assessing the potential for reductions in irish local authority residential energy consumption
DESCRIPTION
A case study of the efficacy of thermal envelope upgrades in a sample of Wicklow County Council's housing stock.TRANSCRIPT
Assessing the potential for reductions in Irish
local authority residential energy
consumption:
A case study of the efficacy of thermal envelope upgrades in
a sample of Wicklow County Council’s housing stock.
Robert Wyse
MSc Climate Change and Sustainable Development
Institute of Energy and Sustainable Development
De Montfort University
September 2012
ii
Abstract
It is recognised that the energy performance of the Irish housing stock is poor, with ambitious
retrofitting targets seen as essential to achieving legally binding energy consumption and CO2
emissions reductions targets. Local authorities are retrofitting their housing stocks, and are not only
subject to stringent energy reduction targets, but are expected to play the role of market maker and
encourage the uptake of retrofitting measures in their area.
This research focuses on Wicklow County Council. Based on the analysis of a sample of 718 dwellings
from their stock, it is evident that the energy performance of an average Wicklow County Council
dwelling is considerably worse than the average dwelling in Co. Wicklow or Ireland. In the absence of
an overarching strategy for retrofitting, the retrofitting interventions employed by Wicklow County
Council are considered on a per-dwelling basis and are driven by external energy assessors. An
analysis of the efficacy of the thermal envelope in Wicklow County Council dwellings, coupled with
an analysis of recommended retrofit interventions, reveals a failure to address significant areas of
heat loss, and hence energy consumption.
Using a purpose built Excel based model, the impact of upgrading the thermal envelope to differing
thermal standards on energy consumption and CO2 emissions in the sample of dwellings was
investigated. Reductions in primary energy consumption of between 23% and 50% and in CO2
emissions of between 24% and 52% are deemed achievable, with potential Government funding of
between €2.3 million and €7.8 million available depending on the thermal standard adopted.
iii
Acknowledgements
And now, after so many months of working on a piece that must be structured ‘just so’, I shall write
freely of my thanks to those who have helped me complete this body of work.
From De Montfort University, I thank my supervisor, Dr. Andrew Wright. What I have produced I’m
sure is quite different to what you had originally envisaged when you suggested retrofitting as a
research topic for one of your students (Lessons learned from Retrofitting, anyone?), and I thank you
for granting me free reign to craft this dissertation as I saw fit. Your advice over the last year or so
has been of immense benefit to me. I’m not quite sure it is the norm for someone to command over
an hour of your time on the phone, yet I did on several occasions, and it was most helpful. Your
understanding and swift actions when I requested a short extension were most appreciated for the
peace of mind they afforded me.
From Wicklow County Council, I thank Breege Kilkenny for agreeing to let me carry out this research
in the first place, and Alan Martin for providing the plethora of source materials that enabled it. Al, it
is staggering to think that this work stemmed from our chance meeting on the Long Hill waiting for a
bike race! Our frequent discussions gave me the insight I needed to complete this report, and I truly
hope it is of some benefit to you. I’m fairly sure the next cuppa is on me.
The fulfilment of this dissertation has coincided with a most difficult time in my personal life. Step
forward Mam and Dad, and my sisters Cathy, Emma, Jenny and Fiona. I may never be able to
adequately express how invaluable your support has been to me over the past few months. The
effort in trying to complete this work given my circumstances quite literally nearly broke me, but
with your help, it did not. Thank you.
William Power; you inspired me to undertake this Masters in the first place. There have been times
over the years when I couldn’t quite say I was thankful to you for that, but now that it's at a close, I
can honestly say that I am a more complete person for having done this. And for that, I am in your
debt.
Auntie Carmel; I have never forgotten your words on how, in order to complete this course, I would
draw upon the same mental and physical strength I drew upon when cycling competitively. Prescient
is not the word. And Auntie Rioghnach; when I bemoan the time and effort this course has
demanded of me, your advice on how the years would have passed anyway gives me much needed
perspective and dare I say, makes me smile. Thank you both for your encouragement over the years.
iv
Paul Price; would you believe that in the end, I never got to use WUFI or Therm in anger!! Not to
worry. I truly enjoy our 'sustainability rants' which have played no small part in shaping this work.
The best of luck over the next month or so as you work towards completing your own dissertation
and please, call on me to review as I called on you.
And last, but absolutely by no means least; Mike Clarke. You are a Gent. Please take a bow, Sir. I
cannot thank you enough for your patience and guidance as I endured the painstaking process of
constructing the model used in this study (which, absurdly, was never even included in my original
plan!). I hope you'll agree it was worth it. Forgive me, but I simply cannot resist;
Dim NumPintsOwed As Integer
NumPintsOwed = 1
And now to rest
And now to heal
And get my life
Back to even keel
v
vi
Table of Contents
Table of Figures ...................................................................................................................................... ix
Table of Tables ....................................................................................................................................... xi
Abbreviations ........................................................................................................................................ xii
Section 1. Introduction ........................................................................................................................ 1
1.1 Context .................................................................................................................................... 1
1.2 Background ............................................................................................................................. 2
1.2.1 Energy Performance of Buildings Directive .................................................................... 2
1.2.2 The Fabric First Approach ............................................................................................... 4
1.2.3 Wicklow County Council ................................................................................................. 5
1.3 Aims and Objectives ................................................................................................................ 7
1.4 Research Questions ................................................................................................................ 7
1.5 Methodology ........................................................................................................................... 8
1.6 Dissertation Structure ............................................................................................................. 8
Section 2. Literature Survey ................................................................................................................. 9
2.1 Introduction ............................................................................................................................ 9
2.2 Drivers for retrofitting in the Irish context ............................................................................. 9
2.2.1 Contributions to energy consumption and CO2 emissions ............................................. 9
2.2.2 Legally binding emission reductions targets ................................................................. 11
2.2.3 Import Dependency ...................................................................................................... 13
2.2.4 Employment .................................................................................................................. 13
2.2.5 Fuel Poverty .................................................................................................................. 13
2.3 Energy performance of the Irish housing stock .................................................................... 14
2.3.1 Regulatory non-compliance .......................................................................................... 14
2.4 Typical Retrofit Interventions in Ireland ............................................................................... 17
2.5 Principles of the Fabric First Approach ................................................................................. 19
2.5.1 Insulated building envelope .......................................................................................... 19
2.5.2 Minimal Thermal Bridging ............................................................................................. 19
vii
2.5.3 Highly air-tight thermal envelope ................................................................................. 21
2.5.4 Ventilation ..................................................................................................................... 22
2.5.5 Moisture management ................................................................................................. 22
2.6 Workmanship ........................................................................................................................ 23
2.7 Key Findings .......................................................................................................................... 24
Section 3. Methodology ..................................................................................................................... 25
3.1 Research Strategy ................................................................................................................. 25
3.2 Data Sources ......................................................................................................................... 25
3.2.1 Wicklow County Council ............................................................................................... 25
3.2.2 Sustainable Energy Authority of Ireland ....................................................................... 25
3.3 Research Model .................................................................................................................... 26
3.3.1 DEAP Calculations ......................................................................................................... 26
3.3.2 Profiling Energy Performance and Thermal Envelope Efficacy ..................................... 27
3.3.3 Modelling retrofit interventions ................................................................................... 28
3.3.4 Model Simplifications and Limitations .......................................................................... 31
3.3.5 Model Accuracy – Individual Dwelling .......................................................................... 32
3.3.6 Model Accuracy – All Dwellings .................................................................................... 33
3.4 Data Quality .......................................................................................................................... 34
3.5 Research Limitations ............................................................................................................. 35
Section 4. Model Output & Data Analysis ......................................................................................... 37
4.1 Physical Profile ...................................................................................................................... 37
4.1.1 Sample Size ................................................................................................................... 37
4.1.2 Dwelling Age ................................................................................................................. 37
4.1.3 Dwelling Type ................................................................................................................ 38
4.1.4 Number of Storeys ........................................................................................................ 38
4.1.5 Structure Type ............................................................................................................... 38
4.2 WCC Dwelling Energy Performance Overview ...................................................................... 39
4.2.1 Average Energy Consumption and CO2 emissions ........................................................ 39
viii
4.2.2 BER Profile ..................................................................................................................... 40
4.2.3 Key findings ................................................................................................................... 42
4.3 Detailed Energy Consumption Analysis ................................................................................ 43
4.3.1 Thermal Envelope Performance ................................................................................... 45
4.3.2 Key Findings .................................................................................................................. 58
4.4 Recommended Interventions Analysis ................................................................................. 59
4.4.1 Sample Creation ............................................................................................................ 59
4.4.2 Sample Analysis ............................................................................................................. 59
4.4.3 Payback and Energy reductions .................................................................................... 61
4.4.4 Key Findings .................................................................................................................. 62
Section 5. Scenario Analysis ............................................................................................................... 63
5.1 Scenario Definition ................................................................................................................ 63
5.1.1 Ventilation ..................................................................................................................... 63
5.1.2 Element Thermal Transmittance ................................................................................... 64
5.1.3 Thermal Bridging ........................................................................................................... 65
5.2 Scenario Output .................................................................................................................... 66
5.2.1 Primary Energy Consumption ....................................................................................... 66
5.2.2 Thermal Envelope Performance ................................................................................... 67
5.2.3 CO2 Emissions Reductions ............................................................................................. 73
5.2.4 BER Profiles ................................................................................................................... 74
5.2.5 Funding Achievable ....................................................................................................... 75
5.2.6 Key Findings .................................................................................................................. 77
Section 6. Conclusions ....................................................................................................................... 79
6.1 Further Research ................................................................................................................... 81
References ........................................................................................................................................... 82
Appendix A – Data Quality .................................................................................................................... 89
Appendix B – Thermal Bridging ‘Y-Factors’ ........................................................................................... 91
ix
Table of Figures
Figure 1 A sample Building Energy Rating (BER) Certificate (SEAI, 2007) ............................................... 3
Figure 2 Energy Flow in Ireland, 2010 ................................................................................................... 10
Figure 3 Ireland's GHG Abatement Cost Curve, 2030 ........................................................................... 11
Figure 4 Purchased Heat Energy and Home Energy Rating over time .................................................. 16
Figure 5 Reductions in thermal transmittance at ground floor / external wall junction where external
insulation stopped at ground level (left) and continued underground (right) (Little a, 2009) ............. 20
Figure 6 Mould risk associated with differing approaches to wall insulation ...................................... 23
Figure 7 The 5 steps of a DEAP Assessment ......................................................................................... 26
Figure 8 Extract from the Master Spreadsheet .................................................................................... 29
Figure 9 The use of Attribute Controls to update energy related planar element attributes .............. 30
Figure 10 Revised Wall related Heat Loss Calculation .......................................................................... 31
Figure 11 Dwelling Age Profile .............................................................................................................. 37
Figure 12 Dwelling Type Profile ............................................................................................................ 38
Figure 13 Average Primary Energy Consumption (left) and CO2 Emissions (right) ............................... 39
Figure 14 BER Profile for dwellings in Ireland, Co. Wicklow and WCC ................................................. 40
Figure 15 Distribution of Assessed and Expected Energy Ratings ........................................................ 41
Figure 16 Primary Energy Consumption (left) and CO2 Emissions (right) breakdowns ........................ 43
Figure 17 Primary Energy Consumption per age band ......................................................................... 44
Figure 18 Primary Energy Consumption (kWh/yr) per BER .................................................................. 44
Figure 19 Total Assessed Heat Loss Breakdown ................................................................................... 45
Figure 20 Air Change rates for average dwellings in Ireland, Co. Wicklow and WCC ........................... 46
Figure 21 Average Ventilation Heat Loss per Dwelling Type ................................................................ 47
Figure 22 Contributions to Total Fabric Area, Total Planar and Total Fabric Heat Loss ....................... 48
Figure 23 Assessed contributions to Fabric Heat Loss .......................................................................... 48
Figure 24 Floor Type and Heat Loss profile........................................................................................... 49
Figure 25 Roof Type and Heat Loss profile ........................................................................................... 50
Figure 26 Roof Insulation Profile........................................................................................................... 50
Figure 27 Wall Type and Heat Loss profile ............................................................................................ 51
Figure 28 Window Type and Heat Loss profile ..................................................................................... 52
Figure 29 Frame Type profile ................................................................................................................ 53
Figure 30 Elemental U-value comparisons (W/m2K) ............................................................................ 54
Figure 31 Thermal Bridging contribution to Fabric Heat Loss .............................................................. 55
Figure 32 Average Heat Loss Parameter per dwelling type .................................................................. 56
Figure 33 Average Net Space Heat Demand per dwelling type ............................................................ 57
x
Figure 34 Breakdown of recommended interventions ......................................................................... 60
Figure 35 Recommended Interventions per BER .................................................................................. 60
Figure 36 Reductions in Total Space Heating Consumption and Primary Energy Consumption .......... 66
Figure 37 Disaggregated reductions in thermal envelope heat loss .................................................... 67
Figure 38 Reductions in ventilation heat loss ....................................................................................... 68
Figure 39 Disaggregated reductions in planar heat loss ....................................................................... 69
Figure 40 Reductions in Thermal Bridging heat loss ............................................................................. 70
Figure 41 Reductions in Heat Loss Parameter for each scenario ......................................................... 71
Figure 42 Reductions in NSHD for each scenario .................................................................................. 72
Figure 43 Reductions in CO2 emissions in each scenario ...................................................................... 73
Figure 44 Assumed BER profiles for each scenario ............................................................................... 74
Figure 45 Number of dwellings per funding bracket per scenario ....................................................... 75
xi
Table of Tables
Table 1 Typical Irish Retrofitting Interventions..................................................................................... 18
Table 2 Air permeability values from various Irish sources .................................................................. 21
Table 3 DEAP Dwelling Report contents ............................................................................................... 27
Table 4 Energy related quantities considered in this study .................................................................. 28
Table 5 Retrofit Interventions and Modelled Attributes ...................................................................... 29
Table 6 Interventions assumed during Model testing .......................................................................... 32
Table 7 Model Test Results ................................................................................................................... 33
Table 8 Model Accuracy ........................................................................................................................ 34
Table 9 Inconsistent Age Bands ............................................................................................................ 35
Table 10 Expected Energy Ratings ........................................................................................................ 41
Table 11 Sample Recommended Interventions .................................................................................... 59
Table 12 Recommended Thermal Envelope Interventions per BER ..................................................... 61
Table 13 Average energy savings, costs and payback times for recommended interventions ............ 62
Table 14 Ventilation related limiting factors ........................................................................................ 63
Table 15 Assumed values of thermal transmittance ............................................................................ 64
Table 16 Assumed Thermal Bridging Factors ........................................................................................ 65
Table 17 Allocation of funding according to energy reductions achieved ........................................... 75
Table 18 Funding available for each scenario ....................................................................................... 76
Table 19 Overview of reductions achieved for all scenarios ................................................................ 77
xii
Abbreviations
ac/h Air changes per hour
BEH Better Energy Homes
BER Building Energy Rating
CO2 Carbon Dioxide
DEAP Dwelling Energy Assessment Procedure
DECLG Department of the Environment, Community and Local Government
DCENR Department of Communications, Energy and Natural Resources
EC European Commission
EP European Parliament
EPA Environmental Protection Agency
EPBD Energy Performance of Buildings Directive
ETS Emissions Trading Scheme
EU European Union
GDP Gross Domestic Product
GHG Greenhouse Gas
GWh Giga-Watt hour
kgCO2 Kilo-gram
kWh Kilo-Watt hour
LZC Low to Zero Carbon
m2 Meters squared (area)
m3 Meters cubed (volume)
MPEPC Maximum Permitted Energy Performance Coefficient
MPCPC Maximum Permitted Carbon Performance Coefficient
MtCO2eq Mega tonnes of Carbon Dioxide equivalent
MVHR Mechanical Ventilation and Heat Recovery
NBERRT National BER Research Tool
NERP National Energy Retrofit Program
Pa Pascals
RET Renewable Technologies
xiii
SAP Standard Assessment Procedure
SEAI Sustainable Energy Authority of Ireland
SEI Sustainable Energy Ireland
sqm Square Meter (area)
TGD Technical Guidance Document
WCC Wicklow County Council
yr Year
1
Section 1. Introduction
1.1 Context
In 2010, the Irish residential sector was responsible for 27% of total final energy consumption and
12.7% of greenhouse gas (GHG) emissions. Given these sizeable contributions, the residential sector
is seen as an important contributor towards the achievement of Irish obligations regarding GHG
emissions under the Kyoto protocol and European Climate and Energy packages.
The stated goal of the National Energy Retrofit Program (NERP) is to reduce the energy consumption
of dwellings in Ireland by an average of 42% by 2020. The NERP is essential to the success of the
National Energy Efficiency Action Plan (NEEAP), itself devised to achieve Ireland’s obligations under
the European Climate and Energy Package. As part of the NEEAP, local authorities are obliged to
increase energy efficiency by 33% by 2020, far in excess of the 20% required for the nation as a
whole (DCENR, 2009, p. 8). As custodians of 6% the national housing stock, Irish local authorities are
undertaking widespread residential retrofits in an effort to meet such targets.
Studies such as that carried out by Wardell & Shanks (2005) suggest that the efficacy of the thermal
envelope in Irish dwellings is poor, with high levels of ventilation heat loss and widespread
deficiencies in insulation. Poor workmanship and regulatory non-compliance are deemed
contributing factors to this situation which has resulted in the energy consumption of Irish dwellings
exceeding European norms. It is understood that reductions in CO2 emissions in the region of 90%
are achievable in the Irish residential sector, however retrofitting measures employed to date in
Ireland are insufficient to deliver such reductions.
Taking Wicklow County Council (WCC) as a case study, this research investigates the reductions in
energy consumption and CO2 emissions achievable across a sample of dwellings should the
principles of the fabric first approach be implemented, and a focus be placed solely on the thermal
envelope whilst retrofitting.
2
1.2 Background
1.2.1 Energy Performance of Buildings Directive
The EU Directive on the Energy Performance of Buildings (EPBD) was adopted into Irish law in 2006.
Two principle aims of this directive are to provide a common methodology for calculating the energy
performance of a building and to provide a system of certification that makes the energy
consumption of a building readily available to the public (EC, 2003). Based on IS EN 13790, and
drawing heavily on the UK Standard Assessment Procedure (SAP), the Dwelling Energy Assessment
Procedure (DEAP) is the official Irish procedure for calculating and assessing the energy performance
of a dwelling and is fully compliant with the methodology framework set out in the EPBD (SEAI a,
2008). The main steps carried out as part of a DEAP survey are described in section 3.3.1.
A DEAP assessment results in the issuance of a Building Energy Rating (BER) certificate, which
indicates the annual primary energy consumption and CO2 emissions of the building. As shown in
Figure 1 (below), ‘A’ rated dwellings (consuming less than 75 kWh/m2/yr) are the most energy
efficient, with ‘G’ rated ones (consuming more than 450 kWh/m2/yr ) the least;
3
Figure 1 A sample Building Energy Rating (BER) Certificate (SEAI, 2007)
4
1.2.2 The Fabric First Approach
Energy consumption in houses is complex, depending on building geometry, the thermal
characteristics of the building envelope and therefore by extension, the external climate. The
ultimate aim of retrofitting dwellings in Ireland must be to create a housing stock which provides a
healthy and comfortable environment for occupants and whose energy consumption is greatly
reduced relative to present levels and largely independent of the vagaries of the Irish climate.
A distinction is made between the thermal and building envelopes; the physical components of the
building envelope – the planar elements such as doors, floors, roof, walls and windows - combine to
form the thermal envelope, which is the enclosure that holds warm or cold air in a structure (Energy
Vortex, n.d.). The fabric first approach emphasises reducing space heating demand to the minimum
possible level by optimising the thermal envelope in terms of air-tightness and heat retention. The
principles underlying this approach are discussed further in section 2.5
The fabric first approach clearly underlies Irish building regulations for new dwellings (DECLG, 2011),
is championed by the Energy Savings Trust in the UK (EST a, 2010) and is the foundation for both
Code for Sustainable Homes (BRE Trust, 2010) and Passivhaus (Schnieders & Hermelink, 2006)
standards.
