fully glazed office building facade designs in denmark · and life cycle costing (lcc) solutions...

FULLY GLAZED OFFICE BUILDING FACADE DESIGNS IN DENMARK Targeting DGNB platinum and Building Class 2020 requirements with the lowest LCC

Giedre Villekjær Pedersen

Master Thesis in Energy-efficient and Environmental BuildingsFaculty of Engineering | Lund University

Lund UniversityLund University, with eight faculties and a number of research centers and specialized in-stitutes, is the largest establishment for research and higher education in Scandinavia. The main part of the University is situated in the small city of Lund which has about 112 000 inhabitants. A number of departments for research and education are, however, located in Malmö and Helsingborg. Lund University was founded in 1666 and has today a total staff of 6 000 employees and 47 000 students attending 280 degree programs and 2 300 subject courses offered by 63 departments.

Master Program in Energy-efficient and Environmental Building DesignThis international program provides knowledge, skills and competencies within the area of energy-efficient and environmental building design in cold climates. The goal is to train highly skilled professionals, who will significantly contribute to and influence the design, building or renovation of energy-efficient buildings, taking into consideration the architec-ture and environment, the inhabitants’ behavior and needs, their health and comfort as well as the overall economy.

The degree project is the final part of the master program leading to a Master of Science (120 credits) in Energy-efficient and Environmental Buildings.

Examiner: Maria Wall (Energy and Building Design)Supervisor: Åke Blomsterberg (Energy and Building Design)

Keywords: glazed façade, thermal comfort, visual comfort, window properties, DGNB certification, Building Class 2020, low-energy design strategies, office building, LCC.

Thesis: EEBD–16/05

Fully Glazed Office Building Facade Designs in Denmark

3

Abstract

The current trend in office building architecture includes large glazed areas that give

transparent architecture. But these buildings have a challenging indoor climate and a higher

energy use than required by current building regulations in Denmark. The limits for

Building Class 2020 (BC2020) is 25 kWh/(m²·year) where an integrated Renewable Energy

Source (RES) is used for lowering an actual building’s energy use.

Now general building quality and sustainability are ensured by building certification

systems. The German Sustainable Building Council (DGNB) certification fulfils the Danish

building market needs and the Danish DGNB certification system was created in 2012.

The combination between a fully glazed office building that reaches DGNB platinum level

and fulfils the previously mentioned BC2020 energy use requirement seems impossible.

The aim of the thesis is therefore to determine if a single-skin fully glazed office building

façade can meet DGNB platinum level where the thermal and visual comforts, building

envelope quality and the best economy are the main criteria. The BC2020 energy

requirements should also be fulfilled.

The office building called “Health Centre” was used as a reference case for a BC building. It

was equipped with two types of offices: landscape and cell. They were facing all four

cardinal directions. The thermal analyses for these cases were performed by simulations for

operative and surface temperatures, while the visual comfort simulations output was a

Daylight Factor (DF). The annual glare analyses as well as point-in-time glare simulations

were created in further investigation for the visual comfort, as it was an issue. The building

envelope quality was ensured by U-value calculations for external wall and the glazed part

of the façade. The next considered element in this thesis was LCC calculations where the

glazed part of the façade was analysed (various g-values, self-cleaning glass, two external

shading types). And the annual energy use calculations summed the analyses up as they

examined whole building performance.

The study concluded that the office building, located in Denmark and equipped with the

fully glazed façade, could meet the DGNB platinum level requirements for the thermal and

visual comforts, the building envelope quality at the lowest price when the cell office layout

was selected. For the landscape offices the DGNB visual comfort platinum requirement was

not reached, as working planes were located too far from façades where daylight levels were

low. The alternative that had the lowest LCC was selected to be the façade with the external

screen shading combination with self-cleaning glass that had U-value of 0.6 W/(m²·K). In

that case, the BC2020 energy use requirement was reached, but the building was not an

energy-efficient office, as the RES implementation provided needed electricity power that

reduced the building’s energy use to the BC2020 level. A larger amount of solar cells had to

be integrated to compensate the building design issues. On the other hand, RES integration

is more environmental-friendly solution than using other sources.

Generally, the office building façade design with large glazed areas is a complex issue, as it

requires detailed analyses of many parameters that influence the overall building quality.


4

Table of contents

Abstract ............................................................................................................. 3 Preface ............................................................................................................... 7 Terminology / Notations .................................................................................... 8

Abbreviations 8 Mathematical notation 8

1 Introduction ............................................................................................... 9 1.1 Background and problem motivation 9 1.2 Aim and hypothesis 10 1.3 Limitations 10

2 Literature review ..................................................................................... 11 2.1 Office building energy use in Denmark 11

Regulations 11 Building Class 2020 or Nearly Zero Energy Building 2020 11

2.2 DGNB certification 12 Platinum level 12 Office building schemes 13

LCC scheme 13 Thermal comfort scheme 14 Visual comfort Scheme 15 Building Envelope Quality Scheme 15

2.3 Design strategies for low-energy offices 16 2.4 Fully glazed office building 18

Advantages 18 Disadvantages / solving methods 18

2.5 Glazed façades types 19 Single-skin façade 19

2.6 Office building layout 20 3 Methodology ........................................................................................... 21

3.1 Computer simulation tools 22 3.2 Modelling Base Case – Health Centre 22

Climate, orientation and surrounding conditions 23 Geometry and layout 24 Description of building elements 26 Input data for energy use and thermal comfort simulations 27

Occupancy 27 HVAC systems and RES 28 Set-points 29 Internal loads 29 Natural ventilation 30 External shading 31

Input data for visual comfort simulations 31 Certification schemes analyses 33

3.3 Parametric study 34 Base Case 34

Single-skin façade 36


5

3.4 Life Cycle Cost 37 4 Results ..................................................................................................... 40

4.1 Base Case 40 Thermal comfort 40 Visual comfort 42 Envelope quality 43 Energy use for the Base Case building 44

4.2 Single-skin façade parametric studies 44 Thermal comfort 45

Design strategies 45 Window frame areas and glass U-values 48 Glass g-values 50 Shading devices 53 Final Cases operative and surface temperatures 55

Visual comfort 57 Glass g-values 57 South and west facing offices work plane daylight levels 58 External shading 58 Glare control 59

Envelope quality 61 4.3 DGNB certification score for Base Cases and Final Cases 62 4.4 Energy use for the building 63

Design Strategies 63 Window frame areas and U-value for glass 63 Glass g-values 64 Shading devices 65 Final case 66

4.5 Life Cycle Cost 66 LCC for glass variations 67 LCC for façades with external shadings and self-cleaning glass 67

5 Discussions .............................................................................................. 69 6 Conclusions ............................................................................................. 72 7 Summary ................................................................................................. 73 8 References ............................................................................................... 74 Appendix A ..................................................................................................... 78 Appendix B ...................................................................................................... 81

B.1 The cell office facing north annual glare 81 B.2 The cell office facing east annual glare 81 B.3 The landscape office facing west annual glare 82

Appendix C ...................................................................................................... 83 C.1 Parametric study plan for the thermal comfort and energy use 83 C.2 Parametric study plan for the visual comfort 84

Appendix D ..................................................................................................... 85 D.1 The maximum ceiling surface temperatures for the design strategies

studies 85 D.2 The maximum window surface temperatures for the design strategies

studies 85


6

D.3 The maximum ceiling surface temperatures for the glass U-values and

the frame areas studies 86 D.4 The maximum window surface temperatures for the glass U-values and

the frame areas studies 86 D.5 The maximum ceiling surface temperatures for the glass g-value studies87 D.6 The maximum window surface temperatures for the glass g-value

studies 87 D.7 The maximum ceiling surface temperatures for the external shading

studies 88 D.8 The minimum window surface temperatures for the external shading

studies 88 D.9 The maximum window surface temperatures for the external shading

studies 89 Appendix E ...................................................................................................... 90

E.1 Heating and cooling demand for different frame percentages and glass

U-values 90 E.2 The building annual energy use with external shading variations 90


7

Preface

The author gratefully acknowledges permission to use the front page picture, which is taken

from the project presentation folder called “Health Centre” located in Denmark. It is made

by the Aart Architects company and the project leading architect Anne Yoon F. Nielsen.

The author would like to thank this thesis supervisor Åke Blomsterberg and sub-supervisor

Peter Hesselholt for the time spent helping/discussing/learning during this thesis process.

