy inasmuch cooling systems diffusion had a dramatic growth in the last 15 year in the housing
sector. The requirement of comfort is however pushing and the capacity of the envelope to reduce and
manage the heat gains with dynamic thermal properties has been introduced in the national regulations
since 2009 [12].
1.2 Analysis of two case studies: Italy and Czech Republic
Every European nation implements the regulations issued by the European Union, at national level, in a
different way one from another. In this paragraph it will be analyzed how the two nations analyzed
through this work, have implanted their regulations.
1.2.1 Italian Regulation
At national level, since the so called Law 10 [8] , Issued in 1991, the emphasis is on energy saving and
rational use of energy and the diffusion of renewable sources. In addition to assigning specific tasks to
local and regional authorities, this law seeks to reduce energy consumption in public and private
buildings with the obligation of energy certification.
The Ministerial Decree of 26 June 2015 [13] concerns the application in the Italian territory of the
European Directive 2010/31/EU. It is an indispensable tool for the promotion of nearly zero energy
buildings. The purpose is to define how the energy performance calculation of buildings, the use of
renewable sources, the requirements and the minimum requirements for energy performance are applied.
The criteria apply to both public and private buildings, new buildings or existing ones undergoing
restructuring. The 26th of June 2015, the Ministry for Economic Development (MISE) announced the
publication of three key decrees for adapting to European building energy efficiency standards and the
deadlines to be met for restructurings.
The first decree [13] is aimed at defining the new ways of calculating the energy performance and the
new minimum efficiency requirements for new buildings and those undergoing renovation.
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A second decree [13] adapts the draft technical design diagrams to the new regulatory framework,
depending on the different types of works: new constructions, major renovations, energy re-
qualifications.
With the third decree [13], the standards for the certification of energy performance of buildings (APEs)
were updated. The new APE model will be valid throughout the country and, along with a new
commercial announcement scheme and the National Energy Certificate Database (SIAPE), will provide
citizens, administrations and operators with more information on the efficiency of the ‘ Building and
plants, allowing for easier comparison of the energy quality of different real estate units and orienting
the market towards buildings with better energy quality.
From 1 January 2021, new buildings and those undergoing significant renovations will have to be
implemented in such a way as to minimize energy consumption and to cover them to a minimum with
the use of renewable sources. For public buildings, this deadline is anticipated until January 1, 2019, the
three measures, will enter into force on 1 October 2015 and will thus allow Italy to be fully in line with
European directives .
Let’s start by analyzing the first of the three decrees (all dated 26 June), which deals with the
methodologies for calculating energy performance and the definition of building requirements and
minimum requirements. It defines the modalities for the application of the methodology for calculating
the energy performance of buildings, including the use of renewable sources, and the minimum energy
performance requirements and requirements for buildings and real estate units. The Decree applies
(Article 6) [13] to the Regions and Autonomous Provinces that have not yet taken measures to transpose
Directive 2010/31 / EU [14]. The decree contributes to the definition and updating:
- the methodologies for calculating the energy performance of buildings in accordance with the
general principles of art. 3 of MD 26/6/2015;
- minimum requirements for buildings and installations;
- building energy classification systems, including the definition of the common information
system, also in collaboration with the Department of Public Function of the Presidency of the
Council of Ministers;
- the monitoring, analysis, evaluation and adaptation of the national and regional energy
legislation referred to in Articles 10 and 13 of the Legislative Decree.
The second decree stipulates that its provisions are directly applicable in the regions and autonomous
provinces that have not yet adopted their own energy performance attestation instruments in accordance
with Directive 2010/31 / EU. If they had adopted their own instruments, they should take measures to
encourage, within two years of the entry into force of the Decree, the adaptation of its regional
instruments to the Guidelines. The decree seeks to promote the homogeneous and coordinated
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application of the certification of the energy performance of buildings and real estates by defining:
- the National Guidelines for the Certification of Energy Performance of Buildings;
- instruments for linking, conciliation and cooperation between the State and regions;
- the establishment of a common information system throughout the national territory for the
management of a national catastrophe of energy performance certificates and thermal
installations.
The Guidelines are contained in Annex 1 to MD 26/6/2015 [13] and include:
- calculation methods, even simplified for small-scale buildings and low-quality energy
performances, with a view to reducing the cost to the citizen;
- the APE format, referred to in Appendix B of the Guidelines, including all energy efficiency
data of the building and the use of renewable sources in it, in order to enable citizens to
evaluate and compare buildings different;
- the sales or lease announcement scheme referred to in Appendix C of the Guidelines, which
uniformizes the information on the energy quality of buildings supplied to citizens;
- the definition of the common information system throughout the national territory.
1.2.2 Regional Legislation
The National MD 26/6/2015 has been transposed in July 17, 2015 and has updated the regional discipline
that defines the minimum energy efficiency requirements of buildings, whether in the case of new
construction or renovation, and how to calculate the energy needs of buildings, by issuing a decree to
the editorial office of a single text, aimed at containing the new implementing provisions. This single
text ,technically described as a Consolidated Law ,was approved by Decree no. 6480 of 30.7.2015 and
was incorporated by Decree no. 224 of January 18, 2016. The need to provide further operational
clarification and to adjust the procedure for the calculation of energy efficiency on buildings also in
relation to some indications highlighted by the Ministry of Economic Development, has led to the
approval, by Decree No.176/2016 , of a new Consolidated Law which therefore replaces the decrees
previously approved.
For these reasons, it was decided to approve this update in order to implement energy saving, rational
use of energy and renewable energy sources in buildings in accordance with the fundamental principles
set out in European Directive 2010/31 / EU 19 May 2010 and Legislative Decree 19 August 2005, no.
192 , as well as the implementing provisions approved by DGR of 17/7/2015.
The provisions contained in Decree No.176 of 12 January 2017 [15] concerning issues related to the
energy-saving of buildings affect different themes: from wrap-around to those relating to technical
installations, sanitary water, lighting, ventilation and of winter and summer air conditioning. In addition,
within the Decree n.176 of 12 January 2017 [15], a section on the energy performance certificate is
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devoted, which should, from 1 January 2016, be present in all buildings at the end of the works and
before Declaration of agility. The Energy Performance Certificate (APE) is the synthetic document
produced by the owner of the building attesting to the value resulting from the calculation of the energy
performance of the building to which it refers. In addition to the APE, Decree No.176 of January 12,
2017 extends the directives in terms of inspections and inspections related to the energy efficiency of
buildings and the energy classification of buildings.
Depending on the requirements we could distinguish three main application areas:
- New construction;
- Major renovations;
- First level;
- Second level;
- Energy retrofit.
The definition of Major renovations is explained through a simple layout presented in the figure below.
Basically first level renovation stands for an intervention which involves more than 50 % of the envelope
and the simultaneous refurbishment of the heating/cooling plant. While the second level renovation
stands for intervention which involves more than 25 % of the envelope and it could also affect the
heating/cooling plant.
Finally, the decree identifies the category of “energy retrofit” for all non-attributable interventions to
previous cases and which have, however, an impact on the energy performance of the building. Basically
they stand for interventions that either involve less than 25 % of the envelope or the installation of a
new heating/cooling plant, consisting on either the simple replacement of the generations systems or the
complete refurbishment of the thermal plant. The figure below shows summarily what is the definition
of an “energy retrofit” intervention.
Figure 1-8: Major renovations definition, by the Ministerial Decree of the 26th of June 2015
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Through this work the interventions analyzed will involve only second level renovations and energy
retrofit interventions. As matter of fact it will be studied how the retrofit of the envelope of the buildings
and the refurbishment of the thermal plant will impact the energy consumptions and the operations costs
of the case studies. The emissions and the distribution system will be left as they are now, therefore no
first level renovation intervention will be analyzed.
So here are listed the verification requested from the decree: verification of energy needs, of the average
coefficient of thermal exchange, of the transparent technical closures and of the efficiency of the plants.
These verifications are made basically comparing the values of the renovated building with the one of a
reference building , which has the same exact characteristics of the building with fixed energy
parameters.
1.2.2.1 Italian national energy certification
At national level, the measure of the energy performance of a building (Epi) indicates how much energy
a building consumes during a year per square meter of treated floor area (TFA). The Epi of an existing
building built before national Law 10/91 is generally between 200 and 300 kWh/m2y with fuel
consumption between 10 and 30 L oil/m2y. The Epi of a building designed and built according to current
legislation is between 15 and 130 kWh/m2y with fuel consumptions between 1.5 and 13 L oil/m2y. The
“APE” [16](Attestato Prestazione Energetica) has a maximum time limit of ten years from its release
and is updated to any renovation or upgrading intervention relating to building elements or technical
installations such as to modify the energy class of the building or the real estate unit. This validity is
subject to compliance with the requirements for energy efficiency control operations of the technical
installations of the building, in particular for thermal installations, including any adjustments required
by the regulations set out in the decree of the President of the Republic of 16 April 2013 , N. 74. In the
Figure 1-9: Energy retrofit interventions definition, by the Ministerial Decree of the 26th of June 2015
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event of non-compliance with these provisions, the APE shall expire on 31 December of the year
following the date on which the first expiry date for the above-mentioned energy efficiency control
operations is foreseen.
Each APE must be drawn up by an authorized person according to Presidential Decree No. 75 of 16
April 2013 [17] and presents, for the building or real estate unit:
- overall energy performance, both in terms of
total primary energy and non-renewable primary
energy, through their respective indices;
- the energy class determined by the global
energy performance index expressed in non-
renewable primary energy;
- the energy quality of the building to contain
energy consumption for heating and cooling,
through the thermal performance indices useful
for winter and summer air conditioning in the
building;
- reference values, such as the minimum energy
efficiency requirements in force under the law;
- carbon dioxide emissions;
- the energy exported;
- recommendations for improving energy
efficiency with proposals for more meaningful
and cost-effective interventions, distinguishing
between major restructuring measures and
energy redevelopment.
In addition, the APE should report information related to improving energy performance, such as
financial incentives and the opportunity to perform energy diagnosis.
The 26/6/2015 Decree [19] also specifies that the authorized subject will have at least one inspection at
the building or real estate unit subject to attestation, in order to find and verify the data necessary for its
predisposition.
1.2.3 Czech Regulation
The Climate Protection Policy of the Czech Republic [19] along with the Strategy on Adaptation to
Climate Change [20] in the Czech Republic represent specific policies regarding climate change. The
Figure 1-10: Italian Energy Performance Certification
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Climate Protection Policy was adopted by the Czech government in March 2017 and replaced former
National Program to reduce the Climate Change impacts in the Czech Republic. The Policy defines main
objectives in the climate protection at the national level to ensure the fulfilment of the greenhouse gas
emission reduction objectives in order to reach international commitments of the Czech Republic.
Furthermore it contributes towards gradual long-term transition to sustainable low emission economy.
The Policy further sets primary and indicative emission reduction targets, which should be reached in a
cost efficient manner. Measures are proposed in the following key areas: energy, final energy
consumption, industry, transport, agriculture and forestry, waste, science, research development and
voluntary tools.
The plan seeks to improve energy efficiency and cut greenhouse gas (GHG) emissions by developing
renewable energy and expanding nuclear power capacity. The plan aims to:
- cut energy consumption per unit of GDP by 3-5% per year;
- increase the share of renewable energy to 16% by 2030;
- increase the share of transport fuel from alternative sources such as gas or biofuels to 20% by
2020.
However, it found the Czech Republic energy intensity and GHG emissions per capita were
comparatively high, and that transport sector emissions continued to increase. The National Climate
Change Plan is thus being reviewed to emphasize measures targeting the industry and transport sectors,
which contribute the most to GHG emissions, as well as to take into account the evolution of domestic,
European and global political negotiations on climate change since 2004.
The Policy covers a period from 2017 to 2030 and provides outlook until 2050. The first evaluation is
planned in 2021 and on the basis of such evaluation the Policy will be updated by 2023. In October 2015
the Czech government adopted the Strategy on Adaptation to Climate Change [19] in the Czech
Republic. This document represents a national adaptation strategy and includes assessment of the
climate change impacts and proposals for specific adaptation measures, legislative and partial economic
analysis, etc.
The Czech Republic’s national indicative targets have been set in line with the document “Update of the
Czech Republic’s State Energy Policy” [21] . This is a key strategic document which aims to ensure a
reliable, safe, and environmentally friendly energy supply for the needs of the population and economy
of the Czech Republic, at competitive and affordable prices under standard conditions. Further to the
passing of Directive 2012/27/EU of the European Parliament and of the Council on energy efficiency,
the Czech Republic has launched a process to transpose it into national legislation.
The most important act regarding energy saving in building construction is represented by the “New
Green Savings 2014+” [22] [19] , the Ministry of the Environment’s program administered by the State
Environmental Fund of the Czech Republic represents the green investment scheme of Czech Republic
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and is focusing on energy savings and renewable energy sources in family houses. The Program’s
objective is to improve the environment by reducing greenhouse gas emissions through the improved
energy efficiency of buildings, the support of residential development with very low energy performance
and the efficient use of energy sources, as well as saving energy in final consumption and stimulating
the economy of the Czech Republic with other social benefits, which are for example, increasing the
quality of citizens living, improving the appearance of cities and municipalities, starting long-term
progressive. Promotes energy saving reconstructions of houses and apartment buildings, replacement of
unsuitable heating sources and usage of renewable energy.
1.2.3.1 Czech national energy certification
On 19 September 2012, the Czech parliament overruled a presidential veto and passed the “Amendment”
[23] which imposes additional obligations on builders of new buildings, as well as on owners of certain
buildings already in use, including the obligation to have an energy performance certificate “EPC”
issued.
The Amendment imposes a new obligation on the owners of completed residential and administrative
buildings already in use. As of 1 January 2015, the owners of such buildings are obliged to ensure the
EPC. The Amendment sets later terms for fulfilment of the above-stated obligations in relation to the
surface area of a building. At the latest by 1 January 2019, all completed residential and administrative
buildings are required to have the EPC.
Furthermore, the building owner must ensure the EPC
prior to any purchase or lease of a whole building or any
purchase of building’s compact parts (residential or non-
residential premises) as of 1 January 2013. After 1
January 2016, even the lease of residential or non-
residential premises shall be subject to the obligation
and the landlord will have to submit the EPC to the
future tenant at the latest by the signing day of the lease
agreement.
With regard to the purchase and lease of the building or
its compact parts, the owner is obliged to ensure the
EPC, submit the EPC to all potential buyers before the
conclusion of the contract and hand over the EPC to the
buyer at the latest by the conclusion of the contract. If
publishing any information or marketing materials with
respect to the purchase or lease of the building or its Figure 1-11: Czech Energy Performance
certification
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compact parts, the owner of the building is obliged to include the data from the EPC.
The EPC shall indicate the building’s energy performance on a scale of A to G, making the information
on expected energy consumption in the building accessible to potential buyers or tenants. It expires
within ten years at the most or as soon as the building undergoes major reconstruction.
The EPCs are to be elaborated and issued exclusively by energy experts authorized and listed by the
Ministry of Industry and Trade. The list of experts will be available on the website of the Ministry. Due
to increased demand of the EPCs at the beginning of next year, a significant increase in price for
elaboration and issuance of the EPC can be expected.
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CHAPTER 2
2 Description: Case study “Lecco”
Within this chapter it will be proposed and analyzed a case study, identified among the many taken into
consideration, chosen on the basis of the data and information actually available to perform this in the
most complete way this work, following the analysis method described and deepened in the previous
paragraphs.
2.1 Geographical and historical overlook
The first case study taken in consideration is a school building located in Lombardy, exactly in the city
of Lecco. The city of Lecco is located on the side of the homonymous lake, oriental branch of the Como
lake, and on the shore of the Adda river, its urban agglomeration has more than 114,000 inhabitants and
includes several neighboring municipalities.
Figure 2-1: Territorial overview of the case study building
At the ground level the entire building is surrounded by a moderate amount of green surface, represented
by the courtyard of the school, the access to the school is possible through a one-way street that goes
beside the main entrance of the school, located on the old part of the school building. Unfortunately the
figure representing the territorial overview of the building is old, therefore it’s not possible to see the
newly constructed residential building present on the right of the school, this will be highlighted later
one in the analysis of the case study.
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The school building is located in an urban area of the city of Lecco, the context in which the proposed
building is inserted is characterized by the presence of settlements for the most part residential and
moderate size, with the main square occupied by a church. The morphology of the area has changed
during the years, finally the street area has been decrease in order to have a bigger sidewalk to protect
the students from the moving cars, and to facilitate the traffic created in the entrance hours from the
student’s parents.
The case study building is an elementary school called “Giosuè Carducci”, as the famous poet,
composed of two part, each of the part has its own structure and was built in a different age, together on
plan they form a L shape around the stairwell, which represents the focus of the whole building.
The elementary school building was initially built
in the 1901, than it went under some
reconstruction until in the 1961 the building was
expanded, a new a body was added to the original
structure, giving to the overall plan a L shape. The
recent part of the building can be identified in
between the 1961-1980 years. Due to the different
building age construction the two parts present
different element structure and different input for
the energy model dynamic simulation, as it will be shown in the following paragraph. The whole
building accounts for a total of 13 classroom distributed so that 4 of them are in the recent part of the
building, while the other are in the old part. As explained the recent part has a significant lower amount
of classes respect to the old one, this is because the recent part was built especially to integrate a school
gym, therefore the major amount of surface area is dedicated to this function.
Figure 2-3: School “Giosuè Carducci”, 2016
Figure 2-2: School “Giosuè Carducci”, 1909
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This is how the whole building looks nowadays, comparing the pictures from the different years it’s
possible to see that the old building hasn’t changed that much. What is visible in this real-life pictures
is than translated into a 3D modelling of the whole case study area, this was done in order to have a
more complete analysis, with more credible results which reflect reality more. In the modeling of the
surroundings the data about the buildings were taken upon a visual inspection confirmed by detailed
researches through the technology available.
Figure 2-4: Capture of the 3D representation of the case study area (21 September 12:00).
From the picture above is also possible to see the shadows on the building and on the surroundings in
order to try to have some ideas about the shading action of the surroundings on the case study building,
highlighted in blue. As seen, the school building is surrounded by moderate height buildings alternated
by a green area around the internal façade.
The urban context in which the building is inserted is characterized by the presence of medium-sized
and small dimensions building that do not rise for more than four floors, except for the new residential
building built in front of the school’s courtyard. The average height and the low density of the
surrounding building make sure that the buildings surrounding the project’s site do not generate shadings
that are particularly incident on the body of factory of the residence, so as to ensure a correct daylight
factor and, above all, do not hinder the possible solar gains in the coldest seasons. To determine the level
of shadowing on the building within one calendar year, an analysis was performed related to the shadows
that are generated during the equinoxes and the solstices, presented in the annexes.
N
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2.2 Architectural construction
To reconstruct the planimetry, the company that administers the building was contacted, through which
it was possible to access the cadastral documentation of the building.
For a better accuracy in the analysis procedure, it was subsequently performed a survey of maximum on
the exterior of the building in order to verify that the dimensions reported on the cadastral plants
correspond exactly to those real.
The whole building, as seen from the pictures, has various element’s structures, the stone structure of
and the tiles inclined roof of the old part is not present in the recent part, where the hollow brick masonry
is used as load-bearing structure and the roof is made of a metal sheet. The differences are visible on the
whole structure, the old part has 3 floor above the ground, opposed to the only 2 of the recent, while the
underground is present in both parts, the function is different as for the recent part is designated for the
gym while the old part is simply used as storage. The plan lets understand the separation of the two
different parts of the building, it also gives an overlook on the inside and surrounding of the school
building’s area.
Figure 2-5: Ground floor plan of the case study building
RECENT PART
OLD PART
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The structural element are different for the two parts of the building, as mentioned before, this means
that they will be studied as two separate entities in the following dispersions analysis. The peculiarity
of the building is that the façade that is exposed on the North-West direction, which is the one on the
street side, has an architectural value, since as seen in the previous pictures it has been constructed more
than 100 years ago, and it still shows the aesthetic characteristic of that particular time. This means that
when proposing the improvement cases there will always be a special attention on this feature, therefore
there won’t be any improvement work that can damage the image of this architectural value.
The floors of the building follow the imprinting of the ground floor, with the difference that on the upper
floors all the space is used for the classroom, therefore the two parts wont’ be separate bodies as it’s
visible here, but they will be connected in order to create a bigger educative space. In order to have a
more detailed view of the building’s distribution and technology reference is made to the annexes, where
it’s possible to see all the plans and the complete overview of the building.
The table here presented gives a
numerical tool in order to
understand the distribution and the
composition of the case study
building. Once more is obvious
that the impact of the old part of
the building is higher than the
recent, therefore in a retrofitting
view the most critical importance
has to be given to the technologies
of the old part. Another important aspect is the one related to the glazing area of the construction, which
represents more or less 20% of the external wall area, in both cases, indicating the need for accurate
analysis regarding the optimization of the windows, and the related thermal bridges. Finally the data
about the Surface-Volume ratio shows that most of the spaces have high ceilings, increasing the volume
of the building, especially increasing the volume of space that has to be heated in order to guarantee
thermal comfort for the users thus increasing the energy needs.
2.3 Energy data collection
The purpose of this first phase is to collect as more information as possible about the building,
considering those concerning the urban, architectural and plant design aspects. The site survey is the
first approach with reality with which one is confronting and plays a very important role within this type
of analysis.
Element Unit Building
Old part Recent Part Whole
Floor # 3+1 2+1 3+1
Floor area [m2] 906.7 467.79 1374.49
Heated Space [m2] 671.46 437.1 1108.56
External Wall area [m2] 754.42 544.5 1298.92
Glazing area [m2] 133.36 112.75 246.11
Average Height [m] 3.5 3.5 3.5
Volume [m3] 3082.7 2163.6 5246.3
S/V [m2/m3] 0.29 0.22 0.26
Table 2.1: Representation of the numerical data representing the building
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2.3.1 Envelope Characteristics
After defining the dimensions of the envelope, the defining analysis has moved on to the definition of
the materials that make up the transparent structure and the vertical and horizontal opaque ones. To
collect this information is
It was essential to have an interview with the headmaster of the school, which became available in
providing the necessary documentation for the retrieval of information concerning materials used in
construction. In fact, in this case it would not have been sufficient to know specifically the thicknesses
and thermal characteristics of the materials that make up the masonry, the floors, the roof and the doors
and windows. Unfortunately the old age of the building, added to the lack of documentation of the public
building defined a big uncertainty on the materials and on the element structures of the building,
therefore it has been taken another step into a research study of the building typology and characteristic
of the European territory, divided by age of construction. In order to do this it has been used the famous
research founded by the IEE [24] called Project Tabula [25], which includes the “Building Typology
Brochures” for each of the partner country in their respective language, through which it was possible
to study the construction characteristics of a numerous example of case studies set with boundary
conditions similar to the specific case study building of this thesis work. Basically the research is a
database in which one can find any construction related information regarding a specific building
typology depending on the location and on the age of construction. Therefore having knowledge about
the case study building’s age, location and typology, and comparing the data of the research with the
personal knowledge and the information received by the school institution the final data about the
construction elements of the building and their characteristic were extrapolated.
Once this phase was completed, it was possible to calculate through the EN ISO 6946 [26] the value of
thermal transmittance of the structural packages and the glazing, which is the thermal flow exchanged
between exterior and interior through a material or a transparent body. This data, obtained by crossing
the related information the orientation and adjacency of each structure with the thermal characteristics
of each layer of material of which it is composed, it has been useful to know the thermal dispersions and
the level of insulation of the building. Regarding the glazed surfaces made up of window, in addition to
the size and exposure it has to be also considered the material of the frame and the type of glass: single,
double, with or without double glazing.
2.3.1.1 Old Part Building
In order to make the distinction more clear the two bodies of the building have been separated in this
paragraph, so that it will be easier to show different characteristics of the structure element of the case
study building. This first section will be focused on the elements of the old part building.
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Construction elements characteristics of the old part of the case study building:
- External Wall: E.W. 1/E.W. 2
This structure is composed of stone masonry stacked vertically. The use of this type material as load-
bearing structure assures an high value of thermal mass for the building. The mass of a building enables
it to store heat, providing “inertia” against temperature fluctuations, the thermal mass will absorb
thermal energy when the surroundings are higher in temperature than the mass, and give thermal energy
back when the surroundings are cooler. This type of masonry is used for the load-bearing structure at
each floor of the old body of the school, with the difference that the upper floor have a lower thickness
of stone “E.W. 2” respect to the ground floor “E.W. 1”. This behavior is typical of the building
constructed with stone masonry.
E.W. 1 0.53 U [W/m2K] 2.26
Component Thickness Conductivity Resistance
[-] [m] [W/mK] [m2K/W]
Internal lime cement plaster 0.015 0.88 0.017
Stone masonry 0.5 2.1 0.24
External lime cement plaster 0.015 0.88 0.017
E.W. 2 0.6 U [W/m2K] 2.10
Component Thickness Conductivity Resistance
[-] [m] [W/mK] [m2K/W]
Internal lime cement plaster 0.015 0.88 0.017
Stone masonry 0.57 2.1 0.271
External lime cement plaster 0.015 0.88 0.017
- Underground Wall: U.W. 1
The walls of the underground floor are ground-contact walls therefore in order to calculate the effect of
the ground instead of the external air in the calculation, the surface resistance have been changed
according to the EN ISO 13370 [27]. The structure is the same as in the other floor with a different
thickness of the masonry layer.
U.W.1 0.75 U [W/m2K] 0.95
Component Thickness Conductivity Resistance
[-] [m] [W/mK] [m2K/W]
Internal lime cement plaster 0.015 0.88 0.017
Brick 0.75 2.1 0.357
Figure 2-6: Stone masonry wall
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- Internal Wall: I.W. 1
The internal wall modelling does not affect the thermal properties of the building, since they’re not part
of the envelope, but in order to have a clear diversification of the different spaces inside the building
they have been modelled, and their structure is the same as the external wall. The same structure is used
as wall in contact to unheated internal spaces.
I.W. 1 0.53 U [W/m2K] 1.88
Component Thickness Conductivity Resistance
[-] [m] [W/mK] [m2K/W]
Internal lime cement plaster 0.015 0.88 0.017
Stone masonry 0.5 2.1 0.238
Internal lime cement plaster 0.015 0.88 0.017
- Internal Slab: I.S. 1
The slab used as horizontal partition to delimitate two different heated space is made of hollow clay
planks set into a composite layer made of steel beams and concrete. This kind of structure is used for
every slab used to separate internal heated spaces, but also for the slab used to separate the last heated
floor of the building from the attic space present under the roof structure, which is unheated.
- Underground Slab: U.S. 1
The underground slab stands for the slab which defines the separation from the ground floor, which is
an heated space, from the underground floor, which is unheated in this case. The structure of this slab is
composed of a brick vault set into a composite layer, as seen before, made of steel beams and cocrete.
I.S. 1 0.285 U [W/m2K] 1.60
Component Thickness Conductivity Resistance
[-] [m] [W/mK] [m2K/W]
Clay Tiles 0.02 0.72 0.028
Composite: Cast Concrete + Steel 0.2 1.304 0.153
Hollow Flat Block 0.05 0.3 0.167
Internal Lime Plaster 0.015 0.88 0.017
Figure 2-7: Hollow clay planks slab
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Figure 2-10: Wood beam structure roof
U.S. 1 0.25 U [W/m2K] 1.36
Component Thickness Conductivity Resistance
[-] [m] [W/mK] [m2K/W]
Burnt Brick 0.15 0.71 0.21
Filling clay layer 0.1 1.3 0.08
Levelling layer 0.06 1.4 0.043
Clay Tiles 0.02 0.72 0.028
- Ground Slab: G.S. 1
The ground slab is the slab present on the underground floor, and which is directly in contact with the
ground. This type of structure is a bit different from the previous ones since here the load bearing layer
is made of reinforced concrete set on a crawl space, used to separate the floor of the slab from the ground.
The use of a crawling space is also used to fight against the humidity produced by the ground, even
though this practice is complicated. In order to calculate the ground-contact coefficient it has been used
the calculation proposed by the UNI 13370 [27], as seen before. Concerning the crawl space, the layer
is considered as a ventilated area, and the standard says that the ventilated layer have no influence in the
thermal resistance calculation.
- Roof : R. 1
The roof structure is typical for the Italian territory, it’s composed by a double structure made of crossed
wooden beam and a small wooden structure used to lay the roof tiles. In this case the roof is put on an
unheated space, therefore it’s thermal efficiency is not significantly relevant for the thermal properties
of the building due to the presence of another slab between heated and unheated spaces.
R. 1 0.26 U [W/m2K] 5.77
Component Thickness Conductivity Resistance
[-] [m] [W/mK] [m2K/W]
Clay tiles 0.02 0.6 0.033
Wood layer 0.06 0.16 -
Wood beam 0.18 - -
G.S. 1 0.65 U [W/m2K] 0.95
Component Thickness Conductivity Resistance
[-] [m] [W/mK] [m2K/W]
Concrete layer 0.05 1.15 0.043
Air Layer 0.3 - -
Reinforced Concrete 0.3 2.3 0.13
Figure 2-9: Basement crawl-space slab.
Figure 2-8: Brick vault slab
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- Glazed surface: W. 1
The windows present in the old part of the building are all the same. The typical window is made of a
single glazed window put into a wooden frame. The frame pattern is visible from the picture taken in
the visual survey done in the first steps of the analysis. The shading system present in the old part of the
building is represented by internal curtains manually adjustable. In order to simulate the manual
adjustment of the curtains, in the simulation model it has been a set an value of 300 W/m2 for the incident
radiation to turn on or off the curtains.
Net U-value 4.7 [W/m2K]
Net R-value 0.1738 [m2K/W]
Glazed Surface
Component Thickness Conductivity Resistance Transmittance g-value
[-] [mm] [W/mK] [m2K/W] [W/m2K] [-]
Clear float 6 1.06 0.0038 5.75 0.87
Frame
Type Transmittance Percentage
[-] [W/m2K] %
Hardwood 2.50 33
Figure 2-11: Single glazed wooden window
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Figure 2-13: Brick internal partition
2.3.1.2 Recent Part Building
In this part of the paragraph it will be presented the characteristics of the envelope of the recent body of
the building, which was built approximately in the 1960 and was added to the original structure of the
school building. Construction elements characteristics of the recent part of the case study building:
- External Wall: E.W. 3
The external wall of the recent body of the building is made of bricks, in this case it’s possible to see
one of the most used techniques used in Italy to build the load bearing perimeter of a building, this is
still used nowadays for new constructions, obviously with some technical adjustment. The construction
is called “cassa vuota” it literally means that the two layer of bricks with inside a non-ventilated layer
of air, make an empty box. In this case, instead of the recent part, the thermal mass is not really high
therefore the thermal inertia of this part of the building is not significant factor, but the overall thermal
properties are better thanks to the quality of the material and the exploit of the air layer.
E.W. 3 0.4 U [m2K/W] 1.15
Component Thickness Conductivity Resistance
[-] [m] [W/mK] [m2K/W]
Internal lime cement plaster 0.01 0.88 0.01
Burnt Brick 0.15 0.6 0.25
Air 0.08 - 0.18
Burnt Brick 0.15 0.6 0.25
External lime cement plaster 0.01 0.88 0.01
- Internal Wall: I.W. 2
Also in this case the internal walling was modelled mainly to separate the internal environment so that
the thermal input of the various spaces could be diversified and therefore more detailed. This type of
structure is also used to separate the unheated spaces present in the inner part of the building, from the
heated spaces.
I.W. 2 0.22 U [m2K/W] 1.62
Component Thickness Conductivity Resistance
[-] [m] [W/mK] [m2K/W]
Internal lime cement plaster 0.01 0.88 0.011
Burnt Brick 0.2 0.6 0.333
Internal lime cement plaster 0.01 0.88 0.011
Figure 2-12: Double layer brick wall
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Figure 2-15: Hollow core concrete slab
- Underground Wall: U.W. 2
In this case the structure of the underground wall is different from the one of the upper floors. The
structure is made of a concrete layer, used to bear the load coming from the surrounding ground. Also
in this case the calculation were made according to UNI 13370 [27].
U.W. 2 0.4 U [m2K/W] 0.70
Component Thickness Conductivity Resistance
[-] [m] [W/mK] [m2K/W]
Internal lime cement plaster 0.01 0.88 0.011
Concrete Layer 0.4 1.6 0.250
- Internal Slab: I.S. 2
The structure used for the slabs is the traditional one used all over italy, also nowadays. It is composed
of a conrete layer lighten by hollow blocks made of brick, from this the name “hollow core concrete
slab”. As seen in the picture in between the hollow block there are reinforced beams shaped as triangles
which represent the stiff part of the slab structure and on top of the little beams and hollow bricks is laid
down another layer of concrete.
This type of structure is used for every slab present in the building, except made for the roof and the
gorund-conctact floor which present some obvious adjustment.
I.S. 2 0.275 U [m2K/W] 1.73
Component Thickness Conductivity Resistance
[-] [m] [W/mK] [m2K/W]
Clay Tiles 0.02 0.72 0.0278
Reinforced Concrete Block 0.18 0.8 0.23
Concrete layer 0.06 1.28 0.047
Internal Lime Plaster 0.015 0.88 0.0170
- Ground slab: G.S. 2
The ground slab is the slab present on the underground floor, and which is directly in contact with the
ground. This structure is assumed really similar to the one present in the old body of the structure
therefore mentions are made to the Figure 2-9.
Figure 2-14: Concrete bearing wall
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Figure 2-16: Single glazed metal window
Ground Slab 0.67 U [m2K/W] 0.72
Component Thickness Conductivity Resistance
[-] [m] [W/mK] [m2K/W]
Linoleum Floor 0.01 0.18 0.056
Concrete layer 0.06 1.15 0.052
Air Layer 0.3 - -
Reinforced Concrete 0.3 2.3 0.13
- Roof: R. 2
The structure of the roof is the same seen in the Figure 2-15 with the simple replacement of the cover of
the slab, in fact the top layer made of ceramic tile is now replaced by an uninsulate corrugated metal
sheet put on top of the structure in order to protect it from the external environment. The roof structure
is slightly inclined, is not the usual structure seen in the old part of the building.
Roof 0.24 U [m2K/W] 2.01
Component Thickness Conductivity Resistance
[-] [m] [W/mK] [m2K/W]
Metal Cladding 0.02 40 0.001
Reinforced Concrete Block 0.24 0.8 0.30
Concrete layer 0.06 1.28 0.047
Lime Plaster 0.01 0.88 0.011
- Glazed surface: W. 2
As for the old part of the building, also in the recent one the windows have approximately the same
structure all over the perimeter. The windows are made of a single pane of clear glass put into a metal
frame without any thermal brake. The shading system is the same as presented before, it is composed
of a manually adjustable curtain, which in the simulation model is translated into a curtain activated on
the exceeding of 300 W/m2 of incident solar radiation.
Net U-value 5.75 [W/m2K]
Net R-value 0.17 [m2K/W]
Glazed Surface
Component Thickness Conductivity Resistance Transmittance g-value
[-] [mm] [W/mK] [m2K/W] [W/m2K] [-]
Clear float 6 1.06 0.0038 5.75 0.87
Frame
Type Transmittance Percentage
[-] [W/m2K] %
Metal 5.88 33
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2.3.2 Internal Conditions
In order to model a more accurate behavior of the heated spaces of the building, during both the cold
and the warm period, it has been decided to create a “typical” profile, able to simulate the parameters
related to the indices and the factors that most influence the internal conditions of the heated and
unheated spaces of the case study building.
Occupancy
The first parameter to set was the one related to the occupancy of the spaces, so it has been defined an
occupancy period and rate of the heated spaces. The analysis has been simulated considering the case
of a typical school day , considering the occupancy only for the classrooms. This means that the internal
gains due to the sensible and latent heat coming from the people are considered only for the classrooms
and not for the other heated spaces. The parameters presented were taken from the guide lines expressed
by the MIUR, in this case the occupancy of the school is intended similar to the one of an office, which
means that it was supposed that the students use the classrooms from Monday to Friday, from 8 to 17.
This is done in order to promote an intense occupancy rate according to a more efficient use of the
spaces, an example can be the exploit of the classrooms in the afternoons for some extra-curricular
activities. The period of occupancy is the same as the one imposed by the school regulation, it is applied
from the 1st of September to the 30th of June. The sensible and latent heat represent the heat gains
produced from the users activity, which contribute to the reduction of energy needs during the winter
period.
Table 2.2: Parameters recreating users’ activity
2.3.2.1 Lighting system and machinery
In addition to these gains it has been considered, for every used space of the case study building the
internal gains produced by the lighting system and the heat coming from the use of typical machinery
used in the school environment according to the EN ISO 12464 [28] and the CIBSE guide A [29].
The simulation of the lighting system was
applied to each of the spaces of the case study,
considered heated and used. In order to
recreate the manual adjustment from the user,
depending on the natural light available linked
to the outside conditions, it was created an accurate activation profile applied to the lighting system. The
Occupancy Density Sensible heat Latent heat
Annual Weekdays [pers/m2] [W/pers] [W/pers]
1st September- 30th June 8:00-17:00 0.5 90 60
Component Occupancy Heat gains
- weekdays [W/m2]
Lighting System 8:00-17:00 7
Machinery 8:00-17:00 5
Table 2.3: Lighting and machinery profile
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activation depends on 4 different profile, one for each season, in which the value of the lighting system
goes from 1 to 0 (1 means on and 0 means off), and depends on the hour of the day. This means that the
value expressing the influence of the lighting system to the internal gains of the heated spaces, is
different for each hour of the day and each season of the year. These activation profile were modelled
following the guidelines provided by the UK building regulations [30], which contains some useful info
through which is possible to recreate real-life internal conditions.
The simulation of the machinery used in the heated spaces was more simple, in this case it was simulated
the heat coming from the use of typical school machineries, as computers or projectors and etc. The
values related to the heat produced that is than considered in the energy simulation as internal gains, are
taken from the EN ISO 12464 [28].
2.3.2.2 Infiltration and Natural Ventilation
The same level of detail and accuracy was used also to simulate the parameters that have a negative
impact on the energy balance of the case study, such as the infiltration and ventilation losses, which are
related to the interaction of the building with the outside air. The infiltration represents the air that from
the outside goes through the imperfection of the building to the inner spaces, increasing the internal
temperature of the conditioned spaces. The infiltration rate is calculated based on the air leakage of the
envelope of the building, both the opaque and the
transparent. It is usually calculated through the use of the
blower door test, which sets the infiltration rate of a building
based on the difference of pressure from the inside to the outside, with a fixed applied pressure of 50
Pa. In this case it was not possible to use this type of test so it was necessary to find some empirical
values, that could be applied to the building of the case study. The CIBSE guide A [29] gives empirical
values for air infiltration rate due to air infiltration for rooms in buildings on normally-exposed sites in
winter, classifying buildings for store height and level of air tightness. Considering that the building is
made of 3 stories above ground and considering the building as “leaky” (which represents an existing
building that does not comply with current regulations), due to the age of the building, the standard
provides an empirical value for the blower door test, after that through a conversion value ( obtained
when dividing the 50 Pa air change rate by the calculated average annual infiltration rate) it is obtained
the requested value for air infiltration rate during the winter period.
Concerning the heat losses
coming from the opening of the
windows, it has been modelled a
profile which provides the standard’s value of natural ventilation rate. The values for the ventilation
rates have been taken from the CIBSE guide A [29], in this case to each heated spaces is assigned a
Infiltration Old part Recent Part
[ach] 0.25 0.22
Table 2.4:Infiltration rate values[ach]
Ventilation Kitchen Toilet Gym Classroom Hall/Corridor
[l/(s*m2)] 0.9 1.2 1.5 0.6 0.3
Table 2.5: Natural ventilation [l/(sm2)] for internal school spaces
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value of natural ventilation considered the minimum in order to maintain indoor air quality, so basically
it’s the air change rate of the heated spaces. The profile created for the natural ventilation of the spaces
is linked to the occupancy schedules, therefore the natural ventilation will be considered when the users
will need to change the air of the enclosure, which is from 08:00 to 17:00, as seen in Table 2.2.
In the case study building there are also some heated spaces
that don’t have any kind of openings in their specific envelope
area, but have to respect the regulations regarding the change
of the air present in the room. In these cases it has been
hypothesized, and then verified through the visual survey, the presence of extract fans, used only for the
recirculation of air as expressed in the standards [29]. The mechanical exhaust fan are powered by
electricity, so in this case they either represent an heat loss in terms of ventilation, and consume energy
to be activated. They were applied to the blind toilet present on the ground floor of the old part of the
building, and the changing room, located underground, in the recent part of the building.
2.3.3 Technological Plant
Other than the data relating to the materials used for the envelope’s structure, the school principal has
made himself available to provide information about the technical plants that supply energy to the entire
building. This information were than verified through the visual survey done in the technical rooms of
the building, in which the plants are installed. The school building is equipped with a central system
used for the thermal heating of the specified heated spaces, and the preparation of the DHW (domestic
hot water) for the building. Combined with the central system there are two small separated system used
for the DHW of the kitchen/washing room, in the old part of the building, and the locker rooms in the
recent part.
The period of activity of the central heating
system is the same as presented by the
guidelines of the MIUR [18], the DHW
preparation instead, is continuous
throughout the entire annual school period. During the day, as seen in the table the heating system is
continuously on while the DHW preparation is strictly linked to the occupancy of the room, as matter
of fact the DHW is required directly from the users while the settings of the heating system are imposed
by the institution. This is due to the fact that most of the heating system present in the school system are
old, therefore in most of the cases the consumption given by the on-off procedure is so high that keeping
the heating system always on may reduce the consumption, in addition the type of system present in this
buildings are quite big and complex therefore it may be a problem to find an adequate technician
Exhaust Changing room Toilet
[l/s] 100 75
[W/(l/s)] 0.6 0.4
Table 2.6: Mechanical exhaust ventilation
Heating DHW
15th October – 15th April 1st September – 30th June
On continuously 8:00 -18:00 weekdays
Table 2.7: Activation periods of the technological plants
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available to do the on-off procedure when needed.
2.3.3.1 Generation System
The production of thermal energy is attributed to the wall-mounted
gas boiler “Carbofuel” produced by the Italian company Riello. The
boiler was installed in the 1998, inside a ventilated technical room
located in the underground level of the old part of the building, and
has a thermal power of 322 kW and an effective thermal power of
290 kW. The old age of the system and of the building made the
search for more detailed information difficult, therefore in order to
model the system in the best way, some of the parameters were
calculated through the use national and European standards.
The efficiency of the boiler was calculated through the use of the UNI
11300-2 [31] with the method of the pre-calculated generation
efficiency for hot water generators. The formula used to calculate the efficiency is:
𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 = 𝐵𝑎𝑠𝑒 𝑣𝑎𝑙𝑢𝑒 + 𝐹1 + 𝐹2 + 𝐹3 + 𝐹4
The base value and the values F1,F2,F3 and F4 depends on the type of boiler considered. In this case
the heating system is composed of a class C sealed chamber boiler, the typical boiler with sealed
chamber and forced draft, are models in which the combustion takes place inside closed sections that
receive the combustion air from outside and which, thanks to an electric fan, push the exhaust fumes
outside in a forced way making them pass through special pipes. The values for a class C boiler are:
The different values of F1, F2, F3, F4 are given by
standard based on the different characteristics of the
installed boiler. The value of F1 is the ratio between
the thermal power installed and the required design
power, therefore it was necessary to calculate the thermal power required to heat the case study building,
this value was calculated thorough the EN ISO 442 [32]. The heating need depends on the climate zone
in which the city of the building is located. Italy has been divided into six climatic zones by the decree
of the President of the Republic of 26 August 1993, n. 412. The coefficients for calculating this
requirement range from 27 to 42 W/m3, corrective coefficients are also foreseen for cases in which
standard conditions are not respected, considering, for example, the level of insulation of the
environment. The city of Lecco is located in the climatic zone E, with a coefficient equal to 37 W/m3,
therefore the design energy need for heating will be the product of this coefficient times the volume of
the heated space. So after calculating the required design power, it will be possible to calculate the ratio
between that value and the actual thermal power in order to calculate the value of F1. The value F2 is
Base
Value
F1 F2 F4
1 2 4
93 0 -2 -5 -4 -1
Table 2.8: Efficiency value for a class C boiler
Figure 2-17: School building boiler
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considered whenever the system is installed outside, while the value F3 when the chimney is higher than
10 m. So the result will be:
𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 = 93 − 4 − 1 = 88
The calculation has given as final value that the boiler installed in the building of the case study has an
efficiency equal to 88%, therefore this value will be used for the simulation calculations.
