FULLY GLAZED OFFICE BUILDING FACADE DESIGNS IN DENMARK

Transcription

1 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 Buildings Faculty of Engineering Lund University

2 Lund University Lund University, with eight faculties and a number of research centers and specialized institutes, 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 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 employees and students attending 280 degree programs and subject courses offered by 63 departments. Master Program in Energy-efficient and Environmental Building Design This 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 architecture 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

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 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. 3

4 Table of contents Fully Glazed Office Building Facade Designs in Denmark Abstract... 3 Preface... 7 Terminology / Notations... 8 Abbreviations 8 Mathematical notation 8 1 Introduction Background and problem motivation Aim and hypothesis Limitations 10 2 Literature review Office building energy use in Denmark 11 Regulations 11 Building Class 2020 or Nearly Zero Energy Building 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 Design strategies for low-energy offices Fully glazed office building 18 Advantages 18 Disadvantages / solving methods Glazed façades types 19 Single-skin façade Office building layout 20 3 Methodology Computer simulation tools 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 Parametric study 34 Base Case 34 Single-skin façade 36 4

5 3.4 Life Cycle Cost 37 4 Results Base Case 40 Thermal comfort 40 Visual comfort 42 Envelope quality 43 Energy use for the Base Case building 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 DGNB certification score for Base Cases and Final Cases 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 Life Cycle Cost 66 LCC for glass variations 67 LCC for façades with external shadings and self-cleaning glass 67 5 Discussions Conclusions Summary References Appendix A Appendix B 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 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 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 5

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 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 6

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. 7

8 Terminology / Notations Fully Glazed Office Building Facade Designs in Denmark Abbreviations AC BC Analysis Case. Base Case. BC2020 Danish Building Class BR15 Building Regulations DF DGNB Daylight Factor. The German Sustainable Building Council (Deutsche Gesellschaft für Nachhaltiges Bauen). DHW DK-GBC DGP DRY FC GWR LCC LT Domestic Hot Water. Green Building Council Denmark. Daylight Glare Probability. Danish Reference Year. Final Case. Glass to wall ratio. Life Cycle Cost. Light Transmittance through the glass. NZEB 2020 Nearly Zero Energy Buildings RES SfB Renewable Energy Source. Together working group for building issues (Samarbetskomitén för Byggnadsfrågor). SC SFP VAV PV Selected Case. Specific Fan Power. Variable Air Volume. Photovoltaics. Mathematical notation g Solar protection factor. R U Thermal resistance (m² K/W) Thermal conductance (W/m 2 K) Thermal conductivity (W/m K) 8

9 Social Environmental Economic Fully Glazed Office Building Facade Designs in Denmark 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 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 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. Sustainability Figure 1: Sustainability three-pillar concept. 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 9

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. 10

11 2 Literature review Fully Glazed Office Building Facade Designs in Denmark 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 At the same time the electricity use increased from 100 kwh/m² in 1975 to over 150 kwh/m² in 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), energyefficiency of buildings has already progressed, as the primary energy use was lowered by 26.3% from 1990 to 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 costefficiency. 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) 11

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 CO 2 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 12

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 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 DKK/m². Table 1: The LCC requirements according the DGNB certification Manual for Office Buildings. Calculation period Life time phases Pricing Included calculations Real price change for different groups 50 years Production, application Building pricing according to Together working group for building issues (SfB) system Replacement prices after lifetime Maintenance prices Energy supply pricing Cleaning prices Total energy use Water need Cleaning areas 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 Calculations and documentation Present value prices for: Initial building prices Maintenance and replacement prices Supply prices Cleaning prices DGNB-DK software (LCC-værktøj 1 ) with areas definition and pricing for building components. 1 The LCC-tool developed for the DGNB certification system (Green Building Council Denmark, 2015). 13

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. Winter period (1. November till 30. April) Operative temperature 2 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 l/s, m². 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. DGNB check list points Summer period (1. May till 31. October) 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 l/s, m². 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. 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. 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. DGNB check list points Requirements according to DS/EN 15251:2007 (Danish Standard Association, 2007). 3 Requirements according to EN ISO 7730:2005 (European Standards, 2005). 14

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 Daylight factor (DF) 3.0% 16 envelope towards inside 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 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 16 glare when is used 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 10 lighting. Electric lighting colour rendering (Ra) Ra 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). 15

16 Table 4: U-values and thermal bridging requirements for building components Category name and their parameters U-value of: Ceiling and roof External wall Ground floor and basement floor Window / Roof window Category name and their parameters 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)) Thermal bridges between: Window and external wall Skylights and roof External wall and foundation Moisture safety Infiltration at 50 Pa Window frame and inner window surface temperature in the external wall Requirements 0.1 W/(m² K) 0.15 W/(m² K) 0.1 W/(m² K) 1.0/1.2 W/(m² K) Requirements 5.5 W/m² 0.03 W/(m K) 0.10 W/(m K) 0.13 W/(m K) 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 Should be documented with blow door test and value must not exceed 0.5 l/(s m²) Not lower than 15 C Check list points 30 Check list points 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 16

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. 17

18 The sources mentioned in this chapter describe several design strategies that lead to lowenergy 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 18

19 Cavity Fully Glazed Office Building Facade Designs in Denmark 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. Outside False ceiling Air Inside Inside Inside Air Wall Floor 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. 19

20 2.6 Office building layout Fully Glazed Office Building Facade Designs in Denmark 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. 20

21 3 Methodology Fully Glazed Office Building Facade Designs in Denmark 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, 21

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 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 1 st to 3 th 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 22

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 _IWEC (EnergyPlus, 2016) for visual comfort analyses. Pedestrian paths / Road Existing buildings Reference building Backyard Existing buildings Figure 5: Building shape and surrounding buildings layout for location with sun path. 23

24 Cell office Geometry and layout Fully Glazed Office Building Facade Designs in Denmark 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. Café Conference Canteen Cell office MR MR Landscape office Landscape office MR Figure 6: Simplified ground floor plan (top left) and the original layout (top right). 1 st to 3 rd 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. 24

25 Table 5: Zones in the building used for simulations/calculations. Area per zone / m² Amount per floor Total area / m² Building level Zone name Canteen Ground floor Conference Ground floor Café Ground floor Stairs/elevator Ground floor 3 rd floor Toilets Ground floor 3 rd floor Installation Ground floor 3 rd floor shafts - Cell offices st floor 3 rd floor Landscape floor 3 rd floor office /corridors Meeting room: 1 st floor 3 rd floor Type each Type type Type 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. 25

26 Shelves Shelves Shelves Façade Fully Glazed Office Building Facade Designs in Denmark 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. Figure 8: The cell office layout facing east. 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: Façade 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. 26

27 Table 6: Name Façade window The studied window properties. 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 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 U-value of: Ceiling and roof External wall Ground floor Window Total thermal transmission of building envelope over three floors Thermal bridge between: Window and external wall External wall and foundation Moisture safety Infiltration at 50 Pa Window frame and inner window surface temperature in the external wall Used for project 0.08 W/(m² K) 0.1 W/(m² K) 0.08 W/(m² K) 0.8 W/(m² K) 5.5 W/m² was assumed to be achieved 0.03 W/(m K) 0.13 W/(m K) Common construction elements were used with damp-roof layer in external walls. Moisture safe construction was also selected for roof and ground floor components. Well-designed details and good workmanship was assumed for this project. In that case required 0.5 l/(s m²) infiltration level was used. 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 ) 27

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. Zone type Area / m² Occupants number per zone / people Total occupant number in the building / people Occupancy time Zone occupancy time (working hours) / % Canteen :30-13:00 19 Conference :00-17:00 23 Café :00-18:00 75 Cell offices 8:00-12: :00-17:00 88 Landscape office 8:00-12: :00-17:00 88 Meeting room 10:00-12: to :00-16:00 30 Toilets :00-17: Stairs/elevator :00-17: Installation shafts :00-17: 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. CO 2 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. 28