Last but not least, author would like to express my gratitude to my husband, nearest family

and friends for support during the thesis process.


8

Terminology / Notations

Abbreviations

AC Analysis Case.

BC Base Case.

BC2020 Danish Building Class 2020.

BR15 Building Regulations 2015.

DF Daylight Factor.

DGNB The German Sustainable Building Council (Deutsche

Gesellschaft für Nachhaltiges Bauen).

DHW Domestic Hot Water.

DK-GBC Green Building Council Denmark.

DGP Daylight Glare Probability.

DRY Danish Reference Year.

FC Final Case.

GWR Glass to wall ratio.

LCC Life Cycle Cost.

LT Light Transmittance through the glass.

NZEB 2020 Nearly Zero Energy Buildings 2020.

RES Renewable Energy Source.

SfB Together working group for building issues

(Samarbetskomitén för Byggnadsfrågor).

SC Selected Case.

SFP Specific Fan Power.

VAV Variable Air Volume.

PV Photovoltaics.

Mathematical notation

g Solar protection factor.

R Thermal resistance (m²·K/W)

U Thermal conductance (W/m2 ·K)

Thermal conductivity (W/m·K)


9

1 Introduction

This master’s thesis focuses on fully glazed office building indoor climate, visual comfort

and Life Cycle Costing (LCC) solutions fulfilling the German Sustainable Building Council

(DGNB) certification system and Building Class 2020 (BC2020) requirements in Denmark,

starting with a reference building analyses, which is located in Copenhagen.

1.1 Background and problem motivation

The current trend in office building architecture includes large glazed areas that provide a

view out and daylight (Bülow-Hübe, 2008). Glazed office buildings are airy and light but

they have a problematic indoor climate and a higher energy use than buildings with

conventional façades (Poirazis, 2005). At the same time, this trend is at odds with building’s

energy use requirements, which are getting stricter.

In Denmark during the last ten years the energy requirement for office building heating,

ventilation, electricity for lighting and building functions, Domestic Hot Water (DHW) and

Renewable Energy Source (RES) has changed from 71.3 kWh/(m² ·year) plus 1650 kWh

divided by heated building Area in 2010 to 41 kWh/(m² ·year) plus 1000 kWh decided by

heated building area in 2015. And by 2020 it must be lower than 25 kWh/(m²·year) with the

mandatory RES use (Thomsen, 2014). This energy use requirement with a renewable source

integration is twice as high as in 2010. And this change challenges the overall building

sustainability.

Now a general building quality and sustainability are ensured through building certification

systems. They require documentation where many aspects must be considered in order to

cover the three-pillar sustainability concept shown in Figure 1.

The DGNB certification fulfils issues that are most important for the Danish building

market: the three-pillar sustainability concept, future-proof for fulfilling European standards

and regulations (Birgisdóttir, 2011). In 2012 the Danish DGNB certification system was

established with three award levels for new buildings: silver, gold and platinum. However,

since 2012 only one office building has been certified as platinum, while the amount of gold

certified ones is high (Green Building Council Denmark, 2015).

The combination of a fully glazed office building that reaches DGNB platinum level and

fulfils the previously mentioned BC2020 energy use requirement seems impossible. This

So

cial

En

vir

on

men

tal

Eco

no

mic

Sustainability

Figure 1: Sustainability three-pillar concept.


10

implies the need for knowledge related to an office building design equipped with fully

glazed façades that can reach future requirements in Denmark.

1.2 Aim and hypothesis

The aim of the thesis is to determine, if a single-skin fully glazed office building façade can

meet DGNB platinum level where the thermal and visual comforts, building envelope

quality and the best economy (LCC) are the main criteria. The BC2020 energy requirements

should also be fulfilled.

Furthermore, the thesis aims at using the fully glazed façade solutions that are available in

the Danish building market in order to create realistic designs, such as a single-skin façade.

The hypothesis of this study is that a new office building with fully glazed façades (as

experienced from the inside) can fulfil the DGNB platinum certification and the BC2020

energy requirements, where they also have a low LCC.

1.3 Limitations

A simplified building layout was used as a Base Case (BC) where an internal layout was

modified. Surrounding buildings were neglected in all BC and parametric studies

simulations/calculations. Façades with external shading devices were used, while none of

internal or middle pane shadings were checked.

The most façade-design-related DGNB certification schemes were selected. But some parts

from these schemes were not analysed in this study:

for thermal comfort scheme – draughts and relative humidity;

for visual comfort scheme - electrical light glare prevention, distribution of an electrical light and electrical light colour rendering;

for envelope quality scheme - a roof and ground slab construction U-values, a design transmission loss for building envelope excluding windows and doors,

thermal bridges between windows, walls and foundation, moisture safety,

infiltration and window frame and inner window surface temperature.

Some of the values used in the study were assumed to meet the DGNB platinum level

requirements, such as thermal bridges for the foundation and the external wall, U-values for

building components except windows and external wall, and the design transmission loss.

The DGNB scheme with LCC requirements were not analysed as they apply for the whole

building and this study has focused on glazed façades. LCC calculations for the study were

performed for the selected façade types with material, replacement, maintenance and

cleaning costs, excluding all other costs. The LCC-tool recommended by the DGNB

certification system was not used, but a new tool created for the Danish building industry

was applied. This tool had the same embedded calculations as required by the DGNB

certification. Finally, the check list points were used for the final DGNB score for offices

studied as the final certification expressed in percentage can be achieved just for whole

building.


11

2 Literature review

This chapter includes a brief literature review related to the thesis topic and provides

background information about the Danish office buildings, their energy use, and

requirements for the BC2020. Furthermore, an overall introduction to DGNB certification

and platinum level schemes with requirements is presented.

Analysis of information collected from various websites, books, magazines, and conference

papers about the design strategies for low energy offices and fully glazed façade types that

were analysed during this thesis research is also presented in the following chapters.

2.1 Office building energy use in Denmark

The 1970’s oil crises led to a huge transformation in the building’s energy use. Since then,

the heating demand for office building was lowered, while electricity use was increased in

terms of primary energy used to produce heat and electricity. The primary energy use for

newly built offices heating, which was around 125 kWh/m² in 1975, decreased to 50

kWh/m² in 2005. At the same time the electricity use increased from 100 kWh/m² in 1975 to

over 150 kWh/m² in 2005. This was caused by the expanded electricity need for computers,

lighting fixtures, cooling down the building and technical equipment. (Marsh, et al., 2008)

In Denmark an energy-efficient building design has been a trend for many years, but 40% of

the total energy used still belongs to buildings. The energy use can and must be reduced by

lowering the energy need in buildings, which is possible from the technical and economic

point of view. (Dal, et al., 2012) The Danish Energy Agency (2015a) claims that nowadays

technology already can save a large amount of energy by having new buildings that produce

more energy than they consume. According to Dal, Rusbjerg & Zarnaghi (2012), energy-

efficiency of buildings has already progressed, as the primary energy use was lowered by

26.3% from 1990 to 2010.

Regulations

The regulations or requirements for building’s energy use are the main tools that can

actually force the building industry to act (Danish Energy Agency, 2015a) and Danish

Building Regulations continuously lower the energy use requirements for all types of

buildings (Dal, et al., 2012). At the same time, regulations focus on the long-term cost-

efficiency. The requirements from European energy performance of buildings directives and

building certifications systems advocate LCC calculations rather than the lowest price

(Danish Energy Agency, 2015b). The long-term cost is already integrated in building

industry.

Building Class 2020 or Nearly Zero Energy Building 2020

As mentioned previously, the political energy ambitions are striving to minimize the fossil

fuel use. As a result, the energy performance of buildings must be lowered and RES must be

included. Here the BC2020 is suggested, which is also known as “Nearly Zero Energy

Buildings (NZEB 2020)”. (Thomsen, 2014)


12

Energy use for office buildings, according to the Building Regulations 2015 (BR15) (2016),

must be lower than 25 kWh/(m²· year) including heating, cooling, ventilation, DHW and

lighting. Other requirements for BC2020 according to the BR15 (2016) are:

The building envelope without windows and doors must have a design transmission loss of maximum 5.7 W/m² for buildings over three floors. “The design

transmission loss per m² of the building envelope is the sum of the total heat

transmission loss through the building envelope excluding windows, roof lights,

glazed outer walls, glazed roofs and skylight domes” (Danish Knowledge Centre for

Energy Savings in Buildings, 2016, p. 7).