Concerning the heated space of the gym, the conditioning is attributed to the installation of a gas air
heater combined with an own burner directly applied onto the vertical external wall, with a max. nominal
thermal power equal to 85 kW. Following the procedure listed before the air heater has an efficiency:
𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 = 93 − 2 − 1 = 90
Figure 2-18: Lateral and front view of the gas air heater installed onto the gym's external wall
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2.3.3.2 Fuel
The systems used for the heating of the selected spaces and for the production of DHW are fueled by
natural gas, methane to be precise. The cost of the methane gas in Italy is equal to 0.7 €/m3, considering
an ideal consumption equal to 9.6 kWh/m3 and dividing this value by the efficiency we have a real
consumption of 8.64 kWh/m3, that sets for the consumption of methane gas a cost of 0.081 €/m3.
2.3.3.3 Emission Gasses
The procedure to calculate the emissions linked to the case study building has been extracted from the
EN ISO 14064-1 [33]. In this case the emission, are in particular the Greenhouse Gasses “GHG”
emissions, caused by the combustion of the methane gas happening in the chamber of the boilers to
generate thermal power used for the heating system and the DHW preparation, and the use of electricity
for the systems present in the building.
The GHG emissions are typically expressed through the means of the equivalent carbon dioxide “CO2e”,
which is a measure for describing how much global warming a given type and amount of greenhouse
gas may cause, using the functionally equivalent amount or concentration of carbon dioxide (CO2) as
the reference. The formula used to calculate the CO2e is:
𝐶𝑂2𝑒 = ∑𝑖(𝐺𝑊𝑃𝑖 ∗ 𝐸𝑖)
Figure 2-19: Table C.1 - GHG global warming potentials, EN ISO 14064.
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- the CO2e is the equivalent CO2 emissions expressed in ton/year;
- GWPi is the Global Warming Potential of each of the GHG considered. The GWP is a relative measure
of how much heat a greenhouse gas traps in the atmosphere, it compares the amount of heat trapped by
a certain mass of the gas in question to the amount of heat trapped by a similar mass of carbon dioxide;
- Ei is the GHG emissions.
The study carried out, consistent with the IPCC principles [34], contemplates CO2 emissions as the most
significant greenhouse gas in terms of quantity and therefore the other greenhouse gases contained in
the table below are neglected. For this reason it can be said that the estimated CO2 emissions in the
study correspond totally to the CO2e emissions indicated by the UNI ISO 14064 standard [33].
The conversion factors used for the combustion of the methane gas is equal to 0.203 kg CO2/kWh, while
the factor for the electricity is equal to 0.519 kg CO2/kWh, values were extracted from the Carbon Trust.
2.3.3.4 Emission System
The emission system for both of the parts of the school
building, is represented by the use of cast iron radiators, put in
each of the spaces considered heated in the case study. The cast-
iron radiators have an high thermal inertia, this means that this
type of radiators will need more time to reach the set point
temperature , thus increasing the energy needs and gas
emissions due to the fact that the boiler has to be activated for
a longer period, increasing the time in which the combustion of natural gas produces thermal energy.
The only exception is the emission system present in the gym,
as matter of fact in this space 3 air heaters, installed on the upper
part of the vertical wall, account for the entire emission of heat
needed. The air heater is a more effective heating emission
system for gyms , rather than traditional radiators, this is due to
the fact that an air heater can be installed at a great height, thus
is possible to heat a bigger volume space, such as the one of a
gym.
2.3.3.5 Control system
The emission system of the heating plant is controlled manually and only through an on/off valve located
on the bottom part of the radiators, and the same type if control is applied to the air heater installed in
the gym. An on/off control system is obviously a symptom on an inefficient system design, since this
Figure 2-20: Existing cast-iron radiators.
Figure 2-21: Existing air heater.
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control implies the absence of the ability to adjust the temperature depending on the different conditions
of the inside and/or the outside., thus defining an increase in the energy use.
2.3.3.6 Distribution System
The data about the distribution system, have been hypothesized according to the visual survey done in
the technical room located in the underground floor of the old part of the building and the standards
regarding the system efficiency [31] . The distribution system is considered as a zone heating system
with horizontal distribution, powered by vertical mullions (usually running in the stair case) as described
in the Prospectus 22 of the EN ISO 11300-2 [31]. The zone heating system is located in the underground
floor with a slip-rings distribution, and a level of insulation insufficient or inexistent (for example pre-
insulated pipe with reduced thickness or bare tube inserted in corrugate pipe).
This suppositions brought a calculated value of 93% for the efficiency of the distribution system of the
case study building, this sets the value of the overall seasonal heating efficiency of the system “ScoP”
equal to 83.7 %.
2.3.3.7 DHW Production
In this case the calculation procedure has been carried out in two different ways, one for the DHW
required for the correct functioning of the toilets present in the building, and another one based on the
presence of two separated boilers installed in the locker room, located in the recent part of the building,
and in the washing room, located in the old part.
The procedure used to calculate the required DHW for a school has been taken from the EN ISO 11300-
2 [31] with the simple formula, applied for each class:
𝑉𝑤 = 𝑎 ∗ 𝑁𝑢 = 0.17 [𝑙
ℎ]
- a is the specific daily requirement in liters / (day × Nu) obtainable from Table 31, and for school is
Figure 2-22: On the left the supposed scheme of the distribution system: Prospectus 22 of the EN ISO 11300-2.
On the right the installed circulation pumps.
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equal to 0.2;
- Nu is a variable parameter depending on the type of building that can be obtained from Table 31, and
for school is equal to the number of students.
This volume of DHW is produced by the central system, described in the § 2.3.3.1, therefore in the
simulation the values related to the efficiency of the DHW preparation will be the same as the one
presented for the central system, considering that the DHW will increase the energy consumption of the
system.
The central system is combined with two standalone methane gas water heater installed in the locker
room and in the washing room, used to produce the DHW needed for the two spaces. The water heater
boiler located in the locker room has a capacity of 150 L and produces a thermal power of 7.2 kWh,
while the one located in the washing room has a capacity of 100 L and thermal power of 4.4 kWh. Both
the water heater can be classified as open chamber boiler, also known as a type B appliance, it is a boiler
or water heater designed to be connected to an evacuating duct for the combustion’s products to the
outside of the installation room, the combustion air is taken directly from the installation environment
that must be permanently aerated. A water heater classified as type B and considered without the
guidance flame, a flame which is always on and allows instantaneous production of hot water to start,
can be considered with an efficiency equal to 77 % according to the EN ISO 11300-2 [31].
2.3.4 Energy classification
The energy certification is based on the comparison of the energy consumption of the real life building
with the ones of the reference building. The reference building has the same geometry as the real
building (shape, volume, floor area, surfaces of construction elements and components), orientation,
territorial location, intended use and boundary conditions, and having predetermined thermal
characteristics and energy parameters defined by standard.
The settings of the reference building are given by the Ministerial Decree of the 26th of June 2015 [18],
in the section of the minimum requirements present in the “Annex A- minimum requirements”.
Reference System: Generation and utilization efficiency set by standard
Reference Envelope: Transmittance set by standard
REAL BUILDING REFERENCE BUILDING
Figure 2-23: Reference Building definition.
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The definition of the energy classes depends on the reference building, in particular on the non-
renewable primary energy “EPgl,nren,rif”. After calculating the energy classes, the definition of the energy
class of the real life building is found thanks to the use of the table here presented, comparing the EPgl,nren
which is the non-renewable primary energy of the real building, with the maximum EPgl,nren,rif of each of
the energy classes.
Class A4 ≤ 0,40 EPgl,nren,rif
0,40 EPgl,nren,rif < Class A3 ≤ 0,60 EPgl,nren,rif
0,60 EPgl,nren,rif < Class A2 ≤ 0,80 EPgl,nren,rif
0,80 EPgl,nren,rif < Class A1 ≤ 1,00 EPgl,nren,rif
1,00 EPgl,nren,rif < Class B ≤ 1,20 EPgl,nren,rif
1,20 EPgl,nren,rif < Class C ≤ 1,50 EPgl,nren,rif
1,50 EPgl,nren,rif < Class D ≤ 2,00 EPgl,nren,rif
2,00 EPgl,nren,rif < Class E ≤ 2,60 EPgl,nren,rif
2,60 EPgl,nren,rif < Class F ≤ 3,50 EPgl,nren,rif
Class G > 3,50 EPgl,nren,rif
Table 2.9: Energy classes of the energy certification Figure 2-24: Energy Performance Certification "APE".
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CHAPTER 3
3 Description: Case study “Buštěhrad”
Within this chapter it will be proposed and analyzed a case study, identified among the many taken into
consideration, chosen on the basis of the data and information actually available to perform this in the
most complete way this work, following the analysis method described and deepened in the previous
paragraphs.
3.1 Geographical and historical overlook
The second case study taken in consideration is a school building
located in Czech Republic, exactly in the city of Buštěhrad.
Buštěhrad (formerly Buštěves or Buckov) is a small, rapidly
developing town in central Bohemia, located 5 km east of Kladno
and 19 km northwest of the center of Prague, at an average
altitude of 322 m. It is based on a remarkable geological base in
the area inhabited for thousands of years, part of its rich history
are extraordinary personalities and events of Czech and European history. City to which also belongs
the east situated settlement Bouchalka , has an area of 7.61 square kilometers and a population of
approximately 3300 of the population.
Figure 3-2: Territorial overview of the case study building
Figure 3-1: Central Bohemia region, CZ
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The case study school building is located in a residential area, as seen from the picture the school is
located on the main road, Tyrsova street, of the small village called Buštěhrad. The area in which the
school is inserted is mainly residential, even though the school building itself represents the limit of the
small village, thus meaning that the school is pretty isolated in the rural context of the Czech lands. The
surrounding area is mainly constituted of small residential buildings that go up to a max of 4 floor height,
with the typical Czech construction technology, luckily the buildings are well spaced therefore there is
no problem involving the overlapping or the excessive shading of one building to an another.
The building taken as case study is the elementary school “Oty Pavla” of Buštěhrad built in the 1891,
which was then placed side by side with another school building erected in the late ’60, in the Figure
3-2Figure 3-3: Oty Pavla school in the 1900-1920 on the left, and Oty Pavla school nowadays on the
right. Is visible as the cross-shaped building present next to the case study building. The Figure 3-3
shows how although a lot of years have passed from the construction of this school, the outer frame of
the building has been kept the same as it was in the 1900. This gives a major importance on the style of
the facades of the building, as matter of fact the façade oriented toward the street (the on the right in the
Figure 3-3) is protected by the Czech Republic culture, as it represents a symbol of their national
architecture technology and style.
Figure 3-4: Capture of the 3D representation of the case study area (21 May 12:00).
Figure 3-3: Oty Pavla school in the 1900-1920 on the left, and Oty Pavla school nowadays on the right.
N
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As said before, and as visible through the Figure 3-4, all the surrounding buildings have a moderate
height respect to the case study building (highlighted in blue), in addition it’s clear that the building is
surrounded by a lot of vegetation, as matter of fact its perimeter is defined by trees of 2/3 stories height.
3.2 Architectural construction
To reconstruct the planimetry, the company that administers the building was contacted, through which
it was possible to access the cadastral documentation of the building. For a better accuracy in the analysis
procedure, it was subsequently performed a survey of maximum on the exterior of the building in order
to verify that the dimensions reported on the cadastral plants correspond exactly to those real.
The building dates back to 1891 and has approximately a square floor plan, it has four above-ground
floors and one story underground and is used as a school building for the first grade of elementary
school. In the underground floor there is a boiler room and storage areas for discarded furniture (school
benches, chairs, etc.). In 1st floor – 3rd floor there are school premises (classrooms, etc.) and the 4th floor
is just an empty under-roof storage story. The vertical support system of the building is a brick wall
made of solid bricks, the thickness of the perimeter walls is 750 mm on the ground floor and 600 mm in
the 1st and 2nd floor while the horizontal supporting structures are wooden beams, mirrored vaults in the
halls, and brick vaults above the underground floor. The staircase of the school building is a U-shaped
two-aisle, the stairs leading to the roof story are spiral reinforced concrete.
During the years the building has going through some renovations, fortunately it was possible to receive
some general info about this small and big operationals:
- In the 1991 the roof was reconstructed, now it present itself as an hipped roof made of brazed
tiles;
- In the 1999/2000 the facades of the buildings were fixed;
- In the 2005 thermostatic valves have been installed on the radiators of the building.
From the picture above it’s possible to understand and see the listed reconstruction interventions done
Figure 3-5: Internal facades of the building (on the left), roof structure (on the right).
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on the building throughout the years.
The table here presented gives an empirical tool in order
to understand the distribution and the composition of the
case study building. An important aspect is the one related
to the glazing area of the construction, which represents
more than 20% of the external wall area indicating the
need for accurate analysis regarding the optimization of
the windows, and the related thermal bridges. Finally the
data about the Surface-Volume ratio shows that most of
the spaces have high ceilings, increasing the volume of the
building, especially increasing the volume of space that has to be heated in order to guarantee thermal
comfort for the users thus increasing the energy needs.
As said before the plan has a semi rectangular shape, with the core representing by the rectangular
shaped staircases located onto the North-West façade of the building. The staircases located inside of
the heated space of the building is next to another staircase, but this one is unheated and is used only to
get to the roof of the structure, therefore represents a buffer zone between the internal stair cases and the
outside environment. The configuration of the internal spaces at the ground floor can be taken as a
reference since all the floor follow the same internal distribution. This school building presents only
Element Unit Building
Floor # 3+1
Floor area [m2] 1558.72
Heated Space [m2] 1025.43
External Wall area [m2] 802.65
Glazing area [m2] 169.5
Average Height [m] 3.85
Volume [m3] 3756.43
S/V [m2/m3] 0.3
Table 3.1: Parameters representing the building
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classes and offices, as matter of fact unlike the case study located in Lecco (§ 2.2) there’s no kitchen
and gym inside the perimeter of the building. In order to solve the absence of the gym inside the building,
the students of the case study school can exploit the outdoor spaces and the gym of the adjacent school
building, while for the absence of the kitchen, the meals are directly given to the students in their
classroom with the use of service food trucks coming directly inside the perimeters of the building.
3.3 Energy data collection
The purpose of this first phase is to collect as more information as possible about the building,
considering those concerning the urban, architectural and plant design aspects. The site survey is the
first approach with reality with which one is confronting and plays a very important role within this type
of analysis.
3.3.1 Envelope Characteristics
After defining the dimensions of the envelope, the defining analysis has moved on to the definition of
the materials that make up the transparent structure and the vertical and horizontal opaque ones. To
collect this information is
It was essential to have an interview with the headmaster of the school, which became available in
providing the necessary documentation for the retrieval of information concerning materials used in
construction. In fact, in this case it would not have been sufficient to know specifically the thicknesses
and thermal characteristics of the materials that make up the masonry, the floors, the roof and the doors
and windows. Unfortunately the old age of the building, added to the lack of documentation of the public
building defined a big uncertainty on the materials and on the element structures of the building,
therefore it has been taken another step into a research study of the building typology and characteristic
of the European territory, divided by age of construction. In order to do this it has been used the famous
research founded by the IEE [1] called Project Tabula [2], which includes the “Building Typology
Brochures” for each of the partner country in their respective language, through which it was possible
to study the construction characteristics of a numerous example of case studies set with boundary
conditions similar to the specific case study building of this thesis work. Basically the research is a
database in which one can find any construction related information regarding a specific building
typology depending on the location and on the age of construction. Therefore having knowledge about
the case study building’s age, location and typology, and comparing the data of the research with the
personal knowledge and the information received by the school institution the final data about the
construction elements of the building and their characteristic were extrapolated.
Once this phase was completed, it was possible to calculate through the EN ISO 6946 [26] the value of
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thermal transmittance of the structural packages and the glazing, which is the thermal flow exchanged
between exterior and interior through a material or a transparent body. This data, obtained by crossing
the related information the orientation and adjacency of each structure with the thermal characteristics
of each layer of material of which it is composed, it has been useful to know the thermal dispersions and
the level of insulation of the building. Regarding the glazed surfaces made up of window, in addition to
the size and exposure it has to be also considered the material of the frame and the type of glass: single,
double, with or without double glazing.
Construction elements characteristics of the old part of the case study building:
- External Wall: E.W. 1/E.W. 2
This structure is composed of burned brick stacked vertically. The use of this type material as load-
bearing structure assures an high value of thermal mass for the building. The mass of a building enables
it to store heat, providing “inertia” against temperature fluctuations, the thermal mass will absorb
thermal energy when the surroundings are higher in temperature than the mass, and give thermal energy
back when the surroundings are cooler. This type of material is used for the load-bearing structure at
each floor of the old body of the school, with the difference that the upper floor have a lower thickness
of stone “E.W. 2” respect to the ground floor “E.W. 1”. This behavior is typical of the building
constructed with bricks.
E.W. 1 0.77 U W/m2K] 0.92
Component Thickness Conductivity Resistance
[-] [m] [W/mK] [m2K/W]
Internal lime cement plaster 0.01 0.88 0.011
Burnt Brick 0.75 0.84 0.89
External lime cement plaster 0.01 0.88 0.011
E.W. 2 0.62 U [W/m2K] 1.10
Component Thickness Conductivity Resistance
[-] [m] [W/mK] [m2K/W]
Internal lime cement plaster 0.01 0.88 0.011
Burnt Brick 0.6 0.84 0.714
External lime cement plaster 0.01 0.88 0.011
- Underground Wall: U.W. 1
The walls of the underground floor are ground-contact walls therefore in order to calculate the effect of
the ground instead of the external air in the calculation, the surface resistance have been changed
according to the EN ISO 13370 [27]. The structure is the same as in the other floor with a different
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thickness of the burnt brick layer.
U.W.1 0.75 U W/m2K] 0.94
Component Thickness Conductivity Resistance
[-] [m] [W/mK] [m2K/W]
Burnt Brick 0.75 0.84 0.893
- Internal Wall: I.W. 1
The internal wall modelling does not affect the thermal properties of the building, since they’re not part
of the envelope, but in order to have a clear diversification of the different spaces inside the building
they have been modelled, and their structure is the same as the external wall. The same structure is used
as wall in contact to unheated internal spaces.
I.W. 1 0.62 U W/m2K] 1.00
Component Thickness Conductivity Resistance
[-] [m] [W/mK] [m2K/W]
Internal lime cement plaster 0.01 0.88 0.011
Burnt Brick 0.6 0.84 0.714
Internal lime cement plaster 0.01 0.88 0.011
- Internal Slab: I.S. 1
The internal slab of the building, used to separate one floor from another, is composed of a mixed
structure composed of an embarkment layer used to lay the flooring on top of the load bearing layer
consisting of wood beams.
I.S. 1 0.5 U W/m2K] 0.97
Component Thickness Conductivity Resistance
[-] [m] [W/mK] [m2K/W]
Internal lime cement plaster 0.02 0.88 0.023
Wood layer 0.015 0.15 0.100
Wood beam 180x240 0.24 0.12 2.000
Wood Decking 0.025 0.15 0.167
Embarkment layer 0.15 1 0.150
Wood subfloor 0.026 0.15 0.173
Wood layer 0.024 0.15 0.160
- Roof Slab: R.S. 1
The structure used for the slab that separates the under-roof layer from the last upper heated space is the
same as the one used for the internal slab. In this case study building, as in Lecco seen in the § 2.3.1,
Figure 3-6: Wood beam slab structure
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the story created just under roof structure and on top of the last heated floor is an under-roof layer used
for storage purposes.
- Underground Slab: U.S. 1
The underground slab stands for the slab which defines the separation from the ground floor, which is
an heated space, from the underground floor, which is unheated in this case. The structure of this slab is
composed of a brick vault set into a composite layer, as seen before, made of steel beams and concrete.
This structure, as seen from the § 2.3.1, is similar to the one seen in the case study building located in
Lecco, this is really important for the purpose of this work because it’s clear that even though the
constructions are located in two different countries they have some similar technologies, due to the
similar construction history of the specific part of central Europe.
U.S. 1 0.25 U [W/m2K] 1.03
Component Thickness Conductivity Resistance
[-] [m] [W/mK] [m2K/W]
Burnt Brick 0.4 0.88 0.455
Embarkment layer 0.3 1 0.300
Wood subfloor 0.026 0.15 0.173
- Ground Slab: G.S. 1
The structure used for the ground slab is really poor, it consists only of a flooring put onto a screed
concrete use a separation layer from the inner space and the ground. This is done because usually the
underground level of the building in Czech Republic are used as storage systems, therefore are usually
unheated.
R.S. 1 0.5 U [W/m2K] 1.23
Component Thickness Conductivity Resistance
[-] [m] [W/mK] [m2K/W]
Internal lime cement plaster 0.02 0.88 0.023
Wood layer 0.015 0.15 0.100
Wood beam 180x240 0.24 0.12 2.000
Wood Decking 0.025 0.15 0.167
Embarkment layer 0.15 1 0.150
Wood subfloor 0.026 0.15 0.173
Wood layer 0.024 0.15 0.160
Figure 3-8: Slab made of vault in steel beams
Figure 3-7: Wood beam ceiling
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- Roof : R. 1
The roof structure it’s composed by a double structure made of crossed wooden beam and a small
wooden structure used to lay the roof tiles. In this case the roof is put on an unheated space, therefore
it’s thermal efficiency is not significantly relevant for the thermal properties of the building due to the
presence of another slab between heated and unheated spaces. Once again here it’s possible to see the
similarities between the construction technologies of the two different countries, § 2.3.1.
- Glazed surface: W. 1
The windows present in the old part of the building are all the same. The typical window is made of a
single glazed window put into a wooden frame. The frame pattern is visible from the picture taken in
the visual survey done in the first steps of the analysis. The shading system present in the old part of the
building is represented by internal curtains manually adjustable. In order to simulate the manual
adjustment of the curtains, in the simulation model it has been a set an value of 300 W/m2 for the incident
radiation to turn on or off the curtains.
Net U-value 4.9 [W/m2K]
Net R-value 0.1757 [m2K/W]
Glazed Surface
Component Thickness Conductivity Resistance Transmittance g-value
[-] [mm] [W/mK] [m2K/W] [W/m2K] [-]
Clear float 6 1.06 0.0038 5.75 0.87
G.S. 1 0.30 U [W/m2K] 3.25
Component Thickness Conductivity Resistance
[-] [m] [W/mK] [m2K/W]
Floor Screed 0.1 1.15 0.087
Stone layer 0.2 1.8 0.11
R. 1 0.26 U [W/m2K] 1.82
Component Thickness Conductivity Resistance
[-] [m] [W/mK] [m2K/W]
Clay tiles 0.02 0.6 0.033
Wood layer 0.06 0.16 0.375
Wood beam 0.18 - -
Frame
Type Transmittance Percentage
[-] [W/m2K] %
Hardwood 2.50 25
Figure 3-9: Stone ground slab
Figure 3-10: Wood beam structure roof
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3.3.2 Internal Conditions
In order to model a more accurate behavior of the heated spaces of the building, during both the cold
and the warm period, it has been decided to create a “typical” profile, able to simulate the parameters
related to the indices and the factors that most influence the internal conditions of the heated and
unheated spaces of the case study building. The profile used for this case study is similar to the one
presented for the case study located in Lecco in the § 2.3.2, therefore in this case there will be a faster
presentation of the data.
Occupancy
The first parameter to set was the one related to the occupancy of the spaces, so it has been defined an
occupancy period and rate of the heated spaces. The analysis has been simulated considering the case
of a typical school day , considering the occupancy only for the classrooms. This means that the internal
gains due to the sensible and latent heat coming from the people are considered only for the classrooms
and not for the other heated spaces. The parameters presented were taken from the guidelines imposed
by the Czech Republic government, which means that it was supposed that the students use the
classrooms from Monday to Friday, from 8 to 17 (as seen in the case study in Lecco). This is done in
order to promote an intense occupancy rate according to a more efficient use of the spaces, an example
can be the exploit of the classrooms in the afternoons for some extra-curricular activities. The period of
occupancy is the same as the one imposed by the school regulation, it is applied from the 1st of September
to the 30th of June. The sensible and latent heat represent the heat gains produced from the users activity,
which contribute to the reduction of energy needs during the winter period.
3.3.2.1 Lighting system and machinery
In addition to these gains it has been considered, for every used space of the case study building the
internal gains produced by the lighting system and
the heat coming from the use of typical machinery.
All the parameters used to simulate the gains in
the school environment are given according to the
EN ISO 12464 [28] and the CIBSE guide A [29].
The simulation of the lighting system was applied to each of the spaces of the case study, considered
heated and used. In order to recreate the manual adjustment from the user, depending on the natural light
Occupancy Density Sensible heat Latent heat
Annual Weekdays [pers/m2] [W/pers] [W/pers]
1st September- 30th June 8:00-17:00 0.5 90 60
Table 3.2: Parameters recreating users’ activity
Component Occupancy Heat gains
- weekdays [W/m2]
Lighting System 8:00-17:00 7
Machinery 8:00-17:00 5
Table 3.3: Light system and machinery profile
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available linked to the outside conditions, it was created an accurate activation profile applied to the
lighting system. The activation depends on 4 different profile, one for each season, in which the value
of the lighting system goes from 1 to 0 (1 means on and 0 means off), and depends on the hour of the
day. This means that the value expressing the influence of the lighting system to the internal gains of
the heated spaces, is different for each hour of the day and each season of the year.
3.3.2.2 Infiltration and Natural Ventilation
The same level of detail and accuracy was used also to simulate the parameters that have a negative
impact on the energy balance of the case study, such as the infiltration and ventilation losses, which are
related to the interaction of the building with the outside air. The infiltration represents the air that from
the outside goes through the imperfection of the building to the inner spaces, increasing the internal
temperature of the conditioned spaces. The CIBSE guide A [29] gives
empirical values for air infiltration rate due to air infiltration for rooms in
buildings on normally-exposed sites in winter, classifying buildings for store
height and level of air tightness. Considering that the building is made of 3 stories above ground and
considering the building as “leaky” (which represents an existing building that does not comply with
current regulations), due to the age of the building, the standard provides an empirical value for the
blower door test, after that through a conversion value ( obtained when dividing the 50 Pa air change
rate by the calculated average annual infiltration rate) it is obtained the requested value for air infiltration
rate during the winter period.
The values for the ventilation
rates have been taken from the
CIBSE guide A [29], in this case
to each heated spaces is assigned a value of natural ventilation considered the minimum in order to
maintain indoor air quality, so basically it’s the air change rate of the heated spaces. The profile created
for the natural ventilation of the spaces is linked to the occupancy schedules, therefore the natural
ventilation will be considered when the users will need to change the air of the enclosure, which is from
08:00 to 17:00.
3.3.3 Technological Plant
Other than the data relating to the materials used for the envelope’s structure, the school principal has
made himself available to provide information about the technical plants that supply energy to the entire
building. This information were than verified through the visual survey done in the technical rooms of
the building, in which the plants are installed. The school building is equipped with a central system
Infiltration Building
[ach] 0.25
Table 3.4: Infiltration rate
Ventilation Kitchen Toilet Gym Classroom Hall/Corridor
[l/(s*m2)] 0.9 1.2 1.5 0.6 0.3
Table 3.5: Ventilation rate for each heated space inside the building
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used for the thermal heating of the specified heated spaces, combined with small separated water boiler
used for the DHW preparation, needed for the school building.
The period of activity of the central heating system is the same as presented by the guidelines of the
government, the DHW preparation instead, is continuous throughout the entire annual school period.
During the day, as seen in the table the heating system is continuously on while the DHW preparation
is strictly linked to the occupancy of the room, as matter of fact the DHW is required directly from the
users while the settings of the heating system are imposed by the institution. This is due to the fact that
most of the heating system present in the school system are old, therefore in most of the cases the
consumption given by the on-off procedure is so
high that keeping the heating system always on
may reduce the consumption, in addition the
type of system present in this buildings are quite
big and complex therefore it may be a problem to find an adequate technician available to do the on-off
procedure when needed.
3.3.3.1 Generation System
The building is heated by three low-pressure hot-water boilers powered by natural gas and has a total
calorific power equal to 150 kW. The system was installed in the 1995 in an adequate technical room
located in the underground story of the building. In this case it was possible to receive all the information
and data related to the machinery used for the heating system of the building. The system can be
classified as a class C boiler and has a forced draft closed with a pressure vessel with an efficiencies
equal to 90%, and the circulation of water is ensured by the use of various pumps located in the technical
room. The heating water temperature is thermally regulated depending on the outside temperature, but
this control is not completely automatic and must be operated by the janitor.
The DHW preparations is left to the small water boiler present at each floor placed in the consumption
Heating DHW
1st October – 30th April 1st September – 30th June
On continuously 8:00 -18:00 weekdays
Table 3.6: Activation profile of the technological plant
Figure 3-11: Boiler system used as heating system Figure 3-12: DHW boiler
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space. The system is constituted by electrical boilers with a max capacity of 125l. The warm water
produced is used to wash people, clean rooms and eat food. The DHW heating water temperature is
thermally regulated depending on the outside temperature, but this control is not completely automatic
and must be operated by the janitor. The existing system is tight so there are no significant losses, the
water quality is good and there is no need to modify it.
3.3.3.2 Fuel
The systems used for the heating of the selected spaces are fueled by natural gas, methane to be precise.
The cost of the methane gas in Czech Republic is equal to 0.5 €/m3 (taken from the CNG Europe [35]),
considering an ideal consumption equal to 10.5 kWh/m3 and dividing this value by the efficiency we
have a real consumption of 9.45 kWh/m3, that sets for the consumption of methane gas a cost of 0.053
€/m3.
3.3.3.3 Emissions Gasses
As said in the § 2.3.3.3 of the case study located in Lecco, the emission gasses taking in consideration
are the Greenhouse Gasses “GHG” emissions, caused by the combustion of the methane gas happening
in the chamber of the boilers to generate thermal power used for the heating system and the DHW
preparation, and the use of electricity for the systems present in the building.
The GHG emissions are typically expressed through the means of the equivalent carbon dioxide “CO2e”,
which is a measure for describing how much global warming a given type and amount of greenhouse
gas may cause, using the functionally equivalent amount or concentration of carbon dioxide (CO2) as
the reference. The formula used to calculate the CO2e is:
𝐶𝑂2𝑒 = ∑𝑖(𝐺𝑊𝑃𝑖 ∗ 𝐸𝑖)
- the CO2e is the equivalent CO2 emissions expressed in ton/year;
- GWPi is the Global Warming Potential of each of the GHG considered. The GWP is a relative measure
of how much heat a greenhouse gas traps in the atmosphere, it compares the amount of heat trapped by
a certain mass of the gas in question to the amount of heat trapped by a similar mass of carbon dioxide;
- Ei is the GHG emissions.
The conversion factors used for the combustion of the methane gas is equal to 0.203 kg CO2/kWh, while
the factor for the electricity is equal to 0.519 kg CO2/kWh, these values were extracted from the Carbon
Trust standards.
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3.3.3.4 Emission system
The emission system is represented by the use of cast iron
radiators, put in each of the spaces considered heated in the
case study. The cast-iron radiators have an high thermal
inertia, this means that this type of radiators will need more
time to reach the set point temperature , thus increasing the
energy needs and gas emissions due to the fact that the boiler
has to be activated for a longer period, increasing the time in
which the combustion of natural gas produces thermal energy.
3.3.3.5 Control system
The radiators located in the toilet and in the hall of the case study building are equipped with thermostatic
valve with a thermostatic head. With the use of the valves it’s possible to adapt the internal temperature
of the heated spaces depending on the outside temperature, thus reducing the energy waste given by the
over-use of thermal energy used for heating.
3.3.3.6 Distribution system
The data about the distribution system, have been hypothesized
according to the visual survey done in the technical room located in the
underground floor of the old part of the building and the standards
regarding the system efficiency [31] . The distribution system is
considered as a zone heating system with horizontal distribution,
powered by vertical mullions (usually running in the stair case) as
described in the Prospectus 22 of the EN ISO 11300-2 [31]. The
distribution system is considered as a zone heating system with horizontal distribution, powered by
vertical mullions running in the interior side of exterior walls.
The pipes present a medium layer of insulation, done with various materials (cotton muslin, cups) not
fixed stably by a protective layer. This suppositions brought a calculated value of 92% for the efficiency
of the distribution system of the case study building, this sets the value of the overall seasonal heating
efficiency of the system “ScoP” equal to 82.8 %.
3.3.3.7 DHW Production
The procedure used to calculate the required DHW for a school has been taken from the EN ISO 11300-
Figure 3-13: Cast iron radiator
Figure 3-14: Distribution scheme
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2 [9] with the simple formula, applied for each class:
𝑉𝑤 = 𝑎 ∗ 𝑁𝑢 = 0.17 [𝑙
ℎ]
- a is the specific daily requirement in liters / (day × Nu) obtainable from Table 31, and for school is
equal to 0.2;
- Nu is a variable parameter depending on the type of building that can be obtained from Table 31, and
for school is equal to the number of students.
The DHW preparation is done by the independent water heater boiler presented in the § 3.3.3.1. The
water heater can be classified as open chamber boiler, also known as a type B appliance, it is a boiler or
water heater designed to be connected to an evacuating duct for the combustion’s products to the outside
of the installation room, the combustion air is taken directly from the installation environment that must
be permanently aerated. A water heater classified as type B and considered without the guidance flame,
a flame which is always on and allows instantaneous production of hot water to start, can be considered
with an efficiency equal to 77 % according to the EN ISO 11300-2 [31].
3.3.4 Energy Classification
In the Czech Republic, the same methodology is used for all regions and all building types. The
recommended calculation procedure is based on published CEN standards and applicable Czech
Technical Standards. The energy performance is expressed by the total annual energy consumption,
including heating, cooling, DHW preparation, mechanical ventilation, lighting and auxiliary energy
needed for standardized building..
The energy labels classifies buildings on an efficiency scale ranging from A (high energy efficiency) to
G (poor efficiency). Class C is a minimum EP requirement level for new buildings and for existing
building going under major renovation.
The aim of the EP certificate is to inform residents and building owners/users, and encourage them to
take energy saving measures, the methodology is described in the EPC implementing regulation [36].
Figure 3-15: Energy classes [kWh/m2y] for different building types
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CHAPTER 4
4 Climatic analysis
In order to be able to fully understand the following energy analysis, and in order to creat a climatic
background it has been decided to analyze the climatic factors of both of the location of the case studies,
and to compare them in order to understand what are the similarities and the difference and how they
could affect the energy analysis.
All the data presented, and thus used to create a climatic background for the thesis work, were taken
from the national agency database. For the Italian data the source used is the ARPA database [37], while
for the Czech ones it has been used the database of Agency for the Protection of Nature and Landscape
Conservation of the Czech Republic [38].
Since the climatic data of Bustehrad were not available, the study has been diverted onto the climatic
conditions of Prague, which will be assumed as the same as Bustehrad.
4.1 Geographical framework
As already explained, the proposed study will involve two cities
located in the Central Europe area, as they are Italy and Czech
Republic. More precisely the city that will be analyzed will be
Lecco and Bustehrad .
Lecco is a city of northern Italy, 50 km north of Milan, the capital
of the province of Lecco. It lies at the end of the south-eastern
branch of Lake Como. The Bergamo Alps rise to the north and
east, cut through by the Valsassina of which Lecco marks the
southern end. The lake narrows to form the river Adda, which
crosses the entire city.
Buštěhrad is a small town in Central Bohemian Region of the
Czech Republic, located 20 km northwest of Prague.
In order to have an idea of the framework of the analysis it has
been decided to present the average temperature of the main city included in the Central Europe Area.
In this case it will be possible to see the reliability of the assumptions made in the introduction and the
possible deviation of the results depending on the city. The Figure 4-2, represents the yearly average
temperature of the main cities of the Central Europe Area, through which it is possible to see the
differences between them. The data used for the analysis were collected from the EPA Network [39].
Figure 4-1: Central Europe framework
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The graph states that the assumption made were reliable, thus the temperature of the regions included in
the CE are close to each other, so the weather will have a similar impact on the energy dispersions of
the buildings located in this area.
4.2 Outdoor dry-bulb temperature
The climatic analysis starts with the study of the outside temperature of the two case study taken in
consideration: Lecco and Buštěhrad. The study will include the comparison of the results.
-3
-1
1
3
5
7
9
11
13
15
17
19
21
January March May July September November
[°C] Milan Praha Berlin Wien Budapest Zagreb Warsaw Bratislava Lubiana
-15
-10
-5
0
5
10
15
20
25
30
35[°C] Lecco Prague
January February March April May June July August September October November December
December Figure 4-2: Central Europe main cities’ yearly average temperature
January February March April May June July August September October November December
December Figure 4-3: Hourly outdoor dry-bulb temperature of the two case studies
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The outdoor temperature recorded in Lecco is higher respect to the one of Buštěhrad almost
homogenously throughout the year. This was highly predictable since Bustehrad is located in Czech
Republic, therefore is situated in a northern location respect to Lecco, which is part of Italy so is still, in
a small scale, affected by the Mediterranean climate.
In order to have a more clear view of the climate of the two case studies, it has been decide to create a
temperature profile for each of the cities, in order to analyze minimum, maximum and average yearly
temperature.
Analyzing the temperature profile is clear that the two locations have similar behavior. The curves
defining the average temperature show that the differences between the hotter climate of Lecco and the
colder climate of Buštěhrad is pretty homogeneous throughout the years, and it seems to be
approximately equal to ¾ °C. The maximum temperatures recorded as similar, even though they are
reached in different periods of the years, on the other hand the minimum are a bit different, since the
lowest Czech temperature recorder is equal to -5 °C while the Italian one is -1 °C.
The major difference is the presence of colder peaks during the winter in Buštěhrad, while in Lecco the
winter’s temperature is more homogeneous as it stays near to 0/1 °C.
4.3 External relative humidity
The second criteria to define the external climatic conditions is the external relative humidity perceived
in the location.
The graph presented in the Figure 4-5, shows once more the compatibility of the results obtained for the
two case studies. Although the value of external relative humidity fluctuates throughout the year, the
two different case studies present a similar behavior.
-6
-2
2
6
10
14
18
22
26
30
34[°C] Lecco Prague Minimum Maximum Average
January February March April May June July August September October November December
December Figure 4-4: Monthly temperature profile of the two case studies
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The climate of Lecco is characterized by low relative humidity during the winter, this could be due to
the presence of the lake, which crosses the city, which lowers the humidity in the cold seasons. On the
other hand the mid-seasons in Prague seem to be the ones with the highest percentage of relative
humidity, this data is crucial for the thermal comfort analysis presented later on in the work.
4.4 Horizontal radiation
The next step is the analysis of the global radiation, which stands for the intensity (irradiance) of
solar radiation falling on the horizontal plane.
30
40
50
60
70
80
90
100% Lecco Prague
0
50
100
150
200
250
300
350[W/m2] Lecco Prague
January February March April May June July August September October November December
December Figure 4-5: Daily average external relative humidity of the two case study location
January February March April May June July August September October November December
December
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Once more the results are similar for the two case studies. It has to be highlighted that the max. radiation
recorded is equal to 350 W/m2 which is not a bad results, creating a starting idea of exploiting the
available radiation.
4.5 Wind exposure
The analysis deals with the intensity and the direction of the recorded data of the wind of the two
locations, in order to understand the impact on the external climate.
In order to have a clear idea of the effect of the wind on the environment it has been decided to present
the Beaufort scale used to classify the effect of the wind speed [40]. The scale relates the effects of the
wind with the ones of the sea, and then classifies the resulting consequences.
Level Speed
Wind Consequence
[m/s] Environment Sea
0 0-0.2 Calm Smoke ascends vertically State zero
1 0.3-1.5 Wind blows The wind drifts the smoke State one
2 1.6-3.3 Light breeze The leaves move State two
3 3.4-5.4 Breeze Leaves and branches constantly shaken State two
4 5.5-7.9 Intense breeze The wind raises dust and dry leaves State three
5 8-10.7 Tense breeze Shrubs with leaves are swirling State four
6 10.8-13.8 Fresh wind Big branches are shaken State five
7 13.9-17.1 Strong wind Whole trees shaken, difficulty walking State six
8 17.2-20.7 Moderate storm Broken branches, impossible walking Sate seven
Table 4.1: Beaufrot scale of wind intensity
The graph presented in the Figure 4-7 shows the average per year of the record values of wind speed
for the two cities taken in exam.
3.33.84.34.85.35.86.36.87.37.88.38.89.39.8
10.310.8
[m/s] Wind Level 3 Wind Level 4 Wind Level 5 Lecco Prague
Figure 4-6: Hourly global radiation of the two case study location
Figure 4-7: Yearly average wind speed values of the two case study location
January February March April May June July August September October November December
December
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Most of the time of the year records a value of wind speed which is classified as Wind level 3 and 4,
therefore no evident impact is made by the wind onto the climatic external conditions of the two case
studies.
4.6 Rainfall precipitation analysis
The effect of rainfall in some cases can be major, therefore in order not to have any possible
complications it has been decided to go on with the rainfall analysis.
It has been decided to represents the distribution of the amount of rainfall precipitations fallen during
an entire year, month by month. The results show higher quantity of precipitation recorded for Buštěhrad
respect to Lecco, even though the quantity seen don’t represent a problem in this case.
0
2
4
6
8
10
12
14
16
18n° days <2mm 2-5mm 5-10mm 10-20mm 20-50mm Prague
<2mm 2-5mm 5-10mm 10-20mm 20-50mm Milan
Figure 4-8: Yearly amount of rainfall precipitation of the two case study location
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4.7 Snow precipitation
The effect of the amount of snow fallen during a year in some cases can be major, therefore in order not
to have any possible complications it has been decided to go on with the rainfall analysis.
In order to do this it has been decided to analyze the amount of snow fallen recorded from the 2012 to
the 2016, thanks to the database mentioned earlier.
The graph presents either the number of days in which it has been recorded snow precipiation and the
amount of snow fallen. Basically it shows that there is a higher number of days of snow in Prague respect
to Lecco, due to the higher latitude and the numerous mountains present.
4.8 Seismic activity
The last step consists on evaluating the seismic activities recorded in the two areas, in order to have a
complete view on the geographical framework of the case studies.
4.8.1 Lecco
The seismic classification of the national territory has introduced specific technical regulations for the
construction of buildings, bridges and other works in geographic areas characterized by the same seismic
risk. Here there is the seismic zone for the territory of Lecco [41].The criteria for updating the Seismic
Hazard Map [42] has divided the whole national territory into four seismic zones based on the value of
the horizontal maximum acceleration (ag) on rigid or flat ground, which has a probability of 10% being
2012
2013
2014
2015
2016
2017
2012
2013
2014
2015
2016
2017
0
5
10
15
20
25
30
0 5 10 15 20 25 30 35 40 45 50 55 60 65
n° days
[mm]
Prague Lecco
Figure 4-9: Amount of snow precipitation for the year 2012-2016 of the two case study location
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exceeded in 50 years. Peak ground acceleration (PGA) is equal to the maximum ground acceleration
that occurred during earthquake shaking at a location.