29 Table 9: The ventilation rates for the BC building zones. Zone name 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: Occupancy ventilation rate Building ventilation rate (low polluted) 5 Design max. total ventilation rate Summer day natural ventilation 6 Set-point for heating, cooling and the DGNB platinum level requirements. 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 none Conference none Café none Stairs/elevator none none Toilets 4.1 none 4.1 none none Installation shafts none none none none none Cell offices Landscape office/corridors Meeting room Name of system Set point DGNB platinum level Heating 20 C 21 C Operative temperature C Cooling 25 C Operative temperature 25.5 C 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 (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. 29

30 Table 11: Fully Glazed Office Building Facade Designs in Denmark The input data for internal loads for cell and landscape offices that was used in the thermal comfort simulations. 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 1 pc 40 W 12 pc 480 W 1 pc screen 17'' 40 W 12 pc screen 17'' 480 W Occupancy load schedule Occupancy load schedule 08:00-12:00 and 13:00-17:00 12:00-13:00 100% 0% 08:00-12:00 and 13:00-17:00 12:00-13:00 100% 70% 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 W/m² Total internal loads W/m² 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 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. 30

31 Natural ventilation during the night was possible only in cell offices, landscape offices and meeting room because they were located on the 1 st to 3 rd 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): 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 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

32 Table 12: Fully Glazed Office Building Facade Designs in Denmark The input data for reflectance and transmittance of the surfaces and components in DIVA. Surface name DIVA grasshopper material names 9 Reflectance / % Transmittance / % Wall GenericInteriorWall_ Ceiling GenericCeiling_ BC Window Glazing_DoublePane_Clear_80-80 LT-value 72% Window Glazing_DoublePane_LowE_65-65 LT-value 67% Window Glazing_DoublePane_LowE_Argon_65-65 LT-value 65% Window Glazing_Electrochromic_Clear_60-60 LT-value 60% Window Glazing_TriplePane_Krypton_47-47 LT-value 47% Frame GenericFloor_ Floors GenericFloor_ Fixed shading OutsideFaçade_ Screen EC_Tinted_30-30 Tables GenericFloor_ Chair GenericFurniture_ Surrounding UotsideFaçade_ buildings Interior glass GlazingSinglePannel_88-88 Fixed shading OutsideFaçade_ PC screen GenericCeiling_ 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 Façade Figure 11: The landscape office floor plan with table layout and row numbers starting from the facade. 9 The default materials data (Solemma, 2016). 32

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. Figure 12: The 1 st floor plan with working Table and view angle for glare analyses shown with arrows. 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: 14 th of April at 09:00 for cell offices and 21 st 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. 33

34 3.3 Parametric study Fully Glazed Office Building Facade Designs in Denmark 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. CN LS LW CE Figure 13: The 2 nd floor plan with highlighted analyses office rooms. The analysis starting point was creating the BC for each office. The selected offices were placed on the 2 nd 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. 34

35 Figure 14: Parametric study plan for the thermal comfort. Table 13: The simulations order with selected design strategies for the parametric study. BC II III IV V VI Base Case BC + Natural ventilation day BC + Natural ventilation day + night BC + Fixed external shading 50% opened (as outline project required) BC + Fixed external shading 50% opened + Natural ventilation day 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. 35

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. 36

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 U g-value 10 / (W/(m² K)) LT-value / % g-value / % EC 12-16Ar 13 4NG 14-16Ar 4EC SC 15 4EC-16Ar 4NG-16Ar 4EC SCW 16-16Ar-4NG-16Ar-4EC SC-16Ar-4NG-16Ar-4EG SCN 17-16Ar-4 NG -16Ar-4EG Colour rendering / % 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. 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 Next step was calculating LCC for the façade alternatives with different external shadings, as presented in Table 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) 37

38 Table 16: Façade alternatives names and descriptions for external shading study. Alternative name Façade description Façade A Façade with glass U-value fixed shading Façade B Façade with glass U-value 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 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 Window with glass U-value 0.6 W/(m² K) Window with glass U-value 0.5 W/(m² K) Window with selfcleaning glass Concrete elements Fixed external shading External screen Changing price after life time / % 38

39 Table 20: Input data for maintenance of construction components. Maintenance of component Worker price DKK / m² Working amount / (m²/h) Window with an easy cleaning access Window with a moderate cleaning access (fixed solar shading in front of window) Window with a self-cleaning glass Concrete elements Fixed external shading External screen Maintenance factor per year 39

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. 40

41 Surface temperatures / C Number of hours 400 Figure 16: Fully Glazed Office Building Facade Designs in Denmark BC - CN BC - CE BC - LS BC - LW 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 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 Max. floor temp. (summer period) Max. ceiling temp. (summer period) Max. floor Min. window temp. (summer period) Min. window temp. (winter period) Max. window temp. (summer period) Max. ceiling / window Max. window temp. (winter period) Min. window BC - CN BC - CE BC - LS BC - LW Figure 17: Four analysed offices surface temperatures for floors, ceilings and windows during summer and winter periods. The DGNB top score requirements are highlighted. 41

42 Daylight factor / % Visual comfort Fully Glazed Office Building Facade Designs in Denmark 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 twice as high than for work planes in the landscape offices. The glare was a problem for work planes located close to windows. Anyway, all cases met the DGNB platinum level BC - CN BC - CE BC - LS BC - LW BC - CN BC - CE BC - LS BC - LW Studied cases Base Case for the cell office facing north Base Case for the cell office facing east Base Case for the landscape office facing south Base Case for the landscape office facing west DF DF on working plane (-s) DGNB platinum (3%) BC2020 (2%) Figure 18: The DF for half of the room and DF for working plane(-s) for offices studied. The DGNB platinum and the BC2020 requirements are also included. As an extra documentation for glare issue, an annual glare and point-in-time glare analyses were performed. It resulted in no glare for the cell office facing north, see Appendix B.1. Other offices annual glare simulations showed that an intolerable glare occurred more than 5% which was the limit for the best glare control, see Appendix B.2 and Appendix B.3. Figure 19: The annual glare analysis for the landscape office facing south where the x-axis represents different months of the year and the y-axis presents the time of day. 42

43 The cell office facing east had a glare problem during mornings, while for south and west facing offices the biggest issue was afternoons. The south facing office was the worst case from the annual glare point of view, as a large amount of intolerable glare levels appeared during winter, spring and autumn seasons, see Figure 19. The annual glare simulations revealed the data and time where the intolerable glare appeared for the offices studied. This information was used for each office point-in-time glare analyses. Figure 20: The fish eye views for point-in-time glare: the cell office facing the north on 14 th of April 09:00 (the top left picture), the cell office facing east on 14 th of April 09:00 (the top right picture), the landscape office facing south on 21 st of September 15:00(the bottom left picture) and the landscape office facing west on 21 st of September 15:00 (the bottom right picture). The north facing office proved that point-in-time glare was below the limit of 35% for the DGP when the best glare control was the target. But for other offices studied views the point-in-time glare levels reached much higher levels, see Figure 20. Here the glare control was needed. Envelope quality U-values for the external wall was calculated to be 0.1 W/(m² K) with the chosen materials, see Table 21. A window U-value (glass U-value of 0.5 W/(m² K) and frame U-value of