The airtightness of 0.5 l/s per m² at 50 Pa must be reached and checked by pressure test.

Ventilation heat recovery efficiency must be higher than 80% and Specific Fan Power (SFP) not higher than 1.8 kJ/m³ for Variable Air Volume (VAV) systems.

Low energy internal lighting.

Indoor CO2 levels must not exceed 900 ppm for a longer period of time.

Windows with the light transmittance of 75% must be used where minimum 15% windows to floor area is applied.

“The energy gains through windows and glazed outer walls must not be less than 0 kWh/m² per year during the heating season” (Bygningsreglementet, 2016, p. 74).

Some windows and thermal indoor climate requirements are lower than the DGNB

certification, which are presented the following section.

2.2 DGNB certification

There are many building certification systems, but DGNB is the only one covering all

lifecycle phases and it can also be easily adapted or applied for existing or coming building

requirements (Green Building Council Denmark, 2012). This resulted in a wide DGNB

certification implementation in Denmark.

The DGNB certification system can be used for various building types, districts or cities.

Each building category has schemes with requirements adapted to the building type (DGNB

System, 2014). Schemes, which are used in the thesis, are presented in this chapter.

Platinum level

DGNB certification systems have silver, gold and platinum levels. The platinum

certification means that 80% of a maximum point must be gathered and minimum 65% from

five main quality sections (environmental, economic, sociocultural and functional aspects,

technology and processes) are reached. The platinum is the top level of certification where

the gold (65%) and silver (50%) levels are much lower. A total of 41 schemes (indicated

with evaluation points 0 - 10) and 213 sub-criteria (indicated with check list points 0 - 100)

are included in the certification. In order to receive the final certification whole building

quality must be assured. (DGNB System, 2014)

For the platinum level the target is that each scheme must receive maximum evaluation

points. Evaluation points are received by the amount of all check list points added together


13

for each scheme and transferred to points from 0 to 10. In this study check list points are

used as expression of the results where the maximum for each scheme studied is 100 check

list points.

Office building schemes

The DGNB office building certification guideline version 2014 1.2 is used for this study.

The most façade-design-related schemes that are as well analysis areas of the study are:

thermal comfort, visual comfort and building envelope quality. But the interest in the LCC

encourages the use of the LCC scheme as well.

LCC scheme

LCC is performed for the building just once where prices for materials, maintenance and

replacement of components, operating and cleaning are included. The requirements for

office buildings are collected from the DGNB certification Manual for Office Buildings

(Green Building Council Denmark, 2015) and presented in Table 1. The maximum 100 of

check list points or 10 evaluation points are received with LCC for whole building less than

21.000 DKK/m².

Table 1: The LCC requirements according the DGNB certification Manual for Office Buildings.

1 The LCC-tool developed for the DGNB certification system (Green Building Council Denmark, 2015).

Calculation period 50 years

Life time phases Production, application

Pricing

Building pricing according to Together

working group for building issues (SfB)

system

Replacement prices after lifetime

Maintenance prices

Energy supply pricing

Cleaning prices

Included calculations

Total energy use

Water need

Cleaning areas

Real price change for different groups

General price increase for building prices 2%

Water and sewer system 3%

Energy 4%

Real discount rate 5.50%

Correction factor for location Copenhagen 1.05%

Reference value Heated floor area in m²

Results that need to be documented

Present value prices for:

Initial building prices

Maintenance and replacement prices

Supply prices

Cleaning prices

Calculations and documentation

DGNB-DK software (LCC-værktøj1) with

areas definition and pricing for building

components.


14

Thermal comfort scheme

The thermal comfort scheme is divided into two parts as the winter and summer periods

must be analysed using the Danish Reference Year (DRY) climate data for the whole

Denmark. The requirements for each period are presented in Table 2, which are collected

from DGNB certification Manual for Office Buildings (Green Building Council Denmark,

2015).

Table 2: DGNB certification thermal comfort scheme top score requirements and check list

points.

2 Requirements according to DS/EN 15251:2007 (Danish Standard Association, 2007). 3 Requirements according to EN ISO 7730:2005 (European Standards, 2005).

Winter period

(1. November till 30. April)

DGNB

check

list

points

Summer period

(1. May till 31. October)

DGNB

check

list

points

Operative temperature2

21 °C ≤ Category A ≤ 25 °C

No more than 50 hours under 21 °C

or over 25 °C.

Activity level at ~1.2 met and

clothing level at ~ 1.0 clo.

PPD - less than 6%

Min ventilation:

10 l/s per person

Low polluted building – 1 l/s, m²

Unoccupied period min. ventilation

0.1-0.2 l/s, m².

30 Category A ≤ 25.5 °C

No more than 50 hours above

25.5 °C.

Activity level at ~1.2 met and

clothing level at ~ 0.5 clo.

PPD - less than 6%

Min ventilation:

10 l/s per person

Low polluted building – 1 l/s, m²

Unoccupied period min. ventilation

0.1-0.2 l/s, m².

30

Draught 3

Category B with draught rating at

20%

Mean air velocity ~ 0.16 m/s at 40%

convection intensity. Include

ventilation diffuses, natural

ventilation or mixed one.

10 Category B with draught rating at

20%

Mean air velocity ~ 0.21 m/s at

40% convection intensity. Include

ventilation diffuses, natural

ventilation or mixed one.

10

Radiant temperature asymmetry and floor temperature 3

Surface temperatures:

Glass façades/wall min. 18 °C

Glass façades/wall max. 35 °C

More than 40% glass in façade must

be analysed more carefully.

5 Surface temperatures:

Ceiling max. 35 °C

Glass façades/wall min. 18 °C

Glass façades/wall max. 35 °C

Floors max. 29 °C

More than 40% glass in façade

must be analysed more carefully.

5

Relative humidity

Relative humidity, ≤ 25%

Absolute humidity, x< 12 g/kg

Must be minimum 95% of occupancy

time.

5 Absolute humidity, x < 12 g/kg

Must be minimum 95% of

occupancy time.

5

https://webshop.ds.dk/da-dk/standard/ds-en-152512007


15

According to the Green Building Council Denmark (DK-GBC) (2015, p. 174):

Operative temperature = room middle point value

Radiant temperature asymmetry and floor temperature = room middle point value

Relative humidity = room middle point value.

Visual comfort Scheme

The visual comfort must be considered, as the daylight levels are very important for the

working place. This DGNB certification scheme includes daylight availability, view to the

outside, glare prevention, electric lighting distribution and colour rendering from it. The top

score requirements are gathered from the DGNB system Denmark guidelines for office

buildings (Green Building Council Denmark, 2015) and presented in Table 3.

Table 3: DGNB certification requirements for visual comfort and check list points.

Category name and their parameters Requirements Check

list

points

Daylight in buildings calculated for 50%

of room area counting from the building

envelope towards inside

Daylight factor (DF) ≥ 3.0% 16

Daylight at permanent working stations

calculated for minimum 80% of all

working stations

DF ≥ 3.0% and ≥ 2.0% for other 20%

of working stations 20

View out Dynamic solar shading that gives view

out when it is used 16

Daylight glare prevention

Glare preventing screen that gives

daylight, view out and reduces direct

glare when is used

16

Electrical light glare prevention No glare from electrical light according

to DS700 standard 6

Electric lighting distribution

Fulfilling DS700 standards and

working station is equipped with task

lighting.

10

Electric lighting colour rendering (Ra) Ra ≥ 90 16

Building Envelope Quality Scheme

The building envelope quality requirements are divided into six categories: insulation level

for building components, thermal bridging, a design thermal transmission of building

envelope, moisture in construction, infiltration at 50 Pa and windows inner surface

temperature. These requirements are presented in Table 4, which are collected from the

DGNB system Denmark guidelines for office buildings (Green Building Council Denmark,

2015).