The fabric first approach is equally applicable to retrofits, with Davies & Osmani (2011, p. 1694)
noting its widespread adoption in the UK. In recognition of the fact that achieving the Passivhaus
standard whilst retrofitting is extremely challenging primarily owing to the difficulties in achieving
low levels of thermal bridging heat loss and high levels of air-tightness with an existing structure
(Hearne, 2012), the Passivhaus Institute have devised the EnerPHit standard for retrofits, the central
tenet of which is a fabric first approach (Feist, 2010).
For several reasons, the fabric first approach should be of interest to local authorities in general and
WCC in particular.
Wardell & Shanks (2005, p. VI) note how local authority tenants have the highest occupancy ratio,
and therefore the highest energy consumption of all tenure types, thus reductions in space heating
demand achieved through retrofitting will be most fully exploited by this occupant type. As outlined
in section 2.5, optimising the thermal envelope should minimise space heating demand, tackle fuel
poverty, ensure good indoor air quality is maintained and eliminate issues relating to mould growth
arising from thermal bridging and surface condensation, where present. Upgrading heating systems
as part of a retrofit will reduce space heating demand and CO2 emissions (particularly where a solid
fuel system or inefficient boiler is replaced) and may alleviate instances of fuel poverty. However,
5
replacing heating systems at the expense of optimising the thermal envelope means current and
future heating loads are not minimised, and health benefits accruing from envelope optimisation are
not realised; an approach not strictly aligned with WCC’s aim to improve the quality of life of its
tenants (Sheehy, 2004, p. 17).
A failure to capitalise on the benefits afforded by the fabric first approach necessitates that the
building fabric be revisited at a later date to upgrade its performance. Given the potentially long lead
time in revisiting dwellings for a second retrofit, health issues and unnecessarily high space heating
related energy consumption and CO2 emissions may persist for some time to come, as noted in (EST
b, 2010, p. 4). This approach is not aligned with Irish government policy to maximise energy savings
to clients and avoid the necessity of undertaking further costly energy upgrade works at a later stage
(DEHLG a, 2010, p. 2).
The expectation has been set that local authorities should lead by example, and act as market
makers and exemplars in the promotion of the energy performance of buildings (Neary, n.d.). In
Wicklow, a county where the average dwelling energy consumption is 14.8% above the national
average (see section 4.2.1 for further details) and that ranks 20th out of 26 counties for retrofitting
grant applications (SEAI a, 2012, p. 1), this is a vital role for WCC to fulfil.
Finally, the approved re-cast of the EPBD (EP, 2012) states that by 2018, all new buildings owned or
occupied by local authorities will need to consume ‘nearly zero’ energy, with extant energy
consumption met via renewable sources. Though no target is explicitly set for existing buildings
becoming ‘near zero’, there is a clear indication that this may occur in the future, with local authority
buildings likely leading the way. An optimised thermal envelope provides the ideal platform for
renewable energies and hence the adoption of the fabric first approach puts in place a strong
foundation for such an eventuality.
1.2.3 Wicklow County Council
Wicklow County Council is one of 4 local authority housing providers in the administrative area of
County Wicklow, which is located on the east coast of Ireland. Perhaps reflective of the level of
construction activity in Ireland in the opening decade of the 21st century, WCC’s housing stock grew
from 1,740 units in 2004 (Sheehy, 2004, p. 10) to between 2,297 (WCC, 2008) and 2,334 (WCC a,
2011) units by 2008, with 90% of dwellings deemed to be in ‘Good’ or ‘Reasonable’ condition
(Sheehy, 2004, p. 24). This however refers to the general, maintained condition of the stock and
bears no relation to its energy performance.
6
In response to government directives, WCC are now placing a strong emphasis on energy efficiency,
and commenced a widespread retrofitting effort in 2010. The first phase of this was to establish the
baseline energy performance of their stock, with Building Energy Rating (BER) Assessors invited to
carry out dwelling energy assessments (WCC b, 2011). A total of 15 assessors were chosen for the
first tranche of assessments which considered 1,973 dwellings, with each assessor being assigned
circa 131 dwellings (WCC c, 2011).
Like other Irish local authorities, WCC receive partial funding for retrofitting work from central
government as part of the Social Housing Investment Program (SHIP), with the amount allocated per
dwelling based on reductions in energy consumption achieved (DEHLG b, 2010). Sheehy (2004, p. 36)
notes that where retrofitting work is carried out, it must meet the standard defined by the building
regulations currently in force. As per government guidance, the retrofitting interventions
implemented by WCC are not confined to the building fabric, and can relate to space and water
heating systems also (WCC d, 2011).
Crucially, and unlike other local authorities such as Tipperary or Carlow/Kilkenny County Councils for
example, WCC do not enjoy the support of a local energy agency with which they can devise an
overall retrofitting strategy. From private communications with Mr. Alan Martin, a representative of
the Housing department in WCC, it is further understood that;
• There is a lack of understanding of how energy is consumed across the stock
• There is an shortage of knowledge and expertise regarding building physics and thermal
envelope optimisation
• Techniques such as thermal bridging analysis, condensation analysis, thermal imagery and
air-tightness testing are not routinely used during retrofits
• In the absence of an overall retrofitting specification, the interventions implemented for any
of the dwellings vary based on recommendations provided by BER Assessors
• With specific reference to the thermal envelope, it is unclear to WCC how effective
recommended interventions are at mitigating heat loss, and hence energy consumption,
across the stock
• There is a preference for internal insulation over external insulation, primarily as this can be
undertaken by internal staff
7
1.3 Aims and Objectives
Given the acknowledged absence of assistance from any external agency, and the general lack of
knowledge of energy consumption across the stock, this research aims to profile the energy
performance of WCC’s dwellings, highlight the impact that the adoption of the fabric first approach
could have on energy consumption and CO2 emissions, and ultimately, contribute to the
development of an overarching retrofitting strategy.
To achieve these aims, several objectives have been identified;
1. Profile the physical characteristics, energy performance and thermal envelope efficacy of a
sample of WCC’s housing stock
2. Analyse a sample of the retrofitting interventions performed by WCC
3. Model the impact of various thermal envelope retrofit strategies on the primary energy
requirement and CO2 emissions of the sample
4. Extrapolate the impact on stock-wide primary energy requirement and CO2 emissions
1.4 Research Questions
To meet the aims and objectives, several research questions have been compiled;
1. What are the physical attributes of dwellings in WCC’s housing stock?
2. In terms of energy consumption and CO2 emissions, how does the average WCC dwelling
compare to the average dwelling in Co. Wicklow or Ireland?
3. How well does the thermal envelope of WCC dwellings perform – what are the areas of
significant heat loss?
4. Are the retrofit interventions being suggested to WCC addressing these areas of significant
heat loss?
5. If the fabric first approach was fully embraced, what is the scale of reductions in energy
consumption and CO2 emissions achievable?
8
1.5 Methodology
This will be a desk based study taking as input a sample of Dwelling Energy Assessment Procedure
Survey reports supplied by Wicklow County Council.
1.6 Dissertation Structure
This report is divided as follows;
Literature Survey; an overview of the drivers for and status of retrofitting in Ireland is presented,
alongside an overview of the state of the Irish housing stock. The principles underlying the fabric first
approach are discussed.
Methodology; an outline of the methodology employed for this research is presented, along with a
description of the model used to facilitate scenario analysis.
Model Output & Data Analysis; a detailed analysis of the energy performance of the sample and
recommended retrofitting interventions is presented.
Scenario Analysis; the impacts of upgrading the thermal envelope in dwellings across the sample to
differing standards are discussed.
Conclusions: concluding remarks are presented along with suggested topics for further research.
9
Section 2. Literature Survey
2.1 Introduction
This section discusses the drivers for retrofitting in an Irish context and describes retrofitting
Interventions typical to Ireland. The principles of the fabric first approach, and its relevance to
retrofitting, are discussed. Irish and European policy is drawn upon, with statistics on energy
consumption and CO2 emissions obtained from authoritative sources such as the Sustainable Energy
Authority of Ireland (SEAI) and the Environmental Protection Agency (EPA). Detailed reports on the
energy performance of the Irish housing stock are used to provide further context.
2.2 Drivers for retrofitting in the Irish context
When considering the drivers for retrofitting in an Irish context, it is useful to begin with the
contribution of the residential sector to overall Irish energy consumption and GHG emissions.
2.2.1 Contributions to energy consumption and CO2 emissions
As illustrated in Figure 2 (below), the residential sector is a major energy consumer, second only to
the transport sector, and in 2010 was responsible for 22% of total primary energy requirement and
27% of total final consumption (SEAI a, 2011, p. 15);
10
Figure 2 Energy Flow in Ireland, 2010
The sector’s contribution to GHG emissions is less significant at 12.7% (7.42 MtCO2eq), with only the
waste sector contributing less (EPA a, 2012, p. 2).
Overall Irish GHG emissions were 0.7% lower in 2010 than in 2009, an artefact of the on-going
economic recession (ibid, p. 1). The harsh winter of 2010 led to an increase in residential related
GHG emissions of 5.3% (ibid, p. 8) and an increase in residential related energy use of 5.9% (SEAI a,
2011, p. 4). However, climate corrected residential energy consumption reduced 2.9% on 2009
figures (ibid, p. 4), something which serves to highlight the impact of climate on Irish residential
energy consumption.
Historically, through the retrofitting of dwellings and other measures, the residential sector “strongly
influenced” (Odyssee, 2011, p. 1) a 9% improvement in the Irish energy efficiency index between
2000 and 2008. Alongside a growing stock of more efficient new dwellings, these measures partially
contributed to a decline of 24.4% in overall climate corrected energy consumption per dwelling
during the period 1990 – 2010 (SEAI a, 2011, p. 69), however this reduction occurred against the
backdrop of an increase in total dwelling numbers from 1,019,723 in 1991 (CSO, 1997, p. 40) to
2,004,175 in 2011 (CSO, 2011, p. 17), resulting in a long term climate corrected increase of 21.1% in
residential energy consumption (SEAI a, 2011, p. 67), and a 12.1% increase in GHG emissions (ibid,
p.68).
11
Through sustained retrofitting, the increased implementation of Low to Zero Carbon (LZC)
technology and the decarbonisation of the electricity grid, 90% reductions in CO2 emissions are
deemed achievable in the residential sector by 2050 (SEAI, 2010, p. 5).
Curtain (2009, p. 24) and Dineen et al. (2010, p. 2) note how retrofitting building fabric is one of the
most effective and cost efficient ways to achieve energy savings in the Irish economy, a view
reinforced by Motherway & Walker (2009, p. 4) in Figure 3 (below), which illustrates how this
abatement opportunity incurs a negative societal cost;
Figure 3 Ireland's GHG Abatement Cost Curve, 2030
2.2.2 Legally binding emission reductions targets
Given its potentially significant contribution and evident cost effectiveness, residential retrofitting is
seen as a key contributor in achieving compliance with legally binding obligations to reduce overall
GHG emissions under the Kyoto protocol and the European Climate and Energy Package.
Irish obligations under the Kyoto protocol are to limit GHG emissions to no more than 13% above
1990 levels by 2012 (DEHLG, 2007, p. 7). The National Climate Change Strategy illustrates how
increased penetration of renewable heating, enhanced building regulations and energy efficiency
12
improvements in local authority housing are the primary contributors from the residential sector
towards Kyoto compliance (ibid, p. 9).
Emissions reductions owing to the economic recession, the permitted inclusion of the impact of
forest sinks and governmental purchase of credits under the European Union Emissions Trading
Scheme (EU-ETS) (EPA b, 2012, p. 3), mean this target, once seen as “extremely challenging” (DEHLG,
2006, p. 8), and first breached in 1998 (SEAI a, 2011, p. 29), now appears likely to be met.
EC (2010) notes three legally binding targets central to the Climate and Energy Package agreed by
the European Parliament and Council in December 2008;
1. A reduction in EU GHG emissions to at least 20% below 1990 levels
2. 20% of EU energy consumption to come from renewable resources
3. A 20% reduction in primary energy use compared with projected levels, to be achieved
by improving energy efficiency
Ireland’s obligations under the Effort Sharing Decision implemented to achieve agreed GHG
reductions is for emissions in sectors of the economies not covered by the EU-ETS to be reduced to
20% below 2005 levels by 2020 (EP, 2009). Crucially however, the contribution of forest sinks is not
permitted (EPA b, 2012, p. 12), thus the proportional reductions required from other participating
sectors, including the residential sector, are increased. It should be noted that Irish local authorities
manage 6% of the national housing stock (DECLG a, 2012).
The National Energy Efficiency Action Programme (NEEAP) (DCENR, 2009) outlines Ireland’s plan of
action to fulfill the agreed 20% reduction in primary energy use.
From a requirement of 32GWh, this plan identifies savings of circa 24GWh, with circa 10.4GWh
(44%) of these being identified in the residential sector alone. Long term trends indicate that as a
result of the NEEAP, energy consumption in the residential sector could be 22.5% lower than
projected levels in 2020 (SEAI b, 2011, p. 30). The 8GWh shortfall in energy savings is expected to be
filled by way of the National Energy Retrofit Program (NERP), a central aim of which is to deliver
energy efficiency upgrades to 1 million residential, public and commercial buildings by 2020 (DCENR,
n.d., p. 8).
It is anticipated that residential related GHG emissions will decrease by 33.8% between 2010 and
2020 as a result of NEEAP & NERP activity (EPA b, 2012, p. 17), yet overall compliance with EU 2020
13
emissions targets for non-ETS sectors is nonetheless expected to be missed by 4.1 – 7.8 MTCO2eq
(ibid, p.4).
Residential retrofitting is also seen as a way to tackle issues other than energy consumption and
GHG emissions.
2.2.3 Import Dependency
Irelands energy import dependency was 86% in 2010 (SEAI a, 2011, p. 4), with imports costing the
exchequer approximately €6 billion in 2008 (DCENR, 2009, p. 8). SEAI (2010) highlights how
retrofitting can contribute greatly to our energy independence and reduce Irish exposure to oil price
volatility.
2.2.4 Employment
The construction sector once generated 24% of Irish GDP (Curtain, 2009, p. 14) and provided 20% of
all jobs in the economy (DKMEC, 2010, p. iii). The recent economic contraction has seen employment
in the sector return to 1998 levels (ibid). A sustained retrofitting programme could sustain 10,000
jobs over a 10 year period (SEAI, 2010, p. 5).
2.2.5 Fuel Poverty
Clinch & Healy (2001, p. 114) define fuel poverty to be an inability to heat the home to an adequate
(safe and comfortable) temperature, owing to low household income and poor household energy
efficiency. This is a widespread issue in Ireland, with over 20% of Irish households affected in 2009
(DCENR, 2011). Fuel poverty is associated with serious respiratory illnesses, with research suggesting
that for every euro invested in energy poverty measures, 42 cents are returned in savings from
health expenditure on all householders (ibid p. 32). Clinch & Healy (2001, p. 114) note how Ireland
suffers from one of the highest rates of excess winter mortality in northern Europe, and link this with
the poor thermal efficiency of the housing stock.
14
2.3 Energy performance of the Irish housing stock
Based on an analysis of 286,793 DEAP surveys, made accessible through the National BER Research
Tool (NBERRT) (SEAI b, 2012), the average primary energy consumption for an Irish dwelling is 262.9
kWh/m2/yr., yielding a D2 rating. Thus, on average, the energy consumption of Irish dwellings must
decrease 42% to achieve a C1 energy rating, the target rating for NERP and local authority related
retrofitting work (Armstrong & Dowling, 2012, p. 1). Average CO2 emissions for an Irish dwelling are
estimated to be 62.6 kgCO2/m2/yr.
By way of international comparison, Irish dwellings in 2006 consumed 27% and 36% more energy
than the average UK and European counterparts respectively. Similarly, the average Irish dwelling
emitted 47% more CO2 than the average UK dwelling and 104% more than the average dwelling in
the EU27 block of nations (SEAI b, 2008, p. 2). Several reasons are proffered for this poor
performance;
• Larger dwelling size
• Fuel use mix for space heating
• Losses in the electricity grid
Both Scheer et al. (2012, p. 2) and DEHLG (c, 2010, p. 4) note rising expectations of internal
temperatures as a factor while regulatory non-compliance has recently been identified as a
significant driver in Irish dwelling energy consumption.
2.3.1 Regulatory non-compliance
Building regulations were first considered in Ireland in 1972 (Curtain, 2009, p. 20). It was only after
the enactment in 1991 of the Building Control Act 1990 that mandatory regulations incorporating
thermal standards came into effect. The Irish building regulations comprise a set of Technical
Guidance Documents, each concerned with a different aspect of building control, with TGD Part L-
Conservation of Fuel and Energy, the most relevant here. TGD Part L has been revised several times.
Changes made in 2002 included reductions in the permitted thermal transmittance (U-value) of the
building fabric planar elements (doors, floors, roofs, walls and windows) while more radical
amendments in the 2008 and 2011 revisions mean dwellings built to standard should consume
between 40% and 60% less energy than their 2005 counterpart, respectively.
15
Headline revisions to Part L of the 2011 Building Regulations (DECLG, 2011) include;
• Acceptable air permeability reduced from 10m³/h/m² to 7m³/h/m²
• Required efficiency for Biomass boilers set at 77%, all other boilers increased to 90%
• The Maximum Permitted Energy Performance Coefficient (MPEPC) set at 0.4
• The Maximum Permitted Carbon Performance Coefficient (MPCPC) set at 0.46
It is understood that merely complying with minimum values of air permeability and meeting default
U-values will not be sufficient to achieve required MPEPC and MPCPC values, thus at least some of
the ‘backstop values’ will need to be exceeded to ensure regulatory compliance (Antonelli & Colley
a, 2012).
In 2011, the national housing stock numbered 2,004,175 dwellings (CSO, 2011, p. 17), with 52.9% of
these constructed prior to 1991 (DECLG b, 2012). Daly (2007) asserts that the large proportion of
dwellings built in a non-regulated context is a significant factor in the poor performance of the Irish
residential sector and in doing so, infers that the presence of building regulations will guarantee
more efficient housing. Indeed, as much is assumed in (EPA, 2010, p. 12), which suggests enhanced
building regulations will contribute a 20% reduction in residential sector GHG emissions by 2020.
However, the efficacy of building regulations is clearly linked with their enforcement, which in
Ireland, falls under the remit of the City and County Councils. Inspections are only required for 12% –
15% of commencement notices, i.e. 85% of newly constructed homes are not required to be
inspected under the issued guidelines (NCA, 2008, p. 3). Local government statistics indicate average
nationwide rates of inspection varied from 23% to 33% over the period 2004 to 2010 (Power, 2012,
p. 27).
Based on data from the NBERRT, Antonelli & Colley (b, 2012) claim that 21% of homes built under
the 2005 regulations failed to meet its main requirements, while 67.7% of homes built under the
2008 regulations fail to meet all of its main requirements, indicating widespread non-compliance
with regulations.
In a study of 150 residential units representative of national trends of dwelling age, built form and
tenure of occupancy, Wardell & Shanks (2005) calculated a 41% reduction in theoretical energy
rating for dwellings constructed between 1997 – 2002 compared with those constructed between
16
1961 and 1980 (pre-regulation era), a reduction attributable to successive improvements to Irish
Building Regulations since 1979. However the study notes this theoretical reduction is not met with
a corresponding reduction in actual energy consumption, which reduced by only 13%.