44 W/(m² K)) were taken from Bsim program and were calculated to 0.8 W/(m² K). They met the DGNB certification top level requirements. Table 21: The external wall consistence for the U-value calculation. Material and R Thickness / m / (W / (m K)) R / (m² K/W) Rse (outside) 0.13 Fibre glass boards Ventilation gap Gypsum weather board Mineral wool Gypsum board Rsi (inside) 0.13 Total thickness R total 9.41 U-value / (W/(m² K)) 0.1 Energy use for the Base Case building The BC building s energy use was simulated to be much higher than BC2020 requirement of 25 kwh/(m² year), see Table 22. Table 22: The BC building s energy use, heating, cooling and DWH demands. Annual energy use 49.5 kwh/(m² year) Heating demand 16 kwh/(m² year) Cooling demand (27.1) kwh/(m² year) DHW 5.5 kwh/(m² year) El for operating building 14.6 kwh/(m² year) Excessive in rooms 10.3 kwh/(m² year) By adding heating and cooling demands, DHW and electricity for building operation did not end up in 49.9 kwh/(m² year), because the primary energy factors of 0.6 and 1.8 are used when calculating the final result. The excessive in rooms is calculated as the overheating in room would be removed by the electricity and this number is added to the final energy use as a punishment for a bad indoor climate. The simple formula is used for the annual energy use calculations, which is embedded in Be15: ((Heating demand + DHW) x 0.6) + (EL x 1.8) + Excessive in rooms [kwh/(m² year)] (3) 4.2 Single-skin façade parametric studies This section presents the results of the façade parametric studies where the design strategies, the frame area and U-value of the window, g-value of the glass and external shading devices were investigated. The parametric study plan is presented in Appendix C.1. The outputs were operative temperatures and surface temperatures, DF for half of the floor and DF at the working planes, an annual glare, point-in-time glare and an annual energy use for the 44

45 building. After the parametric studies had been performed, the FCs were created for each office analysed. These results were used in the DGNB certification check list point score table presented in the end of this section. Thermal comfort The BC building thermal comfort was investigated by integrating some of the design criteria: the natural ventilation and the external shading. The main focus was on the operative and surface temperatures. Operative temperature results were expressed in hours above 25.5 C during the summer period and during the winter in hours below 21 C and above 25 C. Surface temperatures for floors and ceiling were simulated for summer period and windows inner side surface temperature was checked for both periods, as required by the DGNB thermal comfort scheme. The design strategies parametric study property names are presented in Table 23, which are used in the following sections. Table 23: BC II III IV V VI Design strategies numbers explanation for the result table used in this chapter. Base Case BC + Natural ventilation day BC + Natural ventilation day + night BC + Fixed external shading 50% opened (as outline project required) BC + Fixed external shading 50% opened + Natural ventilation day BC + Fixed external shading 50% opened + Natural ventilation day + night Design strategies This chapter presents the thermal comfort results for the design strategies parametric study. This section is divided into two parts where the operative temperature results and the surface temperatures are presented. Operative temperatures Operative temperatures during whole-year analyses were divided into two periods and the total amount of hours during both periods are presented in Figure 21. The north facing cell office BC and the BC with natural ventilation during the night exceeded the DGNB top level requirement and did not receive points for the summer period. Other strategies integration lowered the hours above limits for both periods and met DGNB platinum requirement. The other offices exceeded the operative temperature limit for the summer period but the natural ventilation and external shading integration drastically minimized overheating hours and also improved the indoor climate during the winter period. The external shading and natural ventilation (during day and night) integration showed that offices could reach the DGNB top score requirements (strategy VI), see Figure

46 BC - CN CN-II CN-III CN-IV CN-V CN-VI BC - CE CE-II CE-III CE-IV CE-V CE-VI BC - LS LS-II LS-III LS-IV LS-V LS-VI BC - LW LW-II LW-III LW-IV LW-V LW-VI Number of hours Fully Glazed Office Building Facade Designs in Denmark Surface temperatures Studied cases 21 C Operative temperature 25.5 C (summer period) 21 C Operative temperature 25 C (winter period) DGNB platinum (50 hours) BC Base Case CN/CE Cell office facing north/east LS/LW Landscape office facing south/west II/III/IV/V/VI Design strategies Figure 21: Amount of the exceeded operative temperature hours during the design strategies paramedic studies for offices studied (summer and winter periods). The DGNB top score requirement is also included. Surface temperature results for the design strategies parametric study were divided into: the maximum floor, the maximum ceiling, the minimum window and the maximum window surface temperature sections. The floor temperature was an issue, as presented in Figure 22. All offices except the north facing cell office exceeded the 29 C limit for the summer period, but the external fixed shading implementation reduced the floors temperature to the needed level. The natural ventilation had a small influence after the external shading was integrated. But cases with the natural ventilation and fixed external shading received all check list points for the DGNB platinum level (strategies IV-VI). 46

47 BC - CN CN-II CN-III CN-IV CN-V CN-VI BC - CE CE-II CE-III CE-IV CE-V CE-VI BC - LS LS-II LS-III LS-IV LS-V LS-VI BC - LW LW-II LW-III LW-IV LW-V LW-VI Surface temprature / C BC - CN CN-II CN-III CN-IV CN-V CN-VI BC - CE CE-II CE-III CE-IV CE-V CE-VI BC - LS LS-II LS-III LS-IV LS-V LS-VI BC - LW LW-II LW-III LW-IV LW-V LW-VI Surface temperature / C Fully Glazed Office Building Facade Designs in Denmark Max. floor temp. (summer period) DGNB platinum (29 ºC) BC Base Case CN/CE Cell office facing North/east LS/LW Landscape office facing south/west II/III/IV/V/VI Design strategies Figure 22: The floors surface temperatures during the design strategies paramedic studies for offices studied (summer period). The DGNB top score requirement is also included. Maximum ceiling and window surface temperatures were under the limit and met the requirements, see Appendix D.1 and Appendix D.2. On the other hand, the minimum surface temperature of the window was too low for both landscape offices during the winter period. But the fixed external shading eliminated this problem and the DGNB platinum level was reached (strategies IV-VI), see Figure Studied cases 16 Studied cases Min. window temp. (summer period) Min. window temp. (winter period) DGNB ptatinum (18 ºC) BC Base Case CN/CE Cell office facing north/east LS/LW Landscape office facing south/west II/III/IV/V/VI Design strategies Figure 23: The window minimum surface temperatures during the design strategies paramedic studies for offices studied (summer and winter periods). The DGNB top score requirement is also included. 47

48 BC - CN CN CN CN CN CN CN CN BC - CE CE CE CE CE CE CE CE BC - LS LS LS LS LS LS LS LS BC - LW LW LW LW LW LW LW LW Number of hours Fully Glazed Office Building Facade Designs in Denmark Window frame areas and glass U-values This section presents the thermal comfort results for window frame areas and glass U-values parametric studies. It is divided into two parts where the operative temperature results and the surface temperatures are presented. Operative temperatures Operative temperatures during the whole year are presented in Figure 24. The north facing cell office had just the summer period simulations. If it met the requirements during the summer, then the winter period requirement also was fulfilled. For other offices both periods were included. None of the cases analysed met the summer period requirement but a frame area of 23% had the lowest exceeded hours with both glass U-values for all offices. A smaller frame area led to a bigger overheating problem, but the glass U-value of 0.6 W/(m² K) lowered these issues. This glass U-value was also assumed to be more realistic and possible to achieve in the real project Studied cases 21 C Operative temperature 25.5 C (summer period) 21 C Operative temperature 25 C (winter period) DGNB platinum (50 hours) BC Base Case CN/CE Cell office facing north/east LS/LW Landscape office facing south/west 0.5/0.6 The glass U-value expressed in W/(m² K) 10/15/20/23 Frame area expressed in percentage Figure 24: Amount of exceeded operative temperature hours for four analysed offices where the glass U-value and the frame area were parameters checked (summer and winter periods). The DGNB top score requirement is also included. 48