16

Table 4: U-values and thermal bridging requirements for building components

Category name and their

parameters

Requirements Check

list

points

U-value of:

Ceiling and roof

External wall

Ground floor and basement floor

Window / Roof window

0.1 W/(m²·K)

0.15 W/(m²·K)

0.1 W/(m²·K)

1.0/1.2 W/(m²·K)

30

Category name and their

parameters

Requirements Check

list

points

Total thermal transmission of

building envelope over three

floors (It is calculated by

dividing the heat conduction

through walls (W) with the

building envelope gross area

(m²))

5.5 W/m²

15

Thermal bridges between:

Window and external wall

Skylights and roof

External wall and foundation

0.03 W/(m·K)

0.10 W/(m·K)

0.13 W/(m·K)

15

Moisture safety If common construction is used, building

envelope is moisture proof. For example, light

weight external walls or roof construction

where damp-proof membrane is placed

maximum 1/3 in insulation layer from the warm

side of construction or heavy weight external

wall with insulation on the outside

10

Infiltration at 50 Pa Should be documented with blow door test and

value must not exceed 0.5 l/(s·m²) 15

Window frame and inner

window surface temperature in

the external wall

Not lower than 15 °C

15

2.3 Design strategies for low-energy offices

The design strategies for low-energy buildings located in the northern climate are described

by several authors. The main five strategies are: reduction of heating/cooling demand,

reduction of internal and electricity loads, integration of solar energy, daylight

utilization/control and renewable energy integration.

Firstly, heating and cooling demand can be lowered by optimizing “…building shape,

surface to volume ratio, building envelope, air tightness, heat recovery of ventilation air”

(Haase, et al., 2010, p. 25). Marsh (2008) claims that material choice is crucial, as thermal

conductivity and thermal inertia are the keys to lower heating and cooling demands.

Treldal, Radisch, De Place Hansen and Wittchen (2011) as well as Flodberg (2012) mention

a reasonable glass to floor ration as another important design element. Flodberg (2012) also


17

claims that winter design temperature set-points are important criteria. A high indoor

temperature can also be minimized by glass selection with solar control properties and

shading devices (Bülow-Hübe, 2008). Otherwise, low window U-value mitigates heating

demand while cooling load is not affected (Poirazis, 2005). Ross (2009) also mentioned in

her report that U-values for windows as well as for other building components are important

for heating/cooling demand reduction. Next step is mitigation of thermal bridges between

well insulated structural base and construction elements (NorthPass, 2012). Danish Energy

Agency (2015a) describes all of these design strategies and in addition mentions the need

for an energy-efficient heating system.

The next design strategy is concentrated on lowering electricity use and internal gains. The

first step is the correct selection of electric lighting. According to Dubois and Blomsterberg

(2011), lamp, ballast and luminaire technology, as well as illuminance levels, use of task

light and control of lighting, can reduce electricity use and internal gains problem. After

that, it is important to use energy-efficient equipment that includes lighting fixtures and

ventilation system (Haase, et al., 2010). In NorthPass report (2012) the authors also

mentioned the importance of low energy ventilation system, while heating components with

control system are crucial. Here Danish Energy Agency (2015a) agrees with the need of low

energy households but also mentions the need for energy-efficient heating pumps and

ventilation fans. Flodberg (2012) advises to use demand controlled ventilation, which

reduces previously mentioned fan electricity usage. Treldal, Radisch, De Place Hansen and

Wittchen (2011) also encourage to use demand control ventilation during the winter and try

to integrate natural ventilation during the summer period. Marsh (2008) urges an overall

building and room design with natural ventilation and daylight access as the most important

design strategy.

This leads to the next design strategy called solar energy use. According to Ross (2009), a

passive solar energy can be gained by: building south-west orientation, windows facing

south, and internal thermal mass. Window orientation is also mentioned in NorthPass (2012)

report where south-east and south-west facing openings were concluded to give most

effective passive solar gains during the winter.

Windows also give access to daylight in buildings. The daylight levels are influenced by

several parameters. Küller (2004) claims that size, form, placement, facing direction and

amount of windows are related to indoor daylight. He describes the glazing choice

importance where frame and transmittance are highlighted. According to Dubois and

Blomsterberg (2011), window characteristics as well as interior surface reflectance of a

building are crucial to daylight harvesting. They also describe how the choice of shading

devices influence daylight.

The other device types, such as solar collectors and solar photovoltaic cells are a part of the

latest design strategy – renewable energy usage in buildings. Ross (2009) claims that

ground/water source, active solar, Photovoltaics (PV), and wind power can be integrated in

buildings as RESs. The NorthPass (2012) mentions biomass boilers as one of the

possibilities. Marsh (2008) describes the correlation between the reduction of electricity use

with within-building-placed RES.


18

The sources mentioned in this chapter describe several design strategies that lead to low-

energy office design. The selected strategies for the thesis are described in the methodology

chapter.

2.4 Fully glazed office building

This chapter summarises the fully glazed office building advantages and disadvantages.

They are important to be aware of, as today’s office buildings’ architectural trend is

equipped with large glazed areas (Bülow-Hübe, 2008). According to Poirazis (2005), the

glazing size influences the indoor climate and the energy efficiency of the building as well

as energy use for offices.

Advantages

“Glazed façades give the design a light and open appearance and provide a view out for the

occupant” (Flodberg, 2012, p. 32). According to Bülow-Hübe (2008), spaces equipped with

glazed façades are experienced as more open where the boundary between outside and

inside almost disappears. Other authors claims (Hendriksen, et al., -) that transparency is

one of the major reason for choosing glazed façades as it has a direct contact to the

surroundings. They also say that from the client point of view a transference in architecture

gives an impression for a transparent organisation work which can also represent company’s

openness.

Disadvantages / solving methods

The biggest problem mentioned in several sources is the need for cooling during the summer

period for the northern climate buildings. According to Poirazis and Blomsterberg (2005),

the energy use for glazed envelope offices is larger, as cooling demand is higher than for

traditional building façade. “Thermal comfort problem will arise when windows are large,

both during summer and winter. In such situations a low U-value is required to solve the

winter problem, and a low g-value together with shading devices will solve the summer

problem” (Bülow-Hübe, 2001, p. 155).

Another method to minimize overheating is described by other researches; their solution is

to integrate external shading system (Haase, et al., 2010). Several shading types are also

studied by Poirazis (Poirazis, 2005) who describes fixed external louvres as a significant

help to the overheating problem. On the other hand, according to Bülow-Hübe (2008),

blinds and louvers drastically decrease daylight level in the room. Her study about façades

with 30%, 60% and 100% glazing concludes that huge glazed façades do not provide a

greater amount of daylight, as DF at 1.5 meters from external wall is similar for 30%

windows and 100% with external fixed louvres.

More problems related to fully glazed façades are highlighted by the Flodberg’s study

(2012) about low-energy office buildings, as she concludes that energy use for lighting is

not always lowered by large glazed areas, because the shading devices are used more often

and glare is frequent. Furthermore, two researchers questioned 1800 office workers in

several office buildings around Denmark and some conclusions were: that the main issue

related to windows was glare, and as glazing area increased, the satisfaction with indoor


19

climate decreased (Christoffersen & Johnsen, 1999). Generally, “highly glazed buildings

should be studied more carefully during the design stage, using a sufficiently advanced

simulation tool…” (Poirazis & Blomsterberg, 2005, p. 952).

2.5 Glazed façades types

Glazed façades are a widely used building envelope solution and “as future energy

regulations aim at reducing energy demand of new buildings, there is a need for improving

the performance of the glazed façades” (Winther, et al., 2010, p. 2).

There are many glazed façade systems available in the Danish market. The main three types

are: single-skin, ventilated window and double skin. The fully glazed façades preserved

from the inside are actually not 100% glazed façades seen from the outside. A window

height to false ceiling is not a total height of the storey, see Figure 2.

Figure 2: Sketches for single-skin façade (left), ventilated window (middle) and double skin façade

(right).

Single-skin façade

Poirazis (2005) in his Ph.D. thesis analysed the single-skin façade systems where one of the

alternatives described was 100% glazed façade. He selected different glazing and shading

properties for windows (g-value and U-value) and as simulations output he looked at the

energy use and indoor climate. Another research project claims that “the choice of glazing

properties such as glazing area, U-value (thermal transmittance) of the glazing and profiles,

g-value (the total solar energy transmittance) of the glazing and type of solar shading is

crucial for the energy and indoor climate performance in an office” (BESTFACADE, 2007,

p. 122).

Therefore, variations of g-value, U-value and external shading devices are included in this

thesis and this study focuses just on the single-skin façade systems, which consist of

external wall and window/curtain wall.