Figure 4 (below) illustrates how, for the sample as a whole, an increasing difference between
Purchased Heat Energy (actual energy consumption) & Home Energy Rating (theoretical energy
consumption) was noted amongst newer dwellings (ibid, p. 14);
Figure 4 Purchased Heat Energy and Home Energy Rating over time
While this phenomenon is partially attributed to occupant behaviour, it is further noted that, of the
52 dwellings in the study constructed between 1997 – 2002, no dwelling was fully compliant with
Part L (Conservation of Fuel and Energy), Part F (Ventilation) and Part J (Heat Producing Appliances)
of the Irish building regulations. Only 1 dwelling was fully compliant with Part L in every respect, 29
dwellings fully complied with Part F in every respect (ibid, p. 61) and 27 complied fully with Part J
(ibid, p. 63).
2.3.1.1 Thermal envelope performance
With specific reference to the efficacy of the building fabric, the report notes that based on a visual
inspection, 87% of dwellings are compliant with insulation levels, with non-compliance usually
attributed to inadequate attic insulation (ibid, p. 57). The report notes that:
17
“It was possible to measure wall insulation type and thickness accurately in
the majority of dwellings, through unsealed openings for plumbing and
electrical services, such as waste pipe openings and around the electricity
meter box.” (ibid, p. VI).
The presence of unsealed openings as mentioned, along with poor on-site practice in failing to seal
the void between dry lining and masonry walls at edges of openings such as doors, for example,
contributes to the low level (15%) of infiltration compliance (ibid, p. 57). Low levels of compliance
were also noted for pipe work insulation, with only 10% of dwellings in compliance (ibid, p. 57).
Infra-red thermography and air tightness tests were performed on a subset of 20 dwellings
constructed predominately in the period 1997-2002 to supplement the findings of the visual
inspection. This highlighted significant deficiencies (ibid, p. VII);
• 55% of dwellings had some insulation (typically roof or wall) missing
• 15% of the dwellings had extensive insulation missing
• Local thermal bridging at window sills and lintels etc. was found in 66% of dwellings
• Condensation risk mainly due to missing insulation was found in 33% of living rooms,
bedrooms and wet rooms.
• Average air permeability was recorded as being 11.8m3/hr/m2@50pa, 69% higher than good
practice value of 7.0m3/hr/m2@50pa (ibid, p.39)
• Excessive air leakage (ac/h > 0.5) was found in 37% of dwellings.
2.4 Typical Retrofit Interventions in Ireland
The findings presented thus far suggest a significant improvement in the overall energy performance
of the Irish housing stock is achievable through retrofitting. The NERP is being administered by the
Sustainable Energy Authority of Ireland (SEAI), with grant assistance for residential energy efficiency
interventions available through the Better Energy Homes (BEH) scheme.
Statistics relating to energy efficiency interventions undertaken as part of the BEH scheme between
March 2009 and July 2012 (SEAI c, 2012) are presented in Table 1 (below), alongside those reported
as part of a survey of housing quality undertaken during 2001 – 2002 (Watson & Williams, 2003);
18
Measure SEAI (2012) Watson & Williams
(2003)
Roof Insulation 29% 7%
Cavity Insulation 24%
Dry Lining (internal) Insulation 3% 2-3%
External Insulation 3%
Replacement Windows 22%
External Doors 19%
High efficiency Boiler with heating controls
upgrade
10%
Heating controls upgrade only 3%
Solar Heating 1%
Before / After BER 4%
Integral BER 23%
Table 1 Typical Irish Retrofitting Interventions
Dineen et al. (2010, p. 8) distinguish between ‘shallow’ measures such as roof and cavity insulation
and ‘deep’ measures such as heating controls upgrades and external insulation. SEAI (2010, p. 4)
expand upon this by citing internal and external insulation, high efficiency windows and Mechanical
Ventilation Heat Recovery (MVHR) as deep interventions.
Though both sets of data in Table 1 (above) are not directly comparable (for example, double glazing
is excluded from BEH on cost effectiveness grounds (Curtain, 2009, p. 19)), there is a clear bias
towards shallow retrofit measures that are unlikely to achieve the 90% reductions in GHG emissions
envisioned by SEAI (2010), a finding in keeping with Dineen et al. ( 2010, p. 8). A similar situation is
noted in the UK by Davies & Osmani (2011, p. 1691).
Despite administering the NERP, a scheme with an “easily achievable” (Curtain, 2009, p. 32) target
BER of C1, SEAI (2010, p. 3) conclude there is a need to encourage ‘deep retrofits’, something for
which there appears to be no single definition.
Struabe offers a generic definition, holding a deep retrofit to be one which “extends the viability of
the building 50 to 100 years into the future” (BSC, 2010, p. 6). Others define deep retrofits in terms
of energy consumption reductions, with qualifying levels ranging from to 50% to 90% (Scania, 2010).
Reductions in operating costs is also a commonly used measure, with Bloom & Wheelock (2010, p. 4)
and Curtain & Maguire (2011, p. 4) assuming deep retrofits to achieve 60% and 40% reductions,
respectively.
19
2.5 Principles of the Fabric First Approach
The fabric first approach is central to regulations governing the construction of new dwellings in
Ireland and to the EnerPHit standard for deep retrofits, and as such, can be said be central to the
achievement of the significant emissions reductions deemed possible in the Irish residential sector.
Several interrelated principles underlie the fabric first approach;
• The building envelope should be highly and continuously insulated
• Thermal bridging should be minimal
• The thermal envelope should exhibit low levels of infiltration, yet be well ventilated
• Moisture should be well managed
Given the constraints inherent in an existing structure, the achievement of these principles in a
retrofit scenario can be challenging, particularly aspects relating to thermal bridging and infiltration.
2.5.1 Insulated building envelope
In creating highly insulated building envelope, the objective is to maximise reductions in the
transmittance of heat through building envelope planar elements. The thermal transmittance of any
such planar element is defined by its ‘U-value’, and is measured in W/m2K.
Davies & Osmani (2011, p. 1692) note how, in the UK, improving thermal retention through thermal
insulation of planar elements is the preferred retrofitting approach, possibly reflective of claims that
the energy related attributes of a dwelling’s fabric have the greatest influence on space heating
energy demand and define the extent of fabric and ventilation heat loss in a dwelling (Wardell &
Shanks, 2005, p. 25).
2.5.2 Minimal Thermal Bridging
A principle consideration of the thermal envelope is that insulation levels should be as continuous as
possible, with breaks in the continuity of the level of insulation giving rise to a thermal bridge; a
localised area of reduced insulation, resulting in increased levels of thermal transmittance, hence a
lower surface temperature which can facilitate mould growth (Little & Arregi, 2011).
Aside from the health implications associated with mould growth, thermal bridge related heat loss
can contribute significantly to overall dwelling heat loss. As thermal transmittance through planar
elements decreases as a result of increasing levels of insulation, the proportion of overall heat loss
attributable to thermal bridging increases. Further to this, (Little a, 2009) graphically demonstrates
how the ill-management of thermal bridges can serve to increase the absolute thermal
transmittance through them. Furthermore, it is demonstrated that significant reductions in thermal
20
transmittance through common thermal bridges as found at the eaves, window sills and jambs can
be achieved given sufficient attention to detail. For example, where external insulation is dropped
below ground level, thermal transmittance along the thermal bridge at the junction of ground floor
and external wall (as indicated by Ψ in Figure 5 (below)1) can be reduced over 60%;
Figure 5 Reductions in thermal transmittance at ground floor / external wall junction where external insulation stopped
at ground level (left) and continued underground (right) (Little a, 2009)
Through the use of thermal imagery, Wardell & Shanks (2005) determined that 13 dwellings from a
sample of 20 contained thermal bridging in contravention of Irish building regulations, with 11 and
13 dwellings missing wall and roof insulation respectively.
A brief discussion of how thermal bridging heat loss is accounted for by DEAP and the model used in
this study is provided in Appendix B.
1 See Appendix B for further information on Ψ
21
2.5.3 Highly air-tight thermal envelope
Wardell & Shanks (2005, p. 39) note that infiltration is air exchange that occurs through cracks and
small gaps in the external fabric that are not designed in, such as spaces between window frames
and external walls and small gaps around penetrations through the external envelope. A measure of
infiltration is air permeability, which represents the volume of air passing through each square
meter of building envelope (Sinnott & Dyer, 2012, p. 270). For new dwellings in Ireland, the limiting
value of air permeability is 7m3/h/m2 (DECLG, 2011), a value far in exceedance of other European
countries (EST a, 2010, p. 44).
Table 2 (below) presents sample air permeability values for Irish dwellings derived from various
sources;
(Sedlak &
Sheward, 2008)
(Sinnott &
Dyer, 2012)
(O'Se, 2011)
Number of Tests 32 28 circa 120
Avg. m3/hr/m
2 8.1 9.1 5.0
Max. m3/hr/m
2 20.8 14.4 23.0
Min. m3/hr/m
2 2.1 5.1 0.3
Table 2 Air permeability values from various Irish sources
The maximum values noted here are far in excess of Irish best practice values, with the average
values noted by Sedlak & Sheward (2008) and Sinnott & Dyer (2012) also failing to meet current
regulations. O'Se (2011) notes the lower average and minimum values of air permeability result from
air-tightness being ‘designed in’ to the dwellings being tested. Values of air permeability of 0.82
m3/hr/m2 have been recorded for dwellings retrofitted to the EnerPHit standard (EST, 2011, p. 31), a
figure which highlights the significant scope for reductions in infiltration related heat loss in Irish
dwellings.
In terms of reducing heat losses via infiltration during retrofits, O'Se (2011) notes that renovated
dwellings did not necessarily see significant improvements in air-tightness, though he does not
mention what interventions were undertaken during renovations. Sedlak & Sheward (2008) note
that older, renovated dwellings showed the worst performance, even with new windows installed, a
problem attributed to problems with joints between new and old constructions. Both findings are at
odds with Sinnott & Dyer (2012, p. 272), who note that values of air-tightness in dwellings which had
undergone a retrofit to be on average 35% better than for dwellings which had not, and note that
cavity wall insulation and double glazing installation have the largest effect, reducing air
permeability by 28% and 39% respectively.
22
2.5.4 Ventilation
Whereas infiltration is uncontrolled air movement through the building envelope, ventilation is
controlled air movement, and is required to ensure good indoor air quality is provided for occupants.
Both Little (b, 2009) and Dimitroulopoulou (2012, p. 110) note the health impacts of poor
ventilation, including the onset of respiratory problems such as asthma. The provision of adequate
ventilation in low energy dwellings is a delicate act, balancing the need to maintain air quality and
keep ventilation related heat losses to a minimum. For this reason, mechanical ventilation with heat
recovery is mandatory for low energy standards such as EnerPHit (Feist, 2010, p. 8).
2.5.5 Moisture management
The need for adequate ventilation is furthered by Little & Arregi (2011) who note that humidity in
Irish dwellings is higher than European norms, something which can lead to two types of
condensation; surface and interstitial.
Wardell & Shanks (2005, p. 37) note that surface moisture condensation and mould growth can
occur when the surface temperature is lower than the dew point temperature of the air in the room.
Thus, surface condensation leading to mould growth can occur where relative humidity reaches
100% around a thermal bridge in an area where ventilation is poor. The possibility of such
condensation problem arising was noted in approximately 33% of sample of 20 dwellings (ibid).
In discussing interstitial condensation, Little (a, 2010) focuses on walls, claiming them to be the
planar element most supportive of mould growth. Mould growth can occur at 80% humidity, less
than the 100% required for surface condensation (Little b, 2009). In an earlier age of high infiltration,
little or no insulation and internal heat sources such as open fires, walls could dry out over time with
little mould growth. When a wall is internally insulated, the wall structure cannot dry out, leading to
the potential failure of the insulation system and internal mould growth on the wall (Little a, 2010).
This situation can be avoided through the use of a suitable vapour control layer to limit the moisture
reaching the internal façade of the wall behind the insulation (Little b, 2009) and the suitable
impregnation of the external façade of the wall to prevent rain ingress (Little b, 2010).
Little & Arregi (2011) note how internal insulation at the party wall can lead to cold spots and
potential mould growth in adjacent properties, as shown in Figure 6 (below);
23
Figure 6 Mould risk associated with differing approaches to wall insulation
Note how in Figure 6 (left), the use of external insulation means the wall in House A remains warm,
with the temperature in the corner of House B raised locally. Note the temperature factor (fRsi),
which must be maintained above 0.75 to remove the risk of mould growth. In Figure 6 (right)
internal insulation has been used in House A, which lowers the temperature in the corner of House B
and brings the temperature factor below 0.75, introducing the risk of mould growth.
External insulation keeps materials within the thermal envelope warm and dry, preventing
condensation and mould problems (Little & Arregi, 2011). Instances of thermal bridging are also
lower with external insulation, which is mandatory for the EnerPHit standard, with Internal
insulation only permitted for 25% of wall area where external insulation is not practical or permitted
(Feist, 2010, p. 6).
2.6 Workmanship
EST (2011) and makes clear the level of detail required to achieve EnerPHit levels of air permeability.
Little (a, 2009) and EST (b, 2010) clearly emphasise the need for high levels of design and
workmanship in order to significantly reduce thermal bridging heat loss during a retrofit. Taking a
more holistic view, Sinnott & Dyer (2012, p. 273) conclude that quality workmanship, design,
detailing and construction practice are all essential to successful retrofitting, while (EST b, 2010)
highlights the importance of each team recognising the centrality of their work to the achievement
of a low energy retrofit.
24
2.7 Key Findings
The residential sector is a major contributor to overall Irish energy consumption and CO2 emissions.
Regulatory non-compliance and poor enforcement have combined to create the legacy of a housing
stock where the average performance is considerably poorer than European norms. Evidence
presented in this section suggests it would be unwise to assume newer dwellings do not require
energy efficiency interventions.
Although retrofitting to date has yielded results, the widespread uptake of deep retrofits is deemed
necessary not only to achieve the magnitude of reductions in energy consumption and CO2
emissions deemed possible in the residential sector, but to the achievement of Ireland’s obligations
under internationally binding emissions agreements. The fabric first approach has been shown to
provide a suitable foundation for deep retrofits.
The need for quality workmanship across all disciplines has been identified as a requirement to the
successful achievement of low energy retrofits.
25
Section 3. Methodology
3.1 Research Strategy
Taking WCC as a case study, the strategy is to perform a desk based analysis of a sample of DEAP
survey results. A custom built excel based model will be used to analyse the input files and perform
scenario analysis.
3.2 Data Sources
Two significant sources of primary data are Wicklow County Council and the Sustainable Energy
Authority of Ireland.
3.2.1 Wicklow County Council
External, accredited assessors perform DEAP surveys for WCC, and as per WCC (b, 2011), must
provide the following documents for each survey performed;
1. A copy of the BER certificate issued
2. A detailed report of the assessment exported from DEAP, in both Excel and XML format (the
‘Dwelling Report’)
3. An Excel file containing recommendations made by the assessor on energy efficiency
interventions which could be implemented to achieve the target C1 energy rating for the
dwelling (the ‘Energy Efficiency Report’)
In total, 718 Dwelling Reports and 68 Energy Efficiency Reports provided by WCC are considered in
this study.
3.2.2 Sustainable Energy Authority of Ireland
The SEAI is responsible for the administration of the Building Energy Rating (BER) scheme in Ireland
and maintain the NBERRT, which contains the results of DEAP surveys carried out nationwide to
date. Given that the inputs to this research and the data contained in the NBERRT were collected in
an identical fashion (i.e. a standardised DEAP survey), use of this information facilitates a direct
comparison between dwellings in WCC and those in Ireland and Co. Wicklow.
At the time of use (July, 2012), this database contained 289,593 results, representing approximately
14.4% of the national stock. For comparative purposes, this study assumes the 286,793 non-
26
provisional2 entries to represent the average dwelling in Ireland, while the 8,465 non-provisional
entries for dwellings in Co. Wicklow are deemed to represent the average dwelling in Co. Wicklow.
3.3 Research Model
Key objectives of this research are to;
1) Profile the energy performance and thermal envelope efficacy of a sample of WCC dwellings
2) Model the impact on energy consumption of various thermal envelope retrofit strategies
A custom model, based on the DEAP application used to perform dwelling assessments, has been
created for this purpose.
3.3.1 DEAP Calculations
A DEAP survey is performed using the ‘DEAP’ software application, which is developed and
maintained by the SEAI3. The calculations used by the DEAP application to determine primary energy
consumption and CO2 emissions for a dwelling are fully accessible in (SEI, 2007). The DEAP process
can be broken into several steps, as outlined in Figure 7 (below);
Figure 7 The 5 steps of a DEAP Assessment
Step 1: Determine the Overall Heat Loss Coefficient, which represents total dwelling heat loss by
way of ventilation heat loss, planar heat loss and thermal bridging heat loss. Key inputs here relate
2 There are 3 BER types (SEAI d, 2012, p. 5); Provisional (required for a dwelling that is not yet built but is
offered for sale “off the plans”), Final (required for a newly-built dwelling before it is occupied) and Existing
(required for any existing dwelling that is offered for sale or to let). 3 This study assumes all dwelling assessments were performed using DEAP V3.1.0, the latest version available
at the time WCC undertook their assessments.
Internal Gains(W) Solar Gains (W)
Occupants (W) Window Orientation
Heat Loss -
Doors
Heat Loss -
Floors
Heat Loss -
Roofs
Heat Loss -
Walls
Heat Loss -
Windows
Hot Water
System (W)
Glazing Transmittance
Frame Factor
Area Area Area Area Area Appliances (W) Standardised values
U-value U-value U-value U-value Adjusted
U-value
Lighting (W) of Monthly Insolation
Step 2. Determine Overall Heat Gains (W)
Thermal Bridging Factor (W/m2K)
Fabric Heat Loss (W/K)
Step 1. Determine Overall Heat Loss Coefficient (W/K)
Average Monthly External Temperature (°C)
Ventilation Heat Loss (W/K)
Number of openings (m3/h)
Structural Infiltration (ac/h)
Ventilation Method (ac/h)
Number of sheltered sides
Heating system responsiveness
Step 3. Determine Net Space Heat Demand (kWh/y)
Heat Capacity (thermal mass) of Dwelling (MJ/K)
Average Internal Temperature (°C)
Step 5. Determine total primary energy consumption (kWh/y) and
CO2 emissions (kg/y)
Space heating system(s) efficiency (%) and fuel type
Water heating system(s) efficiency (%) and fuel type
Renewable contributions
Step 4. Determine Annual Space Heating Demand (kWh/y)
Heating system controls
Presence and location of heating system(s) pumps and fans
27
to the number of openings in the dwelling, building envelope element U-values and areas and a
thermal bridging factor.
Step 2: Determine Overall heat gains. Key inputs here relate to the number of lights in the dwelling.
Step 3: Based on standardised assumptions of internal and external temperature, the thermal mass
of the dwellings and solar gains, determine the Net Space Heat Demand (NSHD).
Step 4: Accounting for the responsiveness of any heating system(s) and the presence of controls,
pumps and fans, determine the Annual Space Heating Energy Requirement.
Step 5: Accounting for space and water heating system efficiencies, fuel types used and the presence
of any renewable technologies, determine the primary energy requirements and CO2 emissions for
the dwelling.
The effect of retrofit interventions on overall energy usage can also be modelled for individual
dwellings through the DEAP application. The results of a DEAP survey can be exported to an Excel
file (the ‘Dwelling Report’) containing the following information on separate tabs;
1) Dwelling overview
information
8) Lighting and internal gains
2) Dwelling dimensions 9) Annual Heat Use
3) Ventilation details 10) Annual Space Heat Req.
4) Planar element details 11) Distribution system losses
and gains
5) Heat Loss details 12) Heating system energy
requirements
6) Water heating details 13) Summer internal gains
7) Solar water heating details 14) Dwelling energy requirements
and CO2 emissions
Table 3 DEAP Dwelling Report contents
3.3.2 Profiling Energy Performance and Thermal Envelope Efficacy
In the context of this study, that DEAP can only analyse a single dwelling at a time is a key limitation,
as this this research aims to analyse the performance of 718 dwellings. To circumvent this
limitation, the 718 separate ‘Dwelling Reports’ provided by WCC were parsed using a custom built
Excel Macro and collated into a single Excel ‘Master Spreadsheet’, which forms the basis of the
model used to perform energy profiling and retrofit analysis.