49 BC - CN CN CN CN CN CN CN CN BC - CE CE CE CE CE CE CE CE BC - LS LS LS LS LS LS LS LS BC - LW LW LW LW LW LW LW LW Surface temperature / C Fully Glazed Office Building Facade Designs in Denmark All offices with this U-value and a frame area of 23% met the operative temperature requirements for the winter period and received the DGNB platinum level check list points, whereas the landscape offices could lower the frame area to 15% and still met the winter period requirements. Surface temperatures Surface temperature results for window frame areas and glass U-values parametric studies were divided into: the maximum floor, the maximum ceiling, the minimum window and the maximum window surface temperature sections. The floor temperature was an issue, as presented in Figure 25. All offices except the north facing cell office exceeded the 29 C limit for the summer period. Generally, a smaller frame area led to a higher floor surface temperature and the glass U-value had a minimal influence on that Studied cases Max. floor temp. (summer period) DGNB platinum (29 ºC) BC Base Case CN/CE Cell office facing north/east LS/LW Landscape office facing south/west 0.5/0.6 The glass U-value expressed in W/(m² K) 10/15/20/23 Frame area expressed in percentage Figure 25: The floors surface temperatures during the glass U-values and the frame areas parametric studies (summer and winter periods). The DGNB top score requirement is also included. The maximum ceiling surface temperature exceeded the 35 C limit for the east facing cell office, while the maximum window surface temperatures did not exceed the limit for all offices studied, as presented in Appendix D.3 and Appendix D.4. On the other hand, the minimum surface temperature of the window was too low for the east, south and west facing offices during the winter period. The lower frame area increased the surface temperature for some cases and the 18 C required was reached, see Figure 26. The DGNB certification platinum level for the surface temperatures was reached for the cell office facing north. The window frame area and the U-value change influenced surface temperatures for the other offices, but the cases studied did not reach the needed 49

50 BC - CN CN CN CN CN CN CN CN BC - CE CE CE CE CE CE CE CE BC - LS LS LS LS LS LS LS LS BC - LW LW LW LW LW LW LW LW Surface temperature / C Fully Glazed Office Building Facade Designs in Denmark requirements when all surfaces were taken into consideration. The next step was the g-value parametric study Glass g-values This section presents the thermal comfort results for glass g-values parametric studies. This section is divided into two parts where the operative temperature results and the surface temperatures are presented. Operative temperatures Studied cases Min. window temp. (summer period) Min. window temp. (winter period) DGNB platinum (18 ºC) BC Base Case CN/CE Cell office facing north/east LS/LW Landscape office facing south/west 0.5/0.6 The glass U-value expressed in W/(m² K) 10/15/20/23 Frame area expressed in percentage Figure 26: The window minimum surface temperatures during the glass U-values and the frame areas parametric studies (summer and winter periods). The DGNB top score requirement is also included. Operative temperatures during the whole year are presented in Figure 27. The north facing cell office had just the summer period simulations. If it met the requirements during the summer, then the winter period requirement also was fulfilled. For the other offices both periods were included. The SC with g-value of 0.51 and U-value of 0.6 W/(m² K) was the starting point for each office s analyses. For the north facing office the glass g-value of 0.41 and lower met thermal comfort requirements and received the DGNB platinum check list points. The other offices exceeded the summer period limits even with the g-value of But the DGNB winter period limits were reached with the lower glass g-values, and top score points were received, as shown in Figure 27. Generally, the glass with lower g-value provided a better indoor climate. 50

51 SC - CN CN-0.46 CN-0.41 CN-0.35 CN-0.31 SC - CE CE-0.46 CE-0.41 CE-0.35 CE-0.31 SC - LS LS-0.46 LS-0.41 LS-0.35 LS-0.31 SC - LW LW-0.46 LW-0.41 LW-0.35 LW-0.31 Number of hours Fully Glazed Office Building Facade Designs in Denmark Figure 27: Amount of exceeded operative temperature hours during the glass g-values parametric studies for offices studied (summer and winter periods). The DGNB top score requirement is also included. Surface temperatures Studied cases 21 C Operative temperature 25.5 C (summer period) 21 C Operative temperature 25 C (winter period) DGNB platinum (50 hours) SC Selected Case CN/CE Cell office facing north/east LS/LW Landscape office facing south/west 0.43/0.41/0.35/0.31 The glass g-value Surface temperature results for glass g-values parametric studies were divided into: the maximum floor, the maximum ceiling, the minimum window and the maximum window surface temperature sections. The floor temperature was an issue, as presented in Figure 28. All offices except the north facing cell office exceeded the 29 C limit for the summer period. Generally, a lower glass g-value led to a lower floor surface temperature. The maximum ceiling surface temperature exceeded the 35 C limit for the east facing cell office, while the maximum window surface temperatures did not exceed the limit for all offices studied, as presented in Appendix D.5 and Appendix D.6. On the other hand, the minimum surface temperature of the window was too low for the south facing landscape office during the winter period as it got lower with the lower g-value (except the g-value of 0.31). The window surface temperature was not influenced for the other offices, see Figure

52 Surface temperature / C Surface temperature / C Fully Glazed Office Building Facade Designs in Denmark Studied cases Max. floor temp. (summer period) DGNB platinum (29 ºC) SC Selected Case CN/CE Cell office facing north/east LS/LW Landscape office facing south/west 0.43/0.41/0.35/0.31 The glass g-value Figure 28: The floors surface temperatures during the glass g-value parametric studies (summer period). The DGNB top score requirement is also included. The DGNB certification platinum level for the surface temperatures was reached for the cell office facing north. The glass g-value influenced surfaces temperatures for the other offices, but cases studied for the east facing office did not reach the needed requirements when all surfaces were taken into consideration, while the landscape offices received top score with the glass g-value of If a lower g-value was used, the surface temperature problem was reduced and the influence on the visual comfort increased. That led to further analyses related to the visual comfort Studied cases Min. window temp. (summer period) Min. window temp. (winter period) DGNB platinum (18 ºC) SC Selected Case CN/CE Cell office facing north/east LS/LW Landscape office facing south/west 0.43/0.41/0.35/0.31 The glass g-value Figure 29: The window minimum surface temperatures during the glass g-value parametric studies (summer and winter periods). The DGNB top score requirement is also included. 52

53 Number of hours Fully Glazed Office Building Facade Designs in Denmark Shading devices This section presents the thermal comfort results for external shadings parametric studies. The north facing cell office did not need the shading and was not studied. This section is divided into two parts where the operative temperature results and the surface temperatures are presented. Operative temperatures Operative temperatures during the whole year are presented in Figure 30 and Figure 31. The east and west facing offices did not need the external shading for the winter period in order to meet the thermal comfort requirements and had just the summer period simulations. For the south facing office both periods were included. The two types of shadings were studied and are presented in separate graphs. The externally fixed shading with 50% of transmittance was the most effective one, but the DGNB platinum requirement for operative temperatures in studied offices were not reached, see Figure 30. But the external screen was a very effective solution for reducing hours above the limit as well as the selected on/off control system created the best indoor climate, see Figure 31. The cases with the integrated external screen received the DGNB platinum level Studied cases 21 C Operative temperature 25.5 C (summer period) 21 C Operative temperature 25 C (winter period) DGNB platinum (50 hours) CE Cell office facing east LS/LW Landscape office facing south/west F External fixed shading 50/60/80 Transmittance of the shading Figure 30: Amount of exceeded operative temperature hours during the externally fixed shading parametric studies for offices facing east, south and west (summer and winter periods). The DGNB top score requirement is also included. 53

54 Number of hours Fully Glazed Office Building Facade Designs in Denmark Studied cases 21 C Operative temperature 25.5 C (summer period) 21 C Operative temperature 25 C (winter period) DGNB platinum (50 hours) CE Cell office facing east LS/LW Landscape office facing south/west S External screen shading 20/30 Transmittance of the shading OF On/off shading control system 01 1 ½ - 0 shading control system C Continiuos shading cotrol system Figure 31: Amount of exceeded operative temperature hours during the external screen shading parametric studies for offices facing east, south and west (summer and winter periods). The DGNB top score requirement is also included. Surface temperatures Surface temperature results for external shading devices were divided into: the maximum floor, the maximum ceiling, the minimum window and the maximum window surface temperature sections. The floor temperature was an issue, as presented in Figure 32. Both external shading devices lowered the floors surface temperature to or under the 29 C limit for the summer period (not the externally fixed shading with 60-80% transmittance). Maximum ceiling and window surface temperatures were under the limits and met the requirements as well as the minimum window surface temperatures, see Appendix D.7, Appendix D.8 and Appendix D.9. Both types of the external shading reduced the surface temperatures and allowed to score the DGNB top check list points for all the cases except for the floor temperature during summer with fixed 60% transmittance shading. 54