Outside

Floor

Wall

Air

Cav

ity

Air

Inside Inside

False ceiling

Inside


20

2.6 Office building layout

Poirazis in his thesis describes a common office layout that was developed in Scandinavia,

where a combination between cell-type office and open-plan office is revealed. He claims

that common areas are placed in the middle of the building where services, printers, meeting

rooms are located. The typical width of the cell-office is approximately three meters and

depth of five meters. (2005)

According to Treldal, Radish, De Place Hansen and Wittchen (2011), a typical cell office

length is also around five meters and width is two to three meters with floor-to-ceiling

height of 2.7 m. Later on Flodberg (2012) analysed very-low-office buildings in

Scandinavia and concluded that typical office layout consists of an open plan office that has

possibility to be individual office.

The reference project selected for thesis was fulfilling all the mentioned typical office

characteristics.


21

3 Methodology

There are several methods for studying the thermal and visual comforts, the building

envelope quality, the LCC or the annual energy use in buildings. One of the methods is

selecting a reference building and creating the study case (later called BC).

Figure 3: The process plan for the thesis.

For the thesis the ongoing project called ‘Health Centre’ is used as a reference building. It is

simplified in order to represent a modern Danish office building. The common areas were

located on the ground floor, while cell offices and landscape offices were located on the

other floors. Office layout was designed after the Working Environment guidelines in

Denmark (Videncenter for Arbejdsmiljø, 2016).

Later on, the BC analyses with the selected inputs were performed called parametric studies.

The schematic process plan for this study is show in Figure 3.

Generally, this chapter presents the modelling of the BC where climate, geometry, layout,

building components and technical inputs are described. The DGNB certification schemes,


22

computer programs used for this study and parametric study plans are described in this

chapter.

3.1 Computer simulation tools

LCCbyg programs are calculating LCC with values embedded into the program (prices for

building components, prices for maintenance and replacement, cleaning and other data) that

meets the Danish Standards. Several alternatives can be calculated in the same program

where the present values, 50 years LCC and other data are the outputs. (Statens

Byggeforskningsinstitut, 2016) LCC calculations were achieved using LCCbyg and

following ISO 15686 Service Life Planning standards, while the requirement from the

DGNB certification system was to use their own LCC-tool.

Bsim is a dynamic building simulation program used in Denmark for a thermal indoor

comfort, energy use, daylight conditions, surface temperatures, etc. (Statens

Byggeforskningsinstitut , 2013). In the context of this thesis, the thermal comfort and

window surface temperature analysis was performed using Bsim program for winter and

summer periods. The embedded U-value calculations for windows were also used in the

thesis.

Grasshopper with a plug-in called DIVA is a graphical algorithm editor that uses Rhino 3D

modelling tools, while DIVA plug-in is calculating daylight, solar radiation, etc. (Davidson,

2016a). The visual comfort analysis required by DGNB certification scheme was made

using this program. Here the daylight levels in the office rooms and on the working planes

were studied.

DIVA-for-Rhino is a program for daylight, solar radiation and glare simulations (Davidson,

2016b). For this thesis, the glare analysis was performed using this program.

Rockwool Energy Design tool is used for energy calculations that are adapted to SBi-213

guidelines. The program is free of charge and can be used online. The U-value calculations

for building components are also a part of it. (ROCKWOOL A/S , 2016) The U-value for

the external wall was calculated in this program.

Be15 is an updated Be10 program and is required to be used by the DGNB certification

system for energy use calculations. The Be15 is established by Statens

Byggeforskningsinstitut (SBi) for calculating energy use that is required by the Danish

energy regulations (Statens Byggeforskningsinstitut, 2016a). The energy use for cases

analysed was calculated using this program.

3.2 Modelling Base Case – Health Centre

The building is an outline level project that is located in Peter Bangs Vej in Frederiksberg,

Copenhagen municipality. It is designed to be 2985 m² office building divided into four

floors. A fully glazed façade is the main requirement. Ground floor do not have any external

shading, while 1st to 3th floor is equipped with the secondary skin made of wood and metal

plates creating print and working as shading. It is simplified to be just a vertical-fixed


23

shading louvres as shown in Figure 4. The secondary screen (further called fixed external

shading) was 50% opened or had 50% transmittance.

Figure 4: The cell office façade without external shading (left), an original construction for fixed

external shading (middle) and simplified shading construction for simulations (right).

Climate, orientation and surrounding conditions

The BC project is formed as an L-shape office building facing north and east on the long

sides. It is placed between existing buildings, see Figure 5, though surrounding buildings

were neglected in further analyses.

The building is located in Copenhagen municipality and the weather data used for

simulations was DRY (Statens Byggeforskningsinstitut, 2016b) and

DNK_Copenhagen.061800_IWEC (EnergyPlus, 2016) for visual comfort analyses.

Figure 5: Building shape and surrounding buildings’ layout for location with sun path.

Reference

building

Existing

buildings

Existing

buildings

Backyard

Pedestrian paths / Road

http://cafeg.dk/


24

Geometry and layout

The building layout is simplified for this study where the main functions are: canteen,

conference, café, cell-offices, landscape offices, meeting room and technical core with

stairs, toilets and shafts, see Figure 6.

Figure 6: Simplified ground floor plan (top left) and the original layout (top right). 1st to 3rd floor

the simplified plan (bottom left) and the original layout (bottom right).

Zones used in simulations and calculations are presented in Table 5. A total room height

was assumed to be 2.75 m, while for the thermal and energy use simulations where the

whole building envelope must be included the total floor height of 3.73 m was used, see

Figure 7. This fully glazed façade was preserved from the interior side. The exterior side of

the façade was equipped with 77% glazed areas and the remaining 23% was an external

wall.

Cell office

Cell o

ffice

Landscape

office

MR

Café Conference

Canteen

MR

Landscape

office

MR

http://cafeg.dk/http://cafeg.dk/http://cafeg.dk/


25

Table 5: Zones in the building used for simulations/calculations.

Zone name

Area per zone /

m²

Amount

per floor

Total

area / m²

Building level

Canteen 231.3 1 231.3 Ground floor

Conference 139.1 1 139.1 Ground floor

Café 296.9 1 296.9 Ground floor

Stairs/elevator 154.4 1 154.4 Ground floor – 3rd floor

Toilets 4.3 8 129.9 Ground floor – 3rd floor

Installation

shafts -

- 37.0 Ground floor – 3rd floor

Cell offices 13.6 22 896.8 1st floor – 3rd floor

Landscape

office /corridors 163.2 2 979.4

1st floor – 3rd floor

Meeting room:

Type 1

Type 2

Type 3

18

10.1

12.9

1 each

type 121.9

1st floor – 3rd floor

Figure 7: The office section with floor height for thermal and energy simulations (left) and floor

height for visual comfort simulations (right).

Façade description

The fully glazed façade design was created with one window divided into two parts, as

shown in Figure 7, where the top window was operable for ventilation and cleaning reasons.

A triple glazed window with argon gas between panes were selected.

The structural system was designed with columns and flat-slab floors. The BC façades were

not a load-bearing construction.


26

he analysed office types were a cell office and a landscape office. The cell offices were

facing east and north, while the landscape offices were facing south and west. The cell

office was designed for one person with 11.6 m² heated floor area, see Figure 8. Internal

walls had a 150 mm thickness (25 mm gypsum boards, 100 mm studs and insulation, 25 mm

gypsum boards). A light weight external wall of 432 mm and 325 mm floor deck (250 mm

concrete, 75 mm studs with wooden flooring) were assumed to be the general construction

elements.

The landscape office was designed for 12 persons divided into two groups of six people.

The room was 83.1 m² and had one external wall. Other walls were interior and the one

parallel to external wall was made of interior glass. The layout is shown in Figure 9.

Figure 9: The landscape office layout facing south.

Description of building elements

The BC window was triple glazed window that was available in the Danish building market.

The glass properties were taken from Glass 2015 brochure (Pilkington, 2015) and the

window frame property was selected from Bsim program Data Base (Statens

Byggeforskningsinstitut, 2016b). This data is presented in Table 6, where the U-values,

Light Transmittance through the glass (LT) -value, g-value and frame area/thickness are

included.

Façade

Sh

elv

es

Sh

elv

es

Sh

elv

es

Figure 8: The cell office layout facing east.

Faç

ade


27

Table 6: The studied window properties.

Name

U-value

glass /

(W/(m²·K))

U-value

frame /

(W/(m²·K))

Min. temp.

(-10/+20) /

°C

LT-value

/ %

g-value

/ %

Frame

area /

%

Frame

size /

mm

Façade

window 0.5 1.55 18 72 51 23 130

The BC building fulfilled the DGNB building envelope quality scheme requirements. The

selected and assumed values are presented in Table 7. They were integrated in the energy

use and indoor climate simulations.