28
Information central to determining the energy consumption and CO2 emissions for each dwelling in
the sample is distilled to a single row in the master spreadsheet, thus facilitating data analysis. Table
4 (below) highlights specific energy related quantities central to profiling the energy performance of
the sample;
Assessed Quantity
Ventilation Heat Loss
Planar Element Heat Loss
Thermal Bridging Heat Loss
Fabric Heat Loss
Overall Heat Loss
Net Space Heat Demand
Total Space Heating Primary Energy Demand
Dwelling Primary Energy Demand
Dwelling CO2 Emissions
Table 4 Energy related quantities considered in this study
The analysis of these quantities is presented in section 4.
3.3.3 Modelling retrofit interventions
Upon creation, the data contained within the master spreadsheet is static, that is to say information
contained in one cell is not linked in any way with information in any other cell. To model the
impact on primary energy consumption and CO2 emissions arising from the implementation of
various retrofit interventions, the calculations performed by the DEAP application must be
incorporated into the master spreadsheet. The results of these calculations are represented by
‘modelled quantities’ which are implemented as columns in the master spreadsheet adjacent to the
corresponding ‘assessed quantity’.
Figure 8 (below) shows an extract of the master spreadsheet, with the assessed and modelled values
of Fabric heat loss (FabricHeatLoss [W/K] and MFabricHeatLoss [W/K], respectively) clearly visible;
29
Figure 8 Extract from the Master Spreadsheet
As can be seen, this approach easily facilitates a comparison of ‘before and after’ values for a
quantity, and allows reductions achieved to be determined for a quantity.
The retrofit interventions the model aims to accommodate are listed in Table 5 (below). It is clear
that the implementation of any of the listed interventions will alter the inputs to specific DEAP
calculations. This is managed in the model by associating each retrofit intervention with a ‘modelled
attribute’, also noted in Table 5 (below). The value associated with each modelled attribute can be
manually defined via an ‘attribute control’, which is implemented as a dropdown containing values
relevant to the intervention the modelled attribute represents. The values of modelled attributes
are taken as input to the DEAP calculations embedded within the master spreadsheet. For Floors,
Roofs, Walls and Windows, an attribute control is provided per element type to account for the fact
that there may be several element types per dwelling.
Intervention Modelled Attribute
Alter the number of Chimneys M#Chimneys
Alter the number of Flues M#OpenFlues
Alter the number of extract fans / open vents M#Fans/Vents
Alter the number of mobile gas appliances M#FluelessGas
Improve draught-stripping measures M%Draughtstripped
Improve Door thermal performance MDoorUValue
Improve Floor thermal performance MFloorUValue
Improve Roof thermal performance MRoofUValue
Improve Wall thermal performance MWallUValue
Improve Window thermal performance MFrameType, MGlazingType
Reduce heat loss via Thermal Bridging MBridgingFactor
Table 5 Retrofit Interventions and Modelled Attributes
30
3.3.3.1 Example
By way of example, consider the thermal upgrade of walls.
Several types of wall are present in the sample; 300mm Cavity, 225mm Solid Brick etc. To be able to
model the effect of upgrading the thermal transmittance of 300mm cavity wall to U-value = 0.27
W/m2K by way of external insulation for example, it must be possible to identify all instances of
300mm Cavity wall and then alter the U-value associated with each.
Figure 9 (below) shows an extract of the data captured for Walls in the master spreadsheet, and the
attribute control used to update Wall specific energy related attributes;
Figure 9 The use of Attribute Controls to update energy related planar element attributes
The master spreadsheet extract is interpreted as follows;
• WallType contains the varying types of wall as recorded during the DEAP assessment
• WallArea contains the area associated with the wall type
• WallUValue contains the U-Value of the wall type as recorded during the DEAP assessment
• MWallUValue contains the value of the modelled attribute as selected in the ‘Walls’
attribute control (Figure 9, above, right). This control, located on a separate ‘Interventions’
worksheet in the master spreadsheet, allows a revised U-value be selected for each wall
type present in the sample. By way of the Excel VLOOKUP function, the revised value for the
modelled attribute is applied to all instances of the wall type associated with the modelled
attribute. Note how if the attribute control selection is ‘No Change’ for a particular wall type,
the value of the modelled attribute remains unchanged for that wall type (for example, see
values of WallUValue and MWallUValue for the wall type ‘Stone’, above).
• The suffix ‘1’ indicates that all values relate to the first wall type for the dwelling in question.
300mm Filled Cavity 82.8 0.6 0.6
300mm Cavity 75.1 1.1 0.27
Timber Frame 85.63 0.55 0.55
300mm Cavity 44.51 0.55 0.27
300mm Cavity 10.02 0.6 0.27
Stone 77.05 0.6 0.6
300mm Cavity 82.19 0.47 0.27
WallType 1 WallUValue 1 MWallUValue 1WallArea 1
31
Note how in Figure 10 (below) the model has calculated a revised value of heat loss attributable to
the wall type (MWallHeatLoss) as a result of the reduced U-value;
Figure 10 Revised Wall related Heat Loss Calculation
The method described above is used throughout the model to calculate reductions in heat loss
attributable to ventilation, planar elements or thermal bridging. To better accommodate trouble
shooting, calculations for planar elements are performed on dedicated worksheets in the master
spreadsheet.
3.3.4 Model Simplifications and Limitations
Several simplifications are made in the model;
• DEAP default values are assumed consistent across all assessments
• For ease of analysis, Ground Floor Apartments (45 dwellings), Maisonettes (7 dwellings) and
Top Floor Apartments (36 dwellings) are modelled collectively as ‘Apartments’.
• It is assumed that internal gains remain constant in all houses post-retrofit.
• The model does not account for semi-exposed walls4.
• The model does not account for roof windows, introducing a small error in the estimation of
window related heat loss. See Appendix A for further details.
• It is assumed that chimneys will only ever be blocked up, so the number of chimneys will
only ever reduce.
• Owing to the way in which retrofit interventions are modelled It is not possible to model the
effect of retrofitting some incidences of an element; for any particular element build up, the
model assumes all incidences to be upgraded.
4 An analysis shows that only 0.61% of total walled area is semi-exposed; heat loss through this walled area will
be slightly overestimated in the model, though the error introduced will be insignificant overall.
300mm Filled Cavity 82.8 0.6 0.6 49.68 49.68
300mm Cavity 75.1 1.1 0.27 82.61 20.277
Timber Frame 85.63 0.55 0.55 47.0965 47.0965
300mm Cavity 44.51 0.55 0.27 24.4805 12.0177
300mm Cavity 10.02 0.6 0.27 6.012 2.7054
Stone 77.05 0.6 0.6 46.23 46.23
300mm Cavity 82.19 0.47 0.27 38.6293 22.1913
WallType 1 WallUValue 1 MWallUValue 1WallArea 1 MWallHeatLoss 1WallHeatLoss 1
32
• Depending on the insulation strategy employed for walls, the thermal mass category of a
dwelling may be altered during a retrofit (SEAI a, 2008, p. 90). Any such effects are not
catered for in the model.
• The model does not account for the use of mechanical ventilation systems which are
mandatory in the EnerPHit standard (Feist, 2010, p. 8). This has two noticeable affects;
firstly, reductions in ventilation heat loss will likely be underestimated by the model owing
to the assumed presence of open vents for ventilation and secondly, energy consumption
related to pumps and fans will remain unchanged and hence be underestimated.
• Efficiency gains from replacing open fires with stoves are not accounted for, thus the model
will slightly overestimate space heating energy consumption and associated CO2 emissions in
some scenarios.
3.3.5 Model Accuracy – Individual Dwelling
The accuracy of the model at the individual dwelling level was validated by comparing its output to
that of DEAP for a package of retrofit interventions as applied to a mid-terraced dwelling built during
the 1980’s.
The interventions assumed are outlined in Table 6 (below);
Element Intervention
Chimneys Reduce from 2 to 1
Doors Upgrade to U-value=1.5
Floors No Change
Roofs Double Insulation depth to 300mm
Walls Externally insulate, revised U-
Value=0.3
Windows Upgrade to Triple-glazed, argon filled
Table 6 Interventions assumed during Model testing
33
Model test results are outlined in Table 7 (below);
Quantity DEAP
As
Assessed
Modelled
‘No
Changes’
Difference DEAP
‘With
Changes’
Modelled
‘With
Changes’
Difference
Ventilation Heat Loss
(W/K)
60 60 0.0% 51 51 0.0%
Total Plane Heat Loss
(W/K)
100 100 0.0% 63 62 -1.6%
Total Thermal Bridging
Heat Loss (W/mK)
20.7 20.7 0.0% 20.7 20.7 0.0%
Total Fabric Heat loss
(W/K)
120 121 0.8% 83 83 0.0%
Total Heat Loss (W/K) 180 181 0.6% 134 134 0.0%
Net Space Heat
Demand (kWh/y)
5593 5580 -0.2% 3631 3654 0.6%
Total Space Heat
Primary Energy Req.
(kWh/y)
9406 9288 -1.3% 6579 6367 -3.2%
Total Primary Energy
Req. (kWh/y)
16799 16682 -0.7% 14590 13761 -5.7%
Total CO2 Emissions
(kg/y)
3527 3502 -0.7% 3143 2868 -8.7%
Table 7 Model Test Results
For the ‘No Change’ scenario, variances are insignificant throughout. Small inaccuracies become
exaggerated in the Interventions scenario, resulting in total primary energy requirement and total
CO2 emissions being under-estimated by 5.7% and 8.8% respectively.
3.3.6 Model Accuracy – All Dwellings
The difference between the assessed value (as recorded during the DEAP assessment) and modelled
values (as calculated by the model) for any quantity may vary per dwelling. Owing to simplifications
in the model and rounding errors in Excel, quantities may be overestimated for some dwellings and
underestimated in others. Cumulatively, these differences will introduce an error across the sample.
To provide confidence in the model, it is required to know the scale of this error.
Table 8 (below) outlines the accuracy with which the model replicates assessed values of each
quantity assuming no retrofit interventions (i.e. the ‘No Changes’ scenario);
34
Quantity Average
Modelled
Value
(AMV)
Root
Mean
Square
(RMS)
RMS
as %
AMV
Ventilation Heat Loss (W/K) 50 0.4 0.8%
Total Plane Heat Loss (W/K) 129 0.7 0.5%
Total Thermal Bridging Heat Loss
(W/mK)
25 0.0 0.0%
Total Fabric Heat Loss (W/K) 154 0.8 0.5%
Total Heat Loss (W/K) 204 0.9 0.4%
Net Space Heat Demand (kWh/y) 6703 56.0 0.8%
Total Space Heat Primary Energy Req.
(kWh/y)
13066 553.7 4.2%
Total Primary Energy Req. (kWh/y) 22444 553.8 2.5%
Total CO2 Emissions (kg/y) 5752 180.2 3.1%
Table 8 Model Accuracy
Average Modelled Value: The average value for each quantity, as derived by the model.
Root Mean Square: The Root Mean Square of the difference between assessed and modelled values
of the quantity for each dwelling. This accounts for the fact that the difference between assessed
and modelled values may be positive or negative for any particular dwelling.
RMS as a % of AMV: This provides context on the scale of inaccuracy inherent in the model.
Overall, it can be seen that the model is quite accurate in replicating the assessed values of
quantities, with total primary energy requirement and CO2 emissions being overestimated by 2.5%
and 3.1% respectively.
3.4 Data Quality
In terms of completeness and consistency, the data provided as input to this study was of very good
quality. Several noteworthy items are discussed in Appendix A.
35
3.5 Research Limitations
There are several limitations to this research;
1) Owing to time constraints and to reduce the likelihood of co-ordinating a large body of data
from disparate sources, WCC is the only local authority considered in this study. The methods
used are nonetheless equally applicable to other local authorities.
2) It was intended that a suitable scaling factor be used to extrapolate primary energy and CO2
emissions reductions across the stock, based on those achieved for the sample. This requires the
identification of a dwelling attribute which is captured for each dwelling in the sample and
accurately recorded for each dwelling in WCC’s housing stock. Energy related attributes such as
dwelling age or type are immediately identified as being suitable. However, dwelling type is not
captured for every dwelling in the stock, and while a year of construction could be ascribed to
each dwelling based on internal WCC methodology, this methodology is not consistent with that
used in DEAP (see Table 9, below), meaning comparison is impossible.
DEAP Age Band
(SEAI, 2008)
WCC Age Band
(Sheehy, 2004)
A <1900 <1960
B 1900 - 1929 1960 - 1964
C 1930 -1949 1965 - 1969
D 1950 - 1966 1970 - 1974
E 1967 - 1977 1975 - 1979
F 1978 - 1982 1980 - 1984
G 1983 - 1993 1985 - 1989
H 1994 - 1999 1990 - 1995
I 2000 - 2004 1995 - 1999
J >2005 >2000
Table 9 Inconsistent Age Bands
3) An in-depth analysis of the reductions in heat loss through thermal bridging, and an analysis of
potential issues with surface or interstitial condensation arising from the implementation of
retrofitting interventions, was to have been performed. However, the scale and quality of the
data set received from WCC meant a more detailed analysis of energy consumption and heat
loss could be performed than was originally planned, something deemed to be of greater initial
value to WCC.
36
4) A lack of indicative ‘Y-Factors’ mean estimates of reductions in heat loss arising from thermal
bridges may vary greatly to what can be achieved in practice.
5) The format in which data was received made it difficult to compile a more comprehensive
sample for ‘Recommended Interventions’ analysis.
37
Section 4. Model Output & Data Analysis
This section is based on the output of the model described in section 3.3, and aims to provide an
overview of the energy performance of WCC’s housing stock.
Physical attributes of the dwellings, such as age, construction type and number of storeys are
considered first. Headline indicators of dwelling energy performance, such as energy consumption,
CO2 emissions and BER are then considered, before a detailed analysis of thermal envelope
performance is presented.
An analysis of recommended energy efficiency interventions completes the section.
4.1 Physical Profile
4.1.1 Sample Size
As noted earlier, WCC’s stock is estimated to number between 2,297 and 2,334 dwellings. Assuming
the median value of 2,316, the sample of 718 dwellings represents 31% of the stock.
4.1.2 Dwelling Age
Using the standard DEAP age bands to facilitate consistent data analysis, the age profile of the
sample is shown in Figure 11 (below);
Figure 11 Dwelling Age Profile
A-D ('00-
'66)E ('67-'77) F ('78-'82) G ('83-'93) H ('94-'99) I ('00-'04) J ('05+)
Total 1.4% 16.6% 9.2% 26.5% 18.8% 12.8% 14.8%
0%
5%
10%
15%
20%
25%
30%
38
In keeping with national trends as noted in DECLG (b, 2012), circa 53% of dwellings pre-date the
introduction of the 1991 building regulations, which were the first to formally consider dwelling
thermal performance, and are expected to have poorer energy performance than those built under
more stringent regulations.
4.1.3 Dwelling Type
Figure 12 (below) illustrates how the largest category of dwelling is semi-detached, with mid-terrace
and end of terrace dwellings also contributing heavily to the sample. As would be anticipated for a
local authority, detached dwellings contribute least.
Figure 12 Dwelling Type Profile
4.1.4 Number of Storeys
The majority of dwellings (74%) are 2 storey, while 24% are 1 storey units. 2% of dwellings have
converted attics, and are classified as 3 story dwellings.
4.1.5 Structure Type
The sample is predominantly of masonry structure, with timber frame dwellings comprising only
4.6% of the sample. All timber frame units were constructed post 2000.
6.4% of the 285,583 dwellings recorded in the NBERRT at the time of writing were of timber frame
construction.
Semi-detached Mid-terrace End of terrace Apartment Detached
Total 37.9% 26.6% 19.4% 12.3% 3.9%
0%
5%
10%
15%
20%
25%
30%
35%
40%
39
4.2 WCC Dwelling Energy Performance Overview
This section provides an overview of the energy performance of dwellings in the sample in terms of
average primary energy consumption, average CO2 emissions and overall BER rating. For WCC
dwellings, this information is obtained from the model described in section 3.3. To provide context,
the average energy performance of dwellings in Co. Wicklow (8,465 dwellings) and Ireland (286,793
dwellings) is drawn from the NBERRT.
4.2.1 Average Energy Consumption and CO2 emissions
As shown in Figure 13 (below, left), average primary energy consumption for Irish dwellings stands
at 262.9 kWh/m2/yr, placing them towards the upper end of the D2 energy band. Average primary
energy consumption for dwellings in Co. Wicklow is 7.2% more (281.7 kWh/m2/yr), placing them
firmly in the centre of the D2 energy band. Dwellings in the WCC sample consume on average 301.7
kWh/m2/yr, placing them in the E1 energy band. Thus, WCC dwellings consume 7.1% more than the
average dwelling in Co. Wicklow, and 14.8% more than the average Irish dwelling.
Figure 13 Average Primary Energy Consumption (left) and CO2 Emissions (right)
Figure 13 (above, right) shows the national average CO2 emissions for a dwelling to be 62.6
kgCO2/m2/yr, with the average dwelling in Co. Wicklow emitting 8.2% more (67.7 kgCO2/m2/yr). The
average WCC dwelling emits 77.7 kgCO2/m2/yr, 14.8% more than the average dwelling in Co.
Wicklow, and 24.2% more than the national average.
IrelandCo.
WicklowWCC
kWh/m²/yr 262.9 281.7 301.7
240
250
260
270
280
290
300
310
IrelandCo.
WicklowWCC
kgCO2/m²/yr 62.6 67.7 77.7
0
20
40
60
80
100
40
4.2.2 BER Profile
The BER profile for dwellings in Ireland, Co. Wicklow and WCC is shown in Figure 14 (below);
Figure 14 BER Profile for dwellings in Ireland, Co. Wicklow and WCC
There are proportionately more WCC dwellings in lower energy bands (C3 to G), with
proportionately fewer in higher bands (C2 to A1), indicating the performance of WCC dwellings is
comparatively poor across all bands. Overall, 94% of dwellings considered in this study are currently
below the NERP target energy rating of C1. Contributing factors to this situation are discussed
further in section 4.4.
To further illustrate the energy performance of the sample, a methodology similar to that used by
Curtain (2009, p. 38), can be used to derive expected energy ratings for dwellings in the sample
based on the builing regulations in place at the time of construction. The expected BER for dwellings
built under successive regulatory regimes are listed in Table 10 (below);
A1 A2 A3 B1 B2 B3 C1 C2 C3 D1 D2 E1 E2 F G
Ireland 0.0% 0.0% 0.4% 1.8% 4.2% 8.4% 11.1% 12.4% 13.0% 13.1% 11.8% 6.7% 5.2% 5.1% 6.7%
Co. Wicklow 0.0% 0.0% 0.8% 1.7% 3.2% 6.8% 9.3% 11.0% 12.7% 13.4% 11.9% 7.5% 6.4% 6.4% 9.0%
WCC 0.0% 0.0% 0.0% 0.0% 0.0% 1.8% 3.8% 7.7% 14.3% 20.1% 14.8% 11.4% 7.2% 7.7% 11.3%
0%
5%
10%
15%
20%
25%
41
DEAP Age
Band
Applicable
Building
Regulations
% Sample
constructed
in age band
Expected
BER
A-D ('00-'66) NA
E ('67-'77) 1972 18% E2
F ('78-'82) 1976 9% D2
G ('83-'93) 1982 26% D1
H ('94-'99) 1992 19% C2
I ('00-'04) 2002 13% C1
J ('05+) 2005 15% B3
Table 10 Expected Energy Ratings
Figure 15 (below) presents the distribution of expected and assessed energy ratings for the sample;
Figure 15 Distribution of Assessed and Expected Energy Ratings
Considerably fewer dwellings than anticipated built post-1992 achieve the energy rating expected of
them, with 47% of dwellings expected to meet or exceed a C2 rating, and only 14% of dwellings
doing so. A degree of movement around expected ratings is anticipated over time as dwellings
undergo retrofits, making it difficult to form a view of how this trend persists for older dwellings,
though it does seem apparent. Issues highlighted in Wardell & Shanks (2005) and Antonelli & Colley
(2012) relating to regulatory non-compliance can be considered contributory factors here. The
accepted practice of building dwellings to the preceding standard for some time following the
introduction of revised building regulations (SEAI a, 2008, p. 83) may be another driver for this trend.