PGA is equal to the amplitude of the largest
absolute acceleration recorded on an
accelerogram at a site during a particular
earthquake. Unlike the Richter and moment
magnitude scales, it is not a measure of the
total energy (magnitude, or size) of an
earthquake, but rather of how hard the earth
shakes at a given geographic point. The peak
horizontal acceleration (ag max) is the most
commonly used type of ground acceleration
in engineering applications. It is often used
within earthquake engineering (including
seismic building codes) and it is commonly plotted on seismic hazard maps. In an earthquake, damage
to buildings and infrastructure is related more closely to ground motion, of which PGA is a measure,
rather than the magnitude of the earthquake itself. For moderate earthquakes, PGA is a reasonably good
determinant of damage; in severe earthquakes, damage is more often correlated with peak ground
velocity.
Seismic Zone
Description Horizontal Maximum
Acceleration (ag)
1 Indicates the most dangerous area where severe earthquakes can occur. Ag > 0.25 g
2 Area where severe earthquakes can occur. 0.15 < ag ≤ 0.25 g
3 Area that may be subject to severe earthquakes but rare. 0.05 < ag ≤ 0.15 g
4 It is the least dangerous area, where earthquakes are rare and it is up to
the Regions to prescribe the obligation of anti-seismic design. Ag ≤ 0.015 g
4.8.2 Buštěhrad
A seismic zonation map was included in the building code standards (ČSN 73 0036). Recently a new
map was completed on the basis of earthquake catalogues for Central European countries delimiting
seism genic areas and maximum possible earthquake intensities, as well as information on suppression
of macro seismic intensities. In this map, values of seismic loading are expressed in terms of the macro
seismic intensities (MSK scale) with 10% probability of exceedance in 50 years. Related values
employed for seismic zone delineation for the National Application Document of EUROCODE 8 (CR-
CSN P ENV 1998-1- 1) are expressed in terms of the effective peak acceleration as shown below.
Table 4.2: Lombardy seismic hazard map
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The seismic map of the Czech Republic shows that the zone in which Prague, and its surroundings, are
located is a Seismic Zone 1, with a peak ground acceleration equal to 0.015g, this means that these zones
are not considered seismically active. The classification made is also based on the seismic history of the
related zone, therefore in the area of Prague, among the last decades no earthquakes with high intensity
have been spotted.
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CHAPTER 5
5 Energy Diagnosis: Case study “Lecco”
The chapter will be focused on the presentation of the energy analysis done on the selected building,
following the boundary conditions and the input listed before, chapter 2. The results will be presented
through the means of tables and graphs, in order to represent the significant data chosen to describe the
energy scenario of the building, in the most efficient and self-explanatory way. There will be a major
distinction between the output data coming from the energy simulation describing the energy
consumption of the building, and the one describing the internal condition of the building environment.
The outputs coming from the energy simulation have been divide so that the results can be presented as
“Energy Performance” and “Internal Comfort Condition” of the analyzed building case.
5.1 Energy Performance of the Building
The energy performance of the building represents the output data related to the energy contribution of
the building. This means that are here represented all the data that useful to outline the energy and
environmental framing of the building, analyzed in such detail to easily highlight the major problems.
This has been done, taking in consideration the fact that the work of an energy retrofit starts from the
energy performance of the state of the art and from the critical analysis of the results obtained through
the energy simulation.
5.1.1 Energy Consumption
The energy consumption of the building, calculated through the use of the dynamic energy simulation
software, is here represented as “PE” which stands for Primary Energy, calculated through the
conversion factors presented in the input chapter, , in the § 2.3.3.
Primary Energy Consumptions: 315.27 MWh
Primary Energy Consumptions per area: 307.87 kWh/m2
Energy Classification: Class F
The figure represented below shows how the consumptions of the building is divided into the sub-
elements taken in consideration in the energy modelling design. The consumption due to the heating
system is equal to almost 80% of the total PE, this highlights the importance and the relevance of
decreasing the heating consumption of the school building through the step-by-step approach presented
in this energy retrofit work.
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The results given by the simulation are in line with the typical consumption of a school building, as seen
in the previous chapter. The PE consumptions related to the DHW are relatively low, as seen in the
previous chapter, the hot water consumptions in a school building are typically low due to the non-
constant demand related to the hours in which the school is occupied, indeed the presence of a school
gym and of a school canteen raises the concerns toward the decrease of this specific consumption. As
already highlighted before, this results represent the base guidelines to understand towards which
direction the retrofit has to go in order to maximize the requalification and minimize the waste of money
and time. For this reason in the further analysis the DHW, the Equipment and the Light consumptions
will be considered negligible as the attention will be focused on the reduction of the PE consumptions
of the heating system.
5.1.2 Economic and Environmental Impact
In order to define the environmental impact of the emission produced by the school building , we will
consider the amount of Carbon Dioxide equivalent (CO2e) emissions, considering the hypothesis and
the standard values expressed in the previous chapter about the input boundary conditions. With the
introduction of the CO2e it’s possible to describe with one unit of measure the global impact of the
building, considering the Green House Gas (GHG) emissions of it, linked to the use of electricity and
thermal energy presented in the previous paragraph. Concerning the economic impact, it has been
considered the amount of euros spent every year in order to fulfill the building’s energy needs, both
thermal and electric.
GHG emissions: 50.89 ton CO2e/y
Energy bill: 24592.6 €/y
The graph presented below was made in order to give a complete overview of the impact caused by the
energy-inefficient school building, taken in consideration.
020406080
100120140160180200220240260280300320[kWh/m2y]
76%
15%
4%5%
Heating
DHW
Equipment
Light
Figure 5-1: Primary Energy consumption
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The school building taken in consideration can work as an example, in order to give an idea on what
happens with an old and neglected building. Choosing the year of interest, through the trendline, it’s
easy to locate the wanted output values of GHG emissions [ton CO2e] and the thousands of euros [k€]
needed to run the energy systems of the school building. The impact of the building was calculated
taking in consideration the energy bill and the GHG emissions caused by the combustion of methane,
due to the boilers serving the heating and DHW demand, and the use of electricity, due to the boilers’
electric consumptions and the ones related to the equipment and lighting demand ( as represented in the
previous paragraph).
Figure 5-2: Trendline of the economic-environmental impact of the school building per year
In order to have a more global view on the GHG emissions and on the energy bill of buildings, the Case
Study building has been compared with a Class A1 building, which actually represents the reference
case seen in the previous chapter, and a Class A4
building, which is the highest energy class
possible. The emissions and the bill related to the
fictitious building in energy class A1 and A4,
have been calculated considering the maximum
value of energy consumption for each energy
class calculated in the previous chapter
according to the national energy classification.
The graph here represented highlights the
differences presented between the case study and
energy-efficient building, in terms of euros and CO2e. This graph highlights the importance of
retrofitting the case study since we could experience some major decrease in the energy bills which
means less money spent for the operational of the building, and considering the fact that our case study
is a school, less money spent for the building will mean less money wasted for every citizen.
0 300 600 900 1200 1500 1800 2100 2400 2700
04008001200160020002400280032003600400044004800520056006000
0
10
20
30
40
50
60
70
80
90
100
110[ton CO2e][yrs]
[k€]
Trendline per year
Guide Lines
Intersection Point
68.88%88.62%
45.42%
80.05%
05
101520253035404550556065
Case Study Class A1 Class A4
Energy Bill [k€]
GHG emissions [Ton CO2e]
% - Reduction from Case Study
Figure 5-3: Economic and Environmental Impact -%- of
different energy-class building.
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5.1.3 Heating Consumption
As said in the previous paragraph the major cause of energy consumption in the case study building is
represented by the combustion of natural gas into thermal energy provided to the boiler of the heating
system.
The graph expresses the primary energy
consumed each year in order to produce
enough thermal energy so that the heating
system can balance the building’s losses
and keep the temperature of the heated
spaces at the set point, no matter the
boundary conditions. Going further in
detail, through a critical analysis of the
results coming from this graph, it’s
obvious that the high energy
consumptions are due to excessive dispersions in means of Transmission imposed by a leaky and
inefficient envelope. This means that the attention will be focused primarily on the envelope of the
school building, both opaque and transparent component, so that the consumption can be reduced and
the retrofit can go on, thank to continuous analysis. The graph basically says that the energy retrofit of
the case study has to begin with the optimization of the envelope. Given the fact that the building is
located in the North of Italy and that for this case the months of July and August (in which usually
schools are closed) have not been taken into account, the value of the Solar gains seem reasonable. Also
the values presented in the graph related to the Ventilation losses and the Internal gains are in agreement
with the input data of the model, and with the fact that being the case study a school it’s normal to have
similar values for internal gains and natural ventilation, since the high activity of the students in the
classrooms is balanced by the continuous opening of the windows.
53.68
21.1573.57
232.73233.61
0
40
80
120
160
200
240
280
320
Contributions Dispersions
[KWh/(m2y)]
Energy Use
Transmission
Ventilation
Solar
Internal
Figure 5-4: Annual PE consumption for Heating Demand
05
1015202530354045505560
January February March April May June September October November December
Internal Gains
Solar Gains
Ventilation Losses
Transmission Losses
Energy Use
Figure 5-5: Monthly PE consumption for Heating Demand [kWh/(m2y)]
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To understand the behavior of the variables that contribute to the calculation of the consumption of
primary energy related to the heating demand, it has been presented a graph representing the monthly
condition values of the specified variables. First thing it is possible to double check that every input in
the model was insert in the right way since the results presented are in line with the hypothesis expressed
in the previous chapter. As matter of fact the value of energy use is zero for the months on May to
September and is almost the half of the average month for April and October in which the hating system
is active only for 15 days, and not the whole month as for the others. Of course the highest consumption
is experienced in the coldest month which is January, this is due to the really high transmission losses
(the temperature in January goes below 0°C) and the low solar gains, imposed by the low number of
hours of sun exposure. This is due to the angle of the sun during the winter, which also influences the
shading that the other buildings provide onto the case study, reducing the solar radiation coming into
the building through the glazing area.
5.1.4 Heat Gains
The heat gains of the case study building are a consequence of the input data, presented in the previous
chapter. In order to understand the behavior of the building in terms of positive impacts to the energy
balance, the heat gains calculated through the energy simulation of the study case have been studied and
broken down into the principal sources of gains.
The graph presented highlights the statement made before, the gains coming from the solar radiation
passing through the glazing part of the building, is similar to the ones coming from the internal sensible
and latent heat generated by the Equipment, Light and People present in the heated space. The values
related to the solar gains are relatively high for the climate of the city in which the building is located,
this is due to the high area of glazing part of the building, the fact that the glazing are located in all the
surfaces orientation and the high value of total solar factor “gtot” of the old windows present in the
building, an high gtot means that more solar radiation is transmitted to the inner spaces while less
21.15; 28%
41.83; 56%
4.65; 6%
7.20; 10%
53.68; 72%
Solar
Internal
People
Equipment
Light
Figure 5-6: Heat Gains in terms of kWh/(m2y) and %.
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percentage in reflected and blocked.
The value expressing the sensible and latent heat produced by the people inside the heated space
accounts for almost half of the heat gains of the building, this is in line with the hypothesis presented in
the input chapter, the high activity of students and the elevated number of people inside the space are
the major contributors.
5.1.5 Heat Losses
The analysis goes further in detail, focusing the attention on the variables that contribute to the
dispersion of heat from the case study building. For the analysis presented before, the variables in
discussion, are the Ventilation and the Transmission Losses, which in the energy analysis of the building
are balanced by the sum of Internal Gains, the Solar Gains and the Energy received from the heating
system.
The graph, as the caption says, represents the values in terms of % of the contribution of each element
of both part the of the building, the old and the recent one, to the global Heat Losses of the case study,
this means that looking at the graph it’s possible to understand the negative impact of each element,
taken in account in the energy balance of the case study building. For this analysis the two building’s
part have been considered separated, this is due to the fact that the they have different structures of
envelope’s elements, both opaque and transparent (as seen in the descriptive chapter). For this reason
they present also different output related to the infiltration losses, due to the different air leakages of the
W.O; 19.9
W.U; 0.2W.G; 0.5
F.U; 4.5
F.G; 0.6
F.R; 6.2R; 6.8
W; 9.9
T; 0.4
V; 10.2
I; 5.3 OLD PART
W.O-Walls vs Outside W.U-Walls vs Unheated W.G-Walls vs Ground F.U-Floor vs Unheated
F.G-Floor vs Ground F.R-Floor vs Roof R-Roof W-Windows
T-Thermal bridge V-Ventilation I-Infiltration
W.O; 7.0
W.U; 1.1
W.G; 0.9
F.U; 0.6F.G; 0.6
R; 6.5W; 10.2
T; 0.1
V; 5.6
I; 2.9RECENT PART
Figure 5-7: Contribution in terms of % of the elements of the old part (left) and the recent part (right) of the
building to the global Heat Losses of the case study.
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two parts, linked to the age and structure of the building elements and different input data concerning
the infiltration and the ventilation of the building’s spaces.
The results highlights the similar behavior of the two distinct parts of the building, since in both graphs
the biggest contribution are represented by the elements in contact with the outside, and the losses due
to the infiltration rate. The external walls, “W.O.- Walls vs Outside”, are the elements which have a
bigger negative impact on the building’s performance, followed by the glazing part of the building, “W-
Windows”, as a matter of fact if we sum the % contribution of these two variable of the building we
have that more than 30% of the heat losses of the building comes from the outer envelope of the old
part, and almost 20% comes from the one of the recent part, combined they sum up to 50% of the global
heat losses of the case study. Taking in consideration this facts and data, the first idea that comes to
mind is that the requalification of the external wall and the glazing part of the entire building will be one
of the most challenging part of the energy retrofit, and on the other hand it will be one of the most
significant energy-reduction work.
The high infiltration losses are due to the infiltration rate, presented in the input chapter, linked to the
air leakage of the energy-inefficient envelope of both parts of the building, in this case the absence of
the thermal insulation and the presence of and old bearing structure both in stones and bricks, for each
part of the building, plays the biggest part in conjunction with the presence of old low-transmittance
windows through the entire case study building. Another aspects that contributes to the high value of
infiltration losses, is the fact that instead of natural ventilation, this is not controllable but it’s actually a
phenomenon to which the building is subjected to, therefore it is always present, no matter the occupancy
of the space, and it always affects the heating demand, while the natural ventilation is controlled by the
users present in the heated spaces, which will open the windows, letting natural ventilation, according
the internal and external conditions of the specific space. The infiltration losses and the losses by the
outer envelope are strictly connected, this is because the infiltration is based on the difference of pressure
between the inside and the outside of the heated space, and the pressure inside of the space is linked to
the permeability of the outer skin of the building and the ability of it to keep the designated pressure.
The definition of air permeability is “Infiltration air flowrate per unit surface area of the envelope, at the
reference pressure difference” therefore it’s easy to understand that it depends on the air tightness of the
building, determined by the envelope’s thermal performances. This basically means that with the
improvement of the envelope we will have a double benefit, since there will be an obvious reduction of
heat losses attributed to the envelope’s element and also a reduction coming from the infiltration losses,
due to the increase of air permeability through the addition of thermal insulation to the outer skin of the
case study building.
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5.1.6 Solar Energy Analysis
The solar analysis helps understand the interaction of the building, in this case the building’s envelope,
and the solar radiation coming from the sun, basically this analysis will show the pro and the cons of
letting inside the inner spaces the sun’s radiation. For the purpose of this analysis the solar radiation has
two opposite effect on the building’s performances, a positive one related to the heating solar gains and
a negative one related to the overheating of the spaces.
For the calculation of the heating energy demand the contribution coming from the solar radiation is
accounted as solar gains, therefore in this case the impact of the radiation coming through the envelope
and into the heated space is positive, a way to reduce the energy demand is actually to increase the solar
gains throughout the heating period. On the other hand, the solar radiation coming through the envelope
in the cooling period will increase the internal temperature of the heated spaces giving rise to a possible
phenomenon of overheating, in which the spaces’ temperature may tend to unbearable internal
conditions for the users.
This analysis will provide a global view on the construction design philosophy used, at the time, that
took part in the decision of the building’s orientation.
In this case considering that in the school building there are 4 different glazing’s orientation, it has been
represented the average solar radiation incident on the wall according to the different orientation. The
results presented in the graph are interesting, the first peculiarity is the behavior of the South-West
oriented wall, which actually shows higher values of solar radiation in winter rather than in the mid and
hot season, this is due to the obstacles present around the case study building, as a matter of fact the
South-West part of the building is the only one which is not shaded by a tall building, therefore there
0
50
100
150
200
250
300
350
South-West North-West
North-East South-East
January February March April May June September October November December
December Figure 5-8: Daily average incident solar radiation [Wh/m2] calculated on the 4 different orientation.
Heating Season Cooling Season Heating Season
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will be a bigger amount of solar radiation hitting the surface.
In order to fully understand whether the solar radiation are a benefit or a malus for the case study, it has
been highlighted the two different period, the heating period in which more the radiation the better and
the cooling period in which high solar radiation usually means discomfort. Considering the cooling
season the orientation with the highest values of solar radiation are the South-West and South-East,
which means that the space which will have walls oriented like this will have chance to encounter
overheating, on the other hand this two orientation have the highest values also for the heating period,
as seen before.
The screenshots of the solar analysis run through the dynamic simulation software, attached above, helps
understand the results and commented presented earlier about the output coming from the analysis
related to the incident solar radiation hitting the different vertical component of the case study building.
The comments related to the incident solar radiation graph, are confirmed by these screenshots in which
is possible to see the annual solar radiation [kWh/m2] hitting the envelope of the building. The elements
oriented towards the South West direction (first on the left) are the ones with the biggest values, while
the ones oriented towards North East present the lowest values.
In this case is also visible the shading action of the surrounding buildings towards the case study
building, and the effect that they have on the incident solar radiation. The four different screen shots
refer to the 21 of March, day of the Spring Equinox, at midday.
Figure 5-9: Solar analysis radiation on SW, NW, NE, SE oriented wall (from left to right)
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5.2 Internal Comfort
The factors that determine the quality of the internal space related to the improvement of students’
apprenticeship are related to measurable values. The parameters that define the internal comfort
conditions, related to the design criterion of naturalness, are also identified in the current legislation,
however, specific values derived from the researches conducted to determine the optimal conditions for
improving the learning performance show how some non-normative values are optimal for the well-
being, comfort, and cognitive response of school building tendencies. The following is a summary table
summarizing the standard values, the values included in national legislation (D.M. 18/12/1975), and the
recommended values for the classroom, associated with performance enhancements of learning
compared to sector studies. Usually in the existing school facilities, the cooling system is not present
and the indoor air temperature in the hot and mild seasons is not controlled. The standard value of the
temperature therefore refers to the heating period. The following table highlights the detailed parameters
that will be examined later in the discussion.
PARAMETERS UNIT STANDARD
TEST
VALUES
EFFECTS ON
LEARNING REF.
AIR
Temperature °C 20±2 20-25 +2-4% for every -1°C
ISO
77
30
Ventilation l/sp 3 8 +75 from 5 to 15*
CO2 emission ppm - < 1000 +1-2.5%**
LIG
HT
Illuminance lux 300 Better quality UN
I 10
840
EN
ISO
12
464
-1
Daylighting (FDL) % 3 Shadings control
Useful daylight
Illuminance (UDI) lux <2000 [300-2000]
SO
UN
D
Partitions’ Resistance db 40 Noise from the inside D.M
. 13
/09
/19
97
UN
I 11
367
Windows’ Resistance db 25 Noise from the outside
Walls’ Resistance db 35
Reverberation Time
(TR) s 1.2
Check the noise
frequency of the room
Table 5.1: Natural philosophy’s parameters to maintain comfort conditions and improve learning performances.
Also note that:
* the minimum ventilation value is equal to 3 l/sp and 8 l/sp is a standard value; in the national standard
the value varies from 2.5 to 5 vol/h according to the level of instruction of the school; highlighting the
improve of the learning performance, the scientific literature sets value from 5 to 15 l/sp;
** a values lower than 1000 ppm is associated to an healthier environment and it has been observed a
reduction of 1 to 2.5% of absences due to illness;
The most influent parameter on the learning performances is the light ( from 19 to 48% more than the
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others), this means that the quality and quantity of the natural light that the classroom receives is
significant for the abilities of the students. Therefore, the orientation of the glazing, the ratio glazing/area
of the floor and big openings not oriented towards direct sunlight are the drivers to an inefficient
configuration of the classroom. The different configurations for the various methods of learning that are
carried out in a classroom require different positions of the students in respect to the windows or walls.
The realization of a large glazing, which is a result of the standard limitation for which the ratio between
the surface of the windows and the ones of the floor as to be equal to 1/5-1/7, creates a link between the
inner space and the nature, this is an important principle for the natural philosophy design. In this case
though, the light as an even bigger variable impact related to the position of the users.
In order to evaluate in detail the internal conditions of the classroom, dynamic simulations have been
done on the case study building.
This paragraph of the chapter will be focused on the heated spaces classified as classrooms, therefore to
make the presentation of the results clearer and easier, the classroom have been codified, as seen in the
picture below.
The diversification of the classrooms has been done taking in consideration the different floors and the
different orientation of the glazing present in each classroom. The classrooms of the recent part of the
building are located only on one floor, the first one, while the classes of the old part are located on each
floor from the ground to the third, but the morphology of the classes doesn’t change from one floor to
another, therefore it was useless to show each floor’s plan in this case, but it has been used only the
typical floor. The table helps understand the morphology and the main characteristics of the classrooms,
also in this case the floor have not been considered, but the diversification was made only on the different
opening’s orientation.
Code Openings Floor Ratio
Class [m2] orientation [m2] %
C.X.1 11.66 SE-SW 51 22.86
C.X.2 4.9 SE 35 14.00
C.X.3 10.76 NW-SW 43.68 24.63
C.X.4 6.31 NE 31.27 20.18
C.X.5 6.31 NE 31.27 20.18
C.X.6 9.31 NE 47.17 19.74
C.X.7 12.96 SW 33.92 38.21
C.X.8 6 NW 27.06 22.17
C - Classroom
X - Floor
Figure 5-10: Diversification of the classrooms by window’s orientation
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5.2.1 Thermal Comfort
Thermal comfort is the condition of mind that expresses satisfaction with the thermal environment and
is assessed by subjective evaluation (ANSI/ASHRAE Standard 55) [43]. Maintaining this standard of
thermal comfort for occupants of buildings or other enclosures is one of the important goals of HVAC
(heating, ventilation, and air conditioning) design engineers. Thermal neutrality is maintained when the
heat generated by human metabolism is allowed to dissipate, thus maintaining thermal equilibrium with
the surroundings. The main factors that influence thermal comfort are those that determine heat gain and
loss, namely metabolic rate, clothing insulation, air temperature, mean radiant temperature, air speed
and relative humidity. Psychological parameters, such as individual expectations, also affect thermal
comfort. The Predicted Mean Vote (PMV) model stands among the most recognized thermal comfort
models. It was developed using principles of heat balance and experimental data collected in a controlled
climate chamber under steady state conditions. The adaptive model, on the other hand, was developed
based on hundreds of field studies with the idea that occupants dynamically interact with their
environment. Occupants control their thermal environment by means of clothing, operable windows,
fans, personal heaters, and sun shades. The PMV model can be applied to air-conditioned buildings,
while the adaptive model can be generally applied only to buildings where no mechanical systems have
been installed. There is no consensus about which comfort model should be applied for buildings that
are partially air-conditioned spatially or temporally. Thermal comfort calculations according to
ANSI/ASHRAE Standard 55 [43] can be freely performed with the CBE Thermal Comfort Tool for
ASHRAE 55. Similar to ASHRAE Standard 55 there are other comfort standards like EN 15251 [44]
and the ISO 7730 standard [45].
With regard to thermal comfort, the final figure to be assessed is the degree of well-being perceived by
occupants in the space considered. The useful tool for this purpose is constructed by theoretical
principles and measurement methods for predicting the perceived thermal sensation of people. The
78 eometr-hygrometric environment is described through appropriate physical quantities with
standardized methodologies [46]. The size considered for the comfort temperature is the operating
temperature:
𝑇𝑂𝑃 = ℎ𝑟 ∗ 𝑇𝑚𝑟 + ℎ𝑐 ∗ 𝑇𝑎
ℎ𝑐𝑟
Where:
hr is the radiative exchange coefficient;
Tmr is the mean radiant temperature;
Ta is the air temperature;
hc is the convective exchange coefficient;
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hcr is the adduction coefficient.
According to the EN ISO ISO 7730 [45] and the ASHRAE 55 [43] show as comfort condition:
Top = 20-24°C, UR= 30-70 % in the heating period;
Top = 23-26°C, UR= 30-70 % in the cooling period.
The hours of discomfort are the ones in which the temperature of the heated space, during the cooling
period, is higher than the comfort limit set at 26 °C, as presented before.
Compared to the studies related to the definition of the parameters for improving the I performance, the
set-point temperature in the winter period should be maintained within a range of 20 to 22 ° C. However,
in mid and summer seasons, indoor air temperature can’t be controlled but experimental evidence in the
field of temperature-related learning has shown that a temperature of 22-24 °C improves performance,
even though temperatures ranging from 25 to 32 °C are permitted in the British guidelines and at the
national level no recommended values are stated.
In order to understand the internal thermal conditions of the heated space classified as classrooms inside
the case study building, it has been calculated -in percentage %- the discomfort hours through the energy
simulation software used presented before.
The graph shows, as seen in the caption, the total percentage of discomfort hours during the cooling
season, which means that it has been calculated the ratio in percentage between the total hours of a
normal school day – 8 a.m. to 18:00 p.m. – and the hours, in this range, in which the temperature is
higher than the defined cooling comfort temperature, set at 26 °C. In this calculation it has been
considered only the school days – Monday to Friday – in which the heating system is off, not taking in
consideration the summer period in which the school is not used – from 16th April to 30th June and from
1st to 30th September – in order to have more accurate and realistic outputs.
The classrooms have been divided by exposition, from the small plan previously presented in Figure
5-10 it’s easy to understand the differentiation of the classrooms, by floor (first number of the code for
0
2
4
6
8
10
12
14
16
18
20
22
24
C.0.1 C.1.1 C.2.1 C.0.2 C.1.2 C.2.2 C.1.3 C.2.3 C.2.8 C.1.4 C.1.5 C.1.6 C.1.7
SE-SW SE NW-SW NW NE SW
Figure 5-11: Discomfort hours % of the classrooms, dived by glazing’s orientation, during the cooling
season.
Old Part Recent Part
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the classrooms – C.X) and by glazing’s orientation (second number – C.X.X.). The differentiation by
orientation has been done in order to see the effect of the sun exposure on the classroom, in the cooling
period the building is free floating (no conditioning system is on) and the temperature of the inner spaces
depends mainly on the sun radiation hitting and passing through the glazing part of the envelope, the
amount of radiation depends on the incident angle on the surfaces, linked to the height and the orientation
of the specific surface.
The Figure 5-11 gives a global view on the thermal condition on the different classrooms, in more than
half of them the internal temperature is over the set point for a period equal or greater than 10% of the
time that a student is present in the space, this means that the school is subjected to overheating during
the cooling season, this will be an important input for the energy retrofit design philosophy. It’s obvious
that the thermal comfort performances of the part of the school built in the ’60, the recent part, has better
results than the old one, due to a more global study done at the time of construction on the optimal
orientation of the classrooms, and due to the different structure of the vertical element of the envelope
of the two different part, as a matter of fact the transmittance of the envelope of the recent part is lower
than the one of the old part, therefore in the hot season there will be less heat transfer between the
building and the surroundings , stopping the heat from coming into the inner spaces.
It’s interesting to compare the results output from the Figure 5-11 and the ones from the incident solar
radiation, presented in the previous paragraph §5.1.6. It’s clear that the high value of solar incident solar
radiation hitting the SW and SE oriented wall, in the cooling period, is a major contributor to the
overheating of the classrooms C.X.2 and C.X.3 (at each floor). A curios output is the one related to the
NW oriented classroom, in this case we have result values similar to the ones of the worst case (SE-
SW), this is explained by the small dimension of the heated space, as a matter of fact this is the smallest
heated spaces classified as class room, as seen in Figure 5-10. Due to the small dimension of the space,
the sensible and latent gains coming from the user’s body, become more relevant and the incident solar
radiation is not the major influencer for this particular case.
5.2.2 Adaptive Thermal Comfort Model
Over the past four decades, the PMV model has been adopted by a number of researchers worldwide to
assess indoor thermal environment [47]. In general, PMV model works well in built environment with
HVAC systems. For naturally ventilated (or free-running) buildings, however, the indoor temperature
considered most comfortable increases significantly in warmer climates, and decreases in colder climate
regions [48]. This is not surprising given the fact that ‘‘Fanger was quite clear that his PMV model was
intended for application by the heating, ventilation and air-conditioning (HVAC) industry in the creation
of artificial climates in controlled spaces’’ [47].
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The heat-balanced PMV model does allow the option of changing the level of activity (hence the
corresponding metabolic rate) and clothing. The experimental works (upon which the PMV model is
based), however, was conducted in climate chambers. Such arrangement did not give any indication of
how the occupants would change these two parameters in an attempt to adapt to the surrounding
environment. In practice, more often than not, assumptions have to be made about the on-going activity
and clothing. This tends to limit the application of the PMV model to a more static thermal environment
usually associated with airconditioned spaces [49]. In general, people are not passive recipients of their
immediate environment, but constantly interacting with and adapting to it. The return towards comfort
is pleasurable. Therefore, if there is any discomfort due to changes in the thermal environment, people
would tend to act to restore their thermal comfort. Broadly speaking, there are three different categories
of adaptation – physiological, behavioral and psychological [50] . Physiological adaptation (in terms of
acclimatization) is not likely to play a major role in affecting occupants’ thermal comfort for the
moderate range of thermal conditions prevailing in the built environment. Psychological adaption refers
to the effects of cognitive, social and cultural variables, and describes how and to what the extent habits
and expectations might change people’s perceptions of the thermal environment. Behavioral adaptation
is by far e most dominant factor in offering people the opportunity to adjust the body’s heat balance to
maintain thermal comfort, such as changing the activity and clothing levels & opening/closing windows
and switching on fans. A consequence of adaptive principle is that occupants try and hopefully become
adjusted to their immediate thermal environment.
It has been shown from field studies that PMV model works pretty well in air-conditioned premises, but
not in naturally ventilated buildings. PMV tends to over-predict the subjective warmth in the built
environment, especially in warmer climates. Humphreys [51] argued that thermal comfort standard like
the ISO 7730 based on PMV model was not entirely suitable for general applications, therefore the
ASHRAE Standard 55 [43] was revised to include an adaptive model for naturally ventilated buildings.
5.2.2.1 Adaptive Thermal Comfort Criteria
In order to calculate the adaptive thermal comfort applied to the case study building it has been decided
to follow the instructions and limitations imposed by the CIBSE Guide A [29], in particular the TM52
[52]. The following three criteria, taken together, are used to assess the risk of overheating of buildings
in the UK and Europe. A room or building that fails any two of the three criteria is classed as overheating.
- Criterion 1 Hours of Exceedance (He): sets a limit for the number of hours that the operative
temperature can exceed the threshold comfort temperature (upper limit of the range of comfort
temperature) by one degree or more during the occupied hours of a typical non-heating season
(1st May to the 30th September). The number of hours (He) during which ΔT is greater than or
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equal to one degree (K) during the period May to September inclusive shall not be more than
3% of occupied hours. Provides useful information about the building’s thermal characteristics
and potential risk of overheating over the range of weather conditions to which it will be
subjected.
- Criterion 2 – Daily Weighted Exceedance (We): deals with the severity of overheating, which
can be as important as its frequency, the level of which is a function of both temperature rise
and its duration. This criterion sets a daily limit for acceptability. To allow for the severity of
overheating the weighted Exceedance (We) shall be less than or equal to 6 in any one day. This
criterion covers the severity of overheating, which is arguably more important than its
frequency, and sets a daily limit of acceptability.
- Criterion 3 – Upper Limit Temperature (Tup): sets an absolute maximum daily temperature for
a room, beyond which the level of overheating is unacceptable. It is used to set an absolute
maximum value for the indoor operative temperature the value of ∆T shall not exceed 4°C. The
threshold or upper limit temperature is fairly self-explanatory and sets a limit beyond which
normal adaptive actions will be insufficient to restore personal comfort and the vast majority of
occupants will complain of being ‘too hot’. This criterion covers the extremes of hot weather
conditions and future climate scenarios.
The result of the technical memorandum is that a room that fails any two of the three criteria is classed
as overheated and thus fails the TM52 check. This check has been adopted in this case study, in order
to define the thermal comfort of the classrooms, respecting the hypothesis made in the § 5.2.1, of the
school building. For each classroom in addition to the Operative temperature, already seen in the
previous paragraph, it has been calculated the Daily running mean temperature, which represents the
exponentially weighted running mean of the daily mean outdoor air temperature and the Maximum
adaptive temperature, depending on the running mean temperature and the building category, according
to the guidelines of TM52 [52].
0
2
4
6
8
10
12
14
C.0.1 C.1.1 C.2.1 C.0.2 C.1.2 C.2.2 C.1.3 C.2.3 C.2.8 C.1.4 C.1.5 C.1.6 C.1.7
SE-SW SE NW-SW NW NE SW
Criteria 1 Criteria 2Criteria 3 Limit-Criteria 1Limit-Criteria 2 Limit-Criteria 3
Failed Class
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Figure 5-12: Adaptive Thermal Comfort check of the classrooms divided by orientation, according to TM52
The Figure 5-112 represents the TM52 check applied to the classrooms of the school building, taking in
consideration the different orientations, as seen in§ 5.2.1. The graph represents the output values of the
classrooms related to each of the criteria presented, therefore for every space is presented the % of
exceedance hours for the Criterion 1, the max. daily degree hours in °C for the Criterion 2 and the
maximum ΔT in °C for the Criterion 3; in addition there’s also represented the limit, as a dashed line,
for each of the criteria. In this way it’s easy to understand which and how many classrooms pass the
criteria and are classified as overheated.
Most of the classes don’t pass the criterion 2, and on the other hand easily pass the criterion 3, this means
that even if the class can be considered overheated, the overheating will create an uncomfortable
environment, otherwise the effect of the overheating would be unacceptable for the users of the specific
space. The classes C.1.2 and the C.2.2 are marked in red to highlight the fact that they are classified as
overheated, since both don’t pass the criteria 1 and 2. Keeping in mind the results coming from the
Figure 5-11 it was obvious that the classrooms that would have been classified as overheated were going
to be to ones, with walls oriented towards South-East. The energy retrofit will take into this results and
will increase the internal comfort conditions of the overheated spaces.
5.2.3 Indoor air quality
According to some researches made in 2015 from the Gruppo Studio Nazionale Inquinamento Indoor
(GdS) of ISS, it has been pointed out that the amount of CO2 in the atmospheric air corresponds to 719
mg/m3 (400 ppmv). Usually the concentration of CO2 in the indoor air is higher than the outdoor, and
depends on the presence and number of occupants in the space, which of course require continuously
oxygen to breath and their activities. It is necessary to try to keep the level of CO2 inside a defined range
provided by regulations, in order to avoid unpleasant consequences on the health of people inside the
room, an environmental welfare inside the space must always be guaranteed. For environmental welfare
it is intended the particular psychological condition in which the individual reaches a well-being
condition, in terms of microclimate (hygrometric comfort), air quality (respiratory system), noise
(acoustic comfort) etc.
The Indoor Air Quality (IAQ) represents an important aspect for what concern the public health. The
consequences of an unhealthy work environment could lead to a serious health problem to the people
inside the space, as called Sick-Building Syndrome (SBS) which consists in a collection of symptoms,
such as headache, eyes, nausea, concentration issues, fatigue and particularly sensitivity to the odors.
To ensure a correct development of the lecture and to not occur in unpleasant effects, the amount of
carbon dioxide level inside the closed space should be always verified.
The standard provides some threshold that doesn’t have to be overtaken to avoid dangerous level of
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CO2 inside the space. Of course the main parameter that influenced the level of carbon dioxide is the
ventilation rate, of which the natural regulation provides some standard values according to different
typologies of educational buildings. The level of carbon dioxide in a closed space are reported below in
compliance with the regulation ISO 7730 [45]:
- normal outdoor level of CO2: 350 – 450 ppm;
- acceptable outdoor level: lower than 600 ppm;
- odor problems: 600 – 1000;
- ASHRAE standards: 1000 ppm;
- light drowsiness: 1000 – 2500 ppm;
- light health issues: 3000 – 5000 ppm;
- health problems: > 5000 ppm.
All values above 1000 ppm must be avoided to not encounter health problems. In general, ventilation
rates should keep CO2 concentrations below 1000 ppm to create indoor air quality conditions acceptable
to people inside the space.
Figure 5-13: Distribution in percentage of the CO2 level present in the classroom, divided by orientation.
Fortunately none of the classroom taken in exam present hourly values for CO2 concentration higher
than 2500 ppm, this means that in no circumstances the users of the heated space will have some
noticeable effect on the health. For all the classes studied, the hours during which the concentration falls
in the 1000<CO2<2500 ppm range represent the highest percentage, this means the student during the
school days will usually feel some discomfort due to the concentrations values, but they will never feel
anything more dangerous than discomfort. This output is really important for the internal condition of
an heated space, especially if the heated space is a classroom, since in this case the users need the
maximum comfort possible in order to increase their learning performances, therefore during the
presentation of the optimization cases it will be encountered the possibility to reduce, or at least don’t
increase, the CO2 concentrations inside the classrooms.
0102030405060708090
100
C.0.1 C.1.1 C.2.1 C.0.2 C.1.2 C.2.2 C.1.3 C.2.3 C.2.8 C.1.4 C.1.5 C.1.6 C.1.7
SE-SW SE NW-SW NW NE SW
% <600 ppm 600<CO2<1000 ppm 1000<CO2<2500 ppm
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5.2.4 Daylight Analysis
Natural daylight is one of the most important aspect of the design of buildings, a special attention is
given to the evaluation of the daylight in the public building and in this case, the aim of this section is
to focus the attention on the natural lightning in educational buildings. A good natural daylight promotes
better didactical outcomes of students, better learning and teaching performances and improvements of
the physiological and psychological well-being and comfort of people inside the space. A good design
of daylight is also an advantage for energy saving, limiting the amount of hours in which the electric
lightning is switched on.
Several parameters rule the natural daylight, the standards focused the attention on the aero illuminance
ratio that has to be followed in order to get a uniform and well distributed illuminance inside the room,
which of course, changes according to the different destination of use of the space; for secondary class
the ratio between the transparent and the opaque envelope considered stand in the range of 1/5-1/7
(transparent part should be 1/5-1/7 of the total floor area m2 ).
Shades area or area with an excessive amount of light should be avoided to not experiencing unpleasant
effects as eye fatigue, verifiable both for poor quality of light, and excessive amount of lux that cause
unpleasant glare. For the daylight analyses an important aspect is also the choice of the transparent
envelope used, in particular for what concerns the visible transmittance (τvis) that characterized the
windows. Firstly, a general study of the illuminance on the work place has been evaluated, in order to
see if the values of illuminance where in compliance with the one suggested by the reference standards
[28]. The parameters analyzed are:
- Hourly Daylight Illuminance, expressed in lux
- Useful Daylight Illuminance (UDI), which is defined as the amount of time (expressed as a
percentage) in which, at a certain point, the internal amount of illuminance fall in the range
between 100 and 2000 lux.
- The average daylight factor (DLF), defined as the ratio between the mean lightning inside the
space and the outdoor lightning due to the sky, expressed in %.
The comfort level is necessary to permit people to have an efficient working execution, and that the
activities designated for that particular space are not compromised due to an excessive or low amount
of lux. The daylight factor is a parameter introduced in order to evaluate the natural lightning inside a
closed space, and aim to guarantee an optimal daylight illuminance inside the space. On the inside of a
closed room, the illuminance distributed along the geometry is characterized by three parameters: the
amount of light coming from the outside (sky), the contribution of the light due to reflections of the light
rays hitting the external surfaces and the reflection due to the multiple reflections of the light in the inner
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space. In the evaluation of the illuminance conditions, the analysis is made considering the most
improper case which consists of absence of direct solar radiation, called overcast sky. Imposed the cast
sky as the optimal condition for the calculation and the working plane at an height of 0.85 m from the
ground, the ratio between the internal and external illuminance should be constant and it is independent
on days and hours of the year: the mean daylight factor represents a value, expressed as a percentage,
defined as the ratio between the illuminance calculated at a certain point on the inside and the
illuminance measured on the outside on a horizontal surfaces without obstacles.
In order to not limiting the calculation, the DLF is taken as a mean of more points inside the room aiming
to evaluate the global illumination inside the space. The values of the daylight factor could vary
according to the destination of use, as reported in the table below. Some threshold value are defined in
the standards The value of the daylight factor and
of the illuminance, as explained before in § 5.2, for
educational building is defined by the EN ISO
12464-1 [28]. As seen in the table, all the spaces
classified as classrooms present in the case study
building pass both of the verification imposed by
the standard, either for the minimum for the average
value of Daylight Illuminance and the minimum for
the average value of the DLF.
Daylight Illuminance (UDI) has been calculated,
which consists in the percentage of time in which
the sensor point on the grid registers a value of
illuminance in the range between 100 and 2000 lux,
which are the minimum and maximum threshold of daylight illuminance allowable in the space. Then,
as a further analysis the Over lit Percentage has been evaluated, which consist in the harm illuminance,
hence the percentage of time in which the sensor over-takes the value of 2000 lux.
Figure 5-14: UDI -%- of the classrooms, divided by orientation.
0102030405060708090
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C.0.1 C.1.1 C.2.1 C.0.2 C.1.2 C.2.2 C.1.3 C.2.3 C.2.8 C.1.4 C.1.5 C.1.6 C.1.7
SE-SW SE NW-SW NW NE SW
% <100 lux 100-500 lux 500-2000 lux >2000 lux
% > 3 % [lux] > 300 lux
C.0.1 6.4 V 787 V
C.1.1 6.4 V 787 V
C.2.1 6.4 V 787 V
C.0.2 3 V 354 V
C.1.2 3 V 354 V
C.2.2 3 V 354 V
C.1.3 5.5 V 670 V
C.2.3 5.5 V 670 V
NW C.2.8 5.6 V 687 V
C.1.4 4.7 V 569 V
C.1.5 4.6 V 567 V
C.1.6 5 V 616 V
SW C.1.7 9.7 V 1182 V
NW-SW
NE
SE-SW
DLFOrientation Class
Illuminance
SE
Table 5.2: DLF and Illuminance values for each class.
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The graph represents the percentage, during the school days (as delimited in the previous chapter), of
time in which the value of the illuminance calculated inside each of the classroom falls inside the 4
ranges taken in consideration: less than 100lux, defines an inefficient lighting comfort; included between
100 and 500 lux, which represents the range in which the daylighting can be considered acceptable;
included between 500-2000 lux, which is the best range for illuminance inside a classroom; and over
2000 lux, representing the Over lit percentage. The results presented are in accordance with the ones
coming from the DLF analysis presented in the Table 5.2, the classes in which the daylighting can be a
seen as a problem are the ones oriented on the South East direction (C.X.2), their illuminance’s values
fall more often in the insufficient daylight range than the other classes, while the ones oriented towards
the South West direction present the best values of illuminance.