55 CE-F-50 CE-F-60 CE-F-80 CE-S-20-OF CE-S CE-S-20-C CE-S-30-OF CE-S CE-S-30-C LS-F-50 LS-F-60 LS-F-80 LS-S-20-OF LS-S LS-S-20-C LS-S-30-OF LS-S LS-S-30-C LW-F-50 LW-F-60 LW-F-80 LW-S-20-OF LW-S LW-S-20-C LW-S-30-OF LW-S LW-S-30-C Surface tempreature / C Fully Glazed Office Building Facade Designs in Denmark Figure 32: The floors surface temperatures during the externally fixed shading and the external screen parametric studies (summer period). The DGNB top score requirement is also included. Final Cases operative and surface temperatures This section presents the thermal comfort results for the FCs of each office. This section is divided into two parts where the operative temperature results and the surface temperatures are presented. Operative temperatures Studied cases Max. floor temp. (summer period) DGNB platinum (29 ºC) CE Cell office facing east LS/LW Landscape office facing south/west F/S External fixed shading/screen shading 50/60/80/20/30 Transmittance of the shading OF On/off shading control system 01 1 ½ - 0 shading control system C Continiuos shading cotrol system Operative temperatures during whole year analyses were divided in two periods and the total amount of hours during both periods are presented in Figure 33. The BC with the fixed external shading and natural ventilation (day or day and night) was one of the solutions that met the requirements for operative and surface temperatures for all offices. But for the north facing cell office the external shading was not needed, therefore the FC was selected without it. Generally, there was no need for external shading, a smaller frame area and a lower g-value for this office for meeting the DGNB top score requirements. But the window with glass U-value of 0.6 W/(m² K) should be used, and this case results are presented in Figure

56 Surface temperatures / C Number of hours Fully Glazed Office Building Facade Designs in Denmark The other offices operative temperature limits were minimized when the glass U-value of 0.6 W/(m² K) was used. Then cases with this U-value for glass, the frame area of 15% and the 0.51 g-value for glass were created as secondary alternatives. Here the shading was changed to the external screen shading with an on/off control system. These cases are final and they received the top score for DGNB platinum, see Figure FC - CN FC - CE FC - LS FC - LW 40 Figure 33: Amount of hours that the operative temperature exceeded for FCs during whole year where limits are: 25.5 C or over for the summer period and under 21 C or over 25 C during the winter. Surface temperatures FC - CN FC - CE FC - LS FC - LW Studied cases 21 C Operative temperature 25.5 C (summer period) 21 C Operative temperature 25 C (winter period) DGNB platinum (50 hours) Final Case for Cell office facing north Final Case for Cell office facing east Final Case for Landscape office facing south Final Case for Landscape office facing west Minimum and maximum surface temperatures during the whole year are presented in Figure Max. floor temp. (summer period) Max. ceiling temp. (summer period) Max. floor Min. window temp. (summer period) Min. window temp. (winter period) 56 Max. window temp. (summer period) Max. ceiling / window Max. window temp. (winter period) Min. window FC - CN FC - CE FC - LS FC - LW Figure 34: The offices analysed surface temperatures for floors, ceilings and windows during summer and winter periods. The DGNB top score requirements are highlighted.

57 Daylight factor / % Fully Glazed Office Building Facade Designs in Denmark None of the cases exceeded the required floor, ceiling and window surface temperatures for both periods, after the ventilation system inlet maximum temperature and the heating setpoint were adjusted. This was needed, as the window surface temperature during the winter period got lower than 18 C. These offices fulfilled the DGNB top score requirements for the thermal comfort. Visual comfort The SC visual comfort was analysed using the values described in Appendix C.2. After the g-value parametric study, the AC was created and used for the further parametric study. In these simulations 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 a work plane. Point-in-time glare analyses were performed for the offices facing east, west and south where external shading devices and internal screens were tested. These results were expressed in DGP. Glass g-values This section presents the visual comfort results for glass g-values parametric studies. Analysis of the g-value of glass revealed that DF levels for both floors and a working plane were high in cell offices, as presented in Figure 35. All types of glass gave the needed 2% level for DF, according to the BR15 (Bygningsreglementet, 2016), but high levels of daylight created glare problems (over 5% for DF). Only one case for the landscape office facing west with g-value of 0.31 did not reach the requirements Studied cases SC Selected Case CN/CE Cell office facing north/east LS/LW Landscape office facing south/west 0.43/0.41/0.35/0.31 The glass g-value DF DF on working plane (-s) DGNB platinum (3%) BC2020 (2%) Figure 35: The DF for the half of the room and DF for the working plane for offices analysed with the glass g-value variations. The DGNB platinum and the BC2020 requirement are also included. For the south and west facing offices the g-value of 0.31 minimized the daylight access to working planes to an unacceptable level (DF under 2%), and generally lower g-values than 57

58 Daylight factor / % Fully Glazed Office Building Facade Designs in Denmark 0.51 did not reach the DGNB platinum level for DF at work planes. A low daylight level at the landscape office work planes was an issue. South and west facing offices work plane daylight levels The average DF for working planes with the glass g-value of 0.51 was around 3% as required by DGNB platinum, see Figure 35. But the actual DF for work planes was investigated as well. This section presents the visual comfort results for the DF for work planes located in different rows. Tables were placed in the way, as presented in the methodology chapter. The DF for a work plane placed in the first row was high and it dropped to 2% for row two, which still fulfilled BC2020 requirements. The row 3 did not reach the required daylight level for the work plane, as shown in Figure 36. The average DF for working planes was 3% and it met DGNB requirements. However, DF at working planes located in rows 2 and 3 was not fulfilled, and none of the DGNB check list points were received for the landscape offices ,9 AC - LS - Row 1 AC - LS - Row 2 2 0,8 DF on working plane (-s) DGNB platinum (3%) BC2020 (2%) AC - LS Analysis Case for the landscape office facing south AC - LW Analysis Case for the landscape office facing west Figure 36: The DF for work planes located at different rows for the landscape office facing south and west. 5,9 AC - LS - AC - LW - Row 3 Row 1 Studied cases AC - LW - Row 2 2 0,8 AC - LW - Row 3 External shading The externally fixed shading devices influenced visual comfort, as they provided an interrupted view out and minimized the daylight access. As they latter in some cases were reduced to an unacceptable daylight level, see Figure 37. The east facing cell office façade equipped with external shading reached a 2% DF at working plane BC2020 requirement and 3% level required by the DGNB top score certification. But the landscape offices façade with fixed shading did not reach the DGNB top level for DF at work planes or even some cases the BR15 requirement, see Figure

59 Daylight factor / % Fully Glazed Office Building Facade Designs in Denmark Studied cases CE Cell office facing east LS/LW Landscape office facing south/west F External fixed shading 50/60/80 Transmittance of the shading DF DF on working plane (-s) DGNB platinum (3%) BC2020 (2%) Figure 37: The fixed external shading influence on the DF and the average DF at working planes for the offices facing east, south and west. In order to keep the opportunity to have undisturbed view out when the external shading is in use, the external screen shading should be used with the transmittance of 30 % as it was also used for thermal comfort reasons. Glare control The glare problem was analysed by investigating a point-in-time glare. The DGP is shown for each office case studied with shadings: the externally fixed shading 50% opened, the external screen with 30% transmittance, the internal screen with 30% transmittance and the internal screen with 2% transmittance. The glare control must be integrated as internal shading device in order to meet the DGNB daylight glare prevention requirements. For south facing landscape offices, the externally fixed shading lowered DGP to an acceptable level at 27%, and daylight was still available in the room. This type of shading did not work for the landscape office facing west, see Figure 38. The screen shading (internal and external) minimized the glare issue, but the internal screen with 2% transmittance was the most effective. On the other hand, the daylight levels became very low, which accordingly created the need for the electric lighting. 59

60 Figure 38: The fish eye views for point-in-time glare analyses with external and internal shading devices: the landscape office facing south on 21 st of September 15:00(the top four picture) and the landscape office facing west on 21 st of September 15:00 (the bottom four picture). 60