B3
(2005)
C1
(2002)
C2
(1992)C3
D1
(1982)
D2
(1976)E1
E2
(1972)F G
Assessed BER 2% 4% 8% 13% 20% 15% 11% 7% 8% 11%
Expected BER 15% 13% 19% 26% 9% 18%
0%
5%
10%
15%
20%
25%
30%
42
4.2.3 Key findings
From the analysis presented above, it is clear the energy performance of the average WCC dwelling
is below that of the average dwelling in Co. Wicklow, which in turn is below that of the average Irish
dwelling.
The low level of retrofitting grant applications in Co. Wicklow, as noted in SEAI (c, 2012), may be
indicative of a low level of retrofitting work in general across the county, indicating WCC could
influence behaviour by playing the role of market maker.
The poor performance of WCC dwellings may be partly attributable to comparatively poor thermal
envelope performance, something discussed further in section 4.3.1.
The significant difference in assessed and expected energy ratings for more recently constructed
WCC dwellings is in line with findings of widespread non-compliance highlighted by Antonelli &
Colley (2012).
Assuming the sample to be representative of WCC’s entire stock, the scale of the retrofitting
challenge facing WCC becomes clear when it is considered that 94% of dwellings in the sample have
an energy rating below the C1 target rating.
43
4.3 Detailed Energy Consumption Analysis
An aim of this study is to quantify the impact that the implementation of fabric first approach can
have on energy consumption across the sample of WCC dwellings. The performance of the thermal
envelope is only one of many factors that determine a dwelling’s BER. It is expected, though not
necessarily guaranteed, that where a BER is poor, the performance of the thermal envelope is also
poor. Thus, it is of interest to profile energy consumption in the sample to determine the proportion
of consumption attributable to the performance of the thermal envelope. Primary energy
consumption is the focus of this analysis, as a dwelling’s BER is based on this quantity.
Based on information output from the model, Figure 16 (below) demonstrates that the majority
(59%) of energy consumed across the sample relates to space heating, something directly related to
the performance of the thermal envelope5;
Figure 16 Primary Energy Consumption (left) and CO2 Emissions (right) breakdowns
Water heating is also shown to be a significant contributor to energy consumption at 31%. Pumps
and fans, which, given that 100% of the sample is naturally ventilated, can reasonably be assumed to
be related to heating systems and kitchen hood appliances, contribute only 3% of the consumption,
with lighting contributing 7%.
CO2 emissions are shown to be similarly distributed across the sample.
5 The fuel used to provide heat and occupant behaviour are noted as drivers for space heating energy
consumption, though both are excluded from this research.
59%31%
7%
3%Space
Heating
Water
Heating
Lighting
Pumps and
Fans
60%
30%
7%
3%Space
Heating
Water
Heating
Lighting
Pumps &
Fans
44
Figures 17 and 18 (below) illustrate how the dominant contribution of space heating to overall
energy consumption holds regardless of dwelling age or BER rating;
Figure 17 Primary Energy Consumption per age band
Figure 18 Primary Energy Consumption (kWh/yr) per BER
A-D ('00-
'66)
E ('67-
'77)
F ('78-
'82)
G ('83-
'93)
H ('94-
'99)I ('00-'04) J ('05+)
Pumps & Fans (kWh/y) 6,831 71,847 41,374 120,374 83,201 61,242 64,011
Lighting (kWh/y) 17,491 215,873 117,665 267,429 222,546 168,182 182,122
Water Heating (kWh/y) 57,838 1,211,980 550,307 1,495,570 820,512 518,497 438,126
Space Heating (kWh/y) 301,064 2,444,737 937,398 1,878,732 1,801,213 1,131,154 944,449
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
B3 C1 C2 C3 D1 D2 E1 E2 F G
Pumps & Fans 6,339 13,202 35,798 77,400 98,099 75,903 56,278 31,850 25,764 28,247
Lighting 27,987 49,009 97,680 180,448 231,704 170,004 129,498 83,849 90,370 130,759
Water Heating 50,616 100,807 240,884 538,098 761,039 618,663 547,835 396,147 597,602 1,241,139
Space Heating 105,136 224,335 498,390 1,008,081 1,504,526 1,248,360 1,194,646 907,244 958,560 1,789,469
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
45
No instances of renewable technologies were noted during the dwelling assessments, thus space
heating is, by virtue of its exclusive dependence on fossil fuels, the primary driver of CO2 emissions.
CO2 emissions are shown to have a similar distribution across dwelling types and age bands as
primary energy consumption.
4.3.1 Thermal Envelope Performance
The retrofit interventions considered in this study relate solely to the thermal envelope, a valid and
justified approach given the centrality of the thermal envelope to space heating demand, and the
centrality of this demand to overall energy consumption and CO2 emissions, as demonstrated above.
This section aims to highlight the efficacy of the thermal envelope in the dwellings comprising the
sample by analysing trends in heat loss.
4.3.1.1 Total Heat Loss
Heat escapes the thermal envelope in several ways, most notably via ventilation (both controlled
ventilation and uncontrolled infiltration), via conduction through planar elements and via thermal
bridging. Based on an analysis of the data provided as performed by the model, the relative
contributions of each type of heat loss to total assessed heat loss across the sample are as follows;
Quantity Assessed Value
Ventilation Heat Loss (W/K) 35,885
Planar Heat Loss (W/K) 92,689
Thermal Bridging Loss (W/mK) 17,983
Figure 19 Total Assessed Heat Loss Breakdown
As expected, and in line with Wardell & Shanks (2005), heat loss through the planar elements
dominates, with ventilation related losses accounting for a quarter of all heat lost. Thermal bridging
contributes 12%.
25%
63%
12% Ventilation Heat
Loss
Planar Heat Loss
Thermal Bridging
Loss
46
4.3.1.2 Ventilation Heat Loss
The data suggests that infiltration arising from the physical characteristics of the dwellings such as
the number of storeys and structure type is responsible for approximately 55% of ventilation related
heat loss in the sample, with approximately 45% owing to the presence of openings, such as
chimneys.
Based on data from the NBERRT, average air change rates for dwellings in Ireland (7,221 dwellings
considered), Co. Wicklow (166 dwellings considered) and WCC dwellings are shown in Figure 20
(below);
Figure 20 Air Change rates for average dwellings in Ireland, Co. Wicklow and WCC
Several contributing factors for this comparatively poor performance of WCC dwellings are
suggested;
• Figures for dwellings in Ireland and Co. Wicklow include results of air permeability tests,
which are inherently more accurate than the DEAP algorithm upon which the WCC values
are exclusively based (no air-tightness test values were noted in the sample).
• The average number of chimneys (for which DEAP applies the largest penalty of all openings)
for dwellings in Ireland (0.35) and Co. Wicklow (0.2) is significantly lower than for dwellings
in WCC (1.0)
• There are proportionally more timber frame dwellings (deemed more air-tight then masonry
structures in DEAP) in Ireland (10%) and Co. Wicklow (12%) than WCC (5%)
Ireland Co. Wicklow WCC
ac/h 0.30 0.33 0.79
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
47
Figure 21 (below) illustrates how average ventilation heat loss (W/K) varies per dwelling type in the
sample of WCC dwellings;
Figure 21 Average Ventilation Heat Loss per Dwelling Type
An examination of underlying data reveals that ventilation heat loss correlates strongly with dwelling
volume, with End of Terrace dwellings having the largest volume (209m3), and hence heat loss,
followed by Semi-detached (204m3), with Apartments having the smallest volume (116m3) and heat
loss.
End of
terraceMid-terrace
Semi-
detachedDetached Apartment
W/K 56 53 52 49 30
0
10
20
30
40
50
60
48
4.3.1.3 Fabric Heat Loss
Fabric heat loss consists of heat loss by way of planar elements combined with that lost via thermal
bridging.
The contribution of each planar element to total element area, total planar and total fabric heat loss
across the sample is shown in Figure 22 (below). The contribution of thermal bridging to fabric heat
loss is also shown. Note how each planar element’s contribution to fabric heat loss is less than that
to planar heat loss as a result of the inclusion of thermal bridging.
Figure 22 Contributions to Total Fabric Area, Total Planar and Total Fabric Heat Loss
The assessed contributions to fabric heat loss are as follows;
Heat Loss Type Assessed Value
Door Heat Loss (W/K) 5,216
Floor Heat Loss (W/K) 15,519
Roof Heat Loss (W/K) 12,765
Wall Heat Loss (W/K) 37,833
Window Heat Loss (W/K) 21,346
Thermal Bridging Heat Loss (W/mK) 17,983
Figure 23 Assessed contributions to Fabric Heat Loss
An interpretation of this data along with a detailed analysis of contributing factors is now presented.
Contribution to Total
Fabric Area
Contribution to Total
Planar Heat Loss
Contribution to Total
Fabric Heat Loss
Thermal Bridging 16.2%
Windows 7.3% 23.0% 19.3%
Walls 38.3% 40.8% 34.2%
Roofs 26.7% 13.8% 11.5%
Floors 26.2% 16.7% 14.0%
Doors 1.5% 5.6% 4.7%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
49
4.3.1.3.1 Doors
By contributing 1.5% of total building fabric area across the sample and 4.7% of fabric heat loss,
doors are, per unit area, the worst performing planar element in terms of heat retention. Their small
cumulative area however ensures absolute heat loss is less than any other element6.
4.3.1.3.2 Floors
Floors account for 26% of building fabric area but only 14% of fabric heat loss. As illustrated in Figure
24 (below), the data suggests approximately 96% of this heat loss is attributable to the floor type
‘Ground Floor – Solid’.
Figure 24 Floor Type and Heat Loss profile
4.3.1.3.3 Roofs
Roofs account for 27% of total fabric area and 11.5% of fabric heat loss. Somewhat un-intuitively,
more heat is lost across the sample through floors than roofs, a phenomenon likely due to a greater
presence of attic insulation than the presence of floor insulation. Similar to floors and as noted in
Figure 25 (below), a high degree of uniformity is seen in the roof type profile, with 94% of roof heat
loss attributable to the roof type ‘Pitched Roof, Insulated on Ceiling’;
6 As noted in Appendix A, there are 126 instances where area and heat loss information is not recorded for
doors, thus heat loss attributable to doors is under-reported in the sample.
Ground Floor -
Solid
Exposed / Semi
Exposed
Ground Floor -
Suspended
Partially Heated
Below
Area 96.6% 0.5% 2.8% 0.1%
Heat Loss 96.0% 0.7% 3.0% 0.3%
0%
20%
40%
60%
80%
100%
120%
50
Figure 25 Roof Type and Heat Loss profile
The profile of roof insulation across the sample as noted during dwelling assessments is illustrated in
Figure 26 (below). Insulation thickness was recorded for 646 dwellings and 1,097 roofed areas in the
sample. Only 27% of roofed areas meet or exceed current regulations (~300mm), approximately 7%
of areas have less than 100mm of insulation present, while the insulation in a considerable
proportion of areas is ‘Not Listed’.
Figure 26 Roof Insulation Profile
Pitched Roof –
Insulated on Ceiling
Pitched Roof –
Insulated on Rafter
Room in Roof –
Insulated on sideFlat Roof
Area 92.9% 2.2% 3.7% 1.1%
Heat Loss 94.0% 1.7% 2.6% 1.7%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0mm 25mm 50mm 75mm 100mm 150mm 200mm 250mm>=300
mm
Not
Listed
Contribution 0.64% 0.36% 4.38% 1.55% 24.34% 11.67% 8.66% 2.92% 27.16% 18.32%
0%
5%
10%
15%
20%
25%
30%
51
4.3.1.3.4 Walls
Walls are the largest contributor to total fabric area and fabric heat loss, contributing 38% and 34%
respectively. As illustrated in Figure 27 (below), several wall types are present in the sample;
Figure 27 Wall Type and Heat Loss profile
Several items are noteworthy;
• That 60% of wall area and 51.5% of wall related heat loss is attributable to easily treatable
300mm Cavity construction indicates that significant reductions in wall related heat loss can
be readily achieved.
• A significant portion of wall related heat loss is attributable to concrete hollow block
construction, which contributes 14% and 28% of total wall area and wall related heat loss
respectively. An examination of the data reveals this construction type to be most prevalent
in age bands E (1967 – 1977) and G (1983 – 1993), though some use is noted in band I (2000
– 2004) also, possibly the result of dwellings being extended.
• The proportion of area and heat loss attributable to single leaf, ‘hard to treat’ wall types is
small.
300mm
Cavity
300mm
Filled
Cavity
Concrete
Hollow
Block
225mm
Solid Brick
325mm
Solid Brick
Solid
Mass
Concrete
StoneTimber
Frame
Area 60.3% 8.5% 14.4% 2.3% 0.3% 0.2% 8.4% 5.6%
Heat Loss 51.5% 4.4% 28.5% 2.7% 0.5% 0.6% 8.3% 3.5%
0%
10%
20%
30%
40%
50%
60%
70%
52
4.3.1.3.5 Windows
Windows contribute only 7.3% planar area for the entire sample, yet account for 19% of total planar
heat loss, making them the second worst performing planar element, per unit area.
As Figure 28 (below) illustrates, several glazing types are present in the sample, however Double
Glazed Air and Argon filled units predominate. Interestingly, 10% of all window related heat loss is
attributable to single-glazed units, the majority of which are found in age bands G (1983 – 1993) and
H (1994 – 1999).
Figure 28 Window Type and Heat Loss profile
Window frames must be considered when assessing window related heat loss, with Figure 29
(below) illustrating that over 6% of frames are of thermally inferior metal construction;
Single-glazedDouble-glazed, air
filled
Double-glazed, argon
filled
Triple-glazed, air
filled
Area 6.20% 75.46% 18.10% 0.23%
Heat Loss 10.38% 73.27% 16.35% 0.22%
0%
10%
20%
30%
40%
50%
60%
70%
80%
53
Figure 29 Frame Type profile
4.3.1.3.6 U-Value comparison
Having formed a view of the make-up of various planar elements and their contribution to heat loss
across the sample, it is useful to determine how the thermal performance of WCC planar elements
compares with those at county and national level.
Average thermal transmittance values for planar elements in WCC dwellings are obtained from
assessed data. Values representing Ireland (286,793 dwellings) and Co. Wicklow (8,465 dwellings)
are derived from the NBERRT.
Wood/PVC
Metal no
thermal
Break
Metal 4mm
thermal
Break
Metal 12mm
thermal
Break
Metal 20mm
thermal
Break
% Contribution 93.28% 4.75% 1.87% 0.00% 0.10%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
54
Figure 30 Elemental U-value comparisons (W/m2K)
Several items are noteworthy in Figure 30 (above);
• The average WCC wall U-value is significantly higher than the county and national average.
• The average WCC roof U-value outperforms the county average but is considerably higher
than the national average.
• The average WCC floor U-value is higher than both county and national averages.
• Average window U-values for WCC and Co. Wicklow dwellings match, with negligible
difference to the national average.
• The average WCC door U-value is higher than both county and national averages.
Avg. Wall
U-value
Avg. Roof
U-value
Avg. Floor
U-value
Avg. Window
U-value
Avg. Door
U-value
Ireland 0.65 0.35 0.44 2.77 2.53
Co. Wicklow 0.76 0.44 0.47 2.80 2.41
WCC 0.90 0.41 0.54 2.80 2.87
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
55
4.3.1.4 Thermal Bridging Heat Loss
To examine heat loss through planar elements in isolation ignores heat loss through thermal bridges
which, as noted earlier, contributes 12% to total heat loss and 16% to fabric heat loss across the
sample, a contribution larger than heat loss through roofs and doors combined.
As shown in Figure 31 (below), the contribution of thermal bridging to fabric heat loss increases over
time; a reflection of increasing dwelling size and also of a decreasing contribution of planar heat loss
to fabric heat loss as a result of increasing insulation standards.
Note how the contribution to fabric heat loss for newer dwellings reaches over 23%, highlighting it
as a significant issue to be addressed;
Figure 31 Thermal Bridging contribution to Fabric Heat Loss
A thermal bridging factor of Y=0.157 was recorded for all dwellings in the sample. The average
thermal bridging factor as derived from the NBERRT for dwellings both in Ireland (286,793 dwellings)
and County Wicklow (8,465 dwellings) is Y=0.147, with values as low as Y=0.001 noted.
7 A discussion of Y-Factors is presented in Appendix B.
A-D ('00-
'66)E ('67-'77) F ('78-'82)
G ('83-
'93)
H ('94-
'99)I ('00-'04) J ('05+)
% Contribution 9.7% 10.0% 15.4% 17.4% 19.3% 19.6% 23.2%
0%
5%
10%
15%
20%
25%
56
4.3.1.5 Heat Loss Parameter
As noted previously, total dwelling heat loss (referred to in DEAP as the ‘Heat Loss Coefficient’) is the
combination of ventilation, planar and thermal bridging heat losses. To facilitate comparison across
dwellings of different types and sizes, this can be normalised per unit of floor area. This quantity (the
‘Heat Loss Parameter’) is an indicator of the efficacy of the thermal envelope.
An analysis of the data reveals that the Heat Loss Parameter decreases for newer dwellings, with a
value of 5.5 W/K/m2 for dwellings in age bands A-D (1900 - 1966), and 2.4 W/K/m2 for dwellings in
age band I (2005+).
Average Heat Loss Parameter values per dwelling type in the sample are illustrated in Figure 32
(below);
Figure 32 Average Heat Loss Parameter per dwelling type
Several trends are noticeable;
• Having a total planar area 24% greater than any other dwelling type, detached units have
the largest heat loss parameter.
• Larger ventilation heat loss, a slightly greater average planar area and a greater total area of
concrete hollow block construction are contributing factors in end of terrace units
performing worse than semi-detached units.
• Apartments and mid-terrace dwellings have the lowest heat loss parameter, possibly on
account of their small planar area and low ventilation heat loss.
Detached End of terrace Semi-detached Mid-terrace Apartment
W/K/m² 3.47 3.05 2.67 2.49 2.49
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
57
4.3.1.6 Net Space Heat Demand
The Heat Loss Parameter provides the ability to compare the rate of heat loss per unit floor area
across dwelling types. An aim of this study is to determine reductions in energy consumption
achievable through the implementation of various thermal envelope retrofit strategies, assuming all
other energy related variables, including heating system and fuel type to remain unchanged.
Net Space Heat Demand (NSHD) is the quantity which best relates rates of heat loss with rates of
energy consumption, and is defined as “the heat to be delivered to the heated space by an ideal
heating system to maintain the set-point temperature during a given period of time” (SEAI a, 2008, p.
26).
NSHD is derived by balancing total envelope heat loss with standardised internal and solar gains for
an assumed internal-external temperature difference. The heat capacity (thermal mass) of the
dwelling is accounted for. Notably, NSHD is independent of heating system type and fuel type, thus,
monitoring changes in NSHD as a result of thermal envelope retrofit interventions allows the truest
theoretical impact of thermal envelope related measures on energy consumption to be determined,
ceteris paribus.
Figure 33 Average Net Space Heat Demand per dwelling type
An anticipated, and as highlighted in Figure 33 (above), average NSHD per dwelling type reflects
trends in Heat Loss Parameter.