Table 7: The building envelope design properties description.

Category name and their parameters Used for project

U-value of:

Ceiling and roof

External wall

Ground floor

Window

0.08 W/(m²·K)

0.1 W/(m²·K)

0.08 W/(m²·K)

0.8 W/(m²·K)

Total thermal transmission of building

envelope over three floors

5.5 W/m² was assumed to be achieved

Thermal bridge between:

Window and external wall

External wall and foundation

0.03 W/(m·K)

0.13 W/(m·K)

Moisture safety Common construction elements were used with

damp-roof layer in external walls. Moisture safe

construction was also selected for roof and

ground floor components.

Infiltration at 50 Pa Well-designed details and good workmanship was

assumed for this project. In that case required 0.5

l/(s·m²) infiltration level was used.

Window frame and inner window

surface temperature in the external wall

Fulfil requirements as the supplier documents not

lower than 15 °C temperature for window.

Input data for energy use and thermal comfort simulations

The BC input data for simulations was assumed, as the project was in an outline level. The

inputs used for occupancy, internal loads and HVAC system are presented in this chapter.

The energy use data inputs are presented in Appendix A.

Occupancy

The building was occupied five days per week from 8:00 to 17:00 and closed on weekends

and during holidays (week 7, 28-30, 42, 51-52). Everyday occupancy for each zone in the

building is presented in Table 8. The occupancy factor 4 was not used in the thesis, as the

4 ”The occupancy factor is defined as the actual number of occupied rooms, divided by the total number of rooms… An

occupancy factor of 0.7 in the simulation model spreads out the internal gains evenly.” (Flodberg, 2012, pp. 57-59)


28

fully glazed building was analysed for the worst case scenario which occurred during

summer with the maximum occupancy levels. Some zones did not have any occupancy as

they were used for shorter time than one hour at the time.

The thermal comfort analyses were divided into two periods: summer (week 19-44) and

winter (week 45-18), as the DGNB certification required.

Table 8: Occupancy schedule for all zones in the building.

HVAC systems and RES

The BC was assumed to be a low-polluted building with the VAV ventilation system, which

had a minimum inlet temperature of 18 °C and a maximum of 30 °C. CO2 sensors were

located in the cell and landscape offices. Heat recovery efficiency was assumed to be 80%

with 1.5 kJ/m³ SFP. The pressure drop for the air supply system was 1000 Pa and for the

exhaust 500 Pa.

Different ventilation rates were selected for each building zone. The occupancy ventilation

rate was assigned to all building functions, but in further simulations design maximum total

ventilation rate was used instead. That means some functions were assumed to have design

ventilation rate based on needed air changes in rooms such as: cell offices with six air

changes per hour, landscape offices with four air changes per hour and meeting rooms with

six air changes per hour. The selected data is presented in Table 9.

Zone type Area / m² Occupants

number

per zone /

people

Total

occupant

number in

the building /

people

Occupancy

time

Zone

occupancy

time (working

hours) / %

Canteen 231.3 120 120 11:30-13:00 19

Conference 139.1 120 120 8:00-17:00 23

Café 296.9 120 120 10:00-18:00 75

Cell offices 896.8 1 66

8:00-12:00

13:00-17:00 88

Landscape office 979.4 12 72

8:00-12:00

13:00-17:00 88

Meeting room 121.9 4 to 8 42

10:00-12:00

14:00-16:00 30

Toilets 129.9 - - 8:00-17:00 100

Stairs/elevator 154.4 - - 8:00-17:00 100

Installation shafts 37 - - 8:00-17:00 100


29

Table 9: The ventilation rates for the BC building zones.

The RES was integrated in energy use calculations where 150 m² of solar cells were used.

They provided 22.5 kWp with ten degrees’ tilt toward south.

Set-points

The heating and cooling design temperatures are presented in Table 10. Heating power level

for the BC was 50 W/m². District heating system (45-55 °C) with convectors was used.

DHW was selected to be 100 l/m² per year (Statens Byggeforskningsinstitut, 2014).

Table 10: Set-point for heating, cooling and the DGNB platinum level requirements.

Internal loads

An equipment load was selected for two office rooms: cell and landscape. These two types

of zones had different inputs, as they were further analysed in the thesis. This input data was

used for all thermal comfort simulations and is presented in Table 11.

The energy use simulations were performed with standard internal loads according to SBi -

guidelines 213 (Statens Byggeforskningsinstitut, 2014), which were: 4 W/m² for person load

and 6 W/m² for lighting load.

5 Information selected from DS/EN 15251 (Danish Standard Association, 2007) 6 Information selected from SBi- guidelines 213 (Statens Byggeforskningsinstitut, 2014) 7 Information selected from SBi - guidelines 213 (Statens Byggeforskningsinstitut, 2014) 8 According to DK-GBC (2015) operative temperature is equal to room middle point value.

Zone name Occupancy

ventilation

rate

Building

ventilation

rate (low

polluted) 5

Design

max. total

ventilation

rate

Summer day

natural

ventilation6

Summer

night

natural

ventilation 7

l/s per m² l/s per m² l/s per m² l/s per m² l/s per m²

Canteen 5.2 1 5.2 1.2 none

Conference 8.6 1 8.6 1.2 none

Café 4.1 1 4.1 1.2 none

Stairs/elevator 0.0 1 1.0 none none

Toilets 4.1 none 4.1 none none

Installation shafts none none none none none

Cell offices 0.5 1 4.6 1.2 0.6

Landscape

office/corridors

0.8 1 3.1 1.2 0.6

Meeting room 3.2 1 4.6 1.2 0.6

Name of system Set – point DGNB platinum level

Heating 20 °C 21 °C ≤ Operative temperature8 ≤ 25.5 °C

Cooling 25 °C Operative temperature ≤ 25.5 °C


30

Table 11: The input data for internal loads for cell and landscape offices that was used in the

thermal comfort simulations.

The lighting levels in the working rooms were 200 lux and 100 lux in toilets, while the rest

was 50 lux, as required by DS 700 (Danish Standard Association, 2005). The general

lighting colour rendering was assumed to be 0.95.

Natural ventilation

As mentioned before, the façade window was divided into two where the top window was

operable. This window was used for natural ventilation. According to SBi – guidelines 213

(Statens Byggeforskningsinstitut, 2014), the opening must be 1.5% of the heated floor area

in order to have natural ventilation around three air changes per hour or 1.2 l/s per m². This

was achieved with the manual natural ventilation controlled by occupants opening the

windows when the operative temperature got over 25 °C. The calculated opening for cell

office was 0.2 m², which was achieved with the ten degrees’ maximum window opening

angle, as shown is Figure 10. The landscape office needed 1.36 m² opening, which was

divided by four windows, as the façade for this room was equipped with this number. In this

case, each top window opening area was calculated to be 0.34 m² that was achieved by the

16 degrees’ window opening angle.

Figure 10: The natural ventilation opening angle definition highlighted with black.

Cell office Landscape office

11.6 m² 83.1 m²

Equipment load schedule

08:00-12:00 and 13:00-17:00

12:00-13:00

100%

70%

Equipment load schedule

08:00-12:00 and 13:00-17:00

12:00-13:00

100%

70%

1 pc 40 W 12 pc 480 W

1 pc screen 17'' 40 W 12 pc screen 17'' 480 W

Occupancy load schedule

08:00-12:00 and 13:00-17:00

12:00-13:00

100%

0%

Occupancy load schedule

08:00-12:00 and 13:00-17:00

12:00-13:00

100%

0%

1 person 100 W 12 persons 1200 W

Lighting load schedule

08:00-17:00

100%

Lighting load schedule

08:00-17:00

100%

Task lamp 0.5 W/m² Task lamps 0.5 W/m²

General lighting 4 W/m² General lighting 4 W/m²

Total internal loads 17.71 W/m² Total internal loads 28.37 W/m²


31

Natural ventilation during the night was possible only in cell offices, landscape offices and

meeting room because they were located on the 1st to 3rd floor, where it was burglary safe.

According to SBi – guidelines 213 (Statens Byggeforskningsinstitut, 2014), the manual

night ventilation levels are one or two air changes per hour or 0.6 l/s per m².