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CHAPTER 6
6 Energy Diagnosis: Case study “Buštěhrad”
As seen in the chapter 5, the chapter will be focused on the presentation of the energy analysis done on
the selected building, following the boundary conditions and the input listed before, in the chapter 3.
There will be a major distinction between the output data coming from the energy simulation describing
the energy consumption of the building, and the one describing the internal condition of the building
environment. The outputs coming from the energy simulation have been divide so that the results can
be presented as “Energy Performance” and “Internal Comfort Condition” of the analyzed building case.
6.1 Energy Performance of the Building
The energy performance of the building represents the output data related to the energy contribution of
the building. This means that are here represented all the data that useful to outline the energy and
environmental framing of the building, analyzed in such detail to easily highlight the major problems.
6.1.1 Energy Consumption
The energy consumption of the building, calculated through the use of the dynamic energy simulation
software, is here represented as “PE” which stands for Primary Energy, calculated through the
conversion factors presented in the input chapter, in the § 2.3.3.
Primary Energy Consumptions: 257.38 MWh
Primary Energy Consumptions per area: 251.22 kWh/m2
Energy Classification: Class G
020406080
100120140160180200220240260
[kWh/m2y]
84%
8%
7%4%
Heating
DHW
Equipment
Light
Figure 6-1: Primary Energy Consumption
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The two case studies have similar energy consumption, this was highly predictible since the two
buildings were supposed to be similar in order to present a complete and efficent work. Even though
they have similar consumptions, they have really different energy classification, this is due to the two
different energy scales used in each country.
The Figure 6-1 shows how the consumptions of the building is divided into the sub-elements taken in
consideration in the energy modelling design. The consumption due to the heating system is equal to
more than 80% of the total PE, this highlights the importance and the relevance of decreasing the heating
consumption of the school building through the step-by-step approach presented in this energy retrofit
work. The results given by the simulation are in line with the typical consumption of a school building
as seen in the previous chapter, as matter of fact the percentages are really similar to the ones of the case
study building located in Lecco, as seen in §5.1.1, with the main difference represented by the
consumption due to the DHW preparation. The school building located in Lecco presents an independent
gym, with linked locker rooms, and a kitchen, with a linked washing room, this sparks the DHW demand
of the school, thus increasing the consumption, while the students of the school in Buštěhrad use the gm
of an adjacent school building and they eat pre-cooked meals delivered directly to the school.
As already highlighted before, this results represent the base guidelines to understand towards which
direction the retrofit has to go in order to maximize the requalification and minimize the waste of money
and time. For this reason in the further analysis the DHW, the Equipment and the Light consumptions
will be considered negligible as the attention will be focused on the reduction of the PE consumptions
of the heating system.
6.1.2 Economic and Environmental Impact
In order to define the environmental impact of the emission produced by the school building , it will be
considered the amount of Carbon Dioxide equivalent (CO2e) emissions, considering the hypothesis and
the standard values expressed in the previous chapter about the input boundary conditions. With the
introduction of the CO2e it’s possible to describe with one unit of measure the global impact of the
building, considering the Green House Gas (GHG) emissions of it, linked to the use of electricity and
thermal energy presented in the previous paragraph. Concerning the economic impact, it has been
considered the amount of euros spent every year in order to fulfill the building’s energy needs, both
thermal and electric.
GHG emissions: 53.75 ton CO2e/y
Energy bill: 14022.3 €/y
If we compare the results for the two cases, looking at the § 5.1.2, it’s possible to see that the values of
GHG emissions are really similar, which was predictable considering the similar values of combustion
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of CO2 used, while the cost of the energy bull is much lower in Czech republic due to the low specific
cost of electricity in the country.
The graph presented below was made in order to give a complete overview of the impact caused by the
energy-inefficient school building, taken in consideration. The school building taken in consideration
can work as an example, in order to give an idea on what happens with an old and neglected building.
Choosing the year of interest, through the trendline, it’s easy to locate the wanted output values of GHG
emissions [ton CO2e] and the thousands of euros [k€] needed to run the energy systems of the school
building. The impact of the building was calculated taking in consideration the energy bill and the GHG
emissions caused by the combustion of methane, due to the boilers serving the heating and DHW
demand, and the use of electricity, due to the boilers’ electric consumptions and the ones related to the
equipment and lighting demand ( as represented in the previous paragraph).
In order to have a more global view on the GHG emissions and on the energy bill of buildings, the Case
Study building has been compared with a Class C building, which actually represents the acceptable
energy class for buildings nowadays for the standards,
and a Class A building, which is the highest energy
class possible. The emissions and the bill related to the
fictitious building in energy class A1 and A4, have
been calculated considering the maximum value of
energy consumption for each energy class calculated in
the previous chapter according to the national energy
classification. The graph here represented highlights
the differences presented between the case study and
energy-efficient building, in terms of euros and CO2e.
This graph highlights the importance of retrofitting the
case study since we could experience some major decrease in the energy bills which means less money
0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400
04008001200160020002400280032003600400044004800520056006000
0
10
20
30
40
50
60
70
80
90
100
110[tonCO2 eq.][yrs]
[K€]
Trendline per year
Guide Lines
Intersection Point
Figure 6-2: Trendline of the economic-environmental impact of the school building per year.
47.59%
81.05%
33.75%
76.05%
0
5
10
15
20
25
30
35
40
45
50
55
Case Study Class C Class A
Energy Bill [k€]
GHG emissions [Ton CO2e]
% - Reduction from Case Study
Figure 6-3: Economic and Environmental Impact -
%- of different energy-class building.
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spent for the operational of the building, and considering the fact that our case study is a school and
therefore is a public building, less money spent for the building will mean less money wasted for every
citizen.
6.1.3 Heating Consumptions
As said in the previous paragraph the major cause of energy consumption in the case study building is
represented by the combustion of natural gas into thermal energy provided to the boiler of the heating
system.
The graph expresses the primary energy
consumed each year in order to produce
enough thermal energy so that the heating
system can balance the building’s losses and
keep the temperature of the heated spaces at
the set point. Going further in detail, through
a critical analysis of the results coming from
this graph, it’s obvious that the high energy
consumptions are due to excessive
dispersions in means of Transmission
imposed by a leaky and inefficient envelope. The graph basically says that the energy retrofit of the case
study has to begin with the optimization of the envelope. Given the fact that the building is located in
the North Europe and that for this case the months of July and August (in which usually schools are
closed) have not been taken into account, the value of the Solar gains seem reasonable. Also the values
presented in the graph related to the Ventilation losses and the Internal gains are in agreement with the
input data of the model, and with the fact that being the case study a school it’s normal to have similar
values for internal gains and natural ventilation, since the high activity of the students in the classrooms
is balanced by the continuous opening of the windows.
Recalling the § 5.1.3, it’s possible to see that the value of energy heating demand is similar in the two
case studies, with the only difference involving the solar gains, which in this case are equal to half of
the amount present in the case study located in Lecco, as matter of fact Buštěhrad is located in the north
part of Europe therefore the glazing areas receives a smaller amount of solar radiation, combined with
the orientation of the building. Even though the gain are smaller in this case, the energy needed is less,
due to the smaller value of thermal transmissions through the envelope of the building.
To understand the behavior of the variables that contribute to the calculation of the consumption of
primary energy related to the heating demand, it has been presented a graph representing the monthly
47.90
20.50
54.51
211.84199.54
0
40
80
120
160
200
240
280
320
Contributions Dispersions
[KWh/m2y]
Energy Use
Transmission
Ventilation
Solar
Internal
Figure 6-4: Annual PE consumption for Heating Demand.
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condition values of the specified variables.
First thing it is possible to double check that every input in the model was insert in the right way since
the results presented are in line with the hypothesis expressed in the previous chapter. As matter of fact
the value of energy use is zero for the months on May to September and is almost the half of the average
month for April and October in which the hating system is active only for 15 days, and not the whole
month as for the others.
Of course the highest consumption is experienced in the coldest month which is January, this is due to
the really high transmission losses (the temperature in January goes below 0°C) and the low solar gains,
imposed by the low number of hours of sun exposure. This is due to the angle of the sun during the
winter, which also influences the shading that the other buildings provide onto the case study, reducing
the solar radiation coming into the building through the glazing area.
6.1.4 Heat gains
The heat gains of the case study building are a consequence of the input data, presented in the previous
chapter.
0
4
8
12
16
20
24
28
32
36
40
44
January February March April May June September October November December
Internal Gains Solar Gains Ventilation Losses
Transmission Losses Heating Demand
Figure 6-5: Monthly PE consumption for Heating Demand [kWh/(m2y)]
Figure 6-6: Heat Gains in terms of kWh/(m2y) and %.
20.50; 30%
37.22; 55%
6.40; 9%4.28; 6%
47.89984181; 70%
Solar
Internal
People
Equipment
Light
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In order to understand the behavior of the building in terms of positive impacts to the energy balance,
the heat gains calculated through the energy simulation of the study case have been studied and broken
down into the principal sources of gains.
The graph presented highlights the statement made before, the gains coming from the solar radiation
passing through the glazing part of the building, is similar to the ones coming from the internal sensible
and latent heat generated by the Equipment, Light and People present in the heated space. The values
related to the solar gains are relatively high for the climate of the city in which the building is located,
this is due to the high area of glazing part of the building, the fact that the glazing are located in all the
surfaces orientation and the high value of total solar factor “gtot” of the old windows present in the
building, an high gtot means that more solar radiation is transmitted to the inner spaces while less
percentage in reflected and blocked.
The value expressing the sensible and latent heat produced by the people inside the heated space
accounts for almost half of the heat gains of the building, this is in line with the hypothesis presented in
the input chapter, the high activity of students and the elevated number of people inside the space are
the major contributors.
6.1.5 Heat Losses
The analysis goes further in detail, focusing the attention on the variables that contribute to the
dispersion of heat from the case study building. For the analysis, the variables in discussion, are the
Ventilation and the Transmission Losses, which in the energy analysis of the building are balanced by
the sum of Internal Gains, the Solar Gains and the Energy received from the heating system
W.O; 25.6
W.U; 0.6W.G; 1.0
F.U; 2.6
F.G; 2.1
F.R; 8.6
R; 5.9W; 23.8
R.F; 3.9
T; 0.9
V; 17
I; 9 W.O-Walls vs Outside
W.U-Walls vs Unheated
W.G-Walls vs Ground
F.U-Floor vs Unheated
F.G-Floor vs Ground
F.R-Floor vs Roof
R-Roof
W-Windows
R.F-Roof Windows
T-Thermal bridge
V-Ventilation
I-Infiltration
Figure 6-7: Contribution in terms of % of the elements of the building to the global Heat Losses of the case study.
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The graph, as the caption says, represents the values in terms of % of the contribution of each element
to the global Heat Losses of the case study, this means that looking at the graph it’s possible to
understand the negative impact of each element taken into account in the energy balance of the case
study building.
The results highlights the similar behavior of the two case studies building ( recalling the §5.1.5), since
in both graphs the biggest contribution is represented by the elements in contact with the outside, and
the losses due to the infiltration rate. The external walls, “W.O.- Walls vs Outside”, are the elements
which have a bigger negative impact on the building’s performance, followed by the glazing part of the
building, “W-Windows”, as a matter of fact if we sum the % contribution of these two variable of the
building we have that more than 40% of the heat losses of the building comes from the outer envelope.
Taking in consideration this facts and data, the first idea that comes to mind is that the requalification
of the external wall and the glazing part of the entire building will be one of the most challenging part
of the energy retrofit, and on the other hand it will be one of the most significant energy-reduction work.
The high infiltration losses are due to the infiltration rate, presented in the input chapter, linked to the
air leakage of the energy-inefficient envelope of both parts of the building, in this case the absence of
the thermal insulation and the presence of and old bearing structure both in bricks, for each part of the
building, plays the biggest part in conjunction with the presence of old low-transmittance windows
through the entire case study building. Another aspects that contributes to the high value of infiltration
losses, is the fact that instead of natural ventilation, this is not controllable but it’s actually a phenomenon
to which the building is subjected to, therefore it is always present, no matter the occupancy of the space,
and it always affects the heating demand, while the natural ventilation is controlled by the users present
in the heated spaces, which will open the windows, letting natural ventilation, according the internal and
external conditions of the specific space. The infiltration losses and the losses by the outer envelope are
strictly connected, this is because the infiltration is based on the difference of pressure between the
inside and the outside of the heated space, and the pressure inside of the space is linked to the
permeability of the outer skin of the building and the ability of it to keep the designated pressure. The
definition of air permeability is “Infiltration air flowrate per unit surface area of the envelope, at the
reference pressure difference” therefore it’s easy to understand that it depends on the air tightness of the
building, determined by the envelope’s thermal performances. This basically means that with the
improvement of the envelope we will have a double benefit, since there will be an obvious reduction of
heat losses attributed to the envelope’s element and also a reduction coming from the infiltration losses,
due to the increase of air permeability through the addition of thermal insulation to the outer skin of the
case study building.
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6.1.6 Solar energy analysis
The solar analysis helps understand the interaction of the building, in this case the building’s envelope,
and the solar radiation coming from the sun, basically this analysis will show the pro and the cons of
letting inside the inner spaces the sun’s radiation. For the purpose of this analysis the solar radiation has
two opposite effect on the building’s performances, a positive one related to the heating solar gains and
a negative one related to the overheating of the spaces.
For the calculation of the heating energy demand the contribution coming from the solar radiation is
accounted as solar gains, therefore in this case the impact of the radiation coming through the envelope
and into the heated space is positive, a way to reduce the energy demand is actually to increase the solar
gains throughout the heating period. On the other hand, the solar radiation coming through the envelope
in the cooling period will increase the internal temperature of the heated spaces giving rise to a possible
phenomenon of overheating, in which the spaces’ temperature may tend to unbearable internal
conditions for the users.
In this case considering that in the school building there are 4 different glazing’s orientation, it has been
represented the average solar radiation incident on the wall according to the different orientation. The
results presented in the graph are interesting, the first peculiarity is the behavior of the South oriented
wall, which actually shows higher values of solar radiation in winter rather than in the mid and hot
season, this is due to angle of rotation of the sun, which in the summer is so high in the sky that irradiates
directly only the roof of the building. As a matter of fact the amount of solar radiation hitting the surfaces
is equal for all the directions in the cooling season.
0
50
100
150
200
250
300
350
[W/m2] South East West North
January February March April May June September October November December
Heating Season Cooling Season Heating Season
Figure 6-8: Daily average incident solar radiation [Wh/m2] calculated on the 4 different orientation.
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In order to fully understand whether the solar radiation are a benefit or a malus for the case study, it has
been highlighted the two different period, the heating period in which more the radiation the better and
the cooling period in which high solar radiation usually means discomfort. Considering the cooling
season the orientation with the highest values of solar radiation are the South-West and South-East,
which means that the space which will have walls oriented like this will have chance to encounter
overheating, on the other hand this two orientation have the highest values also for the heating period,
as seen before.
The screenshots of the solar analysis run through the dynamic simulation software, attached above, helps
understand the results and commented presented earlier about the output coming from the analysis
related to the incident solar radiation hitting the different vertical component of the case study building.
The comments related to the incident solar radiation graph, are confirmed by these screenshots in which
is possible to see the annual solar radiation [kWh/m2] hitting the envelope of the building. The elements
oriented towards the South direction (first on the left) are the ones with the biggest values, while the
ones oriented towards North present the lowest values.
In this case is also visible the shading action of the surrounding buildings towards the case study
building, and the effect that they have on the incident solar radiation. The four different screen shots
refer to the 21 of March, day of the Spring Equinox, at midday.
Figure 6-9: Solar analysis radiation on S, E, N, W oriented wall (from left to right)
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6.2 Internal Comfort
The factors that determine the quality of the internal space related to the improvement of students’
apprenticeship are related to measurable values.
6.2.1 Thermal Comfort
Thermal comfort is the condition of mind that expresses satisfaction with the thermal environment and
is assessed by subjective evaluation (ANSI/ASHRAE Standard 55) [43]. With regard to thermal
comfort, the final figure to be assessed is the degree of well-being perceived by occupants in the space
considered. The useful tool for this purpose is constructed by theoretical principles and measurement
methods for predicting the perceived thermal sensation of people. The 98 eometr-hygrometric
environment is described through appropriate physical quantities with standardized methodologies [46].
The size considered for the comfort temperature is the operating temperature:
𝑇𝑂𝑃 = ℎ𝑟 ∗ 𝑇𝑚𝑟 + ℎ𝑐 ∗ 𝑇𝑎
ℎ𝑐𝑟
Where:
hr is the radiative exchange coefficient;
Tmr is the mean radiant temperature;
Ta is the air temperature;
hc is the convective exchange coefficient;
hcr is the adduction coefficient.
According to the EN ISO ISO 7730 [45] and the ASHRAE 55 [43] show as comfort condition:
Top = 20-24°C, UR= 30-70 % in the heating period;
Top = 23-26°C, UR= 30-70 % in the cooling period.
The hours of discomfort are the ones in which the temperature of the heated space, during the cooling
period, is higher than the comfort limit set at 26 °C, as presented before.
Compared to the studies related to the definition of the parameters for improving the I performance, the
set-point temperature in the winter period should be maintained within a range of 20 to 22 ° C. However,
in mid and summer seasons, indoor air temperature can’t be controlled but experimental evidence in the
field of temperature-related learning has shown that a temperature of 22-24 °C improves performance,
even though temperatures ranging from 25 to 32 °C are permitted in the British guidelines and at the
national level no recommended values are stated.
In order to understand the internal thermal conditions of the heated space classified as classrooms inside
the case study building, it has been calculated -in percentage %- the discomfort hours through the energy
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simulation software used presented before.
The graph shows, as seen in the caption,
the total percentage of discomfort hours
during the cooling season, which means
that it has been calculated the ratio in
percentage between the total hours of a
normal school day – 8 a.m. to 18:00 p.m.
– and the hours, in this range, in which
the temperature is higher than the
defined cooling comfort temperature, set
at 26 °C. In this calculation it has been
considered only the school days – Monday to Friday – in which the heating system is off, not taking in
consideration the summer period in which the school is not used – from 1st May to 30th June – in order
to have more accurate and realistic outputs.
The classrooms have been divided by exposition, from the small plan previously presented it’s easy to
understand the differentiation of the classrooms, by floor (first number of the code for the classrooms –
C.X) and by orientation (second number – C.X.X.). The differentiation by orientation has been done in
order to see the effect of the sun exposure on the classroom, in the cooling period the building is free
floating (no conditioning system is on) and the temperature of the inner spaces depends mainly on the
sun radiation hitting and passing through the glazing part of the envelope, the amount of radiation
depends on the incident angle on the surfaces, linked to the height and the orientation of the specific
surface.
The Figure 6-10 gives a global view on the thermal condition on the different classrooms, all of them
present low percentage of discomfort hours. This is in line with the predictions, since the climate of
Buštěhrad is rigid, and the simple opening of the windows (simulate through the use of the dynamic
analysis software) counterbalance the mild climate of the months of May and June. The results presented
in this case study are much better than the one presented for the case study in Lecco (§5.2.1), as said
before this is due to the differences climatic conditions of the two buildings.
6.2.2 Adaptive thermal comfort criteria
In order to have a more global and complex view on the thermal comfort of the inner spaces of the
building, it can be used the adaptive thermal comfort model as showed in §5.2.2.
In order to calculate the adaptive thermal comfort applied to the case study building it’s needed to follow
the instructions and limitations imposed by the CIBSE Guide A [29], in particular the TM52 [52]. In
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
C.0.1 C.1.1 C.2.1 C.0.2 C.1.2 C.2.2 C.0.3 C.1.3 C.2.3 C.1.4 C.2.4
South-West South-East North-East North-West
Figure 6-10: Discomfort hours % of the classrooms, dived by
glazing’s orientation, during the cooling season.
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this case though, the really low amount of hours of discomfort hours, and the mild temperature recorded
inside the classrooms in the cooling room, made useless the study of the adaptive thermal comfort of
the inner spaces of the case study in Buštěhrad.
6.2.3 Indoor air quality
The Indoor Air Quality (IAQ) represents an important aspect for what concern the public health. The
consequences of an unhealthy work environment could lead to a serious health problem to the people
inside the space, as called Sick-Building Syndrome (SBS) which consists in a collection of symptoms,
such as headache, eyes, nausea, concentration issues, fatigue and particularly sensitivity to the odors.
To ensure a correct development of the lecture and to not occur in unpleasant effects, the amount of
carbon dioxide level inside the closed space should be always verified.
The standard provides some threshold that doesn’t have to be overtaken to avoid dangerous level of
CO2 inside the space. Of course the main parameter that influenced the level of carbon dioxide is the
ventilation rate, of which the natural regulation provides some standard values according to different
typologies of educational buildings. The level of carbon dioxide in a closed space are reported below in
compliance with the regulation ISO 7730 [15]:
- normal outdoor level of CO2: 350 – 450 ppm;
- acceptable outdoor level: lower than 600 ppm;
- odor problems: 600 – 1000;
- ASHRAE standards: 1000 ppm;
- light drowsiness: 1000 – 2500 ppm;
- light health issues: 3000 – 5000 ppm;
- health problems: > 5000 ppm.
All values above 1000 ppm must be avoided to not encounter health problems. In general, ventilation
rates should keep CO2 concentrations below 1000 ppm for acceptable indoor air quality conditions.
0
20
40
60
80
100
C.0.1 C.1.1 C.2.1 C.0.2 C.1.2 C.2.2 C.0.3 C.1.3 C.2.3 C.1.4 C.2.4
South-West South-East North-East North-West
% <600 ppm 600<CO2<1000 ppm 1000<CO2<2500 ppm
Figure 6-11: Distribution in percentage of the CO2 level present in the classroom, divided by orientation.
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Fortunately none of the classroom taken in exam present hourly values for CO2 concentration higher
than 2500 ppm, this means that in no circumstances the users of the heated space will have some
noticeable effect on the health. For all the classes studied, the hours during which the concentration is
less than 600 ppm represent the highest percentage, this means the student during the school days will
usually feel some discomfort due to the concentrations values, but they will never feel anything more
dangerous than discomfort. This output is really important for the internal condition of an heated space,
especially if the heated space is a classroom, since in this case the users need the maximum comfort
possible in order to increase their learning performances, therefore during the presentation of the
optimization cases it will be encountered the possibility to reduce, or at least don’t increase, the CO2
concentrations inside the classrooms.
6.2.4 Daylight Analysis
Natural daylight is one of the most important aspect of the design of buildings, a special attention is
given to the evaluation of the daylight in the public building and in this case, the aim of this section is
to focus the attention on the natural lightning in educational buildings. A good natural daylight promotes
better didactical outcomes of students, better learning and teaching performances and improvements of
the physiological and psychological well-being and comfort of people inside the space. A good design
of daylight is also an advantage for energy saving, limiting the amount of hours in which the electric
lightning is switched on.
Firstly, a general study of the illuminance on the work place has been evaluated, in order to see if the
values of illuminance where in compliance with the one suggested by the reference standards [28]. The
parameters analyzed are:
- Hourly Daylight Illuminance, expressed in lux
- Useful Daylight Illuminance (UDI), which is defined as the amount of time (expressed as a
percentage) in which, at a certain point, the internal amount of illuminance fall in the range
between 100 and 2000 lux.
- The average daylight factor (DLF), defined as the ratio between the mean lightning inside the
space and the outdoor lightning due to the sky, expressed in %.
The comfort level is necessary to permit people to have an efficient working execution, and that the
activities designated for that particular space are not compromised due to an excessive or low amount
of lux. The daylight factor is a parameter introduced in order to evaluate the natural lightning inside a
closed space, and aim to guarantee an optimal daylight illuminance inside the space. On the inside of a
closed room, the illuminance distributed along the geometry is characterized by three parameters: the
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amount of light coming from the outside (sky), the contribution of the light due to reflections of the light
rays hitting the external surfaces and the reflection due to the multiple reflections of the light in the inner
space. In the evaluation of the illuminance conditions, the analysis is made considering the most
improper case which consists of absence of direct solar radiation, called overcast sky. Imposed the cast
sky as the optimal condition for the calculation and the working plane at an height of 0.85 m from the
ground, the ratio between the internal and external illuminance should be constant and it is independent
on days and hours of the year: the mean daylight factor represents a value, expressed as a percentage,
defined as the ratio between the illuminance calculated at a certain point on the inside and the
illuminance measured on the outside on a horizontal surfaces without obstacles.
In order to not limiting the calculation, the DLF is
taken as a mean of more points inside the room
aiming to evaluate the global illumination inside
the space. The values of the daylight factor could
vary according to the destination of use, as
reported in the table below. Some threshold value
are defined in the standards The value of the
daylight factor and of the illuminance, as
explained before in § 5.2, for educational building
is defined by the EN ISO 12464-1 [28]. As seen
in the table, all the spaces classified as classrooms
present in the case study building pass both of the
verification imposed by the standard, either for the
minimum for the average value of Daylight Illuminance and the minimum for the average value of the
DLF. Daylight Illuminance (UDI) has been calculated, which consists in the percentage of time in which
the sensor point on the grid registers a value of illuminance in the range between 100 and 2000 lux,
which are the minimum and maximum threshold of daylight illuminance allowable in the space. Then,
as a further analysis the Over lit Percentage has been evaluated, which consist in the harm illuminance,
hence the percentage of time in which the sensor over-takes the value of 2000 lux.
The graph represents the percentage, during the school days (as delimited in the previous chapter), of
time in which the value of the illuminance calculated inside each of the classroom falls inside the 4
ranges taken in consideration: less than 100lux, defines an inefficient lighting comfort; in between 100
and 500 lux, which represents the range in which the daylighting can be considered acceptable; in
between 500-2000 lux, which is the best range for illuminance inside a classroom; and over 2000 lux,
representing the Over lit percentage.
Orientation Class DLF Illuminance
% > 3 % [lux] > 300 lux
South-West
C.0.1 3.4 V 415 V
C.1.1 3.4 V 415 V
C.2.1 3.4 V 415 V
South-East
C.0.2 3.3 V 400 V
C.1.2 3.3 V 400 V
C.2.2 3.3 V 400 V
North-East
C.0.3 3.3 V 400 V
C.1.3 3.3 V 400 V
C.2.3 3.3 V 400 V
North-West C.1.4 3.4 V 412 V
C.2.4 3.4 V 412 V
Table 6.1: DLF and Illuminance values for each class
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The results presented are in accordance with the ones coming from the DLF analysis presented in the
Error! Reference source not found., the classes have similar behaviors, for all of them the range with t
he highest percentage is represented by the on in which the illuminance falls in between 100 and 500
lux, which as said previously guarantees lighting comfort.
Confronting the two case studies, with the help of the Figure 5-14, it’s clear that the classes of the case
study located in Buštěhrad have a similar behavior, regardless the orientation and the floor, while in
Lecco there are big differences. Nevertheless the classrooms of both the case studies present acceptable
values for DLF and UDI, therefore this won’t be an issue during the retrofit work presented in this
master thesis.
0102030405060708090
100
C.0.1 C.1.1 C.2.1 C.0.2 C.1.2 C.2.2 C.0.3 C.1.3 C.2.3 C.1.4 C.2.4
South-West South-East North-East North-West
% <100 lux 100-500 lux 500-2000 lux >2000 lux
Figure 6-12: UDI -%- of the classrooms, divided by orientation.
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CHAPTER 7
7 Envelope Optimization
The optimization of the envelope will not be based on a step by step approach but it will be focused on
single interventions, this means that listed all the possible intervention that can be possibly done on the
envelope, they will be taken separately and each one of them will be analyzed in various aspects such
as: technical, energetical, environmental and economical.
7.1 Design philosophy
For the technical point of view, taking in consideration the output data of the diagnosis previously done
on the buildings, there will be presented for each intervention different case scenarios, in order to fulfill
all the possible needs of the building. This different scenarios will also have different environmental
impact on the building, so that it can be analyzed the differences between normal practice materials and
natural material through the retrofit of the building. In order to study the environmental impact of each
scenario it has been considered for each material composing the building solution introduced in the
specific intervention, the amount of Embodied Energy “EE” and the Embodied Carbon “EC”. Basically
it will be done a life cycle inventory analysis, collecting data about the embodied and operational energy
of the different scenarios, according to the ICE [53] database.
The EE is defined as the total primary energy consumed from direct and indirect processes associated
with a product or service and within the boundaries of cradle-to-gate. This includes all activities from
material extraction (quarrying, mining), manufacturing, transportation and right through to fabrication
processes until the product is ready to leave the final factory gate.
The EC is the sum of fuel related carbon emissions (i.e. embodied energy which is combusted but not
the feedstock energy which is retained with the material) and process related carbon emissions (i.e. non
fuel related emissions which may arise, for example, from chemical reactions). This can be measured
from cradle-to-cradle, cradle-to-grave, or from cradle to grave. The ICE data is cradle-to-gate.
The energetical aspect will be tackled presenting the energy savings given by the single intervention,
and in a similar way the economical one will be estimated through the payback period of the investment.
Therefore the choice of the case scenario will be done trying to find the more interesting solutions
according to the output of the diagnosis previously developed on the case study building.
The interventions considered during this thesis work are done in a deep retrofit perspective, therefore
the standard used as reference is the EPBD 2 [14], which is than acknowledged by the Italian Ministry
with the Ministerial Decree of the 26th June 2015, and in the Czech Republic with the ČSN 73 0540
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[54]. The standard gives a limitation on the thermal transmittance of the elements on which the deep
retrofit will be focused on, those limitations will be seen later on in the analysis of the specific
operations. Since the limit values for the two European countries are a little bit different, in order to
have a more global view and make the comparison of the two cases studies easier, it has been decided
to take as final limitation value the thermal transmittance defined as “Recommended” by the Czech
regulation ČSN 73 0540 [54].
Structure Element Required U Italy
[W/(m2K)]
Required U CZ
[W/(m2K)]
Recommended U
[W/(m2K)]
External Wall 0.28 0.30 0.25
Roof 0.24 0.24 0.20
Attic 0.24* 0.30 0.20
Basement ceiling 0.3625* 0.40 0.32
Slab on ground 0.29** 0.45 0.25
Ground-contact walls 0.28** 0.45 0.25
* In the case of structures delimiting the heated space towards unheated rooms, the transmittance limit
values must be respected by the transmittance of the structure divided by the correction factor of the
heat exchange between heated and unheated environment, as indicated in the UNI TS 11300-1 [55]
standard in tabular form. This applies for both the attic located in the under-roof space, and the basement
located in the underground level. Therefore the correcting value that has to be used is:
Adjacent space Correction factor btr,U
Underground floor
- With external openings 0.8
Attic floor
- High ventilation rate of the attic (e.g. roofs covered with tiles or other
discontinuous roofing materials) without felt or wall covering
1.0
** In the case of structures facing the ground, the transmittance limit values must be respected by the
equivalent transmittance of the structure taking into account the effect of the ground calculated
according to UNI EN ISO 13370 [27].
As it can be seen in the Table 7.3 the limit U values for glazing area, considering a deep retrofit
intervention, are set in both case studies to 1.40 W/(m2K). This is in disagreement with the comparison
of the two regulations done in the previous paragraphs, in which the Italian limitations for each of the
intervention presented were highlighted as more strict.
Table 7.1: Thermal transmittance U limitations in Italy and in CZ, defined by national regulations
Table 7.2: Correction factor btr,U from EN ISO 12831:2006
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Structure Element Required U Italy
[W/(m2K)]
Required U CZ
[W/(m2K)]
Recommended U
[W/(m2K)]
Glazed Surfaces 1.40 1.40 1.20
As previously done, the set limitation that will be used will be the one equal to the U value recommended
in the Czech regulation [54] U equal to 1.20 W/(m2K), which is more strict respect to the required one.
This will guarantee high energy performance to the building’s envelope and also and improvement in
the indoor thermal comfort, decreasing the infiltration and increasing the homogeneity of the internal
temperatures.
Another standards’ limitation is the one setting the solar transmission factor “ggl+sh“ for glazing
components so that: ggl+sh ≤ 0.35.
7.1.1 Technical Analysis
As matter of fact thanks to the analysis of the internal condition, in the § 3.2.1, it has been highlighted
a problem of overheating inside a small number of classrooms therefore in the design process this has
been taken into account. Considering that the case study does not involve the presence of a mechanical
cooling mechanism, the addition of thermal insulation on the outside wall, for the cooling period, won’t
directly imply an increase of comfort inside of the heated spaces, but it will decrease the transpiration
of the external wall structure. In order to quantify the effect of the different thermal insulation applied
to the wall in terms of cooling comfort, it has been considered the thermal inertia of the specific material
used as thermal insulation.
The thermal inertia is the capacity of a building component:
- To attenuate the fluctuations of the internal ambient temperature due to internal and external
heat loads varying in during the day(solar radiation, equipment, artificial light and people);
- Accumulate the heat and release it after a certain number of hours over time.
The summer period, undervalued in the European energy certification of buildings, involves high
consumption for cooling and discomfort conditions in our temperate climates, and must therefore be
taken into account. Being characterized by variable thermal loads around the day and more clearly than
in winter, the summer season calls into question the thermal inertia of the building envelope. The thermal
inertia can be described through two dynamic thermal property:
- Periodic thermal transmittance 𝑌𝑖𝑒 = 𝑈 ∗ 𝑓𝑑 [W/(m2K)];
- Internal thermal capacity Cip [kJ/(m2K)].
Table 7.3: Glazing’s thermal transmittance limitations in Italy and in CZ, defined by national regulations [21] [54]
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The Yie is the product between : the attenuation
factor fd, which represents the ratio between
the amplitude of the exiting thermal flow and
the entering one into a structure element; and
the stationary thermal transmittance U.
The periodic thermal transmittance represents
both the degree of damping of the thermal
wave coming from the outside and the phase
displacement φ of the same wave, which
represents the time which the peak of the
maximum external temperature takes to go completely through a structure element of the specific
building.
The Cip periodic internal thermal capacity, calculated as Yie, according to UNI EN ISO 13786 [42]
represents the capacity of a building component to accumulate the thermal loads coming from inside.
The higher the value of the Cip (mass placed inside), the greater the heat accumulation. The accumulation
of internal thermal loads by a wall makes it possible to keep surface temperatures at acceptable levels,
i.e. with fluctuations and limited values throughout the day, in favor the environmental comfort
conditions for summer.
7.1.2 Economic Analysis
In order to have an economic view of the proposed interventions it has been decided to analyze the
payback time of the investment, based on the intervention’s cost and the energy cost savings obtained
through the years, in order to make this case more global as possible some hypothesis and simplifications
had to be done. The cost of the intervention was calculated in a simple straightforward way, considering
the cost of the materials and of the installation summed with a fixed percentage of increase due to
expenses directly related to the works done for the preparation and use of the construction site (i.e.
scaffoldings, preparation of the land, etc.). This cost is than summed up to the cost of the operational
energy bore every year by the school system considering the new interventions done on the envelope.
This sum is than subtracted to the operational energy cost bore by the school system without the new
intervention, defining the economic benefit of the investment.
𝐵€ = (𝐶0 + ∑ 𝐶𝑟
𝑛
𝑖=0
) − ∑ 𝐶𝑛𝑟
𝑛
𝑖=1
The variables presented are:
- B€ the economic benefit of the investment;
att
enu
ati
on
n
phase displacement
thermal wave
Figure 7-1:Displacement and attenuation of a thermal wave
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- C0 the initial cost of the investment made;
- Cr the operational energy cost of the retrofitted building for each year;
- Cnr the operational energy cost of the non-retrofitted building for each year;
- I the year considered.
In this way it’s pretty clear that when the economic benefit B€ is equal to 0, the “i” of the formula, which
stands for the year considered in the calculation, represents the “payback year”, that can be defined as
the year in which there is no difference between pre and after retrofit in terms of costs.
𝐵€ = (𝐶0 + ∑ 𝐶𝑟
𝑛
𝑖=0
) − ∑ 𝐶𝑛𝑟
𝑛
𝑖=1
= 0
In the calculations, all the cost related to the maintenance have been neglected. Since in this case the
will is to highlight the difference between the cost before and after the works, it has been decided to
assume that the costs related to the maintenance don’t change from the pre and after retrofitted works.
In addition in order to make the case study useful for any country and any application field, in the costs
and the savings no cost deduction coming from the government have been considered, and on top of this
the cost of the investment has been considered without any kind of rate of interest, assuming that the
cost will be bore entirely in the first year.
In order to have comparable results, it has been decided to present the results exclusively in euros, so it
has been adopted a standard rate change from Czech crowns to Euros equal to: 25 CZK = 1 €.
7.1.3 Environmental analysis
Concerning the environmental part, it has been decided to discover and understand the impact of the
retrofitting intervention on the GHG emissions of the buildings. In order to do this, it’s necessary to
introduce the Be, which represents the benefit in terms of GHG emissions of the intervention.
𝐵𝑒 = (𝐸𝐶𝑚 + ∑ 𝐸𝑟
𝑛
𝑖=0
) − ∑ 𝐸𝑛𝑟
𝑛
𝑖=1
The environmental benefit Be is defined by:
- ECm the embodied carbon, from cradle to gate, of the material used for the intervention;
- Er the GHG emission, in terms of CO2e, of the retrofitted building for each year;
- Enr the GHG emission, in terms of CO2e, of the non-retrofitted building for each year;
- I the year considered.
𝐵𝑒 = (𝐸𝐶𝑚 + ∑ 𝐸𝑟
𝑛
𝑖=0
) − ∑ 𝐸𝑛𝑟
𝑛
𝑖=1
= 0
In this way it’s pretty clear that when the emission benefit Be is equal to 0, the “i” of the formula, which
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stands for the year considered in the calculation, represents the “return year”, that can be defined as the
year in which there is no difference between pre and after retrofit in terms of GHG emissions.
As done for the economic part, also in this case some assumptions had to be made in order to simplify
the calculations and to clarify the goal of the work. The goal of this analysis was to understand the
differences between the different case scenarios in terms of GHG emissions. For this reason as emission
produced by the retrofitting intervention it has been considered only the EC of the material used, without
considering the emission cause by the transportation and the installation, so that the comparison could
be focused only on the different materials used in the different cases.
7.2 Case study “Lecco”
According to the needs and the criticalities highlighted through the energy analysis previously presented
in chapter 5 in this section it will be presented the different case scenarios chosen for each retrofit
intervention proposed and considered feasible/energetically beneficial, for the case study school
building located in Lecco.
7.2.1 External thermal insulating coating
The coating of the outer envelope of the
building with thermal insulation, is one of
the most common procedure done in order
to decrease the amount of energy
consumption of the specific building. This
technique allows the building also to
receive a complete makeover of the facades
considering that the thermal coating
includes a new external finish, this can contribute to spark up the aesthetic value of obsolete buildings.
Therefore since the building will radically change its look the external coating of the facades is
considered an invasive procedure. For this reason this technique can’t be applied to all of the facades of
the historical part of the building built at the beginnings of the 20th century. The façade of the old part
of the building oriented towards North-West, which is the only one that is exposed on the street, has
aesthetic architectural value therefore its appearance can’t be modified meaning that no thermal
insulation can be applied. For this type of façade it will be presented later on in the script an internal
insulation solution.
Figure 7-2: NW facade of the old part of the school building
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7.2.1.1 Design choice
Analyzing the output data of the energy diagnosis presented in the §5, it has been decided to present
three different scenario of intervention for this specific procedure. The three different scenario will
change in terms of thermal insulation material and external finish, for the remainder it will be all the
same, as matter of fact in all the scenario the element structure will have the same thermal transmittance
set at 0.25 [W/(m2K)], as defined in Table 7.1.
Scenario Insulation λ d s Finishing
Material [W/mK] [kg/m3] [cm] Material
EXT. 1 EPS with graphite 0.031 35 11 Acrylic
EXT. 2 Rockwool 0.034 115 12 Breathable
EXT. 3 Wood Fiber 0.04 145 14 Breathable
As said in the previous paragraph the three scenarios will have different environmental and economic
impact, this is visible through the Table 7.5 here presented.
Through the table it’s easy to understand the differences between the three presented scenarios, as the
first solution with EPS represents the most common one therefore has the lowest price and highest
environmental impact, while on the opposite the third solution with Wood fiber has an higher cost and
a low environmental impact.
Scenario
Recent part Old part
EE EC Cost EE EC Cost
[MJ/m2] [KgCO2/m2] €/m2 [MJ/m2] [KgCO2/m2] €/m2
EXT. 1 372.12 14.97 44.37 409.33 16.47 44.38
EXT. 2 241.49 11.13 83.44 263.44 12.14 85.38
EXT. 3 216.78 8.29 99.99 233.45 8.93 102.25
The values of EE and EC are taken by the ICE [53], therefore they only refer to cradle-to-gate, this
means that this analysis is purely theoretical and it based on a simple collection of data related to the EE
and EC of the single material composing the building component solution presented, without taking in
consideration the data related to the installation and the processes techniques.
As matter of fact thanks to the analysis of the internal condition, in the § 5.2.1, it has been highlighted
a problem of overheating inside a small number of classrooms therefore in the design process this has
been taken into account. Considering that the case study does not involve the presence of a mechanical
cooling mechanism, the addition of thermal insulation on the outside wall, for the cooling period, won’t
directly imply an increase of comfort inside of the heated spaces, but it will decrease the transpiration
of the external wall structure. In order to quantify the effect of the different thermal insulation applied
Table 7.4: Thermal coating scenario considered for the retrofit intervention located in Lecco
Table 7.5: Environmental and economic analysis of the different scenarios
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to the wall in terms of cooling comfort, it has been considered the thermal inertia of the specific material
used as thermal insulation.
7.2.1.2 Thermal inertia of the case scenario
For this intervention, considering that it is based on the application of material insulation on the outside
of the envelope, the thermal inertia of the different scenarios will be compared based only on the
different values of Periodic thermal transmittance Yie defined by the different material used for each
scenario. Here are presented the values defining the dynamic properties of the different case scenarios
previously defined in the table below.
It’s easy to understand the big overcome of adding thermal insulation to the external face of the walls,
since all of the scenarios present better thermal values compared to the base case, no matter the kind of
material used as thermal insulation. The lower is the value expressing the attenuation fd and the lower is
the amplitude of the thermal flow entering the building component, and at the same time the lower is
the value of the periodic thermal resistance Yie and the higher are the value of the phase displacement φ
and the damping. In addition to that, it’s possible to see the differences and the similarities of the two
construction techniques used in the two different part of the building, as already presented this is due
to different age of construction.
It’s easy to see that the construction element used in the old part made of stone has better dynamic
properties’ value, due to the higher thermal mass respect to the one used in the recent part of the building
made of a double layer of bricks with an air cavity in between. The Table 7.65 is given by the National
Guide Lines [18], and it highlights that the retrofitted building components in all of the case scenarios,
and in all of the part of the building analyzed can be classified as “excellent” from a summer thermal
performance point of view. In addition to this it has to be said that the National Guide Lines [18] sets
also, the limit for the value of the periodic thermal transmittance Yie equal to a maximum of 0.10
[W/(m2K)], therefore all the scenarios are below the limit.
Case
Recent part Old part
fd φ Yie fd φ Yie
- [h] [W/m2K] - [h] [W/m2K]
Base 0.216 11.43 0.246 0.147 11.78 0.341
1 0.04 15.59 0.010 0.034 15.14 0.008
2 0.036 17.22 0.008 0.031 17 0.008
3 0.025 20.58 0.006 0.02 20.67 0.005
φ fd Performance
φ > 12 fd < 0.15 excellent
10 < φ < 12 0.15 < fd < 0.30 good
8 < φ < 10 0.30 < fd < 0.40 average
6 < φ < 8 0.40 < fd < 0.60 sufficient
φ < 6 fd < 0.60 mediocre
Table 7.6: Dynamic properties of the different case scenarios Table 7.7: Limit values set by standard [18]
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7.2.1.3 Heating consumption savings
In this paragraph it will be analyzed the perks of doing the specific intervention explained in the previous
paragraph. In this case the intervention is the application of an external thermal coating onto the facades
of the case study building exception made for the protected façade (as presented in § 7.2.1) and the
perks are represented by the energy and economic savings and the GHG emission reductions.