DetachedEnd of
terrace
Semi-
detachedMid-terrace Apartment
kWh/m²/yr 120 100 89 76 76
0
20
40
60
80
100
120
140
58
4.3.2 Key Findings
Section 4.2 illustrated how the energy performance of WCC dwellings in terms of overall energy
consumption, CO2 emissions and hence BER, is below that of average dwellings in Co. Wicklow and
Ireland. A thorough disaggregation of information provided by Wicklow County Council and as
collated by the model has provided several reasons for this poor performance;
• Ventilation rates are prime facie considerably higher than for average Co. Wicklow and Irish
dwellings; this may be related to a higher average number of chimneys per dwelling in WCC
and lower proportion of timber framed units in WCC.
• Significant deficiencies were noted in attic insulation levels, despite the roof type profile
suggesting a high proportion of roofed areas capable of accommodating 300mm of
insulation.
• The majority of windows across the sample are relatively poorly performing double-glazed
units.
• Average U-values for critical planar elements such as walls and floors fare poorly in
comparison with average values for dwellings in Ireland and Co. Wicklow
The corollary of the above is that there exists significant scope for improvement in the efficacy of the
thermal envelope of dwellings included in the sample. Certainly the significant degree of uniformity
in roof and floor types suggests that any suitable retrofit interventions may have widespread
applicability, while large reductions in heat loss through walls should be readily achievable given the
high proportion of cavity construction in the sample.
It is noted that differences in the relative proportions of dwelling types and their age distribution in
the sample analysed in this study and that present in the NBERRT may play a role in performances
differences noted here, though this is not explored further in this study.
There now follows an analysis of retrofit interventions being recommended to Wicklow County
Council by energy assessors.
59
4.4 Recommended Interventions Analysis
It is clear from sections 4.2 and 4.3 that the thermal envelope in WCC dwellings is poorly performing,
with the output of the model identifying principle areas of heat loss. When performing a dwelling
assessment and recommending interventions to be undertaken, assessors are operating in a
vacuum, unaware of the overall energy performance of WCC’s stock. It is likely, therefore, that
although the interventions they recommend will address the energy consumption of the dwelling in
question, large areas of heat loss at the stock level may remain unaddressed.
Gaining an understanding of the suitability of the interventions being recommended to WCC by
assessors in mitigating heat loss at the stock level is a key research question. An analysis of such
interventions serves not only to highlight the emphasis being placed on the thermal envelope, but
also facilitates the creation of a ‘business as usual’ scenario which can be used to model the impact
of thermal envelope related interventions on heat loss across the sample.
4.4.1 Sample Creation
‘Energy Efficiency’ reports containing assessors recommended retrofit interventions were not
available to the author for every dwelling included in this study, however, a random sample of
reports representing 10% of dwellings below the C1 energy rating (68 in total) was compiled for
analysis. This sample;
• Includes 10% of dwellings from each band below C1 (i.e. C2 – G)
• Includes dwellings of all types included in the sample (Detached, Semi-detached, etc.)
• Covers a broad spectrum of assessors
4.4.2 Sample Analysis
In total, 312 individual retrofit interventions were contained in this sample, which can be
categorised as follows;
Type Sample Interventions
Space and Water
Heating
Replacement boiler
Installation of time and temperature controls
Installation of thermostatic valves
Thermal
Envelope
Wall Insulation
Replacement Windows
Increase Attic Insulation
Lighting Installation of low energy bulbs
Renewable
Technology (RET)
Installation of DHW systems
Table 11 Sample Recommended Interventions
60
The breakdown of interventions is shown in Figure 34 (below);
Figure 34 Breakdown of recommended interventions
As would be expected, an emphasis is placed on heating (both space and water) and thermal
envelope related interventions, with heating related measures dominant in all but the E2 & C2
energy bands, as shown in Figure 35 (below);
Figure 35 Recommended Interventions per BER
Space and
Water Heating
Thermal
EnvelopeLighting RET
Total 143 120 39 10
0
20
40
60
80
100
120
140
160
C2 C3 D1 D2 E1 E2 F G
Space and Water Heating 4 17 27 28 18 12 14 23
Thermal Envelope 6 12 25 18 14 14 11 20
Lighting 2 4 12 6 5 2 3 5
RET 2 3 3 2
0
5
10
15
20
25
30
61
4.4.2.1 Thermal Envelope Interventions
A disaggregation of thermal envelope related interventions per BER reveals the following;
C2 C3 D1 D2 E1 E2 F G Total
Attic 5 6 11 7 8 5 5 6 53
Doors 2 2
Floor 1 1
Walls - Cavity 1 2 3 4 1 1 3 15
Walls - External 1 1 1 1 1 5
Walls - Internal 2 3 1 1 1 8
Walls - Not Specified 3 3 5 2 3 3 3 22
Windows 2 1 3 6
Ventilation 5 1 1 1 8
Total 6 12 25 18 14 14 11 20 120
Table 12 Recommended Thermal Envelope Interventions per BER
There are several key items to be noted;
• Attic insulation is the most frequently recommended intervention for all energy bands,
perhaps reflective of its low cost and ease of installation.
• Replacement doors are infrequently considered, with the only instances occurring in the
lowest energy band.
• Interventions aimed at improving the thermal performance of floors are least frequently
included, and appear at a low energy band (E2), potentially reflecting their costly and
disruptive nature.
• Cavity fill insulation is the most frequently cited approach to reducing heat loss through
walled areas. In a significant number of cases, a target U-value is specified, with no
insulation strategy proposed.
• The replacement of Windows is considered only at lower energy bands.
• Ventilation related interventions primarily refer to draught-stripping and the blocking of
disused chimneys, something perhaps indicative of low implementation costs.
4.4.3 Payback and Energy reductions
Where provided in ‘Energy Efficiency’ reports, the data reveals that heating related interventions
often have superior payback times and offer larger primary energy reductions than thermal
envelope related interventions, possibly due to the significant efficiency increases for boilers and the
switching of fuel types from coal to gas or oil;
62
Average Annual energy
saving (kWh/yr)
Average Cost (€) Average Payback
(years)
Thermal
Envelope
2,917 (112
interventions)
1,977 (44
interventions)
23.1 (44
interventions
Space and Water
Heating
4,474 (112
interventions)
1,186 (55
interventions)
9.35 (55
interventions)
Table 13 Average energy savings, costs and payback times for recommended interventions
4.4.4 Key Findings
In light of the analysis in sections 4.2 and 4.3 on heat loss across the sample of dwellings, this section
has highlighted several noteworthy points.
Firstly, a fundamental tenet of the fabric first approach – that insulation must be continuous around
the thermal envelope – is not being obeyed. The evidence analysed suggests that no assessor has
recommended interventions addressing heat loss through every planar element in any dwelling in
any energy band. However, this is to be expected when assessors are operating in a paradigm where
the aim is to achieve a particular energy rating, as opposed ensuring the thermal envelope is
optimised.
Secondly, significant areas of heat loss remain unaddressed. Heat loss through floors accounts for
14% of fabric heat loss, yet measures to combat it are listed only once, and in that instance, no
target U-value is specified. Windows contribute 19% of total fabric heat loss, yet their replacement
or upgrade is considered only in lower energy bands, perhaps in an effort to replace single glazed
units.
Thirdly, when the sample of interventions is reviewed with a knowledge of comparative planar
element U-value performance (section 4.3.1.3.6), it is clear that recommended interventions are
somewhat focussed on elements where WCC performance is already comparatively good (roof), are
ignored where performance is comparatively bad (floors) and in the most significant case where
performance is particularly poor (walls), internal insulation is proposed more frequently than
external insulation, an arguably more effective solution in light of its lower condensation risk and
more effective treatment of thermal bridges.
63
Section 5. Scenario Analysis
Scenarios are used to demonstrate the effects on overall heat loss, energy consumption and CO2
emissions of upgrading the thermal envelope to each of the following standards;
1. Better Energy Homes (BEH): this scenario assumes the thermal envelope of all dwellings to
be upgraded using only measures funded under the BEH scheme (SEAI c, 2011).
2. Part L: this scenario assumes the thermal envelope of all dwellings to be upgraded to the
standard defined in the latest iteration of the Irish Building Regulations (DECLG, 2011).
3. Wicklow County Council (WCC): this scenario assumes the thermal envelope of all dwellings
to be upgraded using a composite of thermal envelope related interventions noted in
section 4.4.2
4. EnerPHit: this scenario assumes the thermal envelope of all dwellings to be upgraded as
defined in Feist (2010).
5.1 Scenario Definition
Limiting values for ventilation rates, the thermal transmittance of planar elements of the thermal
envelope and thermal bridging factors for each of these scenarios is discussed below.
5.1.1 Ventilation
Limiting factors for air-tightness for each of the standards considered are presented below;
BEH
Scenario
Part L
Scenario
WCC
Scenario
EnerPHit
Scenario
Air Change Rate
(achadj)8
No
Change
0.35 0.25 0.03
No. Chimneys No
Change
Max 1 0 0
No. Flues No
Change
No Change +1 where number
of chimneys was
> 0
0
% Draught-stripping
in place
100% 100% 100% 100%
Table 14 Ventilation related limiting factors
The following assumptions are made;
• All scenarios assume 100% draught-stripping measures in place
• The Part L scenario assumes max 1 chimney per dwelling.
8 Values for different standards have been standardised to air change rate (as required by DEAP) by dividing
permeability values by 20, in accordance with (SEAI a, 2008, p. 13)
64
• WCC scenario assumes not more than 1 chimney, which is converted to a flue for use with a
solid fuel stove. This flue is not room sealed, so is considered to contribute to ventilation
heat loss (SEAI a, 2008, p. 14).
• EnerPHit assumes all chimneys are permanently blocked, all non room sealed flues are
converted to be room sealed and solid fuel stoves with room sealed flues are installed in
place of open fires. Room sealed flues are not considered to contribute to ventilation heat
loss (ibid).
5.1.2 Element Thermal Transmittance
The thermal transmittance values assumed for each planar element in each scenario are presented
in Table 15 below;
BEH
Scenario
Part L
Scenario
WCC
Scenario
EnerPHit
Scenario
Walls Cavity U = 0.27 W/m2K U ≤ 0.55 W/m2K U = 0.27 W/m2K U ≤ 0.15 W/m2K
External U ≤ 0.27 W/m2K U ≤ 0.35 W/m2K U = 0.15 W/m2K U ≤ 0.15 W/m2K
Internal U ≤ 0.27 W/m2K U ≤ 0.35 W/m2K U = 0.35 W/m2K U ≤ 0.30 W/m2K
Roofs Ceiling U = 0.16 W/m2K U ≤ 0.16 W/m2K U = 0.13 W/m2K U ≤ 0.12 W/m2K
Rafter U = 0.20 W/m2K U ≤ 0.25 W/m2K Not Specified U ≤ 0.12 W/m2K
Flat U ≤ 0.27 W/m2K U ≤ 0.25 W/m2K Not Specified U ≤ 0.12 W/m2K
Windows Not Specified U ≤ 1.6 W/m2K
Triple-glazed,
air filled (low-E,
εn = 0.15, hard
coat), 16mm
spacing
U = 1.4 W/m2K
Triple-glazed,
argon filled (low-
E, εn = 0.1, soft
coat), 16mm
spacing
U ≤ 0.85 W/m2K
Triple-glazed,
argon filled (low-E,
εn = 0.05, soft
coat), user defined
U-value
Doors Not Specified U ≤ 1.6 W/m2K U = 1.3 W/m2K U ≤ 0.8 W/m2K
Floors Not Specified U ≤ 0.45 W/m2K Not Specified U ≤ 0.15 W/m2K
Table 15 Assumed values of thermal transmittance
The following assumptions are made;
• Window types have been selected on the basis of their match to the U-value required by the
scenario. For EnerPHit, the use of a user-defined U-value is assumed, as no window type
available in DEAP matches the required U-value.
• All window frames are assumed to be of type ‘Wood/PVC’.
• EnerPHit assumes all external insulation.
65
• No preference for internal or external insulation is assumed for Part L or BEH scenarios,
given they use identical U-values for each.
• External insulation is assumed for all non-cavity walls in all scenarios except the WCC
scenario where internal insulation is assumed to dominate, reflecting a preference for this
method.
• Where a target value for thermal transmittance is ‘Not Specified’, no interventions are
modelled.
5.1.3 Thermal Bridging
As discussed in Appendix B, DEAP accounts for thermal bridging heat loss by applying a Y-Factor to
the entire building envelope area.
All assessments provided as input to this study assumed the default value of Y=0.15.
A value of Y=0.08 can be used where evidence that bridges have been designed according to
Accredited Construction Details have been used (SEAI a, 2008, p. 67); this value is assumed for all
scenarios except EnerPHit to reflect that fact that thermal bridging is assumed to be addressed to a
significant degree during retrofits. The criteria for thermal bridging is more stringent in the EnerPHit
scenario, thus a custom Y-factor per dwelling type has been derived for this scenario9.
The thermal bridging factors assumed in each scenario are presented in Table 16 (below);
BEH Part L WCC EnerPHit
Thermal
Bridging
Factor
Y=0.08 Y=0.08 Y=0.08 Apartment (Y=0.0027)
Detached (Y=0.0033)
End Of Terrace (Y=0.0034)
Mid-Terrace (Y=0.0032)
Semi-Detached (Y=0.0035)
Table 16 Assumed Thermal Bridging Factors
9 The derivation of these values is described in Appendix B.
66
5.2 Scenario Output
The approach outlined above maintains the ability to model changes in primary energy consumption
and CO2 emissions assuming heating systems to remain unchanged, at least in terms of fuel used.
Given the limitations of the model used as outlined in section 3.3.4, and recognising its accuracy as
noted in section 3.3.6, the following sections discuss the scenario output10.
5.2.1 Primary Energy Consumption
The Primary energy consumption profile for the four scenarios is as follows;
BEH
Scenario
Part L
Scenario
WCC
Scenario
EnerPHit
Scenario
Reductions in Total Space
Heating Consumption
39% 44% 56% 87%
Reductions in Total Primary
Energy Consumption
23% 26% 33% 50%
Figure 36 Reductions in Total Space Heating Consumption and Primary Energy Consumption
The BEH scenario is shown to achieve the lowest reductions in energy consumption, both overall and
space heating related, with the Part L scenario only achieving only a further 3% reduction in total
primary energy consumption over the BEH scenario.
10
Note that all reductions presented in this section are relative to the ‘No Changes’ starting point for the
model.
AssessedBEH
Scenario
Part L
Scenario
WCC
Scenario
EnerPHit
Scenario
Pumps and Fans (kWh/y) 448,880 448,880 448,880 448,880 448,880
Lighting (kWh/y) 1,191,308 1,191,308 1,191,308 1,191,308 1,191,308
Water Heating (kWh/y) 5,092,830 5,092,830 5,092,830 5,092,830 5,092,830
Space Heating (kWh/y) 9,438,747 5,746,795 5,229,395 4,135,441 1,253,174
0
2,000,000
4,000,000
6,000,000
8,000,000
10,000,000
12,000,000
14,000,000
16,000,000
18,000,000
67
The WCC scenario fares better, reducing space heating consumption to such an extent that more
energy is consumed heating water. Overall energy consumption is reduced 33%.
As expected, the largest reductions are achieved in the EnerPHit scenario, with total space heating
consumption reduced 87%, and total primary energy consumption reduced 50%.
5.2.2 Thermal Envelope Performance
5.2.2.1 Total Heat Loss
Total heat loss from the thermal envelope can be disaggregated to ventilation heat loss, planar heat
loss and thermal bridging heat loss as follows;
BEH
Scenario
Part L
Scenario
WCC
Scenario
EnerPHit
Scenario
Reductions in Ventilation Heat Loss 2% 12% 23% 34%
Reductions in Planar Heat Loss 36% 40% 50% 74%
Reductions in Thermal Bridging Heat
Loss
47% 47% 47% 98%
Figure 37 Disaggregated reductions in thermal envelope heat loss
Reductions in ventilation heat loss are shown to vary widely from 2% in the BEH scenario to 34% in
the EnerPHit scenario.
AssessedBEH
Scenario
Part L
Scenario
WCC
Scenario
EnerPHit
Scenario
Thermal Bridging Loss (W/mK) 17,963 9,580 9,580 9,580 400
Planar Heat Loss (W/K) 92,689 59,751 55,739 46,565 24,348
Ventilation Heat Loss (W/k) 35,885 35,313 31,571 27,566 23,691
0
20,000
40,000
60,000
80,000
100,000
120,000
140,000
160,000
68
There is a significant difference in the reductions achievable in planar heat loss across the scenarios,
with EnerPHit (74%) achieving more than double that of the BEH scenario (36%). Existing WCC
interventions achieve a 50% reduction in planar heat loss.
The most significant reductions of any type are reserved for thermal bridging heat loss in the
EnerPHit scenario, which is all but eliminated.
5.2.2.2 Ventilation Heat Loss
Average ventilation heat loss per dwelling for each scenario is as follows;
BEH
Scenario
Part L
Scenario
WCC
Scenario
EnerPHit
Scenario
Reductions in average
ventilation heat loss
4% 12% 23% 34%
Figure 38 Reductions in ventilation heat loss
The BEH scenario achieves negligible reductions, with Part L and WCC scenarios achieving 12% and
23% reductions respectively. EnerPHit achieves 34% reductions, with the inaccuracy inherent in this
result arising from limitations of the model.
Assessed BEH ScenarioPart L
Scenario
WCC
Scenario
EnerPHit
Scenario
W/K 50.0 49.2 44.0 38.4 33.0
0.0
10.0
20.0
30.0
40.0
50.0
60.0
69
5.2.2.3 Planar Element Heat Loss
The reductions in heat loss via building envelope elements are shown below;
BEH
Scenario
Part L
Scenario
WCC
Scenario
EnerPHit
Scenario
Windows 0% 38% 44% 65%
Walls 67% 44% 68% 82%
Roofs 59% 58% 64% 70%
Floors 0% 15% 0% 70%
Doors 0% 45% 55% 72%
Figure 39 Disaggregated reductions in planar heat loss
Several items are noteworthy;
• In the Part L scenario, floor heat loss is reduced 15%. It is difficult to see how this disruptive
and costly work will be undertaken to achieve such a small reduction in heat loss. By
comparison, the EnerPHit scenario achieves 70% reductions in floor heat loss.
• Roof heat loss is reduced by a minimum of 58%.
• The reduction in heat loss through walls is significantly lower in the Part L scenario as a
result of the poor target U-values.
• 65% reductions in heat loss through windows are achieved in the EnerPHit scenario.
• The significant reductions in planar heat loss would mean the proportion of fabric related
heat loss attributable to thermal bridging would increase significantly were it not treated.
AssessedBEH
Scenario
Part L
Scenario
WCC
Scenario
EnerPHit
Scenario
Windows (W/K) 21,346 21,332 13,311 11,850 7,487
Walls (W/K) 37,833 12,385 21,101 12,209 6,881
Roofs (W/K) 12,765 5,289 5,320 4,628 3,837
Floors (W/K) 15,519 15,519 13,131 15,519 4,705
Doors (W/K) 5,216 5,216 2,873 2,346 1,443
0
10,000
20,000
30,000
40,000
50,000
60,000
70,000
80,000
90,000
100,000
70
5.2.2.4 Thermal Bridging heat loss
Reductions in thermal bridging heat loss are outlined below;
BEH
Scenario
Part L
Scenario
WCC
Scenario
EnerPHit
Scenario
Reductions in Thermal
Bridging Heat Loss
47% 47% 47% 98%
Figure 40 Reductions in Thermal Bridging heat loss
The reductions in heat loss achieved under the EnerPHit scenario mean that less than 1 W/mK of
heat loss per dwelling in the sample is attributable to thermal bridging, compared with 13.3 W/mK
per dwelling in the other scenarios.