61 For the east facing cell office the external screen lowered the DGP to an acceptable level at 18% and daylight was still available in the room, see Figure 39. The internal screen was effective, but the one with 2% transmittance led to no daylight and the need for electric lighting. Figure 39: The fish eye view of the cell office facing east point-in-time glare at 14 th of April 09:00 analyses with external and internal shading devices. Envelope quality The window U-values for the offices are presented in Table 24. The table is divided into an opening window and a fixed window results. The operable window had lower U-values, as its frame was larger than the fixed window s. Table 24: Frame area counted for whole window / % The window U-value with glass U-values of 0.5 and 0.6 W/(m² K) and the DGNB requirements is presented in table. Frame size / mm Operable window Fixed window DGNB U-value / U-value / requirement (W/(m² K)) (W/(m² K)) Glass U-value of 0.5 W/(m² K) BC Glass U-value of 0.6 W/(m² K) W/(m² K) 61

62 The window alternatives with glass U-value of 0.6 W/(m² K) had lower U-values for the window, and with frame area bigger than 15% it did not meet the DGNB building envelope quality requirement. The U-value above 1.0 W/(m² K) was not acceptable. 4.3 DGNB certification score for Base Cases and Final Cases The check list points score for the DGNB schemes are presented in Table 25. Here the thermal comfort, visual comfort and the building envelope quality scheme results are presented for the BC and the FC for each studied office. All offices, except north facing one during winter period, did not receive check list points for operative temperatures. But all final cases received top score. The surface temperatures were an issue during summer period for BCs, but the top score was reached for all FCs. Table 25: DGNB schemes Cell office facing north Cell office facing east Landscape office facing south Landscape office facing west BC FC BC FC BC FC BC FC Thermal S W S W S W S W S W S W S W S W comfort Operative temperatures Surface temperatures Visual BC FC BC FC BC FC BC FC comfort DF for half of the floor area DF at the work plane View out Daylight glare prevention Building envelope design U-values for building components The DGNB check list points scores for the BCs and the FCs studied BC FC BC FC BC FC BC FC Next analysed scheme was visual comfort. Here BC and FC for each office received maximum of check list points for the DF for half of the floor area. The BC for landscape offices reached the maximum of check list points for DF at work planes, but they did no for FCs. It is because the BC result was calculated to be an average DF for all work planes and not simulated separately for each row. 62

63 Energy use / (kwh/m² year) Fully Glazed Office Building Facade Designs in Denmark The daylight glare prevention was analysed for each office FCs except north facing one as it did not have the glare problem. The glare control solution for landscape offices was the internal screen, while the external or internal screen could be used for the east facing cell office. The last used scheme was the building envelope quality and here both BC and FC for each office received the maximum check list points. 4.4 Energy use for the building The annual energy use for buildings was analysed by implementing various design strategies, changing glass U-value, g-value and adding some external shading devices. The parametric plan is presented in Appendix C.1. Design Strategies The building s annual energy use variations with design strategies are presented in Figure 40. The natural ventilation affected the annual energy use for the building. The combination of natural ventilation and externally fixed shading led to a much lower annual energy use, which almost reached BC2020 requirements ,5 44,3 41,4 30,8 28,2 27,3 BC II III IV V VI Annual energy use BC2020 BC II III IV V VI Base Case BC + Natural ventilation day BC + Natural ventilation day + night BC + Fixed external shading 50% opened (as outline project required) BC + Fixed external shading 50% opened + Natural ventilation day BC + Fixed external shading 50% opened + Natural ventilation day + night Figure 40: The building s annual energy use with implemented design strategies. Window frame areas and U-value for glass The two U-values for glass were selected for analysis: 0.5 and 0.6 W/(m² K). The percentage of the window frame area was investigated and the building annual energy usage was the output, see Figure 41. By extending the glass area, the annual energy use increased. 63

64 Annual energy use / (kwh/(m² year)) Energy use / (kwh/(m² year)) Fully Glazed Office Building Facade Designs in Denmark Heating and cooling demands were also investigated for the same glass U-values and frame areas, as demonstrated in Appendix E.1. Frame area of 20% gave the same heating and cooling demands for both glass U-values. A smaller frame area led to overheating, but lowered the need for heating. The cooling load was affected most BC Glass U-value 0.6 Glass U-value 0.5 BC2020 (25 kwh/(m² year)) Window frame area / % Figure 41: The building s annual energy use variation for different frame percentage and glass U- value of 0.5 and 0.6 W/(m² K). Glass g-values Various g-values for a glass were simulated and the building s annual energy usage was the output presented in Figure 42. Here the SC was a starting point with 15% frame area and U- value for the glass 0.6 W/(m² K). Then the U -value of the window was 0.8 W/(m² K), as required by the project. Lower g-value decreased the annual energy use for the building, but did not reach the BC2020 requirements. 60 SC ,51 0,46 0,40 0,35 0,31 Glass g-value Figure 42: The annual energy use variation for different glass g-values. Annual enrgy use BC2020 (25 kwh/(m² year)) Heating and cooling demands were also investigated for the selected g-values, as shown in Figure 43. The cooling load was affected the most with lower g-value, and the heating load got higher with lower g-values of the glass. The optimal g-value could be 0.4 as they are the most balanced to each other. The cooling load could be lowered by natural ventilation, while still using a high g-value for daylight. 64

65 Heating and cooling demands / (kwh/(m² year)) Heating and cooling demand / (kwh/(m² year)) Fully Glazed Office Building Facade Designs in Denmark Heating demand Cooling demand 10 0,51 0,46 0,40 0,35 0,31 Shading devices Glass g-value Figure 43: Heating and cooling demands for different g-values of the glass. Two types of external shading devices were investigated: a fixed shading and an external screen. The influence on the building s annual energy usage is presented in Appendix E.2. Shading devices lowered the energy use, but did not reach the BC2020 requirements. The fixed external shading with 80% transmittance gave the same energy use as the external screen shading with 30% transmittance. Heating and cooling demands were also investigated for the selected external shadings, as shown in Figure 44. The cooling load was affected most when fixed shading with 50-60% transmittance was used and the heating load was high with fixed shadings. The fixed shading with 80% transmittance and screen shading with 30% transmittance showed almost the same heating and cooling demands. The externally fixed shading with 50% transmittance had the lowest energy use fixed 50% transmittance fixed 60% transmittance fixed 80% transmittance screen 20% transmittance screen 30% transmittance Heating demand Cooling demand Figure 44: Heating and cooling demands with external shadings. 65

66 Final case Fully Glazed Office Building Facade Designs in Denmark The FC was created after the parametric studies for the energy use. After property analyses, the selected parameters were: 23% frame area, g-value of 0.4, the fixed external shading with 50% transmittance and natural ventilation during day and night. At the same time, thermal and visual comfort analyses revealed other properties that were selected as the FC: 15% frame area, g-value of 0.51, an external screen with 20% transmittance and natural ventilation during day and night. These two cases resulted in numbers presented in Table 26. The building did not meet BC2020 requirements. Table 26: The building s annual energy use with selected parameters. Name FC according to design strategies analyses FC according to thermal and visual comfort analyses Annual energy use Heating demand Cooling demand DHW kwh/(m² year) El for operating building Excessive in rooms (3.2) (14.8) The BC2020 requirements were met by increasing area of the solar cells on the roof, see Table 27. For the FC, according to the design strategies, 15 m² (in total 165 m² of PV that produces kwp) of solar panels were needed and 140 m² (in total 290 m² of PV which produces 43.5 kwp) were needed for the FC, according to the thermal and visual comfort analyses. Table 27: Name FC according to design strategies analyses FC according to thermal and visual comfort analyses The building s annual energy use with the selected parameters which met the BC2020 requirements. Annual energy use 4.5 Life Cycle Cost Heating demand Cooling demand DHW kwh/(m² year) El for operating building Excessive in rooms (3.2) (14.8) The LCC was performed for four façade alternatives where glass U-values and glass with self-cleaning property were calculated. Next step was LCC calculations for façade alternatives that were provided with external shadings. 66