The office occupants were leaving windows opened when they experienced the indoor

climate as too warm (over 25 °C). During unoccupied hours, natural ventilation in zones

was assumed to be the infiltration. The infiltration level during opening hours (1) and other

hours (2) was calculated with formulas stated in SBi-213 guidelines (Statens

Byggeforskningsinstitut, 2014):

0.04 + 0.06 × infiltration at 50 Pa [l/(s·m²)] (1)

0.06 × infiltration at 50 Pa [l/(s·m²)] (2)

The infiltration at 50 Pa was assumed to be 0.5 l/(s·m²). The calculated infiltration for

opening hours was 0.07 l/(s·m²) and the rest - 0.03 l/(s·m²).

External shading

The two types of external shading were selected for this study. The vertical-fixed louvers

with different distances were assumed to create 50%, 60% and 80% transmittance for solar

heat and light. The second type was external screen with 20% and 30% transmittance which

did not disturb the view out when it was used. Screens had three control systems: on/off, 1 –

½ - 0 and continuous. The screen with the first control system could be a fully closed or a

fully opened. The screen with the second system could be fully closed, a half opened/closed

or a fully opened. The last control system was adapting to the indoor daylight conditions.

Input data for visual comfort simulations

The daylight level simulations were performed with five bounces for reflections as programs

use Radiance. The nodes were placed at 0.85 m height (working plane) and grid size was

0.2 m by 0.2 m. The reflectance for office rooms surfaces and transmittance for windows

were selected from the available choices in the Grasshopper/DIVA plug-in in Rhino, see

Table 12.


32

Table 12: The input data for reflectance and transmittance of the surfaces and components in

DIVA.

The work plane analyses were performed for four selected offices. The average DF for

working planes was calculated by adding average DF for each working plane and dividing it

by 12 tables (landscape office) located in different rows, see Figure 11. Row 1 with four

tables was located 0.5 m from the façade windows and the other two rows were placed

toward the inner side of the room, as shown in Figure 11.

9 The default materials’ data (Solemma, 2016).

Surface name DIVA grasshopper material names 9 Reflectance / %

Transmittance

/ %

Wall GenericInteriorWall_50 50 -

Ceiling GenericCeiling_70 70 -

BC Window

LT-value 72%

Glazing_DoublePane_Clear_80 - 80

Window

LT-value 67%

Glazing_DoublePane_LowE_65 - 65

Window

LT-value 65%

Glazing_DoublePane_LowE_Argon_65 - 65

Window

LT-value 60%

Glazing_Electrochromic_Clear_60 - 60

Window

LT-value 47%

Glazing_TriplePane_Krypton_47 - 47

Frame GenericFloor_20 20 -

Floors GenericFloor_20 20 -

Fixed shading OutsideFaçade_35 35 -

Screen EC_Tinted_30 - 30

Tables GenericFloor_20 20 -

Chair GenericFurniture_50 50 -

Surrounding

buildings

UotsideFaçade_30 30 -

Interior glass GlazingSinglePannel_88 - 88

Fixed shading OutsideFaçade_35 35 -

PC screen GenericCeiling_80 80 -

Figure 11: The landscape office floor plan with table layout and row numbers starting from the facade.

Façade

1

2

3

2

1

3


33

The average DF for a working plane in cell offices was performed for one working table

equipped with a computer, which was placed 0.5 m from the glazed façade.

The fixed shading devices were investigated, as they influenced the visual comfort in the

offices: lowered daylight access to the room and working tables, influenced the glare issue

as well as created contrasts. Annual glare analyses were performed for the worst case view

for each office room, when person sitting perpendicularly to façade with the view to the

window and computer, as shown in Figure 12.

The point-in-time glare analyses were created after the annual glare studies. The worst cases

were selected for the point-in-time glare analyses and were: 14th of April at 09:00 for cell

offices and 21st of September at 15:00 for landscape offices. These analyses were performed

for the offices facing east, west and south and they were expressed in Daylight Glare

Probability (DGP). For the best glare control class DGP should be ≤ 35% and annual glare

not exceeding 5% for 95% of working hours (Wienold, -).

Certification schemes analyses

The selected four DGNB certification schemes out of the 41 available were assumed to be

mainly related to the fully glazed façade designs: thermal and visual comforts, building

envelope quality and the LCC. Each of the schemes had requirements that are presented in

chapter 2.2.2, but the analyses performed for each scheme during this study were:

For the thermal comfort, operative temperatures in the middle of the room as well as surfaces and window temperatures were investigated.

For the visual comfort, DF for half of the heated floor area, DF for working plane and daylight glare analyses were the parameters investigated.

For the building envelope, quality U-values for windows and external wall were investigated.

For LCC the 50 years’ calculations were performed for façade with different glass, U-values for glass and façade with different shading devices.

Figure 12: The 1st floor plan with working Table and view angle for glare analyses shown with

arrows.


34

3.3 Parametric study

This chapter presents parametric study plans for the selected four offices. Several design

strategies, properties of the glass and windows, as well as external shadings were checked.

Base Case

The parametric study was focused on analysing cell offices and landscape offices. Selected

ones were: cell office facing east (CS) and north (CN), landscape office facing west (LW)

and south (LS), which are highlighted in Figure 13.

The analysis starting point was creating the BC for each office. The selected offices were

placed on the 2nd floor and had one external wall, while other walls were internal and

assumed to be adiabatic for simulations. The floor decks were adiabatic as well. Other input

data used for the parametric studies is presented in the previous chapter.

After the BC office layouts were created, analysis for the thermal comfort started. The

analysis process (the parametric studies plan) is presented in Figure 14. Here some of the

design strategies (natural ventilation and external shading) were selected for the first

parametric study part. Each strategy was simulated separately and in the order, as presented

in Table 13. The second parametric study part was performed with the Selected Case (SC)

where more realistic U-value of the glass 0.6 W/(m²·K) was selected, see Figure 14. The

same parametric study was performed for all four offices.

The outputs for thermal comfort were: the operative temperature, floors, ceiling and window

inner surface temperatures. These outputs were divided into two calculation periods, as

required by the DGNB certification system. The summer and winter periods covered the

whole year.

Figure 13: The 2nd floor plan with highlighted analyses office rooms.

CE

CN

LS

LW


35

Figure 14: Parametric study plan for the thermal comfort.

Table 13: The simulations order with selected design strategies for the parametric study.

BC Base Case

II BC + Natural ventilation day

III BC + Natural ventilation day + night

IV BC + Fixed external shading 50% opened (as outline project required)

V BC + Fixed external shading 50% opened + Natural ventilation day

VI BC + Fixed external shading 50% opened + Natural ventilation day + night

Furthermore, the visual comfort parametric plan was created, as shown in Figure 15. The

separate properties study for glass g-value was needed as it was impossible to find the triple

glazed window with Light Transmittance (LT)-value of 80% (selected for BC). That led to

an Analysis Case (AC) where the window glass had LT-value of 65%. This case was used in

further external shading and working planes analyses (just for landscape offices). Outputs

for the whole parametric study were: DF for half of the floor counting from wall with

window(-s), DF for working planes, the annual glare from worker point of view facing the

computer screen and the window, and the point-in-time glare for some cases.


36

Figure 15: Parametric study plan for the visual comfort.

The Final Case (FC) for each office room was created after all simulations were performed

in order to find out what DGNB certification final check list point score was.

Finally, the BC for the whole building’s annual energy use was created. The same

parametric plan as for the thermal comfort was used, as shown in Figure 14, but the outputs

for these analyses were: the building’s annual energy use, heating /cooling demands and

DHW that were targeting BC2020 requirements.

Single-skin façade

Selected alternatives for the glazed façade were focused on fulfilling requirements: the low

window U-value, the highest total glass transmittance and a neutral colour of the glass. Five

alternative windows were selected for investigation, as indicated in Table 14. No external

shading was used for the BC simulations. But the external shading devices: fixed

wooden/copper plates located 500 mm from façade and rolling screens were selected

options in the further analyses.


37

Table 14: Chosen glass properties used for the parametric studies that were selected from the

Pilkington Glass brochure (Pilkington, 2015).