AssessedBEH
Scenario
Part L
Scenario
WCC
Scenario
EnerPHit
Scenario
Thermal Bridging
Heat Loss (W/mK)17,963 9,580 9580 9580 400
0
2,000
4,000
6,000
8,000
10,000
12,000
14,000
16,000
18,000
20,000
71
5.2.2.5 Heat Loss Parameter
The average Heat Loss Parameter under each of the scenarios is highlighted in Figure 41 (below);
BEH
Scenario
Part L
Scenario
WCC
Scenario
EnerPHit
Scenario
Reductions in
Heat Loss Parameter
28% 33% 43% 67%
Figure 41 Reductions in Heat Loss Parameter for each scenario
Overall, there is little to differentiate the BEH and Part L scenarios. Although more significant
reductions are achieved in the WCC scenario, the EnerPHit scenario achieves a further 24% in
reductions, yielding a total reduction of 67%.
Assessed BEH ScenarioPart L
Scenario
WCC
Scenario
EnerPHit
Scenario
W/K/sqm 2.7 1.94 1.8 1.55 0.89
0
0.5
1
1.5
2
2.5
3
72
5.2.2.6 Net Space Heat Demand
As noted in section 4.3.1.6, reductions in NSHD provide an indication in terms of energy
consumption of the efficacy of the thermal envelope upgrade. Average values of NSHD across the
sample under the 4 scenarios are presented in Figure 42 (below):
BEH
Scenario
Part L
Scenario
WCC
Scenario
EnerPHit
Scenario
Reductions in Net Space Heat
Demand
40% 46% 58% 90%
Figure 42 Reductions in NSHD for each scenario
A similar trend as for all other modelled quantities is noted, with BEH and Part L achieving similar
reductions. WCC scenario performs better, achieving 58% reductions. 90% reductions are achievable
under the EnerPHit scenario.
AssessedBEH
Scenario
Part L
Scenario
WCC
Scenario
EnerPHit
Scenario
Total Net Space Heat Demand
(kWh/y)4,813,454 2,869,843 2,609,215 2,024,773 492,737
0
1,000,000
2,000,000
3,000,000
4,000,000
5,000,000
6,000,000
73
5.2.3 CO2 Emissions Reductions
Total CO2 emissions for the sample under each of the scenarios are as follows;
BEH
Scenario
Part L
Scenario
WCC
Scenario
EnerPHit
Scenario
Reductions in CO2 Emissions 24% 27% 34% 52%
Figure 43 Reductions in CO2 emissions in each scenario
CO2 emissions can be reduced by 24% through addressing heat loss in walls and roofs as per the BEH
scenario. There is negligible improvement in reductions under the Part L scenario. The WWC
scenario sees CO2 emissions reduce by over a third. The largest reductions are reserved for the
EnerPHit scenario, which sees reductions of 52%.
AssessedBEH
Scenario
Part L
Scenario
WCC
Scenario
EnerPHit
Scenario
Total Emissions (kg/y) 4,149,031 3,154,299 3,018,161 2,726,919 1,969,388
0
500,000
1,000,000
1,500,000
2,000,000
2,500,000
3,000,000
3,500,000
4,000,000
4,500,000
74
5.2.4 BER Profiles
To graphically illustrate the impact the fabric first approach can have on the energy performance of
the sample, it is possible to generate a BER profile representative of each scenario, as presented in
Figure 44 (below);
Assessed BEH
Scenario
Part L
Scenario
WCC
Scenario
EnerPHit
Scenario
Number of dwellings at or
above C1
6% 18% 23% 43% 82%
Figure 44 Assumed BER profiles for each scenario
The following points are noteworthy;
• Several dwellings remain with G ratings, despite significant reductions in energy
consumption under the EnerPHit scenario. Initial primary energy consumption for these
units is shown to average 646 kWh/m2/yr.
• Under the EnerPHit scenario, dwellings now achieve A ratings
• As assessed, only 6% of dwellings met or exceeded the C1 rating. Depending on the scenario,
between 18% and 82% of dwellings could do so.
• As per DEHLG (a, 2010), funding will not be provided for any dwellings remaining at or below
F rating post retrofit. This may be as many as 8 to 49 dwellings, depending on the scenario.
A3 B1 B2 B3 C1 C2 C3 D1 D2 E1 E2 F G
Assessed 13 27 55 103 144 106 82 52 55 81
BEH 2 35 90 177 119 121 66 36 23 34 15
Part L 10 35 121 187 103 107 61 37 16 30 11
WCC 33 79 197 126 107 64 45 22 14 26 5
EnerPHit 2 75 245 179 86 34 23 22 15 10 19 4 4
0
50
100
150
200
250
300
75
5.2.5 Funding Achievable
As illustrated in Table 17 (below), government funding for retrofits is based on reductions in energy
consumption per m2 floor area, with C1 remaining the target energy rating (DEHLG a, 2010, p. 2).
Where the cost of implementing planned interventions exceeds the government funding available,
WCC must meet the balance through internal funding.
Primary Energy Consumption
Reductions (kWh/m2/y)
Funding provided
0 – 50 Not Funded
50 -100 50% or €6,000, whichever is lesser
100 – 200 75% or €11,500, whichever is lesser
200 – 300 90% or €15,500, whichever is lesser
300 or more 90% or €18,000, whichever is lesser
Table 17 Allocation of funding according to energy reductions achieved
The number of dwellings achieving reductions of the magnitude required for funding in each
scenario is outlined in Figure 45 (below). Note that dwellings retaining an F or G BER following
retrofit, and therefore are ineligible for funding, are included;
Figure 45 Number of dwellings per funding bracket per scenario
0 to 50
kWh/sqm/yr
(unfunded)
50 to 100
kWh/sqm/yr
100 to 200
kWh/sqm/yr
200 to 300
kWh/sqm/yr
300+
kWh/sqm/yr
BEH Scecnario 395 196 98 20 9
Part L Scenario 328 236 117 26 11
WCC Scenario 124 355 196 30 13
EnerPHit Scenario 3 159 423 98 35
0
50
100
150
200
250
300
350
400
450
76
Accounting only for dwellings that achieve a post-retrofit energy rating of E or higher, the amount of
funding available under each scenario is outlined in Table 18 (below);
BEH
Scenario
Part L
Scenario
WCC
Scenario
EnerPHit
Scenario
Maximum Funding
available
€2,330,500 €2,933,500 €4,689,000 €7,861,000
Table 18 Funding available for each scenario
From this analysis, it is clear that the work performed in a large proportion of dwellings under the
BEH and Part L scenarios would fail to secure funding. Significantly more dwellings achieve 50 to 100
kWh/m2/yr and 100 to 200 kWh/m2/yr in the WCC scenario, so this would appear to be a better
financial choice than either BEH or Part L. The EnerPHit scenario would secure the most funding,
with 59% of dwellings achieving savings between 100 to 200 kWh/m2/yr, and 5% yielding over
300kWh/m2/yr.
77
5.2.6 Key Findings
Accounting for the limitations inherent in the model noted previously in section 3.3, the reductions
achieved for each modelled quantity in each scenario are as follows;
Modelled Quantity BEH
Scenario
Part L
Scenario
WCC
Scenario
EnerPHit
Scenario
Ventilation Heat Loss 2% 12% 23% 34%
Planar Heat Loss 36% 40% 50% 74%
Doors 0% 45% 55% 72%
Floors 0% 15% 0% 70%
Roofs 59% 58% 64% 70%
Walls 67% 44% 68% 82%
Windows 0% 38% 44% 65%
Thermal Bridging Heat Loss 47% 47% 47% 98%
Heat Loss Parameter 28% 33% 43% 67%
Net Space Heat Demand 40% 46% 58% 90%
Total Space Heating Consumption 39% 44% 56% 87%
Total Primary Energy Consumption 23% 26% 33% 50%
Total CO2 Emissions 24% 27% 34% 52%
Table 19 Overview of reductions achieved for all scenarios
The BEH and Part L scenarios are shown to have broadly the same impact on key performance
indicators such as total space heating consumption, total primary energy consumption and total CO2
emissions. This is interesting given the broader scope of the Part L scenario in terms of planar
elements considered and the superior ventilation heat loss reductions achieved. Though the BEH
scenario addresses only walls and roofs, the thermal transmittance values assumed are generally
more stringent than the Part L scenario, resulting in planar heat loss reductions of only 4% less than
Part L.
The WCC scenario fares better, reducing ventilation heat loss by 23% and planar heat loss by 50%.
These reductions are achieved despite failing to address floor heat loss, which in this scenario now
accounts for 33% of remaining planar heat loss. Total primary energy consumption and total CO2
emissions are reduced 33% and 34% respectively in this scenario.
However, these reductions are considerably less than the 50% reductions in total primary energy
consumption and 52% reductions in CO2 emissions achieved in the EnerPHit scenario. The greatest
reductions in all modelled quantities are achieved in this scenario; 34% reduction in ventilation heat
loss, 74% reduction in planar heat loss, 98% reduction in thermal bridging heat loss and a 90%
reduction in Net Space Heat Demand.
78
EnerPHit outperforms other scenarios in terms of funding achievable, and is capable of bringing 82%
of dwellings to or above the C1 target energy rating, a proportion far in excess of the WCC scenario
which manages to bring 43% to this standard or above. Finally, that a small number of dwellings
retain F and G energy ratings following an EnerPHit thermal envelope upgrade serves to underline
the poor performance of some dwellings in the sample.
79
Section 6. Conclusions
Using a custom-built model, dwelling energy assessment reports for 718 dwellings in Wicklow
County Council’s housing stock were analysed in order to profile energy consumption. A scenario
analysis was performed to investigate the efficacy of various thermal envelope upgrade strategies.
Objective 1: Profile dwelling energy performance
This study considers headline indicators of dwelling energy performance to be overall energy
consumption, CO2 emissions and BER rating. The data analysed shows the average dwelling in WCC
to perform poorly in comparison with average dwellings in Co. Wicklow and Ireland on each front. A
detailed analysis of heat loss across the sample highlighted significantly higher levels of ventilation
heat loss in WCC dwellings compared with county and national averages. In terms of planar heat
loss, walls were found to perform particularly poor in comparison with county and national
averages. With 94% of the sample found to be below C1, the target energy rating for the NERP and
government retrofitting work, it is clear a widespread retrofitting effort is required to bring WCC
stock to standard.
Objective 2: Analyse sample retrofit interventions
A sample of 312 retrofit interventions recommended to WCC by external assessors was analysed.
The majority of measures relate to space and water heating, and the thermal envelope. Thermal
envelope related interventions were analysed further and shown not to address significant areas of
heat loss through the thermal envelope and not to concentrate on planar elements whose
performance is demonstrably poorer than county and national averages.
Measures relating to space heating are shown to offer better CO2 reductions and payback times than
thermal envelope related interventions. The economic attractiveness of heating related measures
will encourage their uptake, particularly in a local authority where funding is scarce. However by
implementing such measures at the expense of optimising the thermal envelope, WCC are
committing to higher future energy consumption and CO2 emissions than would otherwise be the
case, and are allowing health issues where they exist to persist.
Objective 3: Model thermal envelope retrofit strategies
WCC’s existing strategy of replacing boilers, upgrading heating systems and making piecemeal
improvements to the thermal envelope is a valid approach and will yield results in terms of energy
consumption and CO2 emissions reductions, but currently does not adequately address the sources
of heat loss in the thermal envelope. Furthermore, health issues, where present, are allowed to
80
persist under this regime. 4 scenarios, each embracing the fabric first approach to differing degrees,
and one a composite of existing WCC thermal envelope related interventions, are used to
demonstrate the primacy of the fabric first approach in reducing energy consumption and CO2
emissions in the sample.
Significant improvements in the energy performance of the stock are possible;
• Primary energy consumption reduced by between 23% and 50%
• Total CO2 emissions reduced by between 24% and 52%
• Between 18% and 82% of dwellings brought to the C1 standard or above
These reductions alone could make a significant contribution to WCC’s obligations regarding energy
efficiency improvements under the NEEAP. Indeed these reductions could go some way to achieving
the 90% reductions in CO2 emissions deemed possible in the residential sector, and are all the more
impressive when it is considered that they are possible solely through addressing the thermal
envelope. With space heating related energy consumption reduced by up to 87%, remaining heat
demand could now be met with gas boilers of greatly reduced size, or through the use of renewable
technologies.
Questions remain over the practicalities of implementing the retrofits assumed here, particularly the
EnerPHit scenario, which may require up-skilling of staff.
Funding of between €2.3 million and €7.8 million could be secured depending on the scenario,
however the financial viability of each scenario requires detailed analysis.
Objective 4: Extrapolate stock-wide impacts of retrofits
As noted in section 3.5, no suitable scaling factor could be determined to allow the reductions in
energy consumption and CO2 emissions across the stock to be estimated. The determination of such
a factor represents an area for further research.
81
6.1 Further Research
Several areas suitable for further research have been identified:
• The determination of a suitable scaling factor to allow savings estimated in this study be
extrapolated to the stock level would provide a more complete view of the savings
achievable for any particular scenario.
• To enhance the model to reflect how heating system upgrades could affect energy
consumption and CO2 emissions across the sample would further validate the efficacy of the
fabric first approach. The consideration of heat pumps here would be of interest.
• The ‘Y-Factors’ assumed in during thermal bridging modelling in this research represent
extremes of the scale; it would be a worthy exercise to determine suitable values for each
dwelling type in WCC’s stock for use in further analysis.
• A cost effectiveness study to demonstrate the financial viability or otherwise of the EnerPHit
scenario in particular represents a worthy exercise.
82
References
Antonelli, L., & Colley, J. (a) (2012) Construct Ireland campaign set to increase Part L compliance.
Construct Ireland, 5 (10), pp. 37 - 39.
Antonelli, L., & Colley, J. (b) (2012) Two thirds of new homes fail energy efficiency rules. Available
from: http://www.constructireland.ie/News/Government/Two-thirds-of-new-homes-fail-energy-
efficiency-rules.html [Accessed July 20 2012]
Armstrong, S., & Dowling, P. (2012) Social Housing retrofit program and Energy Efficiency
Regulations update. Available from:
http://www.aiea.ie/download.ashx?f=Social_Housing_Retrofit_Presentation_DEHLG.pdf [Accessed
July 20 2012]
Bloom, E., & Wheelock, C. (2010) Retrofit Industry Needs Assessment Study Public White Paper.
Available from: http://retrofit.folders.net/Content/Files/RMIPikeWhitePaper082010.pdf [Accessed
July 20 2012]
BRE Trust (2010) Code for Sustainable Homes pushes 'fabric first' approach. Available from:
http://www.building4change.com/page.jsp?id=560 [Accessed July 20 2012]
Building Science Corporation (BSC) (2010. Final Report of the Expert Meeting for Details for Deep
Energy Retrofit. Available from:
http://www.buildingscienceconsulting.com/services/documents/file/20100312_Meeting_Summary.
pdf [Accessed June 20 2012]
Central Statistics Office (CSO) (1997) Ireland Census 91, Volume 10, Housing. Available from:
http://www.cso.ie/en/media/csoie/census/census1991results/volume10/C1991%20Vol%2010.pdf
[Accessed September 4 2012]
Central Statistics Office (CSO) (2011) Census of population 2011 – Preliminary Results. Available
from: http://www.cso.ie/en/media/csoie/census/documents/Prelim%20complete.pdf [Accessed
June 20 2012]
Clinch, J., & Healy, J. D. (2001). Cost-benefit analysis of domestic energy efficiency. Energy Policy, pp.
113-124.
Curtain, J. (2009) Greenprint for a National Energy Efficiency Retrofit Programme. Available from:
http://www.raponline.org/docs/Greenprint_Curtin_IIEA_JobsGrowthandReducedCosts_2009.pdf
[Accessed June 20 2012]
Curtain, J., & Maguire, J. (2011) Thinking Deeper - Financing options for home retrofit. Available
from: http://www.europeanclimate.org/documents/Thinking_Deeper_compressed_2.pdf [Accessed
July 20 2012]
Daly, P. (2007) Laughing Stock - Is most Irish housing worse than a 'G' energy rating? Available from:
http://www.constructireland.ie/Articles/Energy-Performance-of-Buildings-Directive/Is-most-Irish-
housing-worse-than-a-G-energy-rating.html [Accessed June 20 2012]
83
Davies, P., & Osmani, M. (2011) Low carbon housing refurbishment challenges and incentives:
Architects perspectives. Building and Environment, pp. 1691 - 1698.
Department of Communications, Energy and Natural Resources (DCENR) (2009) The National Energy
Efficiency Action Plan 2009 – 2020: Maximising Ireland’s Energy Efficiency. Available from:
http://www.dcenr.gov.ie/NR/rdonlyres/FC3D76AF-7FF1-483F-81CD-
52DCB0C73097/0/NEEAP_full_launch_report.pdf [Accessed June 20 2012]
Department of Communications, Energy and Natural Resources (DCENR) (2011) Warmer Homes. A
strategy for Affordable Energy in Ireland. Available from:
http://energyadvice.ie/AffordableEnergyStrategyFINAL.pdf [Accessed July 20 2012]
Department of Communications, Energy and Natural Resources (DCENR) (No Date) National Retrofit
Program Consultation Paper. Available from:
http://www.dcenr.gov.ie/Energy/Energy+Efficiency+and+Affordability+Division/Retrofit+Consultatio
n.htm [Accessed June 20 2012]
Department of the Environment, Community and Local Government (DECLG) (2011) Conservation of
fuel and energy - Dwellings. Available from:
http://www.environ.ie/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,
27316,en.pdf [Accessed July 20 2012]
Department of the Environment, Community and Local Government (DECLG) (a) (2012) Social and
Affordable Housing. Available from:
http://www.environ.ie/en/Publications/StatisticsandRegularPublications/HousingStatistics/
[Accessed July 20 2012]
Department of the Environment, Community and Local Government (DECLG) (b) (2012) Housing
Statistics - House Building and Private Rented. Available from:
http://www.environ.ie/en/Publications/StatisticsandRegularPublications/HousingStatistics/FileDown
Load,15293,en.xls [Accessed June 20 2012]
Department of the Environment, Heritage and Local Government (DEHLG) (2006) Ireland's pathway
to Kyoto compliance. Review of the National Climate Change Strategy. Available from:
http://www.environ.ie/en/Environment/Atmosphere/ClimateChange/NationalClimateChangeStrate
gy/PublicationsDocuments/FileDownLoad,1289,en.pdf [Accessed June 20 2012]
Department of the Environment, Heritage and Local Government (DEHLG) (2007) National Climate
Change Strategy 2007 - 2012. Available from:
http://www.environ.ie/en/Environment/Atmosphere/ClimateChange/PublicationsDocuments/FileD
ownload,1861,en.pdf [Accessed June 20 2012]
Department of the Environment, Heritage and Local Government (DEHLG) (a) (2010) Circular SHIP
2010/20 Energy Efficiency Programme - Retrofitting. Available from:
http://www.oireachtas.ie/documents/committees30thdail/j-
envherlocgov/correspondence/meetingnumber_j79/2010-Circ12.pdf [Accessed July 20 2012]
84
Department of Environment, Heritage and Local Government (DEHLG) (b) (2010) Circular SHIP
2010/05 Energy Efficiency Programme - Retrofitting. Available from:
http://www.oireachtas.ie/documents/committees30thdail/j-
envherlocgov/correspondence/meetingnumber_j79/2010-Circ12.pdf [Accessed July 20 2012]
Department of Environment, Heritage and Local Government (DEHLG) (c) (2010) Energy Efficiency in
Traditional Buildings. Available from:
http://www.seai.ie/Grants/Better_energy_homes/contractor/Newsletter/Energy_Efficiency_in_Trad
itional_Buildings.pdf [Accessed July 20 2012]
Dimitroulopoulou, C. (2012) Ventilation in European dwellings: A review. Buildings and Environment,
pp. 109 - 125.