67 LCC for glass variations Fully Glazed Office Building Facade Designs in Denmark LCC was calculated for four alternatives, and present value prices are presented in Table 28. Façade 2 was the cheapest one. This alternative had glass U-value of 0.6 W/(m² K) and the lowest initial price. Table 28: LCC prices for façade glass variations in present value. Alternatives Façade 1 Façade 2 Façade 3 Standard façade Initial price / DKK 4,229,175 3,908,175 4,229,175 4,441,035 Maintenance (building envelope) / DKK 540, , , ,877 Cleaning (building envelope) / DKK 1,234,984 1,234,984 1,389, ,370 Total prise (present value) / DKK 6,004,464 5,607,230 6,158,837 5,804,282 LCC trend lines for all alternatives studied during the 50 years period are presented in Figure 45. 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 Figure 45: Trend lines for LCC for glass alternatives during 50 years. LCC for façades with external shadings and self-cleaning glass LCC was calculated for four glazed façade alternatives with external shadings and two glass types. Present value prices are presented in Table 29. Façade D was the cheapest one. Alternatives with shading devices showed that a façade with self-cleaning glass and an external screen gave the lowest LCC price. 67

68 Table 29: LCC prices for façade glass variations in present value. Alternatives Façade A Façade B Façade C Façade D Initial prise / DKK 5,513,175 5,031,675 6,957,675 5,352,675 Maintenance (building envelope) / DKK 2,089, ,724 2,663,426 1,037,957 Cleaning (building envelope) / DKK 3,480,355 1,677,138 1,259, ,528 Total prise (present value) / DKK 11,083,071 7,670,537 10,880,861 6,987,160 LCC trend lines for all alternatives studied during the 50 years period are presented in Figure 46. Façade A Façade B Façade C Façade D Figure 46: Façade with glass U-value fixed shading Façade with glass U-value screen shading Façade with glass U-value 0.6 and self-cleaning glass + fixed shading Façade with glass U-value 0.6 and self-cleaning glass + screen shading Trend lines for LCC for shading and self-cleaning glass alternatives during 50 years. 68

69 5 Discussions This chapter presents discussions related to the thermal comfort, visual comfort, building envelope design and LCC analysed in this study. The annual energy usage of the building is also included. Thermal comfort The thermal comfort for the offices studied was a challenge where the summer period was the most problematic. The possibility for opening the window was a good solution for solving the overheating problem. The natural ventilation improved the indoor climate in each type of office, but no analysis for draught from natural ventilation was performed. The combination of natural ventilation (during day or night, or both) and the fixed external shading (50% transmittance) was needed for offices facing east, west and south to meet the DGNB indoor climate requirements. These simulations were performed with glass U-value of 0.5 W/(m² K), which could be difficult to achieve in a real project. Therefore, further analyses were performed with glass U-value of 0.6 W/(m² K). This change lowered the overheating hours, but led to a larger envelope thermal transmittance. The FCs with both U- values obtained the top level requirements. As mentioned before, the external shading helped to improve the indoor climate. The external screens performed better than fixed shading when simulations made by the Bsim program were analysed. Here the actual properties and control systems were applied. The external screen with on/off control system improved the indoor climate the most, which is why this type of shading was assumed to be the best in this study. The opposite performance of external screens and fixed shadings was calculated by Be15, where the best solution was to have an externally fixed shading. The reason for this was the input limitations in Be15 programs. Bsim results were more reliable, as the program was based on the hourly climate data. During the winter period, the number of hours below 21 C such as the DGNB thermal comfort requires, was low for all the analysed offices. These hours could be eliminated by a HVAC system that could provide a better heating for offices or a zone controlled ventilation. Visual comfort The analysed offices had high daylight levels in rooms and resulted in glare problems, except for the north facing cell office. This office mostly received diffused light, while the others also received direct sunlight. The sunlight falling on the computer screen created indirect glare, which was minimized by external or internal shadings. The externally fixed shading minimized the glare problem for the south facing office, where as it did not work for the west and east facing offices. Shading devices for these offices must be adaptable in order to receive daylight but reduce glare. This could be solved by interior venetian blinds, screens, etc. 69

70 On the other hand, the fixed external shading reduced the daylight in all offices. The east and west facing offices received the needed daylight even when this type of shading was used, while in the south facing office the average DF for work planes did not reach the BC2020 requirements (with 50% and 60% transmittance). In this office the daylight level at work planes located close to windows had a high daylight access, while the other two rows located deeper in the room received very limited daylight. When different working plane rows were analysed, the DF at work planes did not fulfil BC2020 and DGNB requirements. The placement of tables in the landscape office must be changed in order to reach the top score requirements for both regulations. Building envelope design The window frame had a huge influence on the total U-value of the window. The analysed windows U-values could be lowered if the U-value for the frame would be 1.55 W/(m² K). If the glass U-value of 0.6 W/(m² K) is selected and the window U-value is 0.8 W/(m² K), then the frame area must not exceed 15%. When the frame area exceeded 15%, the operable window U-value did not meet the DGNB envelope quality scheme requirement. LCC The LCC analyses were made only for façades with various glass types and shading devices. In order to provide more detailed LCC pricing, the calculations must include energy prices for heating, lighting, etc. and the building site costs. The DGNB LCC scheme required the whole building LCC and this study covered just façade. That is why none of the points could be received for this scheme. Annual energy use Energy usage calculations in Be15 were not dynamic, as the hourly weather data was not used for the location of the building. The actual building s energy usage would be higher because many inputs were assumed. For example, the shading devices could not be specified as external or internal, the shading control type as on/off or continuous was not inserted, inlet temperature for ventilation air must be 18 C, no schedules for internal loads and many other parameters. These assumptions led to the fact that annual energy results are uncertain, but the program is mandatory to use. Another issue with Be15 was RES inputs for PV-cells. Here the main data was inserted but a mutual shading from panels was not included, only shadow angles from the right and the left side of the panel. The design for solar cells in Be15 was very limited. Although, the total annual energy use was high, the BC2020 requirements were met by having more solar cells on the roof. The bigger amount of solar cells covered the building s need for electricity and reduced the need for other energy sources. It is environmentallyfriendly solution that compensates a not so energy-efficient building. But it can also lead to the poorer building design solutions as the amount of PV-panels is the factor that gives the BC2020 title for the building. 70

71 For this study the BC2020 annual energy usage was met, but the heating/cooling demands plus the electricity load were higher than 25 kwh/(m² year). The building was equipped with district heating and the RES. The district heating according to SBi-guidelines 213 (Statens Byggeforskningsinstitut, 2014) was calculated with a primary energy factor 0.6 and for electricity the factor of 1.8 was used. As mentioned before, the electricity need for the building was lowered due to power operated by the PV-cells, although the design for these was very limited in Be15. These two factors minimized the annual energy usage to the required limit. 71

72 6 Conclusions The studied office building located in Denmark and equipped with fully glazed façade could meet the DGNB platinum level requirements for the thermal comfort, visual comfort and building envelope quality that was also the most profitable solution (LCC) after the detailed analyses were performed. The DGNB visual comfort top level requirement was not reached for landscape offices even the tall windows were used. Daylight levels were unacceptable (lower than 2%) for work planes that were located more than two meters from the façade. At the same time the daylight glare problem was created for workers sitting close to the windows. The glare control for highly glazed façades was an issue. The BC2020 energy use requirement for the building with PV-cells on the roof was reached with a single-skin façade system solution, which was available in the Danish building market. This façade had a low glass U-value, window for natural ventilation and external shading device. The selection of the glass g-value influenced both the indoor climate and the visual comfort. The indoor climate improved with a lower g-value for both summer and winter periods, while the glass with a g-value lower than 0.35 drastically reduced the daylight. Anyway, the DGNB visual comfort requirements were met by selecting a high glass g-value and integrating other design strategies such as the external shading. The external shading screen with on/off control system was selected as the best solution in this study, which also had the lowest calculated LCC. The glass U-values, g-values and shading devices had a huge influence on annual energy use calculations. The BC2020 annual energy requirement of 25 kwh/(m² year) was reached but the results are uncertain, as the energy use calculation program (Be15) had many limits for inputs. The building s energy use must be monitored in order to prove the Be15 results. Moreover, the studied building was not an energy-efficient office, as only an integration of a larger area of PV-cells gave the possibility to meet the requirements. The BC2020 encourages to use RES that is also more environmentally-friendly solution that using other sources. On the other hand, it can lead to a poorer general building design which can be compensated by integration of renewable energy sources. To conclude, 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. 72