Scenario
Heating
Primary Energy Energy cost GHG emissions Reduction
[kWh/m2y] [€] [tonCO2] [%]
Base 233.61 17974.10 45.04 -
Ext. Insulation 163.06 12581.87 31.53 30%
From the table it’s easy to understand the profits, speaking about heating consumptions, coming from
the application of the thermal insulation as previously explained. The reduction obtained through the
application of the thermal insulation is equal to 30% of the initial value, this refers to all of the values
presented in the table, so for the: primary energy, energy cost and the GHG emissions.
7.2.1.4 Economic and environmental impact
The cost of the intervention was calculated in a simple straightforward way, considering the cost of the
materials and of the installation taken from the “Prezziario Lombardia”, which is the pricelist for civil
works in the Lombardy region, summed with a 20% of increase due to expenses directly related to works
needed to be done in order to make the application of the thermal insulation possible (i.e. scaffoldings,
preparation of the land, etc.).
Table 7.8: Heating reductions obtained with the external thermal coating
-60
-40
-20
0
20
40
60
80
100
120
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
[k€]
yrs
EXT 1 EXT 2
EXT 3 Payback time
Figure 7-3: Representation of the payback time -x axis- and of the economic benefit -y axis- of each of the case
scenarios chosen for the external thermal insulation, Lecco
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The graph of the Figure 7-3 describes the payback time through a simple x-y diagram, on the y-axis it’s
represented the B€ economic benefit, while on the x-axis it’s represented the years corresponding to the
specific economic benefit. Through the description previously made, it’s easy to understand that the
year in which the value of B€ equal to 0, therefore there’s no benefit and neither a malus, corresponds to
the payback year, which represents the year in which the cost of the investment has been recouped.
The most convenient scenario is represented by the use of EPS with graphite, which as seen before
represents one of the cheapest material used for the thermal coating insulation interventions, to which
corresponds a payback time equal to 6 years. On the other hand the use of Wood fiber insulation material
will lead to the doubling of the payback years since in this case it will be equal to more than 12 years.
Concerning the environmental part, it has been decided to discover and understand the impact of the
retrofitting intervention on the GHG emissions of the buildings.
From the graph is easy to understand that the choice of the material has a small impact on the GHG
emission of a building, therefore choosing as insulation a synthetic material like EPS over a Rockwool
doesn’t mean necessarily that the choice would have a bigger impact on the environment. As said the
graph here presented was done just to have a comparison method between the environmental impact of
the materials used for the retrofitting work, so since the emission due to other important construction
site activities( i.e. transportation and application) have not been considered, the Figure 7-4 can’t give
the real output of how many years the retrofit will take in order to equalize the emission of the building
before the specific work.
7.2.2 Internal thermal insulation
In this paragraph it will be presented a retrofit operation that can be done in order to insulate a protected
façade from the inside of the specific building. As highlighted before in the §7.2.1, the peculiarity of
-10-505
10152025303540455055
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
[tonCO2]
yrs
EXT 1 EXT 2 EXT 3
Figure 7-4: Representation of the return year -x axis- and of the emission benefit -y axis- of each of the case
scenarios chosen for the external thermal insulation, Lecco
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this case study building is the presence of
an architecturally protected façade whose
appearances can’t be modified, and so for
this reason the thermal coating in the
previous intervention, could be applied on
the entire envelope exception made for the
protected façade of the old part of the
building which overlooks the main street.
Basically the intervention can be seen as an application of thermal insulation panels directly onto the
protected façade walls from the inside of the building, therefore no aesthetic restrictions have been
violated.
7.2.2.1 Design choice
As done for the external thermal insulation coating intervention, also in this case it has been considered
3 different intervention scenarios, done with 3 different thermal insulation materials. This is done
because one of the goal of the work here presented is to show the possible energy retrofit intervention
applicable to the specific building, studying the different scenario through various technical aspects.
The three different scenario taken in consideration, as said before, will have an equal thermal
transmittance set at 0.25 [W/(m2K)], they are presented through the Table 7.9.
Scenario Insulation λ d s Finishing Cost
Material [W/mK] [kg/m3] [cm] Material €/m2
INT. 1 Polyester Fiber 0.034 50 12 Plasterboard 37.87
INT. 2 Rockwool 0.035 70 12 Plasterboard 45.73
INT. 3 Calcium Silicate 0.039 115 14 Internal Paint 52.00
For the case scenario “INT. 1” the intervention is based
on the application of calcium silicate insulation panels,
through the use of adhesive and levelling layer, onto the
façade from the inner space. The choice of this
insulation material is given by the fact that the
installation will be done from the inside and the space
insulated is a classroom, therefore it will be very
important to contrast the high production of water vapor
coming from the students and guarantee a moderate IAQ. Calcium silicate based panels ensure a
comfortable indoor climate thanks to the active regulation of air humidity and at the same time warmer
Table 7.9: Internal thermal insulation scenario considered for the retrofit, Lecco
Figure 7-5: NW facade of the old part of the school building
Figure 7-6: Calcium silicate insulation panels
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interior surfaces. Their pH value of 10 acts as an anti-mold, therefore an excellent material for the
restoration of humid spaces. The calcium silicate-based panels are glued with adhesives that guarantee
the capillary connection between the wall and the panel. Of course, the final wall paint must also be of
similar quality because it is really a wrong painting that ruins the intervention and the high quality of
the material just laid.
The application method is different for the case scenario “INT. 2” and “INT. 3”, where the insulation
has been applied through a dry wall system. The insulation of the walls takes place with the installation
of a metal framework made of C-profile mullions and transoms which will guide the application of the
thermal insulation panels, covered by a dry plasterboard wall. The choice of rockwool for the case
“INT.2” is given by the will to give the possibility to exploit the Mass-spring-Mass effect of the dry
system presented, in order to consider a thermal-acoustic insulation scenario. In the “INT.3” it is
presented a low-cost solution defined by the use of an eco-friendly insulation material obtained by the
reuse of PET plastic, in form of polyester fiber insulation panels. This material is completely non-toxic
and it present itself as free from any allergic substance or harmful to health, resistant to molds, moisture,
rodents and insects, free from any substance and chemical treatment and free from resins and glues in
general.
7.2.2.2 Thermal inertia of the case scenario
As presented in the § 7.2.1.2, the envelope will be evaluated also for its summer performances through
the comparison of the thermal inertia of the wall for the solution proposed for each case scenario. In this
case since the intervention involves the application of material insulation from the inside of the spaces,
the thermal inertia of each scenario will be compared through both of the dynamic properties presented
before:
- Periodic thermal transmittance 𝑌𝑖𝑒 = 𝑈 ∗ 𝑓𝑑 [W/(m2K)];
- Internal thermal capacity Cip [kJ/(m2K)].
The Cip periodic internal thermal capacity, calculated as Yie, according to UNI EN ISO 13786 [56]
represents the capacity of a building component to accumulate the thermal loads coming from inside.
The higher the value of the Cip (mass placed inside), the greater the heat accumulation. The accumulation
of internal thermal loads by a wall makes it possible to keep surface temperatures at acceptable levels,
i.e. with fluctuations and limited values throughout the day, in favor the environmental comfort
conditions for summer.
It’s easy to see that the construction element used in the third case scenario has better dynamic
properties’ value, due to the higher thermal mass of the calcium silicate base panel insulation respect to
the dry wall system used in the second and in the third case scenario.
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Phase displacement Attenuation Performance
φ > 12 fd < 0.15 excellent
10 < φ < 12 0.15 < fd < 0.30 good
8 < φ < 10 0.30 < fd < 0.40 average
6 < φ < 8 0.40 < fd < 0.60 sufficient
φ < 6 fd < 0.60 mediocre
The Table 7.109 is given by the National Guide Lines [18], and it highlights that the retrofitted building
components in all of the case scenarios, and in all of the part of the building analyzed can be classified
as “excellent” from a summer thermal performance point of view. In addition to this it has to be said
that the National Guide Lines [18] sets also, the limit for the value of the periodic thermal transmittance
Yie equal to a maximum of 0.10 [W/(m2K)], therefore all the scenarios are below the limit.
7.2.2.3 Criticalities of the intervention
The application of thermal insulation material from the inside perimeter of a building, is a retrofit
intervention which brings to light a lot of risks and significant detail that have to be taken care of.
For this case study the application on the perimeter walls of thermal insulation from the inside space
gives birth to a number of critical thermal bridges, caused by the fact that two different modus operandi,
i.e. internal and external thermal coating of the envelope, have been considered coexisting for the retrofit
of the building.
In the Annexes all the possible thermal bridges occurring in this case of intervention have been studied,
and for each of them it has been presented a “simple” solution capable of limiting the value of the linear
thermal transmittance Ψ so that the construction elements solutions presented in the work comply with
the thermal transmittance -U- limitations imposed in the § 7.1.
The interventions made to reduce the impact of the thermal
bridges occurring, are the punctual application of internal
pre-finished insulation panels applied onto internal walls,
and the application on each floor of the old part of the
building of a suspended ceiling with the addition of a rigid panel insulation material. The pre-finished
insulation is made of pre-coupled boards of PF (polyester fiber) and plaster board with an integrated
vapor barrier, while the suspended ceilings is made of a rigid rockwool panel with a plasterboard
finishing. In order to have a more comprehensive view of the economic investment needed for the global
intervention, all of the processing techniques listed before, i.e. the thermal bridge solution interventions,
have been taking into account in the global cost of investment.
7.2.2.4 Heating consumption savings
Scenario fd φ Yie Cip
- [h] [W/m2K] [kJ/m2K]
Base case 0.147 11.78 0.341 79.9
INT. 1 0.064 14.7 0.014 18
INT. 2 0.063 14.92 0.015 18.3
INT. 3 0.049 17.14 0.012 29.2
Table 7.10: Dynamic properties of the case scenario Table 7.11: Limit values set by standard [18]
Thermal bridge Intervention
Cost
€/m2 €
Suspended insulated ceiling 29.38 19727.49
Insulated dry wall 25.37 4262.16
Table 7.12: Cost of thermal bridge intervention
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In this paragraph it will be analyzed the perks of doing the specific intervention explained in the previous
paragraph. In this case the intervention is the application of an internal thermal coating onto the protected
façade (as presented in § 7.2.2) and the perks are represented by the energy and economic savings and
the GHG emission reductions.
Scenario
Heating
Primary Energy Energy cost GHG emissions Reduction
[kWh/m2y] [€] [tonCO2] [%]
Base 233.61 17974.10 45.04 -
Int. Insulation 139.64 10774.78 27.00 40%
From the Table 7.13 is easy to understand the profits, speaking about heating consumptions, coming
from the application of the thermal insulation as previously explained. The reduction obtained through
the application of the thermal insulation is equal to 40% of the initial value, this refers to all of the values
presented in the table, so for the: primary energy, energy cost and the GHG emissions. This results
brings to light the importance and how easy it is to reduce the impact of a building through simple and
aimed interventions, such the coating of the envelope of the case study building.
7.2.2.5 Economic impact
The difference between the cost of the different case scenarios is small, as seen in the Table 7.15,
therefore the different use of the insulation material presented won’t affect the total cost of the
investment.
From the Table 7.15 and Table 7.14 is easy to understand that the cost, in euro, bore only for the
intervention needed to withstand the thermal bridges has a similar amount respect to the cost bore for
the insulation of the external wall for each case scenario. Actually in this case the cost of the works
related to the thermal bridges account for almost 45% of the total investment needed to withstand the
studied intervention, for this reason the amount needed to bear the total investment of the intervention
doesn’t change depending on the insulation material chosen for each case scenario.
For the case study presented the retrofit intervention here showed of the application of thermal insulation
onto the perimeter wall from the inner spaces is not a standalone intervention but it has to be combined
with the application of the external thermal coating insulation presented in the § 7.2.1.
Table 7.13: Heating reductions obtained with the internal thermal coating, Lecco
Scenario Insulation Cost
Material €/m2 €
INT. 1 Polyester Fiber 37.87 29803.30
INT. 2 Rockwool 45.73 31010.74
INT. 3 Calcium Silicate 52.00 31972.69
Thermal bridge Intervention
Cost
€/m2 €
Suspended insulated ceiling
29.38 19727.49
Insulated dry wall 25.37 4262.16
Table 7.14: Cost of thermal bridge intervention Table 7.15: Cost of the different case scenarios intervention
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For this reason it has been decided to create 3 different
case scenario presenting the combination of the two
intervention presented until now. The first scenario
represents the cheapest and most used combination of
the materials used for the insulation from the outside and
the inside, while the third one represents the most expensive and performing combination.
In order to have an economic view of the proposed interventions it has been decided to analyze the
payback time of the investment, based on the intervention’s cost and the energy cost savings obtained
through the years, in order to make this case more global as possible some hypothesis and simplifications
had to be done. The cost of the intervention was calculated in a simple straightforward way, considering
the cost of the materials and of the installation taken from the “Prezziario Lombardia”, which is the
pricelist for civil works in the Lombardy region, summed with a fixed percentage of increase due to
expenses directly related to the works done for the preparation and use of the construction site (i.e.
scaffoldings, preparation of the land, etc.).
The graph of the Figure 7-7 represents the different economic benefit coming from each of the case
scenarios presented in the Table 7.16.
The case scenario 1, which represents the cheapest one, has a payback time equal to almost 9 year, this
means that before 10 years from the end of the construction the cost of the investment will be equalized
and the money saved thanks to the reduction of the energy needs will go directly into the cashflow of
the case study building. On the other hand the case 3, which represents the most expensive one, has a
payback time equal to 14 years, therefore even the most expensive case scenario has a decent payback
time, highlighting the great benefits descending from the retrofit intervention regarding the vertical
-100
-80
-60
-40
-20
0
20
40
60
80
100
120
140
160
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
[k€]
yrs
INT 1 INT 2
INT 3 Payback time
Table 7.16: Different combination case scenarios
Scenario
Insulation
Material
EXT. INT.
EXT+INT 1 EPS with graphite Polyester Fiber
EXT+INT 2 Rockwool Rockwool
EXT+INT 3 Wood fiber Calcium Silicate
Figure 7-7: Representation of the return year -x axis- and of the emission benefit -y axis- of each of the case
scenarios chosen for the internal thermal insulation
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opaque envelope of the case study building.
7.2.3 Attic Insulation
The old part of the case study school building presents
an unheated space between the roof and the last heated
slab, which is easily accessible. In this paragraph it will
be proposed the insulation of the last heated slab of the
old part of the building through the use of insulation
materials in form of rolls and panels put on the floor of
the attic, so that the insulation performs its benefits only
for the heated space, avoiding heating unused spaces
such as the attic itself. On the other hand, as seen in the general description of the building in the chapter
2, the recent part of the building constructed in the late ’60 doesn’t have this type of space, but the last
heated slab corresponds to the roof. In this case it has been proposed a non-invasive intervention
consisting in the application of thermal insulation onto the last heated slab from the inside space of the
building. This means that in both part of the building it is proposed the thermal insulation of the last
heated slab without intervening on the roof structure.
7.2.3.1 Design choice
The positive aspect of the building that has to be exploit in this case, is the presence in the old part of an
unheated space between the roof and the last heated slab, defined as attic, and the fact that it is easily
accessible, even though unfortunately this space is not present in the recent part of the building. The
attic can be used in two different ways, as a buffer zone which means that it will be considered as an
unusable space and on the other hand it can be used as storage or functional room. For this reason it has
been decided to present two different feasible intervention for the thermal insulation of the attic, one
will concern only the thermal insulation of the last heated slab while the other one will include the
refurbishment of the flooring of the attic, so that this space can be qualified as usable. On the other hand
both of the interventions will be combined with the thermal insulation of the last heated slab of the recent
part of the building from the inside of the building, through the use of a suspended ceiling.
The choice of mineral wools is given by the fact that the insulation is going to be applied in inside spaces
therefore in this case the use of man-made vitreous fiber guarantees the use of a non-toxic and bio
soluble material which will not harm the users. The application of the insulation will be done on the last
floor therefore it will be useful to exploit the thermal and acoustical insulation of the mineral wools.
Scenario Insulation λ d s Flooring Cost
Figure 7-8: Attic in the old part of the building
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In a technical point of view,
considering the old part of the
building, the first intervention can be
properly described as the thermal
insulation of the last heated slab
through the simple and only application on the slab extrados of a roll of rockwool insulation, so that the
attic space and its accessibility can be exploited at the lowest price and labor. In the second option it is
proposed the refurbishment of the attic space, through the use of a glass wool rigid insulation topped
with a dry system flooring, so that the surface can be walkable and the space classified usable.
The intervention proposed for the
slab of the recent part of the
building consists on the insulation
of the last heated slab of the
structure through the application
of a mineral material thermal insulation protected from a plasterboard suspended ceiling applied directly
on the slab intrados.
The choice of rockwool rolls is driven by the fact that it’s the most used intervention whenever there is
a not walkable attic which is accessible and allows an easy manual laying, even though in some cases
wood fiber can also be useful (especially for insulation against summer heat). It is sufficient to lay on
the floor the insulation that may be protected by means of a vapor barrier placed between the insulation
and the floor itself.
For the refurbishment of the attic floor the intervention consists on the application of a separation layer
between the smoothed surface and the rigid glass wool insulation, laid through the use of a wooden
support system, on top of which is needed to lay a walkable layer which will also work as load
distribution. The flooring is made through the use of a dry system composed of a gypsum fiber double
levelling layer topped by a gypsum flooring.
Material [W/mK] [kg/cm3] [cm] Material €/m2
ATT. 1 Rockwool
roll 0.038 26 0.17 - 14.57
ATT. 2 Glasswool
panel 0.033 125 0.14
Dry system
70.24
Table 7.17: Case scenarios of attic retrofit in the old part of the building
Scenario Insulation λ d s Finishing Cost
Material [W/mK] [kg/cm3] [cm] Material €/m2
ATT. 1 Rockwool
panel 0.034 60 0.15 Plasterboard 62.7
ATT. 2 Glasswool
panel 0.032 75 0.14 Plasterboard 77.7
Table 7.18:Case scenarios of attic retrofit in the recent part of the building
Figure 7-9: Roll insulation of the attic
Dry flooring
Insulation
Support system
Figure 7-10: Rigid panel attic insulation
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7.2.3.2 Heating consumption savings
In this paragraph it will be analyzed the perks of doing the specific intervention explained in the previous
paragraph. In this case the intervention is the application of an internal thermal insulation onto the slab
extrados, for the old part of the building, and on the slab intrados for the recent one (as presented in §
7.2.3) and the perks are represented by the energy and economic savings and the GHG emission
reductions.
Scenario
Heating
Primary Energy Energy cost GHG emissions Reduction
[kWh/m2y] [€] [tonCO2] [%]
Base 233.61 17974.10 45.04 -
Attic Insulation 202.79 15647.17 39.21 13%
From the Table 7.19 is easy to understand the profits, speaking about heating consumptions, coming
from the application of the thermal insulation as previously explained. The reduction obtained through
the application of the thermal insulation is equal to 13% of the initial value, this refers to all of the values
presented in the table, so for the: primary energy, energy cost and the GHG emissions. The percentage
of energy savings is in line with the thermal losses analysis presented previously in § 5.1.5, and is quite
reasonable considering that this intervention will concern a quite small surface area.
7.2.3.3 Economic Impact
The cost of the intervention was calculated in a simple straightforward way, considering the cost of the
materials and of the installation taken from the “Prezziario Lombardia”, which is the pricelist for civil
works in the Lombardy region, summed with a fixed percentage of increase due to expenses directly
related to works needed to be done in order to make the application of the thermal insulation possible
(i.e. scaffoldings, preparation of the land, etc.).
The graph presented in the Figure 7-11 represents the economic analysis of the two case scenarios
presented in the § 7.2.3.1. As explained before it has been considered a cost percentage increase due to
construction site works, therefore for this analysis it has been considered a 10% increase of the cost for
the case scenario of rockwool and 20% for the second one of the glass wool taking in consideration the
fact that the second intervention involves an higher labor rate. The results highlights the economic
benefit of the first case scenario, in which the insulation is made with rockwool material in both part of
the building, as matter of fact the payback time is in this case equal to 7 years while for the second
scenario it doubles up to almost 14 years. This means that the scenario has to be chosen considering the
importance of the refurbishment over the cost of the intervention.
Table 7.19: Heating reductions obtained with the attic thermal insulation
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7.2.4 Roof insulation
In this section it will be analyzed the possible case scenarios concerning the refurbishment of the roofing
structure of the two part of the cases study building. As it can be seen from the Figure 7-12 and the
Figure 7-8 the two roofs of the parts of the building are completely different
-40
-30
-20
-10
0
10
20
30
40
50
60
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
[k€]
yrs
ATTIC 1 ATTIC 2
Payback time
Figure 7-11: Representation of the return year -x axis- and of the economic benefit -y axis- of each of the case
scenarios chosen for the attic insulation
Figure 7-12: Google earth capture of the roof of the two parts of the case study school building
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As matter of fact as already highlighted in § 7.2.3 the old part of the building presents an attic space
placed on top of the last heated slab which is covered by a clay tiles hip roof supported by a wood beam
structure, on the other hand the recent part of the building has a typical concrete slab structure roof with
on top a corrugated metal sheet. Therefore it will be presented different case scenarios for this
intervention applicable on each part of the building roof.
This intervention is usually applied whenever the roof is directly in contact with the heated space, i.e.
in the recent part of the building, or/and when there’s the will to transform an attic into an habitable
space, i.e. the attic space in the old part of the building. This means that the intervention for the old part
of the building has to be combined with the insulation of the attic slab presented in the § 7.2.3.1, in order
to insulate all the exposed elements.
7.2.4.1 Design choice
The first design choice has been the decision of neglecting the possibility of refurbish the roofs
transforming them into green roofs or in ventilated ones.
The option of the green roof has been neglected due to the high costs of the intervention and the fact
that it will represent a peculiar work therefore it’s applicability in a large scale would be missing, not
considering also the fact that it will completely transform the exterior of the existing building.
In ventilated roofs the natural cavity, which clearly separates the covering layer from the underlying
insulating layer, facilitates the activation of “ascensional convective motions”, which subtract most of
the heat that would otherwise be transmitted to the underlying layers, and allows moisture to escape
without compromising the thermal insulation power of the underlying layers and the air space itself. In
order to activate this mechanism, the outside air must enter the gap in the gutter and must exit the ridge
through a vent element. In this way in winter the ventilation leaves the insulating material dry, avoiding
condensation, in summer the fresh air, which penetrates from the eaves line, heats up in the air space
and becomes lighter and comes out from the ridge, subtracting heat from the structure. Ventilated roofs,
compliant with the UNI 9460 and UNI 8627 standards, can produce a lowering of the temperature after
the hours of summer insolation and improve the thermal comfort of the attic, especially in cases where
it has been chosen to renovate it to transform it into an attic.
Generally ventilated roofs are applied to make the attic rooms habitable, so considering that the old part
of the building presents an uninsulated attic space, it will be impossible to convert it to habitable,
therefore this choice has been discarded. Concerning the recent part of the building, as said before the
ventilated roof must have a minimum flow section in order to activate the convective motions (UNI
9460) given by the thickness of the air cavity and the inclination and length of the roof, so considering
that the roof has a slope of approximately 5% an high air cavity thickness would be needed, defining
this solution unfeasible.
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For this reason it has been decided to propose a requalification of the existing roof of both of the parts
of the building, consisting on the application of a thermal insulation layer, included all the protection
materials, underneath the existing roof cover. This means that it will be temporarily removed the roofing
covering structure and then re-placed on top of a new supporting structure laid on a new insulation layer
consisting of a different thermal insulation material for each case scenario.
As it can be seen from the Table 7.20 the different case scenarios change only on the type of thermal
insulation material used under the roof structure. As insulation materials it has been decided to present
the same ones used throughout the previous proposed interventions.
7.2.4.2 Thermal inertia of the case scenario
For this intervention, considering that it is based on the application of material insulation on the outside
of the envelope, the thermal inertia of the different scenarios will be compared based only on the
different values of Periodic thermal transmittance Yie defined by the different material used for each
scenario. Here are presented the values defining the dynamic properties of the different case scenarios
previously defined in the Table 5.2.
Scenario
Old part Recent part
fd φ Yie fd φ Yie
- [h] [W/m2K] - [h] [W/m2K]
ROOF 1 0.915 2.87 0.181 0.073 13.5 0.015
ROOF 2 0.515 8.18 0.1 0.048 17.18 0.01
ROOF 3 0.24 12.18 0.049 0.028 20.14 0.006
The lower is the value expressing the attenuation fd and the lower is the amplitude of the thermal flow
entering the building component, and at the same time the lower is the value of the periodic thermal
resistance Yie and the higher are the value of the phase displacement φ and the damping. In addition to
this it has to be said that the National Guide Lines [18] sets also, the limit for the value of the periodic
thermal transmittance Yie equal to a maximum of 0.10 [W/(m2K)], therefore all the scenarios are below
the limit.
It’s easy to understand that the results related to the old part of the building are not satisfactory. This is
Intervention Old part Recent Part
Scenario Insulation λ d s Cost s Cost
Material [W/mK] [kg/cm3] [cm] €/m2 [cm] €/m2
ROOF 1 EPS 0.031 40 14 74.27 13 69.53
ROOF 2 Rockwool 0.036 140 16 89.98 15 89.36
ROOF 3 Wood fiber 0.038/0.042 145/205 17 96.78 17 106.78
φ fd Performance
φ > 12 fd < 0.15 excellent
10 < φ < 12 0.15 < fd < 0.30 good
8 < φ < 10 0.30 < fd < 0.40 average
6 < φ < 8 0.40 < fd < 0.60 sufficient
φ < 6 fd < 0.60 mediocre
Table 7.21: Dynamic properties of the different case scenarios Table 7.22: Limit values set by standard [18]
Table 7.20: Case scenarios of the roof insulation intervention in Lecco
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due to the fact that roof structure is supported by punctual wooden beams that
are not considered in the thermal analysis of the structure, therefore the only
layer opposed to the thermal dispersions is represented from the new inserted
thermal insulation layer. In this case it’s more clear the difference given by
the choice of different thermal insulation, as matter of fact only the
application of a wood fiber insulation layer would guarantee good thermal inertia properties and
therefore would represent the optimal technical solution.
7.2.4.3 Heating consumption savings
In this paragraph it will be analyzed the perks of doing the specific intervention explained in the previous
paragraph. In this case the intervention is the application of an internal thermal insulation onto the slab
extrados, for the old part of the building, and on the slab intrados for the recent one (presented in § 7.2.4)
and the perks are represented by the energy and economic savings and the GHG emission reductions.
Scenario
Heating
Primary Energy Energy cost GHG emissions Reduction
[kWh/m2y] [€] [tonCO2] [%]
Base 233.61 17974.10 45.04 -
Roof Insulation 205.41 15849.68 39.71 12%
From the Table 7.24 is easy to understand the profits, speaking about heating consumptions, coming
from the application of the thermal insulation as previously explained. The reduction obtained through
the application of the thermal insulation is equal to 12% of the initial value, this refers to all of the values
presented in the table, so for the: primary energy, energy cost and the GHG emissions. The percentage
of energy savings is in line with the thermal losses analysis presented previously in § 5.1.5, and is quite
reasonable considering that this intervention will concern a quite small surface area.
Comparing the results here presented with the one given for the attic insulation in § 7.2.3.2 it’s possible
to see that the two interventions basically give the same savings output but they need a much different
amount of money to be done, the choice of choosing one over another has to be done carefully analyzing
all the pros and cons of each of them.
7.2.4.4 Economic Impact
The cost of the intervention was calculated in a simple straightforward way, considering the cost of the
materials and of the installation taken from the “Prezziario Lombardia”, which is the pricelist for civil
works in the Lombardy region, summed with a 20/25 % percentage of increase due to expenses directly
related to works needed to be done in order to make the application of the thermal insulation possible
Old Part Performance
ROOF 1 mediocre
ROOF 2 average
ROOF 3 good
Table 7.23: Performances
of the old part roof
Table 7.24: Heating reductions obtained with the attic thermal insulation in Lecco
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(i.e. scaffoldings, preparation of the land, etc.).
The graph in the Figure 7-13 describes what has already been said before, that this is an high cost
intervention, therefore before pursuing this type of works it has to be considered all the other low cost
scenario previously presented in the attic insulation intervention, § 7.2.3. As matter of fact the solution
ROOF 1 which represent the cheapest case scenario has a payback time equal to 15 years, this remarks
the high costs of this type intervention.
7.2.5 Basement Insulation
In this section of the work presented it will be analyzed the insulation, from the inner spaces, of the
unheated space underneath the heated space of the case study building.
As already seen in § 2.2/3.2 the recent part of
the building does not have any unheated space
under the classrooms, as matter of fact beneath
them is located the gym which takes up the
ground and the underground floor, while on the
other hand the old part of the building presents
an unheated basement located underground
directly underneath the entrance and the
classrooms of the ground floor level. The ceiling
of the basement located in the old part of the building is visible from the Figure 7-14. It’s easy to
understand that the option of applying thermal insulation onto the basement’s ceiling from the inside
it’s not an everyday procedure but it takes an high amount of effort.
Figure 7-13: Representation of the return year -x axis- and of the economic benefit -y axis- of each of the case
scenarios chosen for the roof insulation
Figure 7-14: Basement of the old part of the building
-80
-60
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-20
0
20
40
60
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
[k€]
yrs
ROOF 1 ROOF 2
ROOF 3 Payback time
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7.2.5.1 Criticalities of the intervention
As previously said, this intervention involves only the old part of the building, where the critical analysis
is focused on the ceiling of the basement, which is made of a brick vault.
It’s clear that the application of thermal insulation material from
the basement itself onto the curved ceiling it’s an unfeasible
intervention, a solution could be the one of crafting a tailored
aluminum sub-structure which will help the positioning of the
curved flexible thermal insulation material, as it can be seen in
Figure 7-15. This solution would end up to be way too expensive
and complex than all of the other retrofit intervention proposed,
as matter of fact through the thermal losses chart presented in the
§ 5.1.5 it’s possible to see that the heat dispersed through the basement ceiling accounts for the 4% of
the total dispersion losses of the building through the envelope, therefore this intervention has been
neglected.
So considering that the insulation can’t be applied from the unheated space, the only remaining solution
would be the one of applying the thermal insulation onto to the floor of the ground level, so that the heat
would stay in the heated zones without dispersions towards the unheated underground. But also this
scenario is complex, due to the fact that the structure of the ground floor slab is made of a brick barrel-
vault constructed in the beginning of the 1900 (as all the old part of the building), therefore it will be
difficult to interact with it.
An option could be the one of removing the existing floor and the concrete levelling screed underneath
it in order to replace it with a thermal concrete levelling layer with on top a thermal insulation layer and
a new flooring system. This option will interfere with the structure of the vault slab, therefore a structural
analysis has to be done before going further in the study of the proposed solution, this means that it will
be necessary to strengthen the existing slab with a composite slab. Clearly this is an unfeasible
intervention for the purposes of this thesis work therefore it won’t be taken in consideration.
The last chance would be the one of applying thermal insulation directly onto the existing floor,
enhancing its thermal properties without increasing the load borne from the slab. This could be done
with the application of innovative thermal insulation material with an high thermal conductivity such as
Aerogel, so that the limit thermal transmittance imposed by the standard can be achieved with a low
thickness insulation layer.Here is presented how the new slab of the ground floor level will look, after
the retrofit proposed with the aerogel insulation. Unfortunately the problem in this case is represented
from the high costs of the material, as matter of fact the aerogel solution presented would cost
approximately 250 €/m2 just for the materials, without taking in consideration the costs related to the
Figure 7-15: Vault aluminum structure
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application, and the resulting additional costs due to the all the craft work needed for the joints
connecting the new floor with the existing vertical walls
Insulated Ground floor slab 0.37 U [W/m2K] 0.32
Component Thickness Conductivity Resistance
[-] [m] [W/mK] [m2K/W]
Slab 0.23 0.71 0.324
Levelling layer 0.06 1.4 0.043
Existing floor 0.02 0.72 0.028
Aerogel panel insulation 0.035 0.015 2.333
Vapor barrier 0.003 0.17 0.018
Floating Floor 0.02 0.6 0.033
It’s unreasonable to think that a school may look to an high cost solution like this, considering also the
small impact it would have on the energy savings (§ 5.1.5), therefore also this scenario has been
neglected.
The goal of this thesis work is to present feasible and low-key retrofit intervention applicable to a large
scale of buildings, with similarities to the case studies presented, therefore as briefly explained with
some examples it has been decided not to present any case scenarios for this type of intervention,
considering it unrelated to the topic of this work.
7.2.6 Ground-contact element insulation
The last intervention analyzed is the one taking in consideration the thermal insulation of the structure
elements that are in contact with the ground. The old part of the case study building presents an unheated
underground level used as storage, therefore it will be useless to think to insulate the walls and the floors
of this space considering that insulating an unheated space won’t guarantee any evident thermal benefit
for the upper heated spaces. On the other hand the recent part of the building presents a gym which takes
up two floor of the building, the ground floor and also the underground floor. This means that the
insulation of the walls and of the floor in contact with the ground would directly affect the energy needed
to heat the space and thus decreasing the consumption of gas.
The underground level of the recent part of the case study building is a gym, and as already seen in §
2.3.3.1 the heating system is independent and completely detached from the central heating system of
the building. Therefore it has been proposed to insulate all the partitions of the gym of the school in
order to create a box, in which the system can be turned on only for a couple of hours and then the heat
would be kept into the heated box without interaction with the boundary conditions.
Figure 7-16: Aerogel horizontal insulation
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7.2.6.1 Design choice
The intervention will lean towards the complete thermal insulation of the heated space classified as a
gym, so it won’t be affected from the surrounding anymore. This means that the insulation work will be
separated in:
- thermal insulation of the ground-contact slab;
- thermal insulation of the ground-contact walls;
- thermal insulation of the ceiling adjacent to an heated space.
From the heat losses diagram presented in § 5.1.5 it can be seen that the heat dispersions attributed to
the inefficient thermal properties of the structure elements of the gym, is relatively low and it can be
accounted to more or less 3 % of the total dispersions of the envelope of the entire building. For this
reason this type of intervention is actually recommended whenever there’s an independent space, as this
one, and there’s the will to upgrade it making it self-sustained.
The fact that this intervention most reasonably won’t have a big impact on the energy consumptions of
the building, has led the design choice of the intervention previously listed. As matter of fact the choice
has been directed towards low cost solutions present on the building market right now, without taking
in consideration multiple case scenario as done before.
Component Insulation λ d s Finishing Cost
Material [W/mK] [kg/cm3] [cm] Material €/m2
Ground-contact slab XPS insulation 0.032 35 4 Linoleum flooring 25.24
Ground-contact wall Polyester fiber 0.034 50 6 Dry wall system 31.35
Heated ceiling EPS 0.031 33 4 Suspended ceiling 23.34
For the thermal insulation of the floor facing the ground, it has been proposed to cover the actual flooring
with a rigid panel of XPS insulation, in order to guarantee excellent thermal properties combined with
mechanical resistance, on top of which it will be laid a concrete screed as support to the new flooring
system. In this way it will be created a barrier between the floor of the heated space and the underlying
ground, guaranteeing the appropriate amount of mechanical resistance needed in high impact
environment such as the gym.
For the wall in contact with the ground it has been proposed a simple solution, already analyzed before,
consisting on the application of thermal insulation panels made of polyester fiber directly onto the
vertical walls, protected by a dry wall system. It is obtained from the recycling of PET plastics, free
from any substance allergic or harmful to health, unaffected by mold, moisture, rodents and insects, free
of any substance and chemical treatment and free of resins and glues in general. The use of this material
is really important in this case considering the possible humidity coming from the adjacent ground, and
the fact that the users of this space will be children.
Table 7.25: Component solutions for each of the presented energy retrofit interventions
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Concerning the insulation from the above heated space represented by classrooms it has been decided
to adopt the economic choice of a plasterboard suspended ceiling with the application of rigid panels of
EPS insulation, in order to guarantee high thermal insulation at a low cost. In this case it could have
been considered also the use of a mineral wool insulation suspended ceiling in order to separate the two
environment also in terms of acoustics, since the noise coming form the gym could bother the students
located on the above classrooms, but the high cost of this particular solution combined to the low energy
impact of the entire intervention has classified this type of intervention unrealistic for the case study
represented.
7.2.6.2 Heating consumption savings
In this paragraph it will be analyzed the pros of doing the specific intervention explained in the previous
paragraph. In this case the intervention is the application of thermal insulation onto the perimeter
partitions of the gym located in the recent part of the building (presented in §7.2.6), and the perks are
represented by the energy and economic savings and the GHG emission reductions.
Scenario
Heating
Primary Energy Energy cost GHG emissions Reduction
[kWh/m2y] [€] [tonCO2] [%]
Base 233.61 17974.10 45.04 -
Gym Insulation 223.66 17592.37 43.24 4%
From the Table 7.26 is easy to understand the profits, speaking about heating consumptions, coming
from the application of the thermal insulation as previously explained. The reduction obtained through
the application of the thermal insulation is equal to 4% of the initial value, this refers to all of the values
presented in the table, so for the: primary energy, energy cost and the GHG emissions. As previously
said, this is in accordance with the heat losses analysis presented in § 5.1.5, therefore the low energy
impact was already expected.
7.2.6.3 Economic impact
The cost of the intervention was calculated in a simple straightforward way, considering the cost of the
materials and of the installation taken from the “Prezziario Lombardia”, which is the pricelist for civil
works in the Lombardy region, summed with a fixed percentage of increase, equal to 10 %, due to
expenses directly related to works needed to be done in order to make the application of the thermal
insulation possible (i.e. scaffoldings, preparation of the land, etc.).
Table 7.26: Heating reductions obtained with the thermal insulation of the gym
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The Figure 7-17 shows the payback time considered for the investment needed in order to complete the
retrofit work presented, of complete insulation of the gym located in the recent part of the building. The
return year for this investment is quite high, as it sums up to almost 30 years. This is due to the fact the
energy consumption reduction given by this work is relatively low, while the cost is actually high,
considering that it involves an high amount of surface. For this considerations this intervention can be
considered as an high risk investment, and the choice must be dictated by motivations that overcome the
economic disadvantages here presented.
7.2.7 Glazing optimization
Through the heat losses graph presented in§ 5.1.5, it’s easy to understand the impact that the glazing
surfaces of both of the parts of the building have on the global heat losses of the building coming from
the thermal inefficiency of the envelope. The losses coming from the windows of the old part of the
building account for almost 10% of the envelope’s losses and at the same time the ones of the recent
part account for another 10% of the losses, therefore the two sum up 20% of the losses, without
considering the infiltration losses strictly connected to the presence of leaky windows.
For this reason it has been decided to consider the complete refurbishment of the glazing areas of the
building, which includes the removal of the existing windows and the application of new insulating
windows.
-30
-20
-10
0
10
20
30
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
[k€]
yrs
Gym insulation Payback time
Figure 7-17: Representation of the return year -x axis- and of the economic benefit -y axis- of the work
representing the insulation of the gym
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7.2.7.1 Design choice
The design choice process in this particular case was really straight forward, as matter of fact a the end
of a first phase of data collection it has been decided to refurbish
the old windows of both of the building, replacing them with new
double glazing windows with a frame made of PVC.
This choice has been made considering the low prices of this
solution and the high thermal efficiency that can be achieved even
with market standard solution. In addition to that the PVC frame
comes in a great variety of color and texture, therefore it will be
really simple to recreate the image of the existing wood for the old
part of the building, thus not altering the aesthetic value of the
facades, and the aluminum for the recent part.
Technically the solution proposed consists of a double glazing
window, composed of 33.1/ 16 AR/ 33.1 LE. This means that is
made of a first security laminated float of 6 mm, with a 16 mm of
cavity filled with argon, and a final thermal and low emissivity float of 6 mm. Here it has been presented
the summary table that sums up all the thermal characteristic of the new glazing element:
Glazed Surface
Component Thickness
[-] [mm]
Low E float 6
Argon 16
Clear float 6
The thermal transmittance of the glazing proposed has been calculated through the UNI EN ISO 10077-
2 [43], as it can be seen in the annexes, with the additional help of the Pilkington spectrum online
software.
The choice of the low emissivity glass is given by the fact that with the use of this glasses, it is possible
to reflect inward part of the heat emitted as thermal radiation from the bodies contained in the inhabited
areas, considerably reducing the heat loss. The heat is reflected by the plate treated analogously to what
happens with a mirror that reflects purely luminous radiation.
The reduction of the radiative component of the double glazing is obtained by modifying the
spectrophotonic characteristics of the glasses, by means of the molecular deposition of particularly
selective oxides and metals capable of reflecting the purely thermal radiation. The low emissivity glass
is nothing more than an insulating glass, consisting of two or more plates spaced by one or more spacer
Frame Net U-value Net R-value
Type Transmittance Percentage [W/m2K] [m2K/W]
[-] [W/m2K] % 1.18 0.90
PVC 1.29 33
Figure 7-18: Chosen PVC glazing
Table 7.27: Glazing’s component thermal properties. Thermal transmittance of the proposed windows
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profiles. An insulating glass differs from a simple glass, because it is endowed with a particular
treatment, thanks to which it is possible to contain the dispersions.
Concerning the design of the window the proposed intervention is only the one just presented, but in
this work it has been decided to distinguish another energy retrofit work consisting on the refurbishment
of the od glazing area, as previously explained, and the installation of a mechanical ventilation system.
This is done in order to differentiate a stand-alone work on the windows, which will take in consideration
the only refurbishment of the glazing, from an integrated energy retrofit work in which the optimization
of the envelope is combined with technological solution assigned to the improvement of the internal
condition of the spaces.
The attention to indoor air quality in schools is even shown by the development of many guidelines and
regulations concerning the appropriate ventilation rates to be used for these kind of spaces. A common
experience, is that a big difference can be observed between required and real ventilation rates in these
so sensitive buildings. Many studies in the field have shown that ventilation in classrooms is too poor.
One reason is that often schools do not have mechanical ventilation system; furthermore, when
mechanical systems are installed, often their bad control leads to very expensive operation, so managers
are discouraged to use them, because big ventilation rates means big energy expense and noise, mainly),
taking care of safety and energy saving and having special attention to provide easy maintenance.
The design choices considered now “required” for an efficient home for winter heating and summer air
conditioning include controlled mechanical ventilation with heat recovery to guarantee the correct air
exchange without “ever” opening windows (and therefore saving on heating).
In this case study it will be analyzed a controlled mechanical ventilation with double flow heat recovery:
the stale air extracted from the humid rooms and the air taken from the outside, previously filtered, are
conveyed into a heat recovery unit that ensures the preheating of the renewal air avoiding the
contamination of the two flows. The most common type is the double flow controlled mechanical
ventilation which is characterized by having a double ventilation system, formed by separate distribution
channels:
- A duct controls and regulates air intake;
- the other is dedicated to extract air;
- the air flows in the two ducts are managed by separate electric fans.
The advantages of controlled mechanical ventilation systems with double-flow heat recovery are many
compared to the single-flow version. The main one is the ability to treat, filter, heat or cool outdoor air,
guaranteeing constant exchange and recovery of heat from exhausted air. The heat recovery allows you
to take advantage of all the advantages of ventilation, ensuring the low energy consumption of the
building. In case of restoration this solution would reduce consumption and increase the energy
classification of the building.