Nr. Triple glass components Ug-value10 /

(W/(m²·K))

LT-value

/ %

g-value /

%

Colour

rendering

/ %

1 411EC12-16Ar13–4NG14-16Ar–4EC 0.6 72 51 96

2 SC154EC-16Ar–4NG-16Ar–4EC 0.6 67 46 96

3 6SCW16-16Ar-4NG-16Ar-4EC 0.6 65 40 96

4 6SC-16Ar-4NG-16Ar-4EG 0.6 60 35 95

5 6SCN17-16Ar-4 NG -16Ar-4EG 0.6 47 31 95

3.4 Life Cycle Cost

50 years LCC expressed in a present value was calculated for several fully glazed façades,

where materials, replacements, maintenance and cleaning costs were included. The first

analysis part was the façade alternatives where the glass U-values and self-cleaning glass

types were checked and compared with a standard façade.

The two types of façades gave the overview related to a transparent architecture and a

concrete one, as the standard façade was assumed to be concrete sandwich elements that

fulfilled the building’s envelope requirements. It had a 20% Glass to Wall Ration (GTW),

windows with the glass U-value of 0.6 W/(m²·K) and no external shading. These façade

alternatives are presented in Table 15. The short alternative name was used in the result

section.

Table 15: Façade alternative names and descriptions for glass properties study.

Next step was calculating LCC for the façade alternatives with different external shadings,

as presented in Table 16.

10 U-value for the glass 11 Thickness of the glass in mm 12 Energy-efficient soft low-e Coated Glass (EC) – “Low-emissivity glass (or low-e glass as it is commonly referred to) is a

type of energy-efficient glass designed to prevent heat escaping through your windows to the cold outdoors.” (Pilkington, 2016, p. 1) 13 Argon gas fill between glass layers consists of 90% of Argon. (Pilkington, 2015, p. 74) 14 Clear glass or ‘normal’ glass with U-value 5,8 W/m²·K, LT-value 90 %, g-value 87 % (Pilkington, 2015, p. 15) 15 Self-cleaning glass with titadioxide (Pilkington, 2015, p. 50) 16 Solar control glass with transparent coating (Pilkington, 2015, p. 29) 17 Solar control and energy glass with low emissivity coating that is transparent from inside and preserved as reflective and

with some color from outside (Pilkington, 2015, p. 26)

Alternative name Façade description

Façade 1 Façade with glass U-value of 0.5 W/(m²·K)

Façade 2 Façade with glass U-value of 0.6 W/(m²·K)

Façade 3 Façade with glass U-value of 0.6 W/(m²·K) and self-cleaning glass

Standard façade Façade with 20% windows (glass U-value of 0.6 W/(m²·K)) and 80%

prefabricated concrete elements


38

Table 16: Façade alternatives names and descriptions for external shading study.

Areas used in calculations are presented in Table 17. The external wall part in BC

calculation was excluded.

Table 17: Areas input for LCC calculations.

Construction name Area / m²

External wall for Standard façade 1284

Windows for BC 1605

Windows for Standard façade 321

The input for price calculations is presented in Table 18 and are based on the DGNB LCC

scheme requirements.

Table 18: Input data for LCC calculations in LCCbyg program.

General real price change 2.0%

Energy real price change 4.0%

Discount rate 5.5%

The input data for calculations is presented in Table 19 and Table 20 and was collected from

LCCbyg programs that had embedded data that fulfilled the Danish standards and the

DGNB certification requirements (Statens Byggeforskningsinstitut, 2016). The maintenance

factor presents how many times during one-year period component needs to be maintained

(1 – one time per year, 0.5 – every half a year, etc.). The price for the components after their

life time is expressed in percentage of the initial price at the present value.

Table 19: Input data for construction components.

Construction component

name

Price DKK /

m²

Life time

/ years

Maintenance

factor per

year

Changing price

after life time /

%

Window with glass

U-value 0.6 W/(m²·K)

2435 50 0.5 125

Window with glass

U-value 0.5 W/(m²·K)

2635 50 1 125

Window with self-

cleaning glass

2635 50 1 125

Concrete elements 2800 120 1 125

Fixed external shading 1000 25 2 125

External screen 700 40 0.5 125

Alternative name Façade description

Façade A Façade with glass U-value 0.6 + fixed shading

Façade B Façade with glass U-value 0.6 + screen shading

Façade C Façade with glass U-value 0.6 and self-cleaning glass + fixed shading

Façade D Façade with glass U-value 0.6 and self-cleaning glass + screen

shading


39

Table 20: Input data for maintenance of construction components.

Maintenance of component Worker price

DKK / m²

Working

amount / (m²/h)

Maintenance

factor per year

Window with an easy cleaning

access

405 25 2

Window with a moderate cleaning

access (fixed solar shading in front

of window)

405 13 2

Window with a self-cleaning glass 405 25 0.25

Concrete elements

Fixed external shading 348 3 0.25

External screen 348 3 0.1


40

4 Results

This chapter presents the results of the parametric studies, where the outputs were: the

thermal comfort, visual comfort, building envelope design, LCC and the annual energy use.

The starting point was each office BC studies that did not meet all the requirements for

DGNB schemes and the energy usage of the BC2020.

The further parametric studies were focused on the natural ventilation and the external

shading integration for the fully glazed façades. These strategies improved the thermal

comfort but created some visual comfort problems. That led to the detailed glazed façade

properties analyses, where the glass g-values and U-values, the frame areas and another

external shading were studied. All parametric studies created the FC for each office, which

received the DGNB platinum level for some studied schemes, which are revealed in the

following sections. It also resulted in the energy use that reached the BC2020 requirements.

4.1 Base Case

This section reveals results for the BCs, which are used as the starting point in the further

analysis, as they did not meet the DGNB platinum level requirements and the BC2020

energy use.

Thermal comfort

The BC building thermal comfort was investigated by integrating some of the design

strategies: the natural ventilation and the external shading. The main focus was on the

operative and surface temperatures.

BC operative and surfaces temperatures

The operative temperature results for office rooms were expressed in hours above 25.5 °C

during a summer period and during winter in hours below 21 °C and over 25 °C. The

surface temperature for the floors and ceiling were simulated for summer period and

windows inner side surface temperature were investigated for both periods, as required by

the DGNB thermal comfort scheme.

The BC operative temperatures for the four offices studied are presented in Figure 16. All

offices exceeded the summer period requirement and the east facing office was the worst

case. The cell office facing north and the landscape office facing west met the winter period

requirements, but the other two exceeded the limits. Generally, the summer period was a

dominating one, as all the offices had many overheating hours. This resulted in the fact that

none of the cases received the DGNB top score for both periods.


41

Figure 16: Amount of the exceeded operative temperature hours for BC of offices studied

(summer and winter periods). The DGNB top score requirement is also included.

Minimum and maximum surface temperatures during the whole year are presented in Figure

17. None of the cases exceeded the required maximum ceiling and window surface

temperature for both periods. But the maximum floor surface temperature was an issue for

all offices except the cell office facing north. This office fulfilled all the DGNB top score

requirements for the surface temperatures.

On the other hand, the landscape office facing west had lower than required minimum

window surface temperature and did not receive any of the DGNB check list points. The

offices facing east and south did not fulfil the requirements either.

63

358

184154

1760

128

48

0

100

200

300

400

BC - CN BC - CE BC - LS BC - LW

Num

ber

of

ho

urs

Studied cases

21 °C ≥ Operative temperature ≥ 25.5 °C (summer period)

21 °C ≥ Operative temperature ≥ 25 °C (winter period)DGNB platinum (50 hours)

BC - CN Cell office facing north

BC - CE Cell office facing east

BC - LS Landscape office facing south

BC - LW Landscape office facing west

0

5

10

15

20

25

30

35

40

Max. floor

temp.

(summer

period)

Max.

ceiling

temp.

(summer

period)

Min.

window

temp.

(summer

period)

Min.

window

temp.

(winter

period)

Max.

window

temp.

(summer

period)

Max.

window

temp.

(winter

period)

Surf

ace

tem

per

ature

s /

°C

BC - CNBC - CEBC - LSBC - LW

Max. ceiling / window

Max. floor

Min. window

Figure 17: Four analysed offices surface temperatures for floors, ceilings and windows during

summer and winter periods. The DGNB top score requirements are highlighted.


42

Visual comfort

The BC building visual comfort was analysed using the values described in the

methodology chapter. The main focus was on daylight access to the room that was

expressed with DF for 50% of the heated floor area and DF for the work plane, see Figure

18. All offices had a high DF that could lead to the glare problems (DF over 5%). But the

cell offices work plane DF was t

fully glazed office building facade designs in denmark · and life cycle costing (lcc) solutions...

Documents