Dineen, D. et al. (2010) Modelling residential energy savings due to Ireland's National Retrofit
Programme using DEAP and LEAP. Available from:
http://emf.stanford.edu/files/docs/273/O'Gallachoir-Paper.pdf [Accessed July 20 2012]
DKM Economic Consultants (DKMEC) (2010) Annual Construction Industry Review 2009 and Outlook
2010–2012. Available from:
http://www.environ.ie/en/Publications/StatisticsandRegularPublications/ConstructionIndustryStatis
tics/FileDownLoad,24473,en.pdf [Accessed July 20 2012]
Energy Savings Trust (EST) (a) (2010) Fabric First. Available from:
http://www.energysavingtrust.org.uk/Publications2/Housing-professionals/New-build/Fabric-First-
October-2010-edition [Accessed July 20 2012]
Energy Savings Trust (EST) (b) (2010) CE322. Sheffield EcoTerrace. A refurbishment case study.
Available from: http://www.energysavingtrust.org.uk/Publications2/Housing-
professionals/Refurbishment/Sheffield-EcoTerrace-A-refurbishment-case-study [Accessed August 20
2012]
Energy Savings Trust (EST) (2011) CE 338. Grove Cottage. An advanced refurbishment case study.
Available from:
http://simmondsmills.com/projects/files/CE338_Grove%20Cottage_a%20refurb%20case%20study_F
INAL%2020.06.11.pdf [Accessed August 20 2012]
Energy Vortex (No Date) Energy Dictionary. Available from:
http://www.energyvortex.com/energydictionary/EnergyVortex.htm#EnergyVortex_Home_Page.htm
[Accessed August 20 2012]
Environmental Protection Agency (EPA) (2010) Ireland's Greenhouse Gas Emissions Projections 2010
- 2020. Available from:
http://www.epa.ie/downloads/pubs/air/airemissions/EPA_GHG_Emission_Projections_2010.pdf
[Accessed July 20 2012]
Environmental Protection Agency (EPA) (a) (2012) Ireland's Greenhouse Gas Emissions in 2010.
Available from http://www.epa.ie/downloads/pubs/air/airemissions/GHG_1990-2010_2012_v3.pdf
[Accessed June 20 2012]
85
Environmental Protection Agency (EPA) (b) (2012) Ireland's Greenhouse Gas Emissions Projections
2011 - 2020. Available from:
http://www.epa.ie/downloads/pubs/air/airemissions/EPA_GHG_%20Emission_%20Proj_publication
_2012_final_v1.pdf [Accessed June 20 2012]
European Commission (EC) (2003) Better Buildings. New European Legislation to save Energy.
Available from: http://www.buildup.eu/publications/1133 [Accessed June 20 2012]
European Commission (EC) (2010) The EU Climate and Energy Package. Available from:
http://ec.europa.eu/clima/policies/package/index_en.htm [June 20 2012]
European Parliament (EP) (2009) Decision No. 406/2009/EC of the European Parliament and of the
Council. Available from: http://eur-
lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2009:140:0136:0148:EN:PDF [Accessed June 20
2012]
European Parliament (EP) (2012) Directive 2010/31/EU of the European Parliament and of the
Council of 19 May 2010 on the energy performance of buildings (recast). Available from:
http://www.eceee.org/buildings/EPBD_Recast/EPBD_recast_19May2010.pdf [Accessed July 20
2012]
Feist, W. (2010). Criteria for residential-use refurbished buildings. Available from:
http://www.passivhaus.org.uk/filelibrary/Passivhaus%20Standards/EnerPHit_Criteria_Residential_E
N.pdf [Accessed July 20 2012]
Hearne, J. (2012). EnerPHit: the passive house approach to deep retrofit. Construct Ireland. Available
from: http://www.constructireland.ie/Vol-5-Issue-8/Articles/Passive-Housing/EnerPHit-the-passive-
house-approach-to-deep-retrofit.html [Accessed August 20 2012]
Little, J. (a) (2009) Breaking the Mould - Part III. Available from:
http://www.josephlittlearchitects.com/documents/Breaking_the_Mould_3_Construct_Ireland_Issue
_8_Vol_4.pdf [Accessed August 20 2012]
Little, J. (b) (2009) Breaking the Mould. A study of condensation in single-leaf concrete wall
upgrades. Available from:
http://www.josephlittlearchitects.com/documents/Breaking_the_Mould_1_Construct_Ireland_Issue
_6_Vol_4.pdf [Accessed August 20 2012]
Little, J. (a) (2010) Breaking the Mould - part IV. Condensation Risk Analysis - the standards & the
issues. Available from:
http://www.josephlittlearchitects.com/documents/Breaking_the_Mould_4_Construct_Ireland_Issue
_11_Vol_4.pdf [Accessed August 20 2012]
Little, J. (b) (2010). Breaking the Mould - part V. Comparative simulations of internal insulation
systems. Available from:
http://www.josephlittlearchitects.com/documents/Breaking_the_Mould_5_Construct_Ireland_Issue
_12_Vol_4.pdf [Accessed August 29 2012]
86
Little, J., & Arregi, B. (2011). Thermal bridging: understanding its critical role in energy efficiency.
Available from:
http://www.josephlittlearchitects.com/documents/Thermal_Bridging_Construct_Ireland_Issue_6_V
ol_5.pdf [Accessed July 20 2012]
Motherway, B., & Walker, N. (2009). Ireland's Low-Carbon Opportunity. Available from:
http://www.seai.ie/Publications/Low_Carbon_Opportunity_Study/Irelands_Low-
Carbon_Opportunity.pdf [Accessed July 20 2012]
National Consumer Agency (NCA) (2008) Building Regulations and their enforcement. Available from:
http://corporate.nca.ie/eng/Research_Zone/Reports/Home_Construction/NCA-Home-construction-
Volume-5.pdf [Accessed June 20 2012]
Neary, S. (No Date). Building Standards and Regulations. Available from:
http://www.servecommunity.ie/wp-content/uploads/2010/08/08-Sarah-Neary-New-Building-
Standards-and-Regulations.pdf [Accessed June 20 2012]
Odyssee (2011) Energy Efficiency Profile, Ireland. Available from: http://www.odyssee-
indicators.org/publications/country_profiles_PDF/irl.pdf [Accessed June 20 2012]
O'Se, G. (2011) Dwelling airtightness in Ireland: where we are, and where we're going. Available
from: http://www.constructireland.ie/index2.php?option=com_content&do_pdf=1&id=915
[Accessed August 20 2012]
Power, W. (2012). An investigation of compliance with Technical Guidance Document Part L of the
Irish Building Regulations and the effects thereof on Residential sector Energy Use in Ireland.
Unpublished thesis (MSc), Centre for Alternative Technology.
Scania, V. (2010) What is a Deep Energy Retrofit? Experts at the NESEA Conference respond.
Available from: http://www.energycircle.com/blog/2010/03/11/what-deep-energy-retrofit-experts-
nesea-conference-respond [Accessed July 20 2012]
Scheer, J. et al. (2012) Quantification of energy savings from Ireland's Home Energy saving scheme;
an ex post billing analysis. Energy Efficiency.
Schnieders, J., & Hermelink, A. (2006). CEPHEUS results: measurements and occupants' satisfaction
provide evidence for Passive Houses being an option for sustainable building. Energy Policy, pp. 151 -
171.
Sedlak, P., & Sheward, N. (2008) Advanced Ventilation Approaches for Social Housing (AVASH)- Irish
Sampling & Survey Report. Available from:
http://www.brighton.ac.uk/avash/downloads/iresampsurv/iresampsurvweb.pdf [Accessed August
20 2012]
Sheehy, E. (2004). Wicklow Local Authorities Social and Affordable Housing Action Plan 2004 - 2008.
Wicklow County Council.
Sinnott, D., & Dyer, M. (2012) Air-tightness field data for Dwellings in Ireland. Building and
Environment, pp. 269-275.
87
Sustainable Energy Authority of Ireland (SEAI) (2007) Building Energy Rating. Available from:
http://www.seai.ie/uploadedfiles/InfoCentre/BER/BER_CERT_FINAL(1).pdf [Accessed July 20 2012]
Sustainable Energy Authority of Ireland (SEAI) (a) (2008) Dwelling Energy Assessment Procedure
(DEAP) 2008 Edition, Version 3.1. Dublin: Sustainable Energy Authority of Ireland.
Sustainable Energy Authority of Ireland (SEAI) (b) (2008) Energy in the Residential Sector. 2008
Report. Available from:
http://www.seai.ie/News_Events/Press_Releases/Energy_in_the_Residential_Sector_FNL.pdf
[Accessed June 20 2012]
Sustainable Energy Authority of Ireland (SEAI) (2010) Residential Energy Roadmap 2010 - 2050.
Available from: http://www.seai.ie/Renewables/Residential_Energy_Roadmap.pdf [Accessed June
20 2012]
Sustainable Energy Authority of Ireland (SEAI) (a) (2011) Energy in Ireland 1990 to 2010. Available
from:
http://www.seai.ie/Publications/Statistics_Publications/EPSSU_Publications/Energy%20In%20Irelan
d%201990%20-2010%20-%202011%20report.PDF [Accessed June 20 2012]
Sustainable Energy Authority of Ireland (SEAI) (b) (2011) Energy Forecasts for Ireland to 2020. 2011
Report. Available from:
http://www.seai.ie/Publications/Statistics_Publications/EPSSU_Publications/Energy%20Forecasts%2
0for%20Ireland%20%20for%202020%20-2011%20Report.pdf [Accessed June 20 2012]
Sustainable Energy Authority of Ireland (SEAI) (c) (2011) Better Energy Homes scheme - Contractors
Code of Practice and Standards and Specifications Guidelines. Available from:
http://www.seai.ie/Grants/Better_energy_homes/Code_of_Practice_and_Technical_Specification.p
df [Accessed July 20 2012]
Sustainable Energy Authority of Ireland (SEAI) (a) (2012) Better Energy Homes scheme - Applications
approved by county (March 2009 - 20th June 2012). Available from:
http://www.seai.ie/Grants/Better_energy_homes/Better_Energy_Statistics/applications_by_county.
pdf [Accessed July 20 2012]
Sustainable Energy Authority of Ireland (SEAI) (b) (2012) National BER Research Tool. Available from:
https://ndber.seai.ie/BERResearchTool/Register/Register.aspx [Accessed July 20 2012]
Sustainable Energy Authority of Ireland (SEAI) (c) (2012) Better Energy Homes scheme Statistics.
Available from: http://www.seai.ie/Grants/Better_energy_homes/Better_Energy_Statistics/
[Accessed July 20 2012]
Sustainable Energy Authority of Ireland (SEAI) (d) (2012) BER Research Tool User Information Guide.
Dublin: Sustainable Energy Authority of Ireland.
Sustainable Energy Ireland (SEI) (2007) Dwelling Energy Assessment Procedure (DEAP) Calculation
Workbook Version 2.1.7. Dublin: Sustainable Energy Ireland.
88
Wardell, G., & Shanks, K. (2005) Energy Performance Survey of Irish Housing. Dublin: City of Dublin
Energy Management Agency.
Watson, D., & Williams, J. (2003) Irish National Survey of Housing Quality 2001 - 2002. Available
from:
http://www.environ.ie/en/Publications/DevelopmentandHousing/Housing/FileDownLoad,2446,en.p
df [Accessed July 20 2012]
Wicklow County Council (WCC) (2008) List of Houses at 31st Dec 08. Wicklow County Council.
Wicklow County Council (WCC) (a) (2011) BER Upgrade Database. Wicklow County Council.
Wicklow County Council (WCC) (b) (2011) BER Provision of Services 220611. Wicklow County Council.
Wicklow County Council (WCC) (c) (2011) BER Assessor List Issued 080711. Wicklow County Council.
Wicklow County Council (WCC) (d) (2011) Application Form for BER Upgrade Works. Available from:
http://www.wicklow.ie/apps/wicklowbeta/News/BER.aspx [Accessed July 20 2012]
89
Appendix A – Data Quality
Number of Units
Overall, dwelling reports for 722 dwellings were provided as input to this study. A total of 4
dwellings were excluded as their input files were corrupt, or contained blank worksheets.
The total number of units included in the analysis is 718.
Dwelling Type
1 unit (‘Church Lane’) was assumed to be ‘detached’ in the absence of any other information.
16 units were assigned the dwelling type of ‘House’ during their assessment. Following consultation
with other sources (such as the accompanying Energy Efficiency report, or Google Earth), these were
assigned a dwelling type more consistent with others in the study.
Data Consistency
The following minor inaccuracies were noted, and were held consistent during the modelling of
retrofit interventions;
Doors: Information relating to heat loss through doors was not recorded for 126 dwellings.
Floors: There are 24 instances where top floor apartments incorrectly have values of floor heat loss
ascribed to them (SEAI a, 2008, p. 82).
Roofs: There are 12 instances where ground floor apartments incorrectly have values of roof heat
loss ascribed to them (SEAI a, 2008, p. 82).
Windows: The calculation of heat loss through windows in DEAP factors in several variables. Firstly,
based on the glazing type, a default U-value is assigned. For double and triple glazed units, this can
vary depending on the inter-glazing spacing. The U-value is further altered based on frame type and
the assumed use of curtains (SEAI a, 2008, p. 17). ''Roof' windows incur an additional factor when
the adjusted U-value is being calculated. SEAI (a, 2008, p. 95) shows that the value of orientation
used for roof windows can vary between 'North' and 'Horizontal' based on the pitch of the roof and
the orientation of the window, thus all windows with a horizontal orientation are assumed to be
'roof windows', however it does not follow that all North facing windows will be roof windows (and
this cannot be determined as roof pitch is not captured in the DEAP output files).
Several factors introduce error in the modelled estimation of window related heat loss;
90
Roof Windows: Horizontal units are recorded for only 28 units. All but 2 of these are listed as 'roof
windows' and accordingly, the adjusted U-value used in the model and recorded in the DEAP
assessment differ, introducing a small error in the glazing heat loss. 11 Kiladreenan Close (Row 601,
Window 3) is an example of a Horizontal window that is not listed as a roof window. Hence as it
stands, the adjusted U-value from DEAP output and in the model match. Roof windows or northerly
orientation are recorded in 5 units. The Adjusted U-values in the model and DEAP files differ for each
such window. Thus, without the inclusion of the roof factor in the model, the glazing heat loss for 33
units (4.6% of the sample) are slightly incorrect.
User Defined U-values: A large discrepancy loss (circa 12%) is seen in planar heat loss for 17 Burnaby
Lawns (row 54) as a result of user defined U-values being entered glazed units. The model cannot
recognise user-defined U-values, and in this case, overestimates planar heat loss.
Possible Assessor error, or DEAP version mismatch: See 43 Monastery Grove (row 189). The DEAP
Assessment file clearly shows that both windows are assessed as being 'Double Glazed - Air Filled',
with U-Values of 2.7 and adjusted U-Values of 2.6811. Both windows are Wood/PVC framed with the
same frame factor, over-shading and glazing gap (>=16mm). Neither windows are roof windows.
With areas of 3.54 and 4.37sq.m, the cumulative heat loss is expected to be 21.2 W/K, however the
dwelling report indicates heat loss to be 19.30 W/K, which, prima facie, is incorrect. Creating
windows such as described above in DEAP yields a heat loss of 19.30, though the adjusted U-Values
for the windows are 2.44, not 2.68 as captured in the dwelling report. This introduces an error in the
model, as it uses the seemingly incorrect 2.68 for the assessed adjusted U-value, and then 2.44 as
the modelled one. It is not known how the dwelling report captures one adjusted U-Value yet
presents a conflicting value of heat loss.
Similarly, see 10 Bayview Close (row 17, window 3); here the adjusted U-value in the model matches
that of DEAP, however is different to the adjusted U-value from the DEAP output file, hence a
difference in the heat loss is evident.
In both of these cases, assessor error is possible, or perhaps a different version of DEAP was used for
the assessment than is assumed used for the model.
11
A U-value of 3.0 is required in DEAP to have an adjusted U-value of 2.68
91
Appendix B – Thermal Bridging ‘Y-Factors’
With regards the inclusion of thermal bridging heat loss in DEAP calculations, SEAI (a, 2008, p. 67)
notes the following;
The quantity which describes the heat loss associated with a thermal bridge is
its linear thermal transmittance, Ψ. This is a property of a thermal bridge and is
the rate of heat flow per degree per unit length of bridge that is not accounted
for in the U-values of the plane building elements containing the thermal
bridge. The transmission heat loss coefficient associated with non-repeating
thermal bridges is calculated as:
HTB = ∑(L*Ψ)
where L is the length of the thermal bridge over which Ψ applies.
If details of the thermal bridges are not known, use
HTB = y ∑Aexp
where Aexp is the total area of exposed elements, measured in m2
Y in the above formula represents a multiplier which can have 3 values;
1. Y=0.15 applies in all cases other than 2 or 3 below
2. Y=0.08 applies where construction details conform with Acceptable
Construction Details
3. Y=0.11 applies where a dwelling has been built under to 2005 Building
Regulations
As noted in section 5.1.3, all assessors assumed the default value of Y=0.15 during the dwelling
assessments for dwellings in the sample. The BEH, Part L and WCC scenarios assume a value of
Y=0.08 to reflect an assumed degree of attention towards reducing thermal bridging during retrofits.
The EnerPHit scenario requires more stringent treatment. A stipulation of this standard is that no
thermal bridge will have a thermal transmittance greater than Ψ = 0.01 W/mK (Feist, 2010, p. 8).
What is required is to deduce a suitable Y-Factor for use in the model for the EnerPHit scenario.
92
Assumptions;
• All dwellings are 2 storey, except Apartments which are considered 1 storey.
• All Dwelling footprints are square in nature
• External insulation is used, thus intermediate floor thermal bridge is removed.
Step 1: Estimate length of ground floor and eaves thermal bridges:
Dwelling Type Avg.
Floor
area
(m2)
Assumed
length of
side (m)
Assumed
Number
of
Exposed
Sides
Assumed
Perimeter
(m)
Multiplier for
thermal bridge at
eaves and ground
floor
Assumed
Average
Bridge
Length
(m)
Apartment 47.2 6.9 1 6.87 1 6.87
Detached 75.5 8.7 4 34.77 2 69.53
End of terrace 82.6 9.1 3 27.27 2 54.53
Mid-terrace 80.2 9.0 2 17.92 2 35.83
Semi-detached 79.4 8.9 3 26.72 2 53.45
Step 2: Estimate length of Window related thermal bridges:
Dwelling Type Average
Glazing
Area
(m2)
Assumed
number
of
Windows
Assumed
Window
area
(m2)
Assumed side
length for Window
(m)
Assumed
Average
Bridge
Length (m)
Apartment 8.3 3 2.8 1.7 6.6
Detached 12.7 8 1.6 1.3 5.0
End of terrace 14.5 7 2.1 1.4 5.8
Mid-terrace 13.7 4 3.4 1.9 7.4
Semi-detached 11.1 7 1.6 1.3 5.0
Step 3: Estimate length of Door related thermal bridges:
Dwelling Type Average
Door area
(m2)
Assumed
number
of Doors
Assumed
Door Area
(m2)
Assumed Average
Bridge Length (m)
Apartment 1.91 1 1.91 5.82
Detached 2.72 2 1.36 4.72
End of terrace 1.99 2 1.00 3.99
Mid-terrace 2.40 2 1.20 4.40
Semi-detached 3.03 2 1.51 5.03
93
Step 4: Determine Y Factor:
Assumed
Total Bridge
Length (m)
Ψ
(W/mK)
Heat
flow
(W/K)
Avg. Planar
Element Area
(m2)
Y Factor
(W/K/m2)
Apartment 19.32 0.01 0.193245 97.58216 0.00198
Detached 79.30 0.01 0.792973 243.2564 0.00326
End Of Terrace 64.28 0.01 0.642828 186.1614 0.003453
Mid-Terrace 47.64 0.01 0.476377 148.8264 0.003201
Semi-Detached 63.52 0.01 0.63516 184.0234 0.003452