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Cross-flow heat recovery units are static recovery
systems, i.e. they have no moving elements. They
are characterized by the coupling of usually metal
plates, even if there are recoveries with paper
plates, suitably treated to stiffen them and make
them self-extinguishing. In the case of cross-flow
recovery with metal plates, it is possible to find on
the market units with plates in natural aluminum,
aluminum coated with special epoxy paints in case
of use in corrosive environments, but also with
stainless steel plates used in all those situations where maximum internal hygiene of the machine is
required or where the air passing through it has particularly high temperatures (200 ° C). Finally, in
some cases, to reduce costs or in the case of aggressive environments, plastics or even glass can be used.
The spacing between the plates is variable depending on the type of use. The heat transfer inside a cross-
flow recovery takes place through the heat transfer by convection, on both sides of the plate, and by
conduction through the thickness of the plate itself. Since the convective coefficients are much smaller
than the thermal conductivity of the plates, it follows that the efficiency of the heat exchange is not
substantially influenced by the thickness and the material with which the heat exchanger is made.
Usually the plate heat recovery units are equipped with a bypass damper which excludes part or all of
the outside air from the recovery treatment. This method of reducing the flow rate, is also used in case
of frost risk in winter, or much more simply to take advantage of free-cooling or direct-cooling, ie in all
those situations where the outside air has temperature conditions such as to be able to use it directly to
heat or cool the rooms, without requiring any further treatment. They are systems that allow yields of
40-70%, with the possibility of reaching even 80% in the case of use of heat recovery units with
countercurrent air flows, as it will be used in the case study.
Usually this efficiency is calculated as the ratio between the real and the theoretical difference between
the inlet and outlet temperatures (supposing that the flows have equal masses):
𝜂 =△𝑇𝑟𝑒𝑎𝑙
△𝑇𝑡ℎ=
𝑇𝑖𝑛𝑙𝑒𝑡−𝑇𝑒𝑥𝑡
𝑇𝑖𝑛𝑡−𝑇𝑒𝑥𝑡
To understand the importance of the heat recovery, here it has been brought a practical example:
- Externa air: -5 °C;
- Internal air: 20 °C;
- Inlet air: to determine.
∆Tth = 20 – (-5) = 25 °C; ∆Treal = η*(∆Tth) = η* 25 → Tinlet = η* 25 + Text.
So if it is considered an heat recovery with a η = 80%, than:
Figure 7-19: VMC's heat recovery scheme
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Tinlet = η* 25 + Text = 0.8* 25 + (-5) = 15°C.
With this simple example it’s easy to understand the impact of the presence of an heat recovery system,
which will help the existing generation system bear the heating load of the case study building.
For the reasons above explained, it has been decide to present two separate chances of glazing
optimization: one representing the refurbishment of the existing windows, and the other one including
also the installation of a controlled mechanical ventilation system “CMV”.
Scenario Windows Frame U Ventilation Cost
# glazing Material [W/(m2K)] Type €/m2 €
WIN 1 Double – low e PVC 1.18 Natural 340.00 83677.40
WIN 2 Double – low e PVC 1.18 CMV 465.00 133677.40
The costs presented are higher respect to the ones analyzed until now with the other retrofit solutions
studied. For the costs of the windows it has been considered included all the extra cost related to the
removal and disposal of the existing windows and the following installation of the new glazing,
including the labor needed for the possible brickwork job.
7.2.7.2 Technical Analysis
The technical analysis done on the glazing solution presented is deepened in the annexes regarding the
thermal analysis of the windows proposed.
Concerning the mechanical ventilation, the proposed solution has been considered only after some
technical considerations. First of all in order to have the idea of the machine that had to be installed
some hypothesis had to done. The will was to install a CMV system that could “replace” the opening of
the windows, therefore decreasing the losses for ventilation rationalizing the external flow, and decrease
the internal temperature and the CO2 concentration in the cooling season. Therefore it has been decide
to propose a CMV system with heat recovery and free-cooling switch included.
The free cooling technology is based on the fact that when the outside air reaches a lower temperature
than the internal one, before putting it into the environment, it interrupts the heat recovery function so
as to keep the thermal condition unchanged. The air introduced into the rooms is naturally fresh, for a
natural air conditioning and at no cost. It is particularly useful in mid-seasons or at night in summer
when the outside temperature is more comfortable. Taking advantage of the difference in temperature
between inside and outside, the free cooling technology optimizes the comfort of the rooms without the
use of air conditioning. The system autonomously depending on the external temperature brakes or starts
the activity of the heat exchanger, ensuring a constant well-being and an effective reduction in
consumption.
In order to have a better understanding of the economic impact of the installation of the machine, it has
Table 7.28: Case scenarios considered for the retrofit of the glazing areas of the case study building in Lecco
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been proceeded with the overall dimensioning of the mechanical ventilation, using the ISO 10339 [44].
As said the dimensioning is not accurate, but is done only to estimate the amount of inlet air needed.
Considering (from [44]):
- the “school” crowding index: ns = 0.50 pers/m2 ;
- the “school” external air flow: Qop = 7*10-3 m3/s per person;
- design air flow: Qd = 4800 m3/h;
- project air flow: Qpr = 5000 m3/h.
Basically the calculation has told that the CMV system that has to be installed has to have a capacity
equal to or greater than 5000 m3/h, meaning that the system will be expensive and also complex to
install.
After the considerations it has been decided to adopt this kind of technological solution onto the case
study building in order to admire and comment the possible effects on the energy and comfort parameters
of the heated spaces.
First of all the CMV should decrease the operative temperature of the internal spaces during the cooling
period, especially thanks to the free cooling system which is really effective in the mid seasons and for
night cooling, so that there’s an increase in the thermal comfort perceived by the users. In order to do
this it will be presented the TM52 calculation of adaptive thermal comfort criteria, presented in the §
5.2.2.1. Before presenting the results it will be reminded shortly what are the criteria and how they
interact with the thermal comfort of the spaces:
- Criterion 1 Hours of Exceedance (He): sets a limit for the number of hours that the operative
temperature can exceed the threshold comfort temperature (upper limit of the range of comfort
temperature) by one degree or more during the occupied hours of a typical non-heating season
(1st May to the 30th September).
- Criterion 2 – Daily Weighted Exceedance (We): deals with the severity of overheating, which
can be as important as its frequency, the level of which is a function of both temperature rise
and its duration. This criterion sets a daily limit for acceptability. To allow for the severity of
overheating the weighted Exceedance (We) shall be less than or equal to 6 in any one day.
Criterion 3 – Upper Limit Temperature (Tup): sets an absolute maximum daily temperature for
a room, beyond which the level of overheating is unacceptable. It is used to set an absolute
maximum value for the indoor operative temperature the value of ∆T shall not exceed 4°C. This
criterion covers the extremes of hot weather conditions and future climate scenarios.
The result of the technical memorandum is that a room that fails any two of the three criteria is classed
as overheated and thus fails the TM52 check.
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The graph from the Figure 7-20 can be easily compared to the one from the Figure 5-12, in which it has
been presented the same data, with and without the installation of a CMV system. It’s pretty clear how
profitable is the use of a mechanical ventilation, since from the graph it’s highlighted the fact tat in the
base case two of the classrooms didn’t pass the criteria verification, while with the CMW installation
all the spaces considered can be classified as in agreement with the current thermal comfort regulations.
The same comparison: Base case vs. Installation of CMV, can be done also considering the CO2
concentration inside the classrooms of the case study building.
It will be analyzed the calculation, presented in the § 6.2.3, and it will be compared with the calculation
applied to the case study including the installation of the CMV. Juts for a reminder it will be presented
the CO2 threshold for a classroom presented by the standard [45].
The standard provides some threshold that doesn’t have to be overtaken to avoid dangerous level of
CO2 inside the space. Of course the main parameter that influenced the level of carbon dioxide is the
ventilation rate, of which the natural regulation provides some standard values according to different
typologies of educational buildings. The level of carbon dioxide in a closed space are reported below in
compliance with the regulation ISO 7730 [15]:
- normal outdoor level of CO2: 350 – 450 ppm;
- acceptable outdoor level: lower than 600 ppm;
- odor problems: 600 – 1000;
- ASHRAE standards: 1000 ppm;
- light drowsiness: 1000 – 2500 ppm;
- light health issues: 3000 – 5000 ppm;
- health problems: > 5000 ppm.
The graph presented in the Figure 7-21 can be easily compare with the one presented in the Figure 5-13,
in order to have a first clear understanding of the impact of the CMV.
0.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
C.0.1 C.1.1 C.2.1 C.0.2 C.1.2 C.2.2 C.1.3 C.2.3 C.2.8 C.1.4 C.1.5 C.1.6 C.1.7
SE-SW SE NW-SW NW NE SW
Criteria 1 Criteria 2
Criteria 3 Limit-Criteria 1
Limit-Criteria 2 Limit-Criteria 3
Figure 7-20: Adaptive Thermal Comfort criteria check of the classrooms divided by orientation, considering the
installation of a CMV system. The verification has been done according to TM52
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Basically what can be seen is that the installation of a CMV system, as the one presented, leads to a
drastic reduction of CO2 concentration, bringing them to regulation’s limit. As it can be seen from the
graph, the percentage corresponding to the time in which the CO2 is less than 1000 ppm, accounts for
almost 80 % of the occupied hours, meaning that for the amount of time the concentration inside the
classrooms are lower than the limitation imposed by the ASHRAE. Nevertheless it’s possible to see that
in 20% of the hours in which the classes are occupied the concentration gets as high as 1200 ppm,
exceeding the limitations imposed by the ASHRAE but still guaranteeing an adequate indoor quality.
7.2.7.3 Heating consumption savings
In this paragraph it will be analyzed the pros of doing the specific intervention explained in the previous
paragraph. In this case the intervention is the complete refurbishment of the glazing area, and the
possible installation of a CMV system (presented in §7.2.7.1), and the perks are represented by the
energy and economic savings and the GHG emission reductions.
Scenario
Heating
Primary Energy Energy cost GHG emissions Reduction
[kWh/m2y] [€] [tonCO2] [%]
Base 232.94 17974.10 45.04 -
Glazing 171.06 13455.27 33.07 27%
Glazing + CMV 158.40 12222.39 30.62 32%
The Table 7.29 is clear on the energy results of the proposed intervention. The savings obtained on the
energy consumptions due to the thermal conditioning of the heated spaces of the case study building
through the replacement of the existing windows with updated insulating glazing accounts for 27% of
the total heating energy needs. These results are in agreement on what presented earlier in the § 5.1.5,
considering that it was supposed that the glazing area accounted for 20% of the thermal losses coming
0
20
40
60
80
100
C.0.1 C.1.1 C.2.1 C.0.2 C.1.2 C.2.2 C.1.3 C.2.3 C.2.8 C.1.4 C.1.5 C.1.6 C.1.7
SE-SW SE NW-SW NW NE SW
% <600 ppm 600<CO2<1000 ppm 1000<CO2<1200 ppm
Table 7.29: Heating reductions with the complete refurbishment of the glazing area and CMV combined, Lecco
Figure 7-21: Distribution in percentage of the CO2 level present in the classroom, divided by orientation and
considering the installation of a CMV system, Lecco
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from the envelope inefficiency.
The energy reduction gave by the installation of the CMV system is given by the fact that these
procedure will automatize the inlet of fresh air into the heated spaces. These means that ideally there
won’t be the necessity to open the windows anymore, considering that the inlet of extracted air from the
CMV will bear the needed air recirculation. So the energy savings will be attributed to the fact that the
won’t be any natural ventilation losses, and the losses due to the inlet of external air will be mechanically
controlled, therefore optimizing the process.
7.2.7.4 Economic Impact
The cost of the intervention was calculated in a simple straightforward way, considering the cost of the
materials and of the installation taken from the “Prezziario Lombardia”, which is the pricelist for civil
works in the Lombardy region, which include all the additional expenses directly related to works
needed to be done in order to make the application possible.
The graph presented in the Figure 7-22 represents the payback time of the investment involved for the
refurbishment of the glazing area and the optional installation of a CMV system. The first thing that
jumps to the attention is the fact that the two lines representing the economical behaviors of the two
separate investment have different slopes, this is because the two cases have different impact on the
energy savings of the building, as presented in § 7.2.7.3.
The costs of the inventions presented before, made clear that the refurbishment will be translated into a
big impact investment in this case. The payback year of the investment for the case of the only
refurbishment of the windows is equal to more than 18 years, this means that the cash flow of the case
-140
-120
-100
-80
-60
-40
-20
0
20
40
60
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
[k€]
yrs
WIN 2 WIN 1 Payback time
Figure 7-22: Representation of the payback year -x axis- and of the economic benefit -y axis- of the work
representing the refurbishment of the glazing area of Lecco’s school
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study school building will be negative from the year of the construction until 18 years after.
For the costs of the CMV system, it has been considered the purchase of all the components of the
system, included all the ramifications, and the labor due to the installation. In the price it has been
included, by the manufacturer, the costs for the ordinary maintenance. Nevertheless the graph highlights
the high payback time of the investment involving the CMV installation. This can be lowered thanks to
an integrated approach, which means that it can be proposed a new system involving the combination
of the conditioning system with an integrated ventilation system, as it will be presented later on the in
the work related to the plant system.
7.2.8 Envelope retrofit: Proposed intervention
In order to have a complete view on what has been analyzed until this point, it has been decided to sum
up all the proposed intervention and create some combinations. This means that the retrofit works
proposed are going to be combined together in order to analyze different scale of retrofit. The analysis
goes from to the stand alone cases previously proposed to integrated approach retrofit, in which all the
dispersive components of the envelope have been insulated.
In order to compare all the combination and thus to understand the profit coming from each of the retrofit
scenarios, first it has to be done a summary representation of the multiple cases taken in consideration
for this analysis.
As said, basically what has been done was combine together all the possible retrofit works, previously
explored, in order to get to the maximum energy demand reduction possible through envelope
optimization only. All the scenarios combined are exactly the ones analyzed in the previous paragraphs.
Through this analysis it will be possible to see what are the differences between a retrofit work done
with an integrated approach, and one done with distinct interventions not related to each other.
One of the benefit of designing a retrofit through an integrated approach, is that the impact of the thermal
bridges occurring with the application of thermal insulation can be reduced, as matter of fact intervening
on more elements of the envelope lets the designer have more possibility to develop efficient
connections between them. This will have an evident positive influence on the energy efficiency of the
intervention as well as on the investment needed to fund the works.
The table presented in the figure presented below, shows all the mentioned scenarios that have been
studied, and that are than considered feasible for an energy retrofit intervention applicable to the case
study school building located in Lecco.
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Gym Insulation Glazing Mechanical ventilaiton
EPS rigid Rockwool rigid Wood fiber rigid Polyester fiber Rockwool Calcium Silicate Rockwool roll Glass wool HD EPS HD Rockwool HD Wood fiber HD Synthetic material Low-e CMV Heat recovery
Case 1.1
Case 1.2
Case 1.3
Case 2.1
Case 2.2
Case 2.3
Case 3.1
Case 3.2
Case 4.1
Case 4.2
Case 4.3
Case 5.1
Case 6.1
Case 7.1
Case 8.1
Case 8.2
Case 8.3
Case 9.1
Case 9.2
Case 9.3
Case 10.1
Case 10.2
Case 10.3
Case 11.1
Case 11.2
Case 11.3
Case 12.1
Case 12.2
Case 12.3
Case 13.1
Case 13.2
Case 13.3
Case 14.1
Case 14.2
Case 14.3
Case 15.1
Case 15.2
Case 15.3
Case 16.1
Case 16.2
Case 16.3
Case 17.1
Case 17.2
Case 17.3
Case 18.1
Case 18.2
Case 18.3
Case 19.1
Case 19.2
Case 19.3
Case 20.1
Case 20.2
Case 20.3
Case 21.1
Case 21.2
Case 21.3
Case 22.1
Case 22.2
Case 22.3
Case 23.1
Case 23.2
Case 23.3
Case 24.1
Case 24.2
Case 24.3
Case 25.1
Case 25.2
Case 25.3
Case 26.1
Case 26.2
Case 26.3
Case 27.1
Case 27.2
Case 27.3
Wall external Insulation Wall internal insulation Attic insulation Roof insulationSCENARIO
Figure 7-23: Different case scenarios analyzed for the energy retrofit of Lecco’s school building
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After defining all the case scenarios, the next and final step would be the analysis of them in terms of
reduction of the energy needed to heat the inner space, and the cost of the investment bore by the owner,
in this case the municipality, for the retrofit work.
The graph represented in the Figure 7-24 basically sums all the study done on the envelope of the school
building located in Lecco. It has been decided to represent 27 different retrofit interventions, sub-divided
into 3 case scenarios for each of the interventions, as seen in Figure 7-23.
The energy reduction changes only between the different retrofit interventions, while it stays the same
no matter the case scenario analyzed for each specific intervention. In this way it was possible to
construct a line for each retrofit intervention analyzed, so that this line could represent the range in which
the economic investment, bore for the different case scenarios of the specific intervention, would lay
into. The construction of the Intervention’s line was made joining the three points representing the three
different related case scenarios. So the construction points represent each of the 3 case scenario studied
for the specific intervention, as matter of fact for each line the lowest point represents the most economic
solution analyzed, while the top one represents the most expensive one.
Analyzing the results coming from the graph presented in the Figure 7-24, the first thing that can be
seen is that the exploit of an aimed integrated approach used for an envelope energy retrofit could lead
to a reduction equal to almost 85% of the energy needed for the existing heating system for the space
conditioning of the school building. As said this value has to be considered without any modification of
the technological plants existing nowadays, this remarks even more the great impact achievable with an
aimed retrofit intervention.
The maximum energy reduction is achieved thanks to the intervention classified as “Case 21”, in which
the retrofit is aimed towards the insulation of the external perimeter wall (from the outside and the
inside), the attic extrados, the ground-contact elements of the gym combined with the refurbishment of
the glazing area and the installation of a Controlled Mechanical Ventilation with Heat recovery. The
minimum amount needed to fund the work is equal to 250 thousands of euro.
This means that if we analyze this case, the cost needed to reduce the heating energy needs of 1 kWh,
equal to: CER = 1.54 €/kWh. This cost/reduction analysis [€/kWh] is deepened, for all the other
intervention proposed, in the annexes presented at the end of this research work.
From the graph it is also possible to spot the most cost-effective intervention . This means that the ratio
between the cost of the investment and the energy reduction will be the lowest analyzed. This
intervention is the “Case 1” for which the ratio “cost/energy reduction” is equal to: CER = 0.26 €/kWh.
As matter of fact the use of the economic scenario for this intervention, will lead to a 27 % energy
reduction, with an expense equal to almost 25 thousands of euro. In the “Case 22” the retrofit
intervention is aimed towards the insulation of the external perimeter wall, with the application of
thermal insulation the outside without intervening on the protected façade an all the other dispersive
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envelope components.
It’s clear that the in this case the cheapest intervention is not the most convenient one, as matter of fact
the cheapest solution studied is the “Case 3”, which represents the insulation of the attic and which has
a cost/energy reduction ratio equal to: C€ = 0.60 €/kWh; which is lower respect to other cases.
This does not mean that the intervention proposed in the “Case 3” is not feasible and should be avoided,
but it’s just to point out which will be the direction to take, in case of a deep retrofit work. Then of
course in case of necessity or in case of particular boundary conditions one could decide to choose one
solution over another, no matter the cost-effectiveness comparison.
1
2
3
4
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
0
25
50
75
100
125
150
175
200
225
250
275
300
325
350
375
400
425
10% 15% 20% 25% 30% 35% 40% 45% 50% 55% 60% 65% 70% 75% 80% 85%
[k€] Investment cost
Energy reduction
Case 1 Case 2 Case 3 Case 4 Case 5 Case 6 Case 7
Case 8 Case 9 Case 10 Case 11 Case 12 Case 13 Case 14
Case 15 Case 16 Case 17 Case 18 Case 19 Case 20 Case 21
Case 22 Case 23 Case 24 Case 25 Case 26 Case 27
Figure 7-24: Analysis of the heating energy demand reduction % – x axis- and the cost of the investment [k€] - y
axis- of the different case scenarios considered for the for the energy retrofit of Lecco’s school building
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7.3 Case study “Bustehrad”
According to the needs and the criticalities highlighted through the energy analysis previously presented
in chapter 6 in this section it will be presented the different case scenarios chosen for each retrofit
intervention proposed and considered feasible/energetically beneficial, for the case study school
building located in Bustehrad.
The case study analyzed locate in Buštěhrad has the same exact peculiarities as he one locate in Lecco,
as it will be seen throughout the chapter.
7.3.1 External thermal insulation coating
The coating of the outer envelope of the
building with thermal insulation, is one
of the most common procedure done in
order to decrease the amount of energy
consumption of the specific building.
This technique allows the building also
to receive a complete makeover of the
facades considering that the thermal
coating includes a new external finish,
this can contribute to spark up the
aesthetic value of obsolete buildings.
As done for the case study locate in Lecco, § 7.2.1, since the building will radically change its look the
external coating of the facades is considered an invasive procedure. For this reason this technique can’t
be applied to all of the facades of the historical part of the building built at the beginnings of the 20th
century. The façade of the old part of the building oriented towards South-East, which is the only one
that is exposed on the street, has aesthetic architectural value therefore its appearance can’t be modified
meaning that no thermal insulation can be applied. For this type of façade it will be presented later on
in the script an internal insulation solution.
7.3.1.1 Design choice
Analyzing the output data of the energy diagnosis presented in the §5, it has been decided to present
three different scenario of intervention for this specific procedure. The three different scenario will
change in terms of thermal insulation material and external finish, for the remainder it will be all the
same, as matter of fact in all the scenario the element structure will have the same thermal transmittance
Figure 7-25:SE facade of the old part of the school building
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set at 0.25 [W/(m2K)], as defined in Table 7.1
Scenario Insulation λ d s Finishing Cost
Material [W/mK] [kg/m3] [cm] Material €/m2
EXT. 1 EPS with graphite 0.031 35 10 Acrylic 44.78
EXT. 2 Rockwool 0.034 115 11 Breathable 59.32
EXT. 3 Wood Fiber 0.04 145 13 Breathable 69.14
The results presented are in line of what seen before, for the case located in Lecco (§ 7.2.1), as the most
economic solution is represented by the first option, in which the insulation material chosen is the EPS
with graphite.
The attention is caught by the differences between the prices presented in the cost analysis of the two
case study presented. The prices shown for the case study located in Buštěhrad has overall lower prices
respect to the one of Lecco. With a detail analysis is possible to notice that actually the cost of the
solution 1 (the one with the EPS with graphite) has pretty much the same cost, in the two different
countries, and this is due to the fact that it’s safe to say that it is the most used material for thermal
external coating for Czech Republic and Italy. Concerning the costs of the two natural materials, the
costs in CZ are much lower to the ones applied in Italy, this can be linked to the fact that the use of
natural materials is more diffused in countries like Czech Republic, in which the production of these
materials doesn’t rely 100% on big international companies as in Italy, therefore making the market
more competitive. In this way the differences between the different material, for the school of Buštěhrad
is really low, making the choice of the material based more on the technical analysis rather than the
economic one.
7.3.1.2 Thermal Inertia of the case scenarios
For this intervention, considering that it is based on the application of material insulation on the outside
of the envelope, the thermal inertia of the different scenarios will be compared based only on the
different values of Periodic thermal transmittance Yie defined by the different material used for each
scenario. Here are presented the values defining the dynamic properties of the different case scenarios
previously defined.
Phase displacement Attenuation Performance
φ > 10 fd < 0.15 excellent
10 < φ < 12 0.15 < fd < 0.30 good
8 < φ < 10 0.30 < fd < 0.40 average
6 < φ < 8 0.40 < fd < 0.60 sufficient
φ < 6 fd < 0.60 mediocre
Table 7.30: Thermal coating scenario considered for the retrofit of the case study located in Buštěhrad
Scenario fd φ Yie
- [h] [W/m2K]
Base case 0.102 14.450 0.24
EXT. 1 0.024 17.217 0.009
EXT. 2 0.019 18.209 0.005
EXT. 3 0.012 21.6 0.003
Table 7.31: Dynamic properties of the scenarios Table 7.32: Limit values set by standard [18]
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The thermal inertia calculated for the base case ( i.e. outside walls without any kind of insulation), is
higher compared to the one of Lecco, this is due to fact that the perimeter walls in Czech Republic during
the 1900 were completely made of burnt bricks piled together in order to reach a thickness equal to more
than 60 cm, meaning that the structure was highly capable of absorbing and keeping the heat. As for the
cost of the solutions, the differences between the different values expressing the thermal inertia of the
different solutions is not high, as for the school in Italy, this evens a little bit all the solution on the
technical point of view.
Even though the differences are not that high, the best solution is represented by the application of wood
fiber insulation (EXT. 3), for which the thermal inertia of the wall reaches values so that the phase
displacement is equal to more than 20 hours, meaning that the time lag between reaching the maximum
external temperature in the inner spaces is more than 20 hours.
7.3.1.3 Heating consumption savings
In this paragraph it will be analyzed the perks of doing the specific intervention explained in the previous
paragraph. In this case the intervention is the application of an external thermal coating onto the facades
of the case study building exception made for the protected façade and the perks are represented by the
energy and economic savings and the GHG emission reductions.
Scenario
Heating
Primary Energy
Energy cost
GHG emissions Reduction
[kWh/m2y] [€] [tonCO2] [%]
Base 199.05 10303.04 42161.00 -
Ext. Insulation 136.72 7076.70 28958.52 31%
Is easy to understand the profits, speaking about heating consumptions, coming from the application of
the thermal insulation as previously explained. The reduction obtained through the application of the
thermal insulation is equal to 31% of the initial value, this refers to all of the values presented in the
table, so for the: primary energy, energy cost and the GHG emissions.
The results are in agreement of what seen for the case study located in the city of Lecco, § 7.2.1.3. This
represented the first comparable results obtained till now. From these results it’s obvious that the impact
of the interventions are quite similar.
7.3.1.4 Economic Impact
The cost of the intervention was calculated in a simple straightforward way, considering the cost of the
materials and of the installation of the specified work interventions. The analysis has been based on the
Table 7.33: Heating reductions obtained with the external thermal coating applied onto the case study Buštěhrad
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experience gained analyzing multiple case studies located in Czech Republic, and considered relevant
for the work intervention presented. Using this Czech case studies as guide lines, it has been possible to
create a small database recreating the costs for all the interventions, also through the help of Czech
Republic native colleague that collaborated with the thesis analysis. It was also possible to understand
the labor costs of the interventions which were than summed as a fixed percentage of increase, together
with the expenses directly related to works needed to be done in order to make the application of the
thermal insulation possible (i.e. scaffoldings, preparation of the land, etc.).
The three case scenarios represented have different behavior respect to the ones seen for the case study
located in Lecco, § 7.2.1.4. Taken in exam the most economic case, pointed out as the EXT.1, even
though the cost of the material is the same as the one seen in Italy, the lower energy reduction given by
the energy efficient intervention combined with the lower cost of gas in Czech Republic (thus decreasing
the positive impact given by the reduction of energy needs on the energy bill) leads to an longer payback
time respect to Lecco.
Another peculiarity is again, that the three case scenarios in this case (especially the EXT.2 and the
EXT.3) have smaller differences between each other, making the choice even more difficult. In the case
of Lecco the most expensive solution had a payback time double respect to the most economic one,
while for Bustehrad the differences are less obvious.
7.3.2 Internal thermal insulation
In this paragraph it will be presented a retrofit operation that can be done in order to insulate a protected
façade from the inside of the specific building. As highlighted before in the , the peculiarity of this case
study building is the presence of an architecturally protected façade whose appearances can’t be
modified, just as it was analyzed for the case study located in Lecco, § 7.2.2.
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EXT 1 EXT 2
EXT 3 Payback time
Figure 7-26: Representation of the payback time -x axis- and of the economic benefit -y axis- of each of the
case scenarios chosen for the external thermal insulation, Buštěhrad
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7.3.2.1 Design choice
As done for the external thermal insulation coating intervention, also in this case it has been considered
3 different intervention scenarios, done with 3 different thermal insulation materials. This is done
because one of the goal of the work here presented is to show the possible energy retrofit intervention
applicable to the specific building, studying the different scenario through various technical aspects.
The three different scenario taken in consideration, as said before, will have an equal thermal
transmittance set at 0.25 [W/(m2K)], they are presented through the Table 5.7.
Scenario Insulation λ d s Finishing Cost
Material [W/mK] [kg/m3] [cm] Material €/m2
INT. 1 Calcium Silicate 0.039 115 12 Internal Paint 53.27
INT. 2 Rockwool rigid panels 0.035 70 11 Plasterboard 40.86
INT. 3 Polyester Fiber 0.034 50 10 Plasterboard 33.83
Comparing the costs presented for the two case studies, it’s clear that as before also in this case the costs
of the interventions calculated in Czech Republic are lower than the one in Italy. One peculiarity is
represented by the cost of the Calcium silicate solution (INT.1) which has approximately the same price
in both countries. This is mainly due to the fact that the solution is rarely used in Czech Republic, as
matter of fact considering that its main features are the summer performances, it’s understandable that
a cold country like Czechia doesn’t really look for this kind of solution.
For the case scenario “INT. 1” the intervention is based on the application of calcium silicate insulation
panels, through the use of adhesive and levelling layer, onto the façade from the inner space. The choice
of this insulation material is given by the fact that the installation will be done from the inside and the
space insulated is a classroom, therefore it will be very important to contrast the high production of
water vapor coming from the students and guarantee a moderate IAQ.
The application method is different for the case scenario “INT. 2” and “INT. 3”, where the insulation
has been applied through a dry wall system. The insulation of the walls takes place with the installation
of a metal framework made of C-profile mullions and transoms which will guide the application of the
thermal insulation panels, covered by a dry plasterboard wall. The choice of rockwool for the case
“INT.2” is given by the will to give the possibility to exploit the Mass-spring-Mass effect of the dry
system presented, in order to consider a thermal-acoustic insulation scenario. In the “INT.3” it is
presented a low-cost solution defined by the use of an eco-friendly insulation material obtained by the
reuse of PET plastic, in form of polyester fiber insulation panels.
Table 7.34: Internal thermal insulation scenario considered for the retrofit, Buštěhrad
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7.3.2.2 Thermal inertia of the case scenario
As presented in the § 7.2.1.2, the envelope will be evaluated also for its summer performances through
the comparison of the thermal inertia of the wall for the solution proposed for each case scenario. In this
case since the intervention involves the application of material insulation from the inside of the spaces,
the thermal inertia of each scenario will be compared through both of the dynamic properties presented
before:
- Periodic thermal transmittance 𝑌𝑖𝑒 = 𝑈 ∗ 𝑓𝑑 [W/(m2K)];
- Internal thermal capacity Cip [kJ/(m2K)].
The Cip periodic internal thermal capacity, calculated as Yie, according to UNI EN ISO 13786 [56]
represents the capacity of a building component to accumulate the thermal loads coming from inside.
The higher the value of the Cip (mass placed inside), the greater the heat accumulation. The accumulation
of internal thermal loads by a wall makes it possible to keep surface temperatures at acceptable levels,
i.e. with fluctuations and limited values throughout the day, in favor the environmental comfort
conditions for summer.
It’s easy to see that the construction element used in the third case scenario has better dynamic
properties’ value, due to the higher thermal mass of the calcium silicate base panel insulation respect to
the dry wall system used in the second and in the third case scenario.
Phase displacement Attenuation Performance
φ > 10 fd < 0.15 excellent
10 < φ < 12 0.15 < fd < 0.30 good
8 < φ < 10 0.30 < fd < 0.40 average
6 < φ < 8 0.40 < fd < 0.60 sufficient
φ < 6 fd < 0.60 mediocre
As expected the results show higher values of internal thermal capacity for the Calcium Silicate solution
(INT.1) due to the higher mass of the insulation material. The results here presented are comparable to
the ones of Lecco, even though in this case the internal thermal capacity values of each scenario is lower,
meaning that there structure will be less able to store the heat coming from the inside, due to the fact
that there’s more mass on the outside of the structure.
7.3.2.3 Criticalities of the intervention
As seen in the § 7.2.2.3, this type of intervention is complex, and it involves certain operation
criticalities, that are going to be briefly shown again.
For this case study the application on the perimeter walls of thermal insulation from the inside space
Scenario fd φ Yie Cip
- [h] [W/m2K] [kJ/m2K]
INT. 1 0.241 18.230 0.010 21.45
INT. 2 0.018 19.870 0.006 15.15
INT. 3 0.013 20.34 0.004 13.00
Table 7.35: Dynamic properties of the scenario, Bustehrad Table 7.36: Limit values set by standard [18]
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gives birth to a number of critical thermal bridges, caused by the fact that two different modus operandi,
i.e. internal and external thermal coating of the envelope, have been considered coexisting for the retrofit
of the building.
In the Annexes all the possible thermal bridges occurring in this case of intervention have been studied,
and for each of them it has been presented a “simple” solution capable of limiting the value of the linear
thermal transmittance Ψ so that the construction elements solutions presented in the work comply with
the thermal transmittance -U- limitations imposed in the § 7.1.
The interventions made to reduce the impact of the thermal
bridges occurring, are the punctual application of internal
pre-finished insulation panels applied onto internal walls, and
the application on each floor of the old part of the building of
a suspended ceiling with the addition of a rigid panel
insulation material. The pre-finished insulation is made of pre-coupled boards of PF (polyester fiber)
and plaster board with an integrated vapor barrier, while the suspended ceilings is made of a rigid
rockwool panel with a plasterboard finishing. In order to have a more comprehensive view of the
economic investment needed for the global intervention, all of the processing techniques listed before,
i.e. the thermal bridge solution interventions, have been taking into account in the global cost of
investment.
7.3.2.4 Heating consumption savings
In this paragraph it will be analyzed the perks of doing the specific intervention explained in the previous
paragraph. In this case the intervention is the application of an internal thermal coating onto the protected
façade and the perks are represented by the energy and economic savings and the GHG emission
reductions.
Scenario
Heating
Primary Energy Energy cost GHG emissions Reduction
[kWh/m2y] [€] [tonCO2] [%]
Base 199.05 10303.04 42161.00 -
Int. Insulation 124.09 6423.07 26283.80 38%
Once again, the actual energy reduction obtained with the thermal insulation of the vertical components
of the structure for the case study in Buštěhrad is lower respect to the one in Lecco. This could be due
to simple considerations, as the thermal losses diagram presented in § 6.1.5 highlights the impact of the
glazing are onto the energy leakage of the building, also in agreement with the Glazing/opaque ratio
stated for the building.
Overall an energy reduction higher than 30% of the initial case is reached, meaning that the even with a
Intervention Cost
€/m2 €
suspended ceiling 19.84 17856.00
insulated dry wall 17.45 3141.00
Table 7.37: Cost of the intervention, CZ
Table 7.38: Heating reductions obtained with the internal thermal coating, Buštěhrad
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partial retrofit (considering only the opaque wall) an evident difference can be made.
7.3.2.5 Economic Impact
For the case study presented the retrofit intervention here showed of the application of thermal insulation
onto the perimeter wall from the inner spaces is not a standalone intervention but it has to be combined
with the application of the external thermal coating insulation presented in the § 7.3.1.
For this reason it has been decided to create 3
different case scenario presenting the combination of
the two intervention presented until now. The first
scenario represents the cheapest and most used
combination of the materials used for the insulation
from the outside and the inside, while the third one
represents the most expensive and performing combination.
In order to have an economic view of the proposed interventions it has been decided to analyze the
payback time of the investment, based on the intervention’s cost and the energy cost savings obtained
through the years, in order to make this case more global as possible some hypothesis and simplifications
had to be done.
The cost of the intervention was calculated in a simple straightforward way, considering the cost of the
materials and of the installation of the specified work interventions. The analysis has been based on the
experience gained analyzing multiple case studies located in Czech Republic, and considered relevant
for the work intervention presented. It was also possible to understand the labor costs of the interventions
which were than summed as a fixed percentage of increase, together with the expenses directly related
to the site work area.
The payback time for the investment involving the thermal insulation of the vertical wall either from the
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INT 1 INT 2
INT 3 Payback time
Scenario
Insulation
Material
EXT. INT.
1 EPS with graphite Polyester Fiber
2 Rockwool Rockwool rigid panels
3 Wood fiber Calcium Silicate
Table 7.39: Case scenario combination, Buštěhrad
Figure 7-27: Representation of the return year -x axis- and of the emission benefit -y axis- of each of the case
scenarios chosen for the internal thermal insulation, Buštěhrad
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inside and the outside of the case study building located in Buštěhrad, is clearly a point of disagreement
between the two case studies located in two different parts of Central Europe.
It’s clear that the impact of the retrofit of the vertical opaque envelope is much higher in the case study
located in Lecco, respect to the one of Buštěhrad. As matter of fact the cheapest solution studied for the
Italian case presents a payback time which is half of the one of the Czech’s. This can be read as a signal
for which an integrated approach, considering all the construction elements.
The drastic difference is given by the fact that the two case study reach different energy reduction with
the analyzed intervention, plus the two thermal losses diagram combined with the lower cost of gas in
Czechia highlight the difficulty in lowering the costs of the energy bill in Buštěhrad.
7.3.3 Attic Insulation
As seen through the paper, the same intervention proposed for the case study located in Lecco, will be
applied onto the case study of Buštěhrad in order to compare the differences and the similarities.
The case study presents an unheated space
between the roof and the last heated slab, easily
accessible. In this paragraph it will be proposed
the insulation of the last heated slab of the old
part of the building through the use of insulation
materials in form of rolls and panels put on the
floor of the attic, so that the insulation performs
its benefits only for the heated space, avoiding
heating unused spaces such as the attic itself.
7.3.3.1 Design choice
The positive aspect of the building that has to be exploit in this case, is the presence in the old part of an
unheated space between the roof and the last heated slab, defined as attic, and the fact that it is easily
accessible, even though unfortunately this space is not present in the recent part of the building. The
attic can be used in two different ways, as a buffer zone which means that it will be considered as an
unusable space and on the other hand it can be used as storage or functional room.
Scenario Insulation λ d s Flooring Cost
Material [W/mK] [kg/m3] [cm] Material €/m2
1 Rockwool roll insulation 0.038 26 15 - 11.31
2 Glasswool rigid panel 0.033 125 13 Dry system 53.03
Table 7.40: Case scenarios of attic retrofit for the school building of Bustehrad
Figure 7-28: Roof structure of Bustehrad’s school
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For this reason it has been decided to present two different feasible intervention for the thermal
insulation of the attic, one will concern only the thermal insulation of the last heated slab while the other
one will include the refurbishment of the flooring of the attic, so that this space can be qualified as
usable.
Once more it’s clear the difference between the two interventions, which are similar to the one presented
for Lecco. This highlights the cost effectiveness of applying roll insulation instead of a rigid one
combined with a new floor system. Although it has to be said that the attic placed in the school building
is spacious and it has also roof light windows which can be a significant factor in the case of a complete
refurbishment of the space. From the surveys and the analysis done, without considering the two
different economic benefit given by the scenarios, the most suitable solution would be the one of
restoring the attic in order to make it useful, maybe also deciding to heat it.
7.3.3.2 Heating consumption saving
In this paragraph it will be analyzed the perks of doing the specific intervention explained in the previous
paragraph. In this case the intervention is the application of an internal thermal insulation onto the slab
extrados, for the old part of the building, and on the slab intrados for the recent one (as presented in §
5.2.3) and the perks are represented by the energy and economic savings and the GHG emission
reductions.
Scenario
Heating
Primary Energy
Energy cost
GHG emissions
Reduction
[kWh/m2y] [€] [tonCO2] [%]
Base 199.05 10303.04 42161.00 -
Attic Insulation 167.97 8694.31 35577.91 16%
The energy effectiveness of the intervention it’s pretty clear, and it’s also in line with the heat losses
diagram presented in § 6.1.5. As it was assumed since the energy savings coming from the opaque wall
in this case were lower than the Italian case, the insulation applied to the roof would have a bigger
impact for the school of Buštěhrad as shown by the Table 7.41.
7.3.3.3 Economic impact
The cost of the intervention was calculated in a simple straightforward way, considering the cost of the
materials and of the installation of the specified work interventions. The analysis has been based on the
experience gained analyzing multiple case studies located in Czech Republic, and considered relevant
for the work intervention presented. It was also possible to understand the labor costs of the interventions
Table 7.41: Heating reductions obtained with the attic thermal insulation applied onto the case study Buštěhrad
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which were than summed as a fixed percentage of increase, together with the expenses directly related
to the site work area.
The solution ATTIC 1, representing the choice of thermal insulating the attic extrados with the
application of roll insulation, has outstanding results. The payback time for this scenario is less than 5
years, meaning that the doing this work will automatically show a profit for the school, in terms of real
money, after less than 5 years from the construction year. This exploit was not a real surprise, since from
the cost analysis previously done, the huge benefit were already evident.
7.3.4 Roof insulation
In this section it will be analyzed the possible case scenarios
concerning the refurbishment of the roofing structure of the case
study building. The building presents an attic space placed on
top of the last heated slab which is covered by a clay tiles hip
roof supported by a wood beam structure.
This intervention is usually applied whenever the roof is directly
in contact with the heated space, i.e. in the recent part of the
building, or/and when there’s the will to transform an attic into
an habitable space, i.e. the attic space in the old part of the building.
7.3.4.1 Design choice
It has been decided to propose a requalification of the existing roof of both of the parts of the building,
consisting on the application of a thermal insulation layer, included all the protection materials,
underneath the existing roof cover. This means that it will be temporarily removed the roofing covering
structure and then re-placed on top of a new supporting structure laid on a new insulation layer consisting
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ATTIC 1 ATTIC 2 Payback time
Figure 7-29: Representation of the return year -x axis- and of the economic benefit -y axis- of each of the case
scenarios chosen for the attic insulation in Buštěhrad
Figure 7-30: Bustherad's roof structure
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of a different thermal insulation material for each case scenario.
Scenario Insulation λ d s Cost
Material [W/mK] [kg/m3] [cm] €/m2
ROOF. 1 EPS with graphite 0.031 40 15 43.39
ROOF. 2 Rockwool 0.036 140 17 53.21
ROOF. 3 Wood Fiber 0.038/0.042 145/205 19 78.75
These case shows even more the differences on the construction market of the costs applied in Italy and
the one applied in Czech Republic. The cost for the intervention involving the use of EPS with graphite
is actually really cheap, compared to the costs found in the Italian database, therefore it could represent
an interesting solution, economically speaking.
7.3.4.2 Thermal inertia of the case scenario
For this intervention, considering that it is based on the application of material insulation on the outside
of the envelope, the thermal inertia of the different scenarios will be compared based only on the
different values of Periodic thermal transmittance Yie defined by the different material used for each
scenario. Here are presented the values defining the dynamic properties of the different case scenarios
previously defined.
The structure of the roof of the case study building located in Buštěhrad is really similar to the one of
Lecco’s school, as seen in § 3.3.1, therefore the results may not vary a lot.
Phase displacement Attenuation Performance
φ > 10 fd < 0.15 excellent
10 < φ < 12 0.15 < fd < 0.30 good
8 < φ < 10 0.30 < fd < 0.40 average
6 < φ < 8 0.40 < fd < 0.60 sufficient
φ < 6 fd < 0.60 mediocre
The lower is the value expressing the attenuation fd and the lower is the amplitude of the thermal flow
entering the building component, and at the same time the lower is the value of the periodic thermal
resistance Yie and the higher are the value of the phase displacement φ and the damping. In addition to
this it has to be said that the National Guide Lines [18] sets also, the limit for the value of the periodic
thermal transmittance Yie equal to a maximum of 0.10 [W/(m2K)], therefore all the scenarios are below
the limit.
It’s easy to understand that the results related to the old part of the building are not satisfactory. This is
Scenario fd φ Yie
- [h] [W/m2K]
ROOF 1 0.915 2.87 0.181
ROOF 2 0.515 8.18 0.1
ROOF 3 0.24 12.18 0.049
Table 7.43: Dynamic properties of the scenario, Bustehrad Table 7.44: Limit values set by standard [18]
Table 7.42: Case scenarios of the roof insulation intervention in Bustehrad
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due to the fact that roof structure is supported by punctual wooden beams that
are not considered in the thermal analysis of the structure, therefore the only
layer opposed to the thermal dispersions is represented from the new inserted
thermal insulation layer. In this case it’s more clear the difference given by
the choice of different thermal insulation, as matter of fact only the
application of a wood fiber insulation layer would guarantee good thermal inertia properties and
therefore would represent the optimal technical solution.
7.3.4.3 Heating consumption savings
In this paragraph it will be analyzed the perks of doing the specific intervention explained in the previous
paragraph. In this case the intervention is the application of an internal thermal insulation onto the slab
extrados, for the old part of the building, and on the slab intrados for the recent one and the perks are
represented by the energy and economic savings and the GHG emission reductions.
Scenario
Heating
Primary Energy
Energy cost
GHG emissions
Reduction
[kWh/m2y] [€] [tonCO2] [%]
Base 199.05 10303.04 42161.00 -
Roof Insulation 174.44 9028.80 36946.68 12%
The energy savings are much lower than the case of the attic insulation, highlighting once more the
effectiveness of the case presented in the § 7.3.3, respect to the one presented in this paragraph. In
addition the results here presented are in agreement on what seen for the case study located in Lecco, as
also in that case the roof insulation had lower energy benefit respect to the attic insulation.
7.3.4.4 Economic Impact
The cost of the intervention was calculated in a simple straightforward way, considering the cost of the
materials and of the installation of the specified work interventions. The analysis has been based on the
experience gained analyzing multiple case studies located in Czech Republic, and considered relevant
for the work intervention presented. Using this Czech case studies as guide lines, it has been possible to
create a small database recreating the costs for all the interventions, also through the help of Czech
Republic native colleague that collaborated with the thesis analysis. It was also possible to understand
the labor costs of the interventions which were than summed as a fixed percentage of increase, together
with the expenses directly related to works needed to be done in order to make the application of the
thermal insulation possible (i.e. scaffoldings, preparation of the land, etc.).
Old Part Performance
ROOF 1 mediocre
ROOF 2 average
ROOF 3 good
Table 7.45: Performances
of the old part roof
Table 7.46: Heating reductions obtained with the attic thermal insulation in Bustehrad
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The graph describes what has already been said before, that this is an high cost intervention, therefore
before pursuing this type of works it has to be considered all the other low cost scenario previously
presented in the attic insulation intervention. As matter of fact the solution ROOF 1 which represent the
cheapest case scenario has a payback time equal to 12 years, this remarks the high costs of this type
intervention.
7.3.5 Basement insulation
The basement structure of the school building located in Buštěhrad is also a composed of a vault slab,
as in Lecco, therefore as seen in the Italian case study, § 7.2.5) the intervention consisting on the
insulation of the slab delimiting the ground floor heated spaces from the underground level, is no feasible
for this specific research work.
7.3.6 Ground-contact element insulation
The detailed description made in § 3.3.1, shows that the ground floor of the school building taken as
case study, is in direct contact with the ground through a stone made slab. As seen from the plans
attached to the paper, the underground floor of the building covers only part of the ground floor area,
leaving the majority of it exposed to the ground. In order to limit the heat transfer between the floor and
the inners spaces, it has been suggested to insulate the extrados of the ground floor slab.
Concerning the ground-contact element of the underground floor, they have not been considered for the
calculation, since they are delimiting an unhated space.
7.3.6.1 Design choice
For the design choice of the insulation of the floor of the ground level of the school building it has been
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ROOF 1 ROOF 2
ROOF 3 Payback time
Figure 7-31: Representation of the return year -x axis- and of the economic benefit -y axis- of each of the case
scenarios chosen for the roof insulation in Buštěhrad
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used a similar approach respect to the one presented for the case study of Lecco, § 7.2.6. Considering
that the impact of this work would be not so high, consulting the heat losses diagram presented in the
energy analysis of the building, it has been decided to present the most economical solution found on
the market.
The choice made was the removal of the existing floor and the supposed levelling layer, and a
consequent application of rigid thermal insulation with a dry floor system. As matter of fact it has been
supposed that the existing structure has made of a 4 cm screed used as levelling layer and on top a 2 cm
tile flooring, therefore the removal of these two layers will be equal to a 6 cm empty spot. This spot will
be than filled with XPS rigid insulation pre-coupled with a strengthening leveling layer which will be
the support of the new dry floor systems. Basically the existing layers will be replaced by a rigid thermal
insulation with supporting layer of 4.5 cm with a dry floor system of 1.5 cm, equalizing the thickness of
material removed.
Scenario Insulation λ d s Finishing Cost
Material [W/mK] [kg/cm3] [cm] Material €/m2
GROUND 1 XPS insulation 0.032 35 4.5 Dry flooring 34.25
The cost presented takes in consideration also the removal of the existing layer that represents the
existing flooring system.
7.3.6.2 Heating consumption savings
In this paragraph it will be analyzed the perks of doing the specific intervention explained in the previous
paragraph. In this case the intervention is the application of an internal thermal insulation onto the slab
extrados, for the old part of the building, and on the slab intrados for the recent one and the perks are
represented by the energy and economic savings and the GHG emission reductions.
Scenario
Heating
Primary Energy Energy cost GHG emissions Reduction
[kWh/m2y] [€] [tonCO2] [%]
Base 199.05 10303.04 42161.00 -
Ground Insulation 191.90 9941.95 40683.36 3.5%
The energy reduction given by this intervention is low impact, as matter of fact if affects only 3.5 % of
the heating energy use of the building, therefore the intervention can’t be qualified as energy effective.
7.3.6.3 Economic Impact
The cost of the intervention was calculated in a simple straightforward way, considering the cost of the
materials and of the installation of the specified work interventions. The analysis has been based on the
Table 7.48: Heating reductions obtained with the ground floor thermal insulation in Bustehrad
Table 7.47: Case scenarios for the ground floor insulation in Bustehrad
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experience gained analyzing multiple case studies located in Czech Republic, and considered relevant
for the work intervention presented. Using this Czech case studies as guide lines, it has been possible to
create a small database recreating the costs for all the interventions, also through the help of Czech
Republic native colleague that collaborated with the thesis analysis.
The intervention work proposed is a low energy impact retrofit, therefore the slope defining the
economic benefit derived from it each year is really low, it almost tends to a flat line. This meaning that
it won’t be possible to see any major changes during the years after this intervention. As said before this
type of work can be considered in case of an integrated approach retrofit involving all the dissipative
components, otherwise it is almost useless.
7.3.7 Glazing optimization
Through the heat losses graph presented in § 6.1.5, it’s easy to understand the impact that the glazing
surfaces of the building have on the global heat losses of the building coming from the thermal
inefficiency of the envelope, as matter of fact it accounts for more than 20 % of the total thermal losses.
For this reason it has been decided to consider the complete refurbishment of the glazing areas of the
building, which includes the removal of the existing windows and the application of new insulating
windows.
7.3.7.1 Design choice
The technology used is the same used for the case study in Lecco, § 7.2.7.1.
Technically the solution proposed consists of a double glazing window, composed of 33.1/ 16 AR/ 33.1
LE. This means that is made of a first security laminated float of 6 mm, with a 16 mm of cavity filled
with argon, and a final thermal and low emissivity float of 6 mm. Here it has been presented the summary
-20
-10
0
10
20
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
[k€]
yrs
GROUND 1 Payback time
Figure 7-32: Representation of the return year -x axis- and of the economic benefit -y axis- of each of the case
scenarios chosen for the ground floor insulation in Buštěhrad
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table that sums up all the thermal characteristic of the new glazing element:
Glazed Surface
Component Thickness
[-] [mm]
Low E float 6
Argon 16
Clear float 6
The thermal transmittance of the glazing proposed has been calculated through the UNI EN ISO 10077-
2 [57], as it can be seen in the annexes, with the additional help of the Pilkington spectrum online
software.
The choice of the low emissivity glass is given by the fact that with the use of this glasses, it is possible
to reflect inward part of the heat emitted as thermal radiation from the bodies contained in the inhabited
areas, considerably reducing the heat loss. The heat is reflected by the plate treated analogously to what
happens with a mirror that reflects purely luminous radiation.
Concerning the design of the window the proposed intervention is only the one just presented, but in
this work it has been decided to distinguish another energy retrofit work consisting on the refurbishment
of the od glazing area, as previously explained, and the installation of a mechanical ventilation system.
This is done in order to differentiate a stand-alone work on the windows, which will take in consideration
the only refurbishment of the glazing, from an integrated energy retrofit work in which the optimization
of the envelope is combined with technological solution assigned to the improvement of the internal
condition of the spaces.
In this case study it will be analyzed a controlled mechanical ventilation with double flow heat recovery:
the stale air extracted from the humid rooms and the air taken from the outside, previously filtered, are
conveyed into a heat recovery unit that ensures the preheating of the renewal air avoiding the
contamination of the two flows. The most common type is the double flow controlled mechanical
ventilation which is characterized by having a double ventilation system, formed by separate distribution
channels:
- A duct controls and regulates air intake;
- the other is dedicated to extract air;
- the air flows in the two ducts are managed by separate electric fans.
For the reasons above explained, it has been decide to present two separate chances of glazing
optimization: one representing the refurbishment of the existing windows, and the other one including
also the installation of a controlled mechanical ventilation system “CMV”.
Frame Net U-value Net R-value
Type Transmittance Percentage [W/m2K] [m2K/W]
[-] [W/m2K] % 1.18 0.90
PVC 1.29 33
Table 7.49: Glazing’s component thermal properties. Thermal transmittance of the proposed windows
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Scenario Windows Frame U Ventilation Cost
# glazing Material [W/(m2K)] Type €/m2 €
WIN 1 Double – low e PVC 1.18 Natural 290.00 43500.00
WIN 2 Double – low e PVC 1.18 CMV 415.00 93500.00
The costs presented are higher respect to the ones analyzed until now with the other retrofit solutions
studied. For the costs of the windows it has been considered included all the extra cost related to the
removal and disposal of the existing windows and the following installation of the new glazing,
including the labor needed for the possible brickwork job.
Once again the costs found in Czech Republic are lower respect to the one presented in the Italian case,
as highlighted by the Table 7.50.
7.3.7.2 Technical Analysis
The technical analysis done on the glazing solution presented is deepened in the annexes regarding the
thermal analysis of the windows proposed.
Concerning the mechanical ventilation, the proposed solution has been considered only after some
technical considerations. First of all in order to have the idea of the machine that had to be installed
some hypothesis had to done. The will was to install a CMV system that could “replace” the opening of
the windows, therefore decreasing the losses for ventilation rationalizing the external flow, and decrease
the internal temperature and the CO2 concentration in the cooling season. Therefore it has been decide
to propose a CMV system with heat recovery and free-cooling switch included.
In order to have a better understanding of the economic impact of the installation of the machine, it has
been proceeded with the overall dimensioning of the mechanical ventilation, using the ISO 10339 [58].
As said the dimensioning is not accurate, but is done only to estimate the amount of inlet air needed.
Considering (from [58]):
- the “school” crowding index: ns = 0.50 pers/m2 ;
- the “school” external air flow: Qop = 7*10-3 m3/s per person;
- design air flow: Qd = 5950 m3/h;
- project air flow: Qpr = 6000 m3/h.
Basically the calculation has told that the CMV system that has to be installed has to have a capacity
equal to or greater than 6000 m3/h, meaning that the system will be expensive and also complex to
install.
After the considerations it has been decided to adopt this kind of technological solution onto the case
study building in order to admire and comment the possible effects on the energy and comfort parameters
Table 7.50: Case scenarios considered for the retrofit of the glazing areas of the case study building in Bustherad
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of the heated spaces.
First of all the CMV should decrease the operative temperature of the internal spaces during the cooling
period, especially thanks to the free cooling system which is really effective in the mid seasons and for
night cooling, so that there’s an increase in the thermal comfort perceived by the users. In order to do
this it has been calculate once again the percentage of hours in which a typical user will feel thermal
discomfort, defined as the percentage of hours in which the Operative temperature is higher than 26°C.
The graph easily highlights the drastic reduction of the hours of discomfort measured inside the classes
of the school building located in Bustehrad. It has to be said that even before the intervention of the
CMV the values of discomfort were not alarming, considering the results presented in § 6.2.1, linked to
the cool temperatures present in Czech Republic.
The same comparison: Base case vs. Installation of CMV, can be done also considering the CO2
concentration inside the classrooms of the case study building.
It will be analyzed the calculation, presented in the § 6.2.3, and it will be compared with the calculation
applied to the case study including the installation of the CMV. Juts for a reminder it will be presented
the CO2 threshold for a classroom presented by the standard [45].
The standard provides some threshold that doesn’t have to be overtaken to avoid dangerous level of
CO2 inside the space. Of course the main parameter that influenced the level of carbon dioxide is the
ventilation rate, of which the natural regulation provides some standard values according to different
typologies of educational buildings. The level of carbon dioxide in a closed space are reported below in
compliance with the regulation ISO 7730 [15]:
- normal outdoor level of CO2: 350 – 450 ppm;
- acceptable outdoor level: lower than 600 ppm;
- odor problems: 600 – 1000;
- ASHRAE standards: 1000 ppm;
- light drowsiness: 1000 – 2500 ppm;
- light health issues: 3000 – 5000 ppm;
0.00
0.50
1.00
1.50
2.00
2.50
3.00
C.0.1 C.1.1 C.2.1 C.0.2 C.1.2 C.2.2 C.0.3 C.1.3 C.2.3 C.1.4 C.2.4
South-West South-East North-East North-West
Figure 7-33: Discomfort hours % of the classrooms, dived by glazing’s orientation, during the cooling season.
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- health problems: > 5000 ppm.
The graph presented in the Figure 7-21 can be easily compare with the one presented in the Figure 5-13,
in order to have a first clear understanding of the impact of the CMV.
As expected the installation of the CMV will reduce the concentration of the CO2 inside the classrooms,
so that the distribution will be homogeneous and that it won’t be reached the threshold of the ASHRAE
equal to 1000 ppm. Comparing the two case studies in this case the ventilation is more effective, since
the final concentration values are homogeneously lower, even though it has to be said the existing case
locate in Buštěhrad was already better than the Italian, IAQ talking.
7.3.7.3 Heating consumption savings
In this paragraph it will be analyzed the pros of doing the specific intervention explained in the previous
paragraph. In this case the intervention is the complete refurbishment of the glazing area, and the
possible installation of a CMV system, and the perks are represented by the energy and economic
savings and the GHG emission reductions.
Scenario
Heating
Primary Energy
Energy cost
GHG emissions
Reduction
[kWh/m2y] [€] [tonCO2] [%]
Base 199.05 10303.04 42161.00 -
Glazing 136.86 7083.60 28986.73 31%
Glazing + CMV 128.94 6673.69 27309.36 35%
The glazing refurbishment is highlighted as an energy effective retrofit work, this was foreseeable thanks
to the previous analysis done on the existing building, in addition to that the bigger glazing area respect
to the Italian case study determines an higher reduction for the Czech school.
0
10
20
30
40
50
60
70
80
90
100
C.0.1 C.1.1 C.2.1 C.0.2 C.1.2 C.2.2 C.0.3 C.1.3 C.2.3 C.1.4 C.2.4
South-West South-East North-East North-West
% <600 ppm 600<CO2<1000 ppm 1000<CO2<2500 ppm
Table 7.51: Heating reductions with the complete refurbishment of the glazing area and CMV combined, Buštěhrad
Figure 7-34: Distribution in percentage of the CO2 level present in the classroom, divided by orientation and
considering the installation of a CMV system, Buštěhrad
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7.3.7.4 Economic Impact
The cost of the intervention was calculated in a simple straightforward way, considering the cost of the
materials and of the installation of the specified work interventions. The analysis has been based on the
experience gained analyzing multiple case studies located in Czech Republic, and considered relevant
for the work intervention presented. Using this Czech case studies as guide lines, it has been possible to
create a small database recreating the costs for all the interventions, also through the help of Czech
Republic native colleague that collaborated with the thesis analysis.
The assumptions made until this point are confirmed by the economic analysis of the case scenarios
presented. The refurbishment of the glazing area (WIN 1) represents a beneficial intervention, as the
moderate payback time, equal to less than 15 years, is contrasted by the large amount of energy that can
be reduced with the intervention, keeping in mind the environmental impact of the energy retrofit.
The combined intervention (WIN 2) is less convenient, since in this case it has an higher payback time,
but in a bigger view it represents the intervention with the best impact on the existing building,
considering the increase of IAQ inside the classrooms.
7.3.8 Envelope retrofit: Proposed intervention
In order to have a complete view on what has been analyzed until this point, it has been decided to sum
up all the proposed intervention and create some combinations. This means that the retrofit works
proposed are going to be combined together in order to analyze different scale of retrofit. The analysis
goes from to the stand alone cases previously proposed to integrated approach retrofit, in which all the
dispersive components of the envelope have been insulated. In order to compare all the combination and
thus to understand the profit coming from each of the retrofit scenarios, first it has to be done a summary
representation of the multiple cases taken in consideration for this analysis.
-100
-80
-60
-40
-20
0
20
40
60
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
[k€]
yrs
WIN 1 WIN 2 Payback time
Figure 7-35: Representation of the payback year -x axis- and of the economic benefit -y axis- of the work
representing the refurbishment of the glazing area of Bustehrad’s school
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Ground Insulation Glazing Mechanical ventilaiton
EPS rigid Rockwool rigid Wood fiber rigid Polyester fiber Rockwool Calcium Silicate Rockwool roll Glass wool HD EPS HD Rockwool HD Wood fiber HD Synthetic material Low-e CMV Heat recovery
Case 1.1
Case 1.2
Case 1.3
Case 2.1
Case 2.2
Case 2.3
Case 3.1
Case 3.2
Case 4.1
Case 4.2
Case 4.3
Case 5.1
Case 6.1
Case 7.1
Case 8.1
Case 8.2
Case 8.3
Case 9.1
Case 9.2
Case 9.3
Case 10.1
Case 10.2
Case 10.3
Case 11.1
Case 11.2
Case 11.3
Case 12.1
Case 12.2
Case 12.3
Case 13.1
Case 13.2
Case 13.3
Case 14.1
Case 14.2
Case 14.3
Case 15.1
Case 15.2
Case 15.3
Case 16.1
Case 16.2
Case 16.3
Case 17.1
Case 17.2
Case 17.3
Case 18.1
Case 18.2
Case 18.3
Case 19.1
Case 19.2
Case 19.3
Case 20.1
Case 20.2
Case 20.3
Case 21.1
Case 21.2
Case 21.3
Case 22.1
Case 22.2
Case 22.3
Case 23.1
Case 23.2
Case 23.3
Case 24.1
Case 24.2
Case 24.3
Case 25.1
Case 25.2
Case 25.3
Case 26.1
Case 26.2
Case 26.3
Case 27.1
Case 27.2
Case 27.3
Wall external Insulation Wall internal insulation Attic insulation Roof insulationSCENARIO
Figure 7-36: Different case scenarios analyzed for the energy retrofit of Lecco’s school building
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As said, basically what has been done was combine together all the possible retrofit works, previously
explored, in order to get to the maximum energy demand reduction possible through envelope
optimization only. All the scenarios combined are exactly the ones analyzed in the previous paragraphs.
Through this analysis it will be possible to see what are the differences between a retrofit work done
with an integrated approach, and one done with distinct interventions not related to each other.
One of the benefit of designing a retrofit through an integrated approach, is that the impact of the thermal
bridges occurring with the application of thermal insulation can be reduced, as matter of fact intervening
on more elements of the envelope lets the designer have more possibility to develop efficient
connections between them. This will have an evident positive influence on the energy efficiency of the
intervention as well as on the investment needed to fund the works.
After defining all the case scenarios, the next and final step would be the analysis of them in terms of
reduction of the energy needed to heat the inner space, and the cost of the investment bore by the owner,
in this case the municipality, for the retrofit work.
The graph represented in the Figure 7-24 basically sums all the study done on the envelope of the school
building located in Lecco. It has been decided to represent 27 different retrofit interventions, sub-divided
into 3 case scenarios for each of the interventions, as seen in Figure 7-23.
The energy reduction changes only between the different retrofit interventions, while it stays the same
no matter the case scenario analyzed for each specific intervention. In this way it was possible to
construct a line for each retrofit intervention analyzed, so that this line could represent the range in which
the economic investment, bore for the different case scenarios of the specific intervention, would lay
into. The construction of the Intervention’s line was made joining the three points representing the three
different related case scenarios. So the construction points represent each of the 3 case scenario studied
for the specific intervention, as matter of fact for each line the lowest point represents the most economic
solution analyzed, while the top one represents the most expensive one.
Analyzing the results coming from the graph presented in the Figure 7-24, the first thing that can be
seen is that the exploit of an aimed integrated approach used for an envelope energy retrofit could lead
to a reduction equal to 85% of the energy needed for the existing heating system for the space
conditioning of the school building. As said this value has to be considered without any modification of
the technological plants existing nowadays, this remarks even more the great impact achievable with an
aimed retrofit intervention.
The maximum energy reduction is achieved thanks to the intervention classified as “Case 21”, in which
the retrofit is aimed towards the insulation of the external perimeter wall (from the outside and the
inside), the attic extrados, the ground-contact elements of the ground floor combined with the
refurbishment of the glazing area and the installation of a Controlled Mechanical Ventilation with Heat
recovery. The minimum amount needed to fund the work is equal to 250 thousands of euro. This means
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that if we analyze this case, the cost needed to reduce the heating energy needs of 1 kWh, will be equal
to: CER = 1.48 €/kWh.
This graph is useful for a comparison done considering the two figure representing the cost-energy ratio
of the interventions studied for the two different case studies (Figure 7-24). As matter of fact the two
cases representing the most energy effective scenario are exactly the same, they present more or less the
same percentage of energy reduction and investment costs, thus the cost of energy saving “CER” is quite
similar too. This means that the strategies applied for the case study located in Lecco are also applicable
to the Czech one, actually they will have a similar impact on the building, either economically and
energetically.
1
2
34
5
6
78
9
10
11
12
13
14
15
16
17
18
19
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21
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27
0
25
50
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100
125
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200
225
250
275
300
325
350
375
400
10% 15% 20% 25% 30% 35% 40% 45% 50% 55% 60% 65% 70% 75% 80% 85%
[k€] Investment cost
Energy reduction
Case 1 Case 2 Case 3 Case 4 Case 5 Case 6 Case 7
Case 8 Case 9 Case 10 Case 11 Case 12 Case 13 Case 14
Case 15 Case 16 Case 17 Case 18 Case 19 Case 20 Case 21
Figure 7-37: Analysis of the heating energy demand reduction % – x axis- and the cost of the investment [k€] - y
axis- of the different case scenarios considered for the for the energy retrofit of Bustehrad’s school building
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CHAPTER 8
8 Plant Optimization
The energy retrofit of the case study building, will not be focused only onto on the envelope of the
structure, but will be aimed also on the upgrade and optimization of the existing technological plants.
The optimization will be set on the presentation of multiple technologies applicable to the existing
conditions. The optimization will be base on the implementation of Photovoltaic panels, and the
refurbishment of the heating and DHW generation systems, in favor of new and up to date technologies.
The chapter will be split in two parts. One part will analyze an optimization solution of the existing
plants without interfering with the energy efficiency of the envelope of the building. The other part will
study different solutions involving the combination of gas-free technologies and the envelope insulation.
8.1 Photovoltaic system
The plant optimization will begin with the improvement of the existing system, with the application of
Photovoltaic panels on the roof structure of the two case study buildings.
For the Photovoltaic system, it has been decided to install an adequate amount of photovoltaic panels
with the following characteristics:
- Each module has an height of approximately 1 m and a length of 1.5 m;
- The material used for the panel is made of monocrystalline silicon, with an efficiency of 0.2;
- The peak power of each module is equal to 300 Wp;
- Efficiency of the system equal to 0.85.
So that the installation of this system could cover as much as possible the electricity needs of the specific
case study building. In order to exploit all the possible energy production given by the PV modules, it
has been decided to do a simple parametric study, for the optimization of the inclination angle and the
distance between the panels.
With the results obtained through the optimization analysis it will be possible to dimension the number
of PV panels that can be installed onto the structure, and the percentage of electricity needs covered.
8.1.1 Parametric solar radiation analysis
The parametric analysis is performed in order to optimize the positioning of the photovoltaic module
onto the roof structures of the specific case, so that the panels can receive the maximum amount of solar
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radiation available.
For this study it has been used a modelling software “Rhino” with a parametric analysis plug-in
“Grasshopper”. After the modelling of the context and the geometry of the building, it has been decided
what was going to be optimized by the software and what was going to be chosen by the designer.
In order to do this, it has to be designated the constraints and the parameters that are going to be
parametrized.
After this settings have been made, the solar radiation analysis can be performed onto the panels put in
the starting position ( equal to the suggested position), thus the optimization can be started.
8.1.1.1 Case study “Lecco”
Fort the “G. Carducci” school building of Lecco, the starting point has been locating and choosing the
pitch on which the PV panels will be installed. It has been decided to use the roof of the recent part of
the building, more precisely the pitch facing the South-West direction with an angle of 10 °.
Constraints:
- Position: South facing roof pitch;
- Height and length of each of the strings;
- Max tilt angle of the module: ⟂ to the pitch;
- Min tilt angle of the module: // to the pitch;
- Max distance between the modules: 100 cm;
- Min distance between the module: 0 cm.
Parameters:
- Tilt angle of the modules;
- Distance between the modules.
Figure 8-1: Solar radiation analysis on the PV panels placed in the starting position on the roof of Lecco’s school
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The starting position for Lecco, is equal to PV panels
with a tilt angle of 35°, as it is the recommended
inclination for the area, and relative distance between
each other equal to 50 cm. Here is also represented how
the PV panels have been grouped on the roof of the
building. It has been decide to create 4 strings made of a fixed number of PV panels.
The results of the optimization are presented through the table below, through which it is obvious that
the modification of the tilt angle and the distance of the module has a positive impact on the incident
radiation. The position that will be taken into account for the dimensioning is the optimized one, which
takes in consideration the shadings of the context.
Starting position Optimized position
Distance Tilt Radiation Distance Tilt Radiation
[cm] [°] [kWh/m2] [cm] [°] [kWh/m2]
String 1 50 35 1022.44 100 24 1047.75
String 2 50 35 967.21 100 21 997.2
String 3 50 35 971.95 100 20 993.5
String 4 50 35 936.9 100 22 954.27
The final step consists on evaluating the efficiency of the system and evaluate the production of the PV
panels. Considering the efficiency of the single module and of the system, and the number of PV panels
used, the energy production will be equal to 10202.28 kWh/y.
8.1.1.2 Case study Buštěhrad
Fort the school building of Buštěhrad, it has been decided to use the pitch of the roof facing the South-
East direction with 30 ° angle.
H b Area Panels
[m] [m] [mq] #
String 1 1 9.5 9.5 6
String 2 1 9.5 9.5 6
String 3 1 18 18 12
String 4 1 16.5 16.5 11
Table 8.1: PV panels dimension, Lecco
Table 8.2: Solar radiation optimization of the PV panels positioning, Lecco
Figure 8-2: Solar radiation analysis on the PV panels placed in the starting position of Bustehrad’s school
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The starting position for Bustherad, is equal
to PV panels with a tilt angle of 30°, as it is
the recommended inclination for the area,
and relative distance between each other
equal to 50 cm. Here is also represented how
the PV panels have been grouped on the roof
of the building. It has been decide to create 5 strings made of a fixed number of PV panels.
The results of the optimization are presented through the table below, through which it is obvious that
the modification of the tilt angle and the distance of the module has a positive impact on the incident
radiation. The position that will be taken into account for the dimensioning is the optimized one, which
takes in consideration the shadings of the context.
Starting position Optimized position
Distance Tilt Radiation Distance Tilt Radiation [cm] [°] [kWh/m2] [cm] [°] [kWh/m2]
String 1 50 30 1012.4 120 30 1044.37 String 2 50 30 1012.4 120 30 1044.37 String 3 50 30 1012.4 120 30 1044.37 String 4 50 30 1012.4 120 30 1044.37 String 5 50 30 1012.4 120 30 1044.37
In this case it’s obvious that the absence of vertical shadings onto the panels, clears the view thus the
optimization was not necessary for the tilt angle.
The final step consists on evaluating the efficiency of the system and evaluate the production of the PV
panels. Considering the efficiency of the single module and of the system, and the number of PV panels
used, the energy production will be equal to 9628.64 kWh/y.
8.2 Stand-Alone plant refurbishment
The first option that will be considered is the plant optimization of the existing building through a
complete refurbishment of the generation systems. This operation will be combined with the application
of Photovoltaic panels placed on top of the roof structure.
This intervention will not be combined with any energy retrofitting of the envelope, meaning that it will
only be focused onto the technological part of the building. The will was to analyze and understand the
impact of the efficiency of the technological plat onto the high energy demand of the building.
Since the envelope will not be modified, its energy performances wont’ be changed, thus we will be still
talking about a low energy efficiency building. So it has been decided to propose the refurbishment of
the plants, removing all the existing heating and DHW generations systems, and the installation of a
h b Area Panel
[m] [m] [mq] #
String 1 1 14.73 14.73 10
String 2 1 11.84 11.84 8
String 3 1 8.95 8.95 6
String 4 1 6.5 6.5 4
String 5 1 4.45 4.45 3
Table 8.3: PV panels dimension, Buštěhrad
Table 8.4: Solar radiation optimization of the PV panels positioning, Buštěhrad
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new condensation boiler which will cover the heating and DHW demand, combined with the application
of Photovoltaic panels, that will cover part of the electrical bill, as presented in § 8.1.
8.2.1 Case study “Lecco”
The refurbishment of the technological plant of the school located in Lecco, as previously said, will
consist on removing the existing generation systems, presented in the § 2.3.3, and the installation of a
new condensation boiler, with the combination of PV technology.
8.2.1.1 Design choice
In order to understand the impact of the boiler, it has been proceeded in an overall and fast dimensioning
of the new generation system. Considering the energy analysis done on the existing building, § 5.1.1,
and the analysis done onto the efficiency of the existing plant, it has been decided that a condensation
boiler with the power equal to 200 kW, will be sufficient to cover the heat and DHW demand of the
building in the existing conditions.
It has to be considered also the contribution of the PV panels, as in this case the production will be equal
to 10202.28 kWh/y. Comparing the energy demand, needed for the lighting and equipment system, as
well as the electricity needed to run the generations system, the energy produced by the PV panels is
equal to 85 % of the total electricity needs of the school case building.
The cost of the intervention was calculated in a simple straightforward way, considering the cost of the
materials and of the installation taken from the “Prezziario Lombardia”, which is the pricelist for civil
works in the Lombardy region.
The costs for the refurbishment of the technological plant has been
reported through a simple table. The costs of the Condensation
boiler, include: the removal of the old generation system, and the
installation of a control unit, for the modulation and the regulation
of the new heating and DHW system. With the installation of a new
generation system, it has been decided to implement the existing radiators with the installation of
Thermoelectric radiators valve “TRV”, so that the control of the emission system could be somehow
optimized. The costs of the PV system includes: the cost for the panels, the application, the sub-structure
onto which the panels will be installed, the put in action, and the control units of the system. Basically
the costs presented are intended as the final costs to have a new fully functioning generation and PV
system.
The major changes will be imposed by the new regulation system, installed onto the radiators and onto
the condensation boiler, so that the functioning of these can be now controlled either manually and
Implementation Cost
€
Condensation Boiler 18677
TRV valves 6160
PV system 24000
Table 8.5: Plant 1 costs, Lecco
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automatically, considering the occupation time and the outside temperature, thus reducing the energy
loss during the unoccupied hours. The new boiler will work only when students are present in the
classroom so basically from 06:00 to 18:00 ( considering that in the morning the radiators have to be
heated up a little earlier respect to the start of the lessons), and will also be turned off automatically
during the holiday or weekends, or whenever the outside temperature is higher than the one perceived
on the inside of the classrooms.
8.2.1.2 Consumption reduction
In this paragraph it will be analyzed the perks of doing the specific intervention explained in the previous
paragraph. In this case the intervention is the complete refurbishment of the generations systems of the
building with the addition of a PV system, the perks are represented by the energy and economic savings
and the GHG emission reductions.
Basically it will be compared the consumption of the building in the existing condition “Base case” and
the consumption that will be obtained if a refurbishment would be done “Plant 1”.
As it can been seen from the table, this intervention will lead to a total of 42 % of reduction of the
consumption, thus of the yearly expenses and the GHG emissions.
8.2.1.3 Economic Impact
The economic impact of the intervention is represented through an x-y axis graph, representing the
payback time of the investment and the economic benefit achievable through the energy reduction given
by the intervention.
The results show a satisfying value of payback time of the intervention, equal to 8 years. This means
that through the stand-alone intervention of refurbishment of the technological plant, it will be possible
to reduce the consumption of the school of more than 40 % and to see a positive cash flow incoming in
approximately 8 years. This highlights the impact of a well-designed and updated system, even though
the building itself in inefficient.
Primary Energy GHG emissions Operational Cost Reduction
Base Plant 1 Base Plant 1 Base Plant 1 Plant 1
[kWh/m2y] [kWh/m2y] [tonCO2] [tonCO2] [€] [€] %
Heating 232.94 136.37 45.04 26.36 15946.66 11272.97 41%
DHW 46.07 35.20 8.91 6.81 3593.17 2907.45 24%
Equipment 11.31 1.98 2.74 0.48 578.08 316.75 83%
Light 15.15 2.65 3.67 0.64 773.98 424.10 83%
Total 305.47 176.20 60.36 34.29 20891.89 14921.28 42%
Table 8.6: Reduction of the electric and thermal energy consumption of the school building of Lecco
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Through the considerations previously done it’s understandable how big is the impact of a proper
technological plant on the emissions and consumptions of a building. The first question that comes to
mid looking at these results is: “What happens than if I combine an envelope retrofit intervention with
a refurbishment of the plant? These field of application will be explored later on in the thesis work.
8.2.2 Case study “Bustehrad”
The refurbishment of the technological plant of the school located in Bustehrad, as previously said, will
consist on removing the existing generation systems, presented in the § 3.3.3, and the installation of a
new condensation boiler, with the combination of PV technology.
8.2.2.1 Design choice
In order to understand the impact of the boiler, it has been proceeded in an overall and fast dimensioning
of the new generation system. Considering the energy analysis done on the existing building, § 6.1.1,
and the analysis done onto the efficiency of the existing plant, it has been decided that a condensation
boiler with the power equal to 120 kW, will be sufficient to cover the heat and DHW demand of the
building in the existing conditions.
It has to be considered also the contribution of the PV panels, as in this case the production will be equal
to 9463.52 kWh/y. Comparing the energy demand, needed for the lighting and equipment system, as
well as the electricity needed to run the generations system, the energy produced by the PV panels is
equal to 55 % of the total electricity needs of the school case building.
In this case it can be seen that the energy produced by the PV system is pretty much the same in the two
case study, while of course the percentage of needs covered is difference due to the higher starting
electric consumption of the case study located in Lecco.
-60-40-20
020406080
100120140160
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
[k€]
yrs
Plant 1 Payback time
Figure 8-3: Representation of the payback time -x axis- and of the economic benefit -y axis- of each of the
case scenarios chosen for the plant refurbishment, Lecco
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The costs for the refurbishment of the technological plant has been
reported through a simple table. The costs of the Condensation
boiler, include: the removal of the old generation system, and the
installation of a control unit, for the modulation and the regulation
of the new heating and DHW system. With the installation of a new
generation system, it has been decided to implement the existing radiators with the installation of
Thermoelectric radiators valve “TRV”, so that the control of the emission system could be somehow
optimized. The costs of the PV system includes: the cost for the panels, the application, the sub-structure
onto which the panels will be installed, the put in action, and the control units of the system. Basically
the costs presented are intended as the final costs to have a new fully functioning generation and PV
system. As it was expected also in this case the costs for the equipment and the installation is cheaper
in Czech Republic respect to Italy, considered the lower market value of the case study.
The major changes will be imposed by the new regulation system, installed onto the radiators and onto
the condensation boiler, so that the functioning of these can be now controlled either manually and
automatically, considering the occupation time and the outside temperature, thus reducing the energy
loss during the unoccupied hours. The new boiler will work only when students are present in the
classroom so basically from 06:00 to 18:00 ( considering that in the morning the radiators have to be
heated up a little earlier respect to the start of the lessons), and will also be turned off automatically
during the holiday or weekends, or whenever the outside temperature is higher than the one perceived
on the inside of the classrooms.
8.2.2.2 Consumption reduction
In this paragraph it will be analyzed the perks of doing the complete refurbishment of the generations
systems of the building with the addition of a PV system, they will be represented by the energy and
economic savings and the GHG emission reductions.
Basically it will be compared the consumption of the building in the existing condition “Base case” and
the consumption that will be obtained if a refurbishment would be done “Plant 1”.
Primary Energy GHG emissions Operational Cost Reduction
Base Plant 1 Base Plant 1 Base Plant 1 Plant 1
[kWh/m2y] [kWh/m2y] [tonCO2] [tonCO2] [€] [€] %
Heating 199.05 110.35 44.06 24.43 10303.04 5711.68 45%
DHW 19.50 18.69 4.32 4.14 2127.57 2038.95 4%
Equipment 15.72 7.07 4.07 1.83 1418.43 638.29 55%
Light 9.08 4.09 3.67 1.65 819.79 368.91 55%
Total 237.78 140.20 56.12 32.05 14668.84 8757.83 41%
Implementation Cost
€
Condensation Boiler 15688
TRV valves 4620
PV system 16337
Table 8.7: Plant 1 costs, Bustehrad
Table 8.8: Reduction of the electric and thermal energy consumption of the school in Bustehrad
Thesis Report | Paolo Lo Conte
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As it can been seen from the table, this intervention will lead to a total of 41 % of reduction of the
consumption, thus of the yearly expenses and the GHG emissions.
Comparing the results of the Czech case study with the Italian one, it’s incredible to see how close the
total reduction of the two are. This is a clear sign of how similar the two case studies are, and therefore
how similar will be the results coming from the energy retrofit of the specific building. The fact that the
reduction are similar is due to the fact that the existing technological plants are pretty similar, exception
made for the gym’s system in Lecco, as matter of fact they are both equipped with 20 years old gas
boiler.
8.2.2.3 Economic Impact
The economic impact of the intervention is represented through an x-y axis graph, representing the
payback time of the investment and the economic benefit achievable through the energy reduction given
by the intervention.
The results show a satisfying value of payback time of the intervention, equal to 6 years. This means
that through the stand-alone intervention of refurbishment of the technological plant, it will be possible
to reduce the consumption of the school of more than 40 % and to see a positive cash flow incoming in
approximately 6 years. This highlights the impact of a well-designed and updated system, even though
the building itself in inefficient.
Comparing the results of the two case studies, the payback time of the two investment are really close
to each other, one again the Czech case study presents a lower payback time due to lower investment
cost. Overall the results can be qualified as satisfying, as the two payback time of the case studies are
low and they are close to each other,
-60-40-20
020406080
100120140160
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
[k€]
yrs
Plant 1 Payback time
Figure 8-4: Representation of the payback time -x axis- and of the economic benefit -y axis- of each of the
case scenarios chosen for the plant refurbishment, Bustehrad
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8.3 Heat pump technology
The results coming up from the envelope optimization of both of the case studies( § 7.3.8,7.2.8) show
in the same way the presence of a whole between the most energy performing cases an the rest. As
matter of fact through the graphs in the Figure 7-24 and Figure 7-36 it’s possible to see a gap between
the cases with an energy reduction lower than 70 % and the ones with an higher percentage. It has been
decided to take those energy performing cases, and implement them with the refurbishment of the
technological plant with the installation of a PV system to cover the energy need of the building (§ 8.1)
and a gas-free technology as the Air/water heat pump to cover the heating and DHW needs.
It has been decided to neglect all the cases without the installation of VMC, since the insulation of the
envelope will require a mechanical system to guarantee an appropriate indoor quality, which otherwise
can’t be reached.
A heat pump generator is a system composed of several elements capable of transferring thermal energy
from a body at a lower temperature to a higher temperature one, using electrical energy. The advantage
in using this type of system derives from the ability to supply more thermal energy (in heating mode)
than the electric one used by the generator as it absorbs heat from the external environment.
The principal characteristic, which is also what makes a heat pump system a very efficient and high
efficiency system, is the source used to withdraw or transfer heat. Heat pumps can be of different types:
- Air / air
- Air / water
- Water / air
- Water / water
- Earth / water
Heat pumps that use air as the source are the most widespread, the most economical, but also those with
a lower efficiency. Using air, it must never be too cold: the ideal temperature to provide heating in winter
is constant at 0 ° C. In rigid climates or with frequent changes in temperature, the pump requires auxiliary
devices such as a defrosting system that uses energy, reducing the COP (Coefficient Of Performance).
The COP of a heat pump is a dimensionless coefficient that indicates the level of performance of the
system. COP is the result of the ratio between energy supplied and energy consumed: the higher the
COP, the higher the efficiency. For example, if a machine has a COP = 4, it means that for each kWh of
electricity consumed, 4 kWh of thermal energy are returned. In cooling mode, the heat pump reverses
the cycle, but the principle remains the same. In this case the performance indicator is defined as EER
(Energy Efficient Ratio).
The most performing heat pumps, thanks to a constant source sampling temperature, are those of the
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Earth/water and Water/water type. The soil, starting from 6-8 meters of depth, maintains a constant
temperature in the space of a year which is approximately around 10-15 ° C. At the same time the ground
water maintains a constant temperature around 10-12 °C during the year.
8.3.1 Design choice
As previously said the most efficient heat pumps are the geothermal ones, which exploit the mild and
constant temperature of the ground or of the ground water. But at the same time they are the most
complex ones to install, thus the most expensive.
The use of a earth/water heat pump involves a geothermic plant, with the essential needs to install a
geothermal probe in the ground at a depth of 100 m or more. In order to do this it must be possible to
access the subsoil and have no restrictions on drilling. Not all types of subsoil are suitable, it’s necessary
a type of subsoil with a sufficiently high thermal conductivity, i.e. a good ability to transport heat.
For pumps that use water as a source, it is first necessary to identify an aquifer and make sure that it is
possible to collect water from it. The difficulty consists in fact, in addition to identifying the aquifer, in
the need to obtain an authorization from the territorial municipality. This is due to the fact that if there
were breakages in the probes, the thermal liquid would risk to leak and pollute water and subsoil.
As matter of fact the water/water heat pump systems can be open loop, directly exploiting the ground
water, or in a closed loop, with an intermediate heat transfer fluid as in the classic geothermal
applications
So in addition to what said previously in the case of an open loop circuit, in which the water is pumped
into the machine and then given back to the aquifer, several controls on the temperature and the quality
of the return water have to be performed in order not to alter the water present in the aquifer. Open loop
applications require the presence of one or more boreholes for water collection and its return. Finally
the municipality usually taxes the use of the aquifer applying a cost for the extraction of the water, which
has to be added in the operational costs of the plant.
For all these reasons the application of geothermal plant has been discarded in favor of a simpler
technology as the air/water heat pump. Moreover the decision has been made considering that the air
heat pumps have the advantage that they exploit a source always available, they don’t need any
expensive boreholes or heat exchangers and no authorization for the use at all. Plus has seen in the
climatic analysis done in the chapter 4, the climate of the two locations during the winter season will
not be a problem for the installation of the heat pump. As matter of fact it is not too rigid as the average
monthly temperature is around 0 and -2 °C and is not too humid too, thus not reducing the efficiency of
the pump due to the defrosting of the machine.
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8.3.2 Case study “Lecco”
In order to understand the impact of the boiler, it has been proceeded in an overall and fast dimensioning
of the new generation system. Considering the energy analysis done on the possible optimization of the
building, § 7.2.8, and the analysis done onto the efficiency of the existing plant, it has been decided that
a condensation boiler with the power equal to 80 kW, will be sufficient to cover the heat and DHW
demand of the building in the existing conditions, with a COP equal to 3.5 as defined by standards [19].
It has to be considered also the contribution of the PV panels, as in this case the production will be equal
to 10202.28 kWh/y. This is equal to the 85 % of the energy demand, needed for the lighting and
equipment system of the school case building.
The cost of the intervention was calculated in a simple
straightforward way, considering the cost of the heat pump and of
the installation. This costs have been decided based on a cross
analysis of the multiple offers received by specific companies, for
the specific heat pump.
The combined cases analyzed for this analysis focused in the application of Heat pump onto enrgy
performing envelopes are the followings.
Basically what has been done was to select the most performing case scenario analyzed in the Envelope
retrofit (considering only the ones with VMC) and apply to the building an air/water heat pump, in order
to see what could be the most energy reduction achievable with the retrofit of the case study building.
8.3.2.1 Building’s energy reduction
Different from the cases analyzed till now, the installation of a PV system combined with an heat pump
will involve the consumption of the entire building. This will mean that this intervention will affect all
Gym Insulation Glazing Mechanical ventilaiton
EPS rigid Rockwool rigid Wood fiber rigid Polyester fiber Rockwool Calcium Silicate Rockwool roll Glass wool HD EPS HD Rockwool HD Wood fiber HD Synthetic material Low-e CMV Heat recovery PV system Heat pump
Case 28.1
Case 28.2
Case 28.3
Case 29.1
Case 29.2
Case 29.3
Case 30.1
Case 30.2
Case 30.3
Case 31.1
Case 31.2
Case 31.3
Case 32.1
Case 32.2
Case 32.3
Technological PlantSCENARIO
Wall external Insulation Wall internal insulation Attic insulation Roof insulation
Implementation Cost
€
Air/Water Heat pump 40000
TRV valves 6160
PV system 24000
Table 8.9: Heat Pump costs, Lecco
Figure 8-5: Different case scenarios, involving an Heat pump, for the energy retrofit of Lecco’s school building
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the components of the building, it will be possible to see PE reduction in terms of heating, DHW, lighting
and equipment. Furthermore there won’t be any gas technology present after the retrofit, since the heat
pump will run only on electricity.
PE [kWh/(m2y)] Annual Total Reduction
Heating DHW Equipment Lights PV panels* Total € Ton CO2 %
Base 232.94 46.07 11.31 15.15 - 305.47 - - -
Case 28 21.50 19.41 15.15 11.31 22.14 45.24 17798.09 51.42 85.2%
Case 29 11.62 19.41 15.15 11.31 22.14 35.36 18473.87 53.37 88.4%
Case 30 10.55 19.41 15.15 11.31 22.14 34.29 18547.05 53.59 88.8%
Case 31 16.69 19.41 15.15 11.31 22.14 40.43 18127.07 52.37 86.8%
Case 32 11.39 19.41 15.15 11.31 22.14 35.12 18489.74 53.42 88.5%
* refers to the energy production of the PV panels per year divided by the net surface of the building.
The Table 8.10 shows some outstanding results regarding the installation of an air/water Heat pump
combined with PV system onto the school building case study, considering also the retrofitted envelope.
The range of the achievable total PE energy consumption of the retrofitted building goes from 34 to 45
kWh/(m2y) with a reduction from 85 to almost 89 %. This means that choosing one of the scenario here
presented it’s possible the reduce the energy reduction of the building so that the retrofitted building
could be certified as an A4 energy class building ( § 2.3.4) , which is the lowest class possible.
8.3.2.2 Economic Impact
The graph represented in the Figure 8-6 basically sums all the study done on the envelope of the school
building located in Lecco. It has been decided to represent 5 different retrofit interventions, sub-divided
into 3 case scenarios for each of the interventions, as seen in Figure 8-5.
The energy reduction changes only between the different retrofit interventions, while it stays the same
no matter the case scenario analyzed for each specific intervention. In this way it was possible to
construct a line for each retrofit intervention analyzed, so that this line could represent the range in which
the economic investment, bore for the different case scenarios of the specific intervention, would lay
into. The construction of the Intervention’s line was made joining the three points representing the three
different related case scenarios. So the construction points represent each of the 3 case scenario studied
for the specific intervention, as matter of fact for each line the lowest point represents the most economic
solution analyzed, while the top one represents the most expensive one.
The graph shows what has already been said previously, the application of the heat pump combined with
the PV system could lead to a minimum PE total energy reduction of 85 % to which it corresponds a
minimum investment cost of 240 thousands of euro, which translates to a CER equal to 0.92 €/kWh and
a payback time of 12 years. Meaning that the cheapest integrated intervention will guarantee an elevated
Table 8.10: Heating reductions with the installation of a Heat pump onto an efficient envelope, Lecco
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reduction of energy, with a moderate expense as it is 240 thousands of euro.
The graph shows that the application of the heat pump combined with the PV system could lead to a
maximum PE total energy reduction of 89 % to which it corresponds a minimum investment cost of 320
thousands of euro, which translates to a CER equal to 1.24 €/kWh and a payback time of 16 years.
Comparing the two extreme results the “case 28” and the “Case 32”, the most cost-effective seems to
be the Case 28, even though it will reach a lower energy reduction. This particular intervention will
involve of course the installation of a air/water Heat pump combined with a PV system, onto an envelope
with insulated external walls (either from the inside and outside), performing low-e double gazing and
CMV.
8.3.3 Case study “Bustehrad”
In order to understand the impact of the boiler, it has been proceeded in an overall and fast dimensioning
of the new generation system. Considering the energy analysis done on the possible optimization of the
building, § 7.3.8, and the analysis done onto the efficiency of the existing plant, it has been decided that
a condensation boiler with the power equal to 50 kW, will be sufficient to cover the heat and DHW
demand of the building in the existing conditions, with a COP equal to 3.5 as defined by standards [19].
It has to be considered also the contribution of the PV panels, as in this case the production will be equal
to 9463.52 kWh/y. This is equal to the 55 % of the energy demand, needed for the lighting and equipment
system of the school case building.
28
31
32
29
30
200
225
250
275
300
325
350
375
400
425
450
82.5% 83.0% 83.5% 84.0% 84.5% 85.0% 85.5% 86.0% 86.5% 87.0% 87.5% 88.0% 88.5% 89.0% 89.5% 90.0%
[k€] Investment cost
Energy reduction
Case 28 Case 29 Case 30 Case 31 Case 32
Figure 8-6: Analysis of the heating energy demand reduction % – x axis- and the cost of the investment [k€] - y
axis- of the different case scenarios considered for the for the Heat pump installation in Lecco’s school building
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The cost of the intervention was calculated in a simple
straightforward way, considering the cost of the heat pump and of
the installation. This costs have been decided based on a cross
analysis of the multiple offers received by specific companies, for
the specific heat pump.
It’s clear that, as seen throughout the entire thesis work, the costs for the Czech case are lower due to
lower starting energy consumption, and the lower costs for materials and labor.
The combined cases analyzed for this analysis focused in the application of Heat pump onto energy
performing envelopes are the followings.
Basically what has been done was to select the most performing case scenario analyzed in the Envelope
retrofit (considering only the ones with VMC) and apply to the building an air/water heat pump, in order
to see what could be the most energy reduction achievable with the retrofit of the case study building.
8.3.3.1 Building’s energy reduction
Different from the cases analyzed till now, the installation of a PV system combined with an heat pump
will involve the consumption of the entire building. This will mean that this intervention will affect all
the components of the building, it will be possible to see PE reduction in terms of heating, DHW, lighting
and equipment. Furthermore there won’t be any gas technology present after the retrofit, since the heat
pump will run only on electricity.
PE [kWh/(m2y)] Annual Total Reduction
Heating DHW Equipment Lights PV panels* Total € Ton CO2 %
Base 199.05 19.50 15.72 9.08 - 243.36 - - -
Case 28 28.60 2.04 9.09 15.73 20.03 35.42 12132.33 44.74 82.7%
Case 29 17.24 2.04 9.09 15.73 20.03 24.06 12898.38 47.56 87.9%
Case 30 16.74 2.04 9.09 15.73 20.03 23.56 12932.38 47.69 88.2%
Case 31 22.09 2.04 9.09 15.73 20.03 28.91 12571.63 46.36 85.7%
Case 32 21.70 2.04 9.51 16.15 20.03 29.36 12624.27 46.55 86.1%
Gym Insulation Glazing Mechanical ventilaiton
EPS rigid Rockwool rigid Wood fiber rigid Polyester fiber Rockwool Calcium Silicate Rockwool roll Glass wool HD EPS HD Rockwool HD Wood fiber HD Synthetic material Low-e CMV Heat recovery PV system Heat pump
Case 28.1
Case 28.2
Case 28.3
Case 29.1
Case 29.2
Case 29.3
Case 30.1
Case 30.2
Case 30.3
Case 31.1
Case 31.2
Case 31.3
Case 32.1
Case 32.2
Case 32.3
Technological PlantSCENARIO
Wall external Insulation Wall internal insulation Attic insulation Roof insulation
Implementation Cost
€
Air/Water Heat pump 25000
TRV valves 4620
PV system 16337
Table 8.11: Heat Pump costs,
Bustehrad
Table 8.12: Heating reductions with the installation of a Heat pump onto an efficient envelope, Bustehrad
Figure 8-7: Different case scenarios, involving an Heat pump, for the energy retrofit of Bustehrad school building
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* refers to the energy production of the PV panels per year divided by the net surface of the building.
The Table 8.12 shows some outstanding results regarding the installation of an air/water Heat pump
combined with PV system onto the school building case study, considering also the retrofitted envelope.
The range of the achievable total PE energy consumption of the retrofitted building goes from 34 to 45
kWh/(m2y) with a reduction from 82 to 88 %. This means that choosing one of the scenario here
presented it’s possible the reduce the energy reduction of the building so that the retrofitted building
could be certified as an A4 energy class building ( §3.3.4) , which is the lowest class possible.
The results coming from the Table 8.12 and the Table 8.10 are once again really similar, meaning that
the impact of the installation of an heat pump will be pretty much the same. Furthermore this intervention
will guarantee in both cases the achievement of the energy class A4, even though the total energy
consumption reached in the Czech case study is lower respect to the Italian one, due to the different
energy starting point of the two cases.
8.3.3.2 Economic impact
The graph represented in the Figure 8-8 basically sums all the study done on the envelope of the school
building located in Lecco. It has been decided to represent 5 different retrofit interventions, sub-divided
into 3 case scenarios for each of the interventions, as seen in .
The energy reduction changes only between the different retrofit interventions, while it stays the same
no matter the case scenario analyzed for each specific intervention. In this way it was possible to
construct a line for each retrofit intervention analyzed, so that this line could represent the range in which
the economic investment, bore for the different case scenarios of the specific intervention, would lay
into. The construction of the Intervention’s line was made joining the three points representing the three
different related case scenarios. So the construction points represent each of the 3 case scenario studied
for the specific intervention, as matter of fact for each line the lowest point represents the most economic
solution analyzed, while the top one represents the most expensive one.
The graph shows what has already been said previously, the application of the heat pump combined with
the PV system could lead to a minimum PE total energy reduction of 82.5 % to which it corresponds a
minimum investment cost of 180 thousands of euro, which translates to a CER equal to 0.88 €/kWh and
a payback time of 10 years. Meaning that the cheapest integrated intervention will guarantee an elevated
reduction of energy, with a moderate expense of less than 200 thousands of euro.
The graph shows that the application of the heat pump combined with the PV system could lead to a
maximum PE total energy reduction of 88 % to which it corresponds a minimum investment cost of 230
thousands of euro, which translates to a CER equal to 1.10 €/kWh and a payback time of 13 years.
Comparing the two extreme results the “case 28” and the “Case 32”, the most cost-effective seems to
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be the Case 28, even though it will reach a lower energy reduction. This particular intervention will
involve of course the installation of a air/water Heat pump combined with a PV system, onto an envelope
with insulated external walls (either from the inside and outside), performing low-e double gazing and
CMV.
Comparing the Figure 8-7 and the Figure 8-5 it is possible to have a final and global view on the possible
effects of the specific integrated strategies onto different buildings located in different part of Central
Europe. Once more the results in terms of percentage, in this case percentage of total PE reduction, are
very similar for the two case study, they almost coincide. On the other hand it is possible to see that the
low cost of labor materials, makes the intervention in Czech Republic more feasible, as the “Case 28”
has a payback time of only 10 years, which is not really different from the 12 years seen for the Italian,
but still guarantees to the investor a low risk intervention, which will profit his bank account and at the
same time definitely decrease the energy emissions, contributing in the GHG emission reduction plans
present throughout all Europe.
28
3132
29
30
160
180
200
220
240
260
280
300
320
340
360
82.5% 83.0% 83.5% 84.0% 84.5% 85.0% 85.5% 86.0% 86.5% 87.0% 87.5% 88.0% 88.5% 89.0% 89.5% 90.0%
[k€] Investment cost
Energy reduction
Case 28 Case 29 Case 30 Case 31 Case 32
Figure 8-8: Analysis of the heating energy demand reduction % – x axis- and the cost of the investment [k€] - y
axis- of the different case scenarios considered for the for the Heat pump installation in Bustehrad school building
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Conclusions
This thesis work addresses the necessary implementation of an integrated strategy promoting a large-
scale energy retrofitting of the public educational building stock in the Central Europe area. It develops
tailored planning for these buildings so to address the long-term objective of deep retrofitting promoting
a technologically logical step-by-step approach that can be managed with affordable budgets. This work
supports the overall program goal of reducing carbon emission in the cities of Central Europe, creating
an enabling framework to promote large scale energy retrofit of existing public educational buildings.
This has been done analyzing in terms of energy and costs two different case studies school buildings
located in two different part of the CE area, Italy and Czech Republic.
The data analyzed, starting from the preliminary weather analysis of the two different location, has
shown positive feedback throughout the entire work. As matter of fact the innovativeness of this work
is to focus the analysis onto school building localized in the CE, thus with the assumption that the
geographical boundaries of this area could actually correspond to climatic boundaries, so that the
climatic conditions are homogeneous.
The energy analysis done onto the existing case study school buildings has confirmed the second
assumption, for which even though the building structures and building techniques used throughout
Europe are different, schools of the CE area with similar construction age have comparable energy
consumption. Meaning that it is possible to asses and identify a common starting point for the energy
retrofit process of multiple eductional buildings located in the CE area.
The results coming from the energy analysis have been used as guidelines for the energy retrofit process.
The first part of the retrofit process involved the re-cladding of the school buildings through an energy
optimization of the envelope, thus insulating the building’s elements in contact with the outside
environment. This highlights two important aspects which have to be taken into account as fundamentals
for the retrofit process. Intervening on the most vulnerable elements (in terms of energy performances)
of the two buildings, has pointed out which are the most beneficial interventions.
As matter of fact, thanks to an accurate energy analysis of the existing case, it was possible to propose
aimed energy retrofit intervention which were applied in the same way onto the different school
buildings and that had, most importantly, similar impact onto the energy and economic consumptions
of the case studies. Basically this means that it was possible to spot the most energy-efficient
intervention for the two case studies, and that above all, they matched and had similar impact on the
existing buildings.
The work than steps into a detail analysis on the perks of using an integrated approach for the energy
retrofit interventions. It has been possible to analyze different scenarios involving different level of
detail, going from a simple refurbishment of the roof structure to a combined insulation of multiple
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188
dispersive elements. The results show that the exploit of an integrated approach pays off not only on the
energy and emission reduction level, but also on an economic one, pointing out the fact that aimed
combined intervention, with high investment costs, can also represent the most economically beneficial.
Moreover this work is able to mark guide lines which lead to an energy retrofit capable of reducing the
consumptions of the school buildings to a maximum of almost 90% of the initial value, with non-
invasive low budget interventions , transforming the real estate into a low energy building, certifiable in
the A4 energy class. These guidelines are based on the results extracted from the analysis done onto the
two case study, which means that they can be successfully applied to educational buildings with similar
properties located in the Central Europe area, fulfilling the goal of this thesis work.
A small and last consideration has to be done on the simple economic impact analysis done onto the
most energy-efficient intervention proposed. The investment costs considered throughout this thesis
work were calculated, without the addition of any financial benefit coming from the municipality, State
or European Union, in order to have a more plain and comparable cost. But analyzing the payback time
given by the analysis done, it’s clear that the retrofit process has to be supported by these authorities,
with some financial help, so that the combination of these benefits with aimed integrated approach
interventions re-defining the energy retrofit from possible to feasible.
Thesis Report | Paolo Lo Conte
Bibliography
[1] European commission database, "2020 Climate & Energy package," [Online]. Available:
https://ec.europa.eu/clima/policies/strategies/2020_en.
[2] "Kyoto Protocol," in COP3 Conference of the UNFCCC, Kyoto, 1997.
[3] "Attachment 3:European Directive," in Energy Efficiency Directive EED 2012/27/UE.
[4] Europena commission datatabase, "EU building stock observatory," [Online]. Available:
https://ec.europa.eu/energy/en/eu-buildings-database.
[5] Luísa Dias Pereira, Daniela Raimondo,Stefano Paolo Corgnati, "Energy consumption in schools
– A review paper".
[6] "Italian Official Gazette n° 148," Italian republic, 07/06/1976.
[7] ENEA, "Guide to the energy efficiency of the school building," 2017.
[8] Italian Republic, "Norme per l'attuazione del Piano energetico nazionale in materia di uso
razionale dell'energia, di risparmio," Law no. 10, 9 January 1991.
[9] Italina National Energy Strategies, "Italian Energy Efficiency Action Plan," EEAP 2014, 2014.
[10] "Energy Rennovation," JRC Science and Policy Report, 2015.
[11] Arch. Roberto De marchi, "Ri-costruire a quasi km 0," 22 November 2013.
[12] Italia Republic, "DPR 59/09," Nuovo quadro di disposizioni obbligatorie (requisiti sull’efficienza
energetica degli edifici) che sostituiscono le indicazioni “transitorie” dell’Allegato I del
DLgs311/06., no. Decreto del Presidente della Repubblica n. 59, 2 April 2009.
[13] Ministro dello sviluppo economico di concerto con i Ministri dell’ambiente e della tutela del
territorio e del mare, delle infrastrutture e dei trasporti e per la semplificazione e la pubblica
amministrazione, "Linee guida nazionali per la certificazione energetica degli edifici," Decreto
interministeriale del 26 giugno , 2015.
[14] European Energy commision, Energy Performance Buildings Directive 2 - EPBD 2, Directive
2010/31/EU.
[15] Ministero dello Sviluppo economico, Aggiornamento delle disposizioni in merito alla disciplina
per l'efficenza energetica degli edifici e al relativo attestato di prestazione energetica, DECRETO
N. 176 DEL 12 GENNAIO 2017, 12/01/2017.
[16] Gazzetta Ufficiale della Repubblica Italiana, Disposizioni urgenti per il recepimento della
Thesis Report | Paolo Lo Conte
Direttiva 2010/31/UE del Parlamento europeo e del Consiglio del 19 maggio 2010, sulla
prestazione energetica nell'edilizia, DECRETO-LEGGE n. 63, 4 giugno 2013.
[17] Regolamento recante disciplina dei criteri di accreditamento per assicurare la qualificazione e
l'indipendenza degli esperti e degli organismi a cui affidare la certificazione energetica degli
edifici, DECRETO DEL PRESIDENTE DELLA REPUBBLICA n. 75, 16 aprile 2013.
[18] Decreto del Ministero dello sviluppo economico 26 giugno 2015, Linee guida nazionali per la
certificazione energetica.
[19] "International Energy Agency "IEA"," [Online]. Available:
https://www.iea.org/policiesandmeasures/energyefficiency/.
[20] Tabula research facility, "National Scientific Report "Czech Republic"," in Typology Approach
for Building Stock Energy Assessment, 2015.
[21] European Union Law, Government Resolution No 362, EUR-LEX, 18 May 2015.
[22] European Union Law, Directive No. 1/2014, EUR-Lex.
[23] International Energy Agency of Czech Republic, "Act No. 406/2000 Coll," in Energy
Management Act, 01/01/2013.
[24] Executive Agencies for SMEs, Intelligent Energy Europe Programme (IEE), European
Commission, 2007-2013.
[25] European Commission, "Typology Approach for Building Stock Energy Assessment," in
Intelligent Energy Europe, 2009-2012.
[26] EN ISO 6946, "Calculation methods," in Building components and building elements. Thermal
resistance and thermal transmittance, European Committee, 2017.
[27] EN ISO 13370, "Calculation methods," in Thermal performance of the building. Heat trasnfer via
ground, European Committee, 2007.
[28] EN ISO 12464 - 1, "Indoor work places," in Light and lighting. Lighting of work places, European
Committee, 2011.
[29] CIBSE Guide A: Environmental Desing, CIBSE, 2015.
[30] "National Calculation Methodology," in UK Building Regulations Part L2, 2006.
[31] EN ISO 13000-2, "Evaluation of primary energy need and of system efficiencies for space heating,
domestic hot water production, ventilation and lighting for non- buildings," in Energy
performance of buildings- Part 2, European Committee, 2014.
[32] UNI EN 442, "Technical specifications and requirements," in Radiators and convectors-Part 1,
Italian Committee.
Thesis Report | Paolo Lo Conte
[33] EN ISO 14064-1, "Specification with guidance at the organization level for quantification and
reporting of greenhouse gas emissions and removals," in Greenhouse gases- Part 1, European
Committee, 2006.
[34] Intergovernamental Panel on Climate Change "IPCC" , Guidelines for National Greenhouse Gas
Inventories, 2016.
[35] CNG Europe, "Map of Natural Gas Vehicle (NVG) Compressed natural gas (CNG) filling stations
in Europe," [Online]. Available: http://cngeurope.com/.
[36] IEA Czech Republic, "Regulation No. 148," in Energy Management Act, 2007.
[37] Agenzia Regionale per la Protezione dell'Ambiente, " ARPA Lombardia," [Online]. Available:
http://www.arpalombardia.it/Pages/Ricerca-Dati-ed-Indicatori.aspx.
[38] Ceske Republicky, "Republicky, Agenture ochrany prírody a krajiny Ceske," [Online]. Available:
http://www.ochranaprirody.cz/.
[39] "EPA", European Network of the Heads of Environment Protection Agencies,
"http://epanet.pbe.eea.europa.eu/european_epas," [Online].
[40] ARPA Lombardy, "Beaufort Scale for wind intensity".
[41] Regioncal Council of Lombardy, Decree no 2129, 2014.
[42] "PCM Ordinance n 3519," in Seismic Hazard, 28 April 2006.
[43] ASHRAE Standard 55, Thermal Environmental Condition for Human Occupancy, 2013.
[44] EN ISO 15251, Indoor environmental input parameters for design and assessment of energy
performance of buildings addressing indoor air quality, thermal environment, lighting and
acoustics, European Committee, 2007.
[45] EN ISO 7730, Predicting the perceived thermal sensation of a human being within confined
moderate environments, 1997.
[46] UNI EN ISO 7726, Measurement of physical quantities that affect the thermal sensations, 1995.
[47] J. van Hoof , Forty years of Fanger’s model of thermal comfort: comfort for all Indoor Air, 2008.
[48] RJ de Dear, GS Brager, "Thermal comfort in naturally ventilated buildings: revisions to ASHRAE
Standard 55," in Energy building, vol. Energy Build , 2015.
[49] R. de Dear, "Indoor Air," in Thermal comfort in practice, 2014.
[50] Roaf S, Nicol F, Humphreys M, Tuohy P, Boerstra A, "Twentieth century standards for thermal
comfort: promoting high energy buildings," Architectural Science review, 2011.
[51] MA Humphreys, "Thermal comfort temperatures world-wide – the current position.," in
Renewable Energy, 1996.
Thesis Report | Paolo Lo Conte
[52] CIBSE, "The limits of thermal comfort: Avoiding Overheating in European Buildings," in
Technical Memorandum 52, Oct 2013.
[53] Sustainable Energy Research Team (SERT), Inventory of Carbon and Energy(ICE), University of
Bath UK.
[54] ČSN 73 0540, Thermal protection of buildings, Czech Committee.
[55] EN ISO 11300-1, "Determination of the building's thermal energy requirements for summer and
winter air conditioning".Energy performances of buildings- Part 1.
[56] EN ISO 13786, "Calculation methods," in Thermal performance of building components -
Dynamic thermal characteristics , 2008.
[57] EN ISO 10077-2, "Calculation of thermal transmittance- Numerical method for frames," in
Thermal performance of windows, doors and closures - Part 2, 2012.
[58] UNI 10339, Aeraulic system for internal comfort, Italian Committee, 1995.
[59] The Chartered Institution of Building Services Engineers, Degree-days: Theory and Application,
2006.
[60] Italian Republic, Decreto del Presidente della Repubblica n. 412, 31 ottobre 2009.
[61] European Environment Agency, "Heating degree days," [Online]. Available:
https://www.eea.europa.eu/data-and-maps/indicators/heating-degree-days-1/assessment.
Thesis Report | Paolo Lo Conte
Appendices
Appendix I – Validation of the energy models
In order to see if the energy model made, is reliable, a verification has to be performed. The verification
in basically based on comparing the consumptions coming from the energy model with the real ones
coming from the energy bill.
In this case the parameter that will be compared is the amount in mc/year of natural gas used by the
heating system to fulfill the heating needs throughout the entire thermal season. To do this it’s necessary
to standardize the results coming from the software and the ones coming from the bill, these is due to
the fact that the two have to be equal in order to be comparable. This will be translated into a Degree-
days standardization.
As matter of fact the first calculation will involve the Degree days. Degree-days are essentially the
summation of temperature differences over time, and hence they capture both extremity and duration of
outdoor temperatures. The temperature difference is between a reference temperature and the outdoor
air temperature. The reference temperature is known as the base temperature which, for buildings, is a
balance point temperature, i.e. the outdoor temperature at which the heating (or cooling) systems do not
need to run in order to maintain comfort conditions. [59]
Degree-days may be calculated using different approaches and therefore different input data [59]. For
the purposes of the validation the degree-days will be calculated as the following:
𝐷𝐷 = ∑(𝑇𝑜 − 𝑇𝑠𝑒𝑡 𝑝𝑜𝑖𝑛𝑡
𝑛
𝑖=1
)
Where:
- To is the daily average outside temperature;
- Tset point is the set point temperature equal to 20 °C;
- i is equal to number of days included in a thermal season.
This will represent the actual degree days per year, which are the ones considered for the energy bill.
Unfortunately the software is not able to do this calculation for each year, changing the weather
conditions depending on the year analyzed. Therefore it has been calculated only the DD corresponding
on the outside temperature of a specific year, present in the software database.
Finally in order to standardize these two different DDs it will be presented the standard’s DD [60] [61]
(depending on the climatic zone of the city), which as the one of the software is only one, not depending
on the year.
The comparison will be done through the consultation of the energy bills referring to the thermal season
Thesis Report | Paolo Lo Conte
of the 2015-2016 and of the 2016-2017, made available from the schools’ authorities.
The second and final step, involves the comparison of the two standardize quantities, for the two
different case studies.
Finally in order to verify the reliability of the two models it’s necessary to calculate the Deviation of the
results coming from the energy model. The deviation represents how different the results coming from
the energy model are compared the ones coming from the energy bill.
As it can be seen both of the energy models can be considered reliable, as the deviation is less than ± 10
%. As matter of fact the consumption of natural gas, expressed in [m3/year], coming from the energy
model is only 2.2 percent lower respect to the real consumptions, obtained through the energy bill,
meaning that during the modelling of the case study it has been done a slight under consideration. The
deviation for the Czech case study is equal to – 3.6%, meaning that the results coming from the energy
model are slightly lower than the real ones.
Bustehrad Degree days
Standard 3431
2015-2016 3198
2016-2017 3545
Software 3644
Standardize Consumptions
Source year m3/year
Software - 22135
Energy bill
2015-16 23227
2016-17 22651
Average 22939
Deviation -3.6%
Standardize Consumptions
Source year m3/year
Software - 23013
Energy bill
2015-16 23518
2016-17 23518
Average 23518
Deviation -2.2%
Lecco Degree days
Standard 2383
2015-2016 2166
2016-2017 2186
Software 2750
- Lecco - Bustehrad
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Appendix II – Thermal analysis of the window
For the thermal analysis of the elements, it has been used the thermal transmittance analysis of the
frame of the window, the study of the thermal bridge between the frame and the glass, the verification
of presence of condensation in the main joints, using the software Therm.
The thermal transmittance of the window (Uw) was found using the calculation method presented in the
standard UNI EN ISO 1077-2 [43], in which the elements are divided in frame , glass, and glass’ spacer.
Uw = AgUg + AfU𝑓 + Lgψ
g
Atot
- Uw is the thermal transmittance of the window
- Ug is the thermal transmittance of the glass
- Lg is the length of the glass
- Ag is the area of the glass
- Af is the area of the frame
- 𝜓 is the linear thermal transmittance due to the thermal bridge of the window
For the thermal calculations that will be explored further in detailed, it has been considered the boundary
conditions as shown in the figure below.
Boundary Conditions Temperature[°C] U Transmittance [W/m2k]
External -5 25
Internal vertical 20 7.7
Internal incremented 20 5
Internal horizontal 20 10
The presence of the boundary condition “Internal incremented” is done in order to consider better the
surfaces affected by a small value of thermal exchange due to convection and irradiation( it was used
Glass Length Lg Glass Area Ag Frame Area Af
[m2] [m2] [m2]
0.95 1.83 0.57
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wherever there were sudden change of direction).
The choice of the glass was accurately done thanks to the spectrum online software given by Pilkington:
Following the UNI EN ISO 10077-2 [43] the calculation of the transmittance of the frame (Uf) was done
replacing the glass with an insulation panel, with conductivity of λ= 0.035 W/m2K.
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The section of the proposed glazing is:
The results from the software are:
Frame + Insulation Panel Frame Edge
U [W/m2K] 1.14 0.6971
b [m] 0.085 0.190
Following the standard, it was later considered the real case( in which the window is composed by a
frame and a glass) , using the same boundary condition as before.
For what concerns the conductivity of the gap between the two glazings, filled with argon, it was
calculated with an hand calculation starting from the value of the Ug.
Ug = 1 W/m2K sv = 0.006 m seq = 0.016 m
λv= 0.8 W/mK Rsi= 0.13 m2K/W Rse= 0.04 m2K/W
1
𝑈𝑔 = 𝑅𝑔
𝑅𝑔 = 𝑠𝑣
𝜆𝑣 +
𝑠𝑣
𝝀𝑣 +
𝑠𝑒𝑞
𝜆𝑒𝑞 + 𝑅𝑠𝑖 + 𝑅𝑠𝑒
Material Characteristics
Component
Thermal
conductivity
[W/mK]
Insulation 0.035
PVC 0.19
Gaskets (EPDM) 0.25
Spacer (PVC) 0.19
Polyammide 6.6 0.3
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𝑠𝑒𝑞
𝝀𝑒𝑞 = 𝑅𝑔 −
𝑠𝑣
𝝀𝑣 +
𝑠𝑣
𝝀𝑣 + 𝑅𝑠𝑖 + 𝑅𝑠𝑒 = 0.815 m2K/W
𝝀𝑒𝑞 = 0.02 W/mK
Therefore the following calculation will be done with the value of 0,02 W/mK for the gap in between
the two glazing.
The section of the proposed glazing is:
The results from the software are:
Frame + Insulation Panel Frame Edge
U [W/m2K] 1.18 1.135
b [m] 0.085 0.190
At this point we were able to calculate the thermal bridge that occurs due to the 10 eometrical
irregolarities and the material choosen. This evaluation has been done using the subtraction of the fluxes.
We can calculate the thermal conductivity of the joint:
Vertical Section:
Horizontal Section
- Lѱ,2D = thermal conductivity [W/mK]
- Uf,g = thermal conductivity of the frame in the case of frame+ glass [W/m2K]
- bf = I of the frame [m]
- Ue = thermal conductivity of the glass in the case of frame+glass [W/m2K]
- be = length of the glass [m]
We proceed in the calculatin of the thermal linear trasmittance ψ:
Material Characteristics
Component
Thermal
conductivity
[W/mK]
Argon 0.02
Glass 1
PVC 0.19
Gaskets (EPDM) 0.25
Spacer (PVC) 0.19
Polyammide 6.6 0.3
Silica gel 0.13
Lѱ,2D = Uf,gbf + Uebe = 0.461
W/mK Lѱ,2D = Uf,gbf + Uebe = 0.469
W/mK
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Vertical Section
Horizontal Section
- - Uf,p= thermal conductivity of the fram in the case fram+ insulation panel [W/m2K]
- - Ug = thermal conductivity of the glass [W/m2K]
- - bg = length of the glass [m]
Now that there are all the needed values the work can go on and calculate the global thermal
transmittance of the window and check if it is acceptable.
𝑈𝑤 = 𝐴𝑔𝑈𝑔 + 𝐴𝑓𝑈𝑓 + 𝐿𝑔𝜓𝑔
𝐴𝑡𝑜𝑡= 1. 16 𝑊/𝑚2𝐾
The value obtained is lower than the limit presented in the § 7.2.7, equal to 1.3 W/m2K.
The second step that has to be done in order to satisfy the limitation imposed by the standards is the
verification of the solar transmission factor “ggl+sh“ for glazing components so that: ggl+sh ≤ 0.35. In order
to do the verification it has been followed the EN ISO 11300-1 [41].
First of all it has to be considered that the reduction factor, imposed by standard. The reduction factor
goes from 0 to 1, changing depending on the type of shading applied onto the analyzed windows. The
reduction factor is strictly related to the transmission factor for the glass “ggl” calculated through the
use of the Pilkington spectrum software. Finally it has to be accounted also for the exposition factor
“Fw” which considers the variation of the transmittance of total solar energy as a function of the angle
of incidence of solar radiation.
- ggl+sh/ggl = 0.5;
- ggl = 0.58 (Pilkington spectrtum);
- Fw = 0.916 ( considering the worst orientation, which for double glazing is represented by
East/West in May).
Considering that :
𝑔𝑔𝑙+𝑠ℎ =0.5∗ 𝑔𝑔𝑙
𝐹𝑤 = 0.316 ≤ 0.35
Therefore the verification is satisfied.
Ѱ= Lѱ,2D -Uf,pbf - Ugbg = 0.0396 W/mK
Ѱ= Lѱ,2D -Uf,pbf - Ugbg = 0.0461 W/mK
Thesis Report | Paolo Lo Conte
Appendix III – Economic index of the scenarios
The economic index CER (Cost of Energy Saving, expressed in €/kWh) provides interesting results
regarding the economic feasibility of an intervention. This index clearly defines the economic
disbursement sustained by the user for each unit of energy saved as a result of the redevelopment
intervention.
In the present study, a value of the simplified CER will be used, defined as the ratio between the sum of
the costs of the initial investment and the expected energy savings at the end of the useful life of the
realized energy measure. The CER is expressed as follows:
𝐶𝐸𝑅 =∑ 𝐶𝑛
𝑖=0
∑ 𝐸𝑟𝑖𝑠𝑝,𝑖𝑛𝑖=1
Where:
- C = costs incurred for the intervention in the i-th year;
- Erisp,I = energy saved in the i-th year following the intervention.
In this formula only the costs I related to the initial intervention I0 are considered (therefore, the energy
costs before and after intervention are not included). The annual maintenance and operation costs were
excluded as no changes in the cost between the intervention and post-intervention were considered for
these items. Likewise, there are no financial burdens because the investment paid is considered entirely
within the first year, therefore no type of payment is deferred.
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Representation of the CER value [€/kWh] for each of the envelope optimization scenarios, Lecco:
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Representation of the CER value [€/kWh] for each of the Heat pump optimization scenarios, Lecco:
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Representation of the CER value [€/kWh] for each of the envelope optimization scenario, Buštěhrad:
Thesis Report | Paolo Lo Conte
Representation of the CER value [€/kWh] for each of the Heat pump optimization scenarios, Lecco:
Thesis Report | Paolo Lo Conte
Appendix IV – Dimensioning verification of radiators
The use of an Heat pump in a retrofit intervention, is subjected to a further verification, which is the
compatibility of this technology, which works with lower temperature respect to a gas boiler, with the
presence of cast iron radiators.
In order to do this it has been done a verification on the actual dimensions of the radiators. This means
that, considering the actual quality and properties of the existing radiators it has been calculated the right
amount of elements per radiators needed, to fulfill the thermal needs of all the heated spaces of the two
case study buildings, considering the installation of an air/water Heat pump. The man particular of heat
pumps is that they work with an average ∆T = 30 K, while gas boiler work with a ∆T = 50 K which is
the best fit for high thermal inertia cast iron radiators.
First of all it has been calculated the new Thermal Power of the existing radiatios, considering the ∆T =
30 K of the heat pump.
Radiators properties Value Formula
Thermal power with Δt = 50 K
100 W Average of radiator's thermal power
found in different data sheets
ΔT, real 30 K T,average - T,internal ambient
n 1.3 From data sheets
Thermal power with Δt = 30 K
51.48 W
After that it went on a visual survey of each of the rooms of the heated spaces of the case study buildings,
in order to collect the information about the number of elements each radiator has, and the amount of
radiators found in each classroom. Both of the school buildings presented radiators composed of 16
elements, in addition to that, only the case study located in Lecco presented some classrooms with
radiators composed of 40 elements.
Below it will be summed all the calculations done in order to perform the verification in both of the case
studies analyzed throughout the thesis work.
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Case study: Elementary School G. Carducci , Lecco
Thermal need Verification
kWh/year W kWh/year Need < Power
Kitchen 1381.31 4 0 3294.40 14469.01 verified
Class-C01 1036.26 4 0 3294.40 14469.01 verified
Toilet 1 299.36 1 0 823.60 3617.25 verified
Class-C02 694.40 2 0 1647.20 7234.51 verified
Hall 1150.53 4 0 3294.40 14469.01 verified
Washign room 833.52 3 0 2470.80 10851.76 verified
Class-C12 596.84 5 0 4118.00 18086.27 verified
Toilet 2 506.70 1 0 823.60 3617.25 verified
Class-C13 915.45 4 0 3294.40 14469.01 verified
Class-C11 986.63 2 0 1647.20 7234.51 verified
Toilet 3 632.72 1 0 823.60 3617.25 verified
Class-C14 827.61 0 2 4118.00 18086.27 verified
Class-C15 831.71 0 3 6177.00 27129.40 verified
Class-C16 1219.46 0 2 4118.00 18086.27 verified
Class-C22 1076.67 4 0 3294.40 14469.01 verified
Toilet 2 690.77 1 0 823.60 3617.25 verified
Class-C23 1133.93 3 0 2470.80 10851.76 verified
Hall 2 1569.81 4 0 3294.40 14469.01 verified
Class-C28 1070.55 5 0 4118.00 18086.27 verified
Class-C21 1253.43 3 0 2470.80 10851.76 verified
Hall 2 2355.92 4 0 3294.40 14469.01 verified
Hall 2 1172.73 4 0 3294.40 14469.01 verified
Hall 3 977.03 4 0 3294.40 14469.01 verified
Class-C17 665.90 0 3 6177.00 27129.40 verified
Changing room 1413.51 2 0 1647.20 7234.51 verified
Space# radiators
16 el.
# radiators
40 el.
Thermal power
Thesis Report | Paolo Lo Conte
Case study: Elementary School of Bustehrad
Thermal need Verification
kWh/year W kWh/year Need < Power
Class Room 1.05 1280.95 4 3088.50 13564.70 verified
Class Room 1.03 1249.01 4 3088.50 13564.70 verified
Class Room 1.02 1302.32 4 3088.50 13564.70 verified
Cloak Room 1.06 832.68 2 1544.25 6782.35 verified
Cloak Room 1.07 762.94 2 1544.25 6782.35 verified
Changing room 1.08 400.06 2 1544.25 6782.35 verified
Entrance,Hall,Stairs 1.04;1.01;1.10 1492.69 3 2316.38 10173.53 verified
Class Room 2.05 1295.66 4 3088.50 13564.70 verified
Class Room 2.03 1289.81 4 3088.50 13564.70 verified
Class Room 2.02 1274.68 4 3088.50 13564.70 verified
Class room 2.06 1208.79 4 3088.50 13564.70 verified
Hall,Stairs 2.01;2.08 941.10 3 2316.38 10173.53 verified
Common room 2.04 484.69 1 772.13 3391.18 verified
Class Room 3.06 2067.61 4 3088.50 13564.70 verified
Class Room 3.03 2059.30 4 3088.50 13564.70 verified
Class Room 3.02 1977.08 4 3088.50 13564.70 verified
Class room 3.07 1901.88 4 3088.50 13564.70 verified
Hall,Stairs 3.01;3.10 1719.26 3 2316.38 10173.53 verified
Common room 3.05 240.24 1 772.13 3391.18 verified
Girls Bathroom 1.09 714.14 1 772.13 3391.18 verified
Boys bathroom 1.11 203.80 1 772.13 3391.18 verified
Girls Bathroom 2.07 905.56 1 772.13 3391.18 verified
Boys bathroom 2.09 176.87 1 772.13 3391.18 verified
Girls Bathroom 3.08 1029.81 1 772.13 3391.18 verified
Boys bathroom 3.09 467.57 1 772.13 3391.18 verified
n.
radiators
Thermal powerSpace
Elementary school G.Carducci, Lecco
First Level
Graphic Table | Paolo Lo Conte
Scale 1:200
Elementary school G.Carducci, Lecco
Second Level
Graphic Table | Paolo Lo Conte
Scale 1:200
Elementary school G.Carducci, Lecco
Underground Level
Graphic Table | Paolo Lo Conte
Scale 1:200
Elementary school G.Carducci, Lecco
Ground Level
Graphic Table | Paolo Lo Conte
Scale 1:200
Elementary school G.Carducci, Lecco
Underground Level
Graphic Table | Paolo Lo Conte
Scale 1:200
Elementary school G.Carducci, Lecco
Elevation BB
Graphic Table | Paolo Lo Conte
Scale 1:200
Elementary school Bustehrad
First Level
Graphic Table | Paolo Lo Conte
Scale 1:200
Elementary school Bustehrad
Second Level
Graphic Table | Paolo Lo Conte
Scale 1:200
Elementary school Bustehrad
Roof Structure
Graphic Table | Paolo Lo Conte
Scale 1:200
Elementary school Bustehrad
Underground Level
Graphic Table | Paolo Lo Conte
Scale 1:200
Elementary school Bustehrad
Ground Level
Graphic Table | Paolo Lo Conte
Scale 1:200
Elementary school Bustehrad
Elevation AA
Graphic Table | Paolo Lo Conte
Scale 1:200