73 7 Summary The combination between a fully glazed office building that reaches DGNB platinum level and fulfils the BC2020 energy use requirement in Denmark 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 thesis is divided into eight chapters that are in total covering whole thesis. The main six are presented in this summary. Chapter One give the introduction to the thesis topic and background. Chapter Two provides the needed information collected from existing sources in order to get the overall understanding about the office building energy use in Denmark, BC2020, DGNB certification, design strategies integration, fully glazed façades and finally the office building layout. Chapter Three describes the methodology used for the thesis. Here the computer simulation tools, modelling of the reference building with the cell and landscape offices, input data as well as the parametric study plans are included. The results are reported in Chapter Four. This chapter is subdivided into five sections: base case, single-skin façade parametric studies, the DGNB certification score, energy use for the building and the life cycle costing (LCC). It is followed by Chapter Five where the discussions related to the thermal and visual comforts, building envelope design, LCC and annual energy use are expressed. Conclusions are drawn in Chapter Six where 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 best 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. 73

74 8 References BESTFACADE, Best Practice for Double Skin Facades. s.l.:intelligent Energy Europe. Birgisdóttir, H., Icelandic Green Building Council. [Online] Available at: [Accessed 3 February 2016]. Bygningsreglementet, Bygningsreglementet.dk. [Online] Available at: [Accessed 10 March 2016]. Bülow-Hübe, H., Energy-Efficient Window Systems, Lund: Doctoral Dissertation, Lund University. Bülow-Hübe, H., Daylight in Glazed Office Buildings, Lund: Department of Architecture and Built Environment, Division of Energy and Building Design, Lund University. Carlos, J. S. & Corvacho, H., Ventilated Double Window for the Preheating of the Ventilation Air Comparison of Its Performance in a Northern and a Southern European Climate. Journal of Renewable Energy, Volume 2013, pp Christoffersen, J. & Johnsen, K., Vinduer og dagslys - en feltundersøgelse i kontorbygninger, Hørsholm: Statens Byggeforskningsinstitut, SBI. Dal, P., Rusbjerg, J. & Zarnaghi, A. A., Energy Efficiency Policies and Measures in Denmark in 2012, Copenhagen: Danish Energy Agency. Danish Energy Agency, 2015a. Energy Policy Toolkit on Energy Efficiency in New Buildings Experiences from Denmark, s.l.: Danish Energy Agency. Danish Energy Agency, 2015b. Introduktion til LCC på bygninger, s.l.: Danish Energy Agency (in Danish). Danish Knowledge Centre for Energy Savings in Buildings, [Online] Available at: [Accessed 5 May 2016]. Danish Standard Association, DS 700, Charlottenlund: Dansk Standard (in Danish). Danish Standard Association, DS/EN 15251, Charlottenlund: Dansk Standard (in Danish). Davidson, S., 2016a. Grasshopper. [Online] Available at: [Accessed 3 May 2016]. 74

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76 Mingzhe, L., MODELLING AND CONTROL OF INTELLIGENT GLAZED FAÇADE, Copenhagen: PhD Thesis, Aalborg University. Mingzhe, L. et al., Investigation of different configurations of a ventilated window to optimize both the energy balance and the thermal comfort, Copenhagen: PhD Thesis, Aalborg University. NorthPass, Very Low-Energy House Concepts in North European Countries, s.l.: Inteligent Energy Europe. Pilkington, GLASFAKTA 2015, s.l.: Pilkington Danmark A/S (in Danish). Pilkington, Pilkington. [Online] Available at: [Accessed 16 February 2016]. Poirazis, H., Single Skin Glazed Office Buildings, Lund: Licentiate Thesis, Lund University. Poirazis, H., Single and Double Skin Glazed Office Buildings, Lund: Doctoral Dissertation, Lund University. Poirazis, H. & Blomsterberg, Å., Energy and Thermal Analysis of Glazed Office Buildings Using a Dynamic Energy Simulation Tool. In: Ninth International IBPSA Conference: proceedings of a conference, August , Montréal. ROCKWOOL A/S, ROCKWOOL. [Online] Available at: [Accessed 3 May 2016]. Ross, B. M., Design with Energy in Mind, Waterloo: Mater thesis, University of Warterloo. Solemma, DIVA for Rhino. [Online] Available at: [Accessed 10 May 2016]. Statens Byggeforskningsinstitut, sbi.dk/en/bsim (in Danish). [Online] Available at: [Accessed 2 April 2016]. Statens Byggeforskningsinstitut, SBi-anvisning 213 (in Danish), s.l.: Aalborg University. Statens Byggeforskningsinstitut, 2016a. (in Danish). [Online] Available at: [Accessed 15 April 2016]. 76

77 Statens Byggeforskningsinstitut, 2016b. (in Danish). [Online] Available at: [Accessed 1 April 2016]. Statens Byggeforskningsinstitut, 2016c. LCCbyg. [Online] Available at: (in Danish) [Accessed 3 Maj 2016]. Thomsen, K. E., Danish national plans for Nearly Zero Energy Buildings, Copenhagen: Danish Building Research Institute, SBi. Treldal, J., Radisch, N. H., Hansen, E. J. D. P. & Wittchen, K. B., Energioptimering af kontorbygninger, Hørsholm: Statens Byggeforskningsinstitut, Aalborg Universitet. Videncenter for Arbejdsmiljø, Videncenter for Arbejdsmiljø (in Danish). [Online] Available at: [Accessed 12 May 2016]. Wienold, J., -. Daylight Glare analysis and metrics. [Online] Available at: [Accessed 4 May 2016]. Winther, F. V., Heiselberg, P. K. & Jensen, R. L., Intelligent glazed facades for fulfilment of future energy. In: Towards Sustainable Cities and Buildings: 3rd Nordic Passive House Conference: proceeding of a concerance, 7-8 October 2010, Aalborg. 77

78 Appendix A Input data collected from Be15 program used for the thesis. Health Centre The building Building type Rotation Area of heated floor Area heated basement Area existing / other usage Heated gross area incl. basement Other 0,0 deg 2985,5 m² 0,0 m² 0,0 m² 2985,5 m² Heat capacity 120,0 Wh/K m² Normal usage 45 hours/week time Heat supply and cooling Basic heat District heating supply Wood stoves, Yes gas radiators etc. Solar cells Yes Mechanical Yes cooling Room temperatures, set points Heating 20,0 C Wanted 23,0 C Natural 24,0 C ventilation Mechanical 25,0 C cooling Heating store 15,0 C Dimensioning temperatures Room temp. 20,0 C Outdoor -12,0 C temp. Room temp. 15,0 C store External walls, roofs and floors Building Area (m²) U b Dim.Inside Dim.Outside (C) component (W/m²K) (C) External wall 488,7 0, Ground slab 746,3 0,08 0,

79 Roof over 746,3 0, building Total 1981, Foundations etc. Building l (m) Loss b Dim.Inside Dim.Outside (C) component (W/mK) (C) Foundation 128,6 0, ground floor around offices Windows 644,6 0, Total 773, Ventilation Zone Area (m²) Fo, - ti ( C) qn (l/s m²), Winter qi,n (l/s m²), Winter qm,s (l/s m²), Summer qn,s (l/s m²), Summer qn,n (l/s m²), Night Canteen 231,3 0, ,07 0,03 5,2 1,2 0 Canteen no 231,3 0, ,07 0, people Conference 139,1 0, ,07 0,03 8,6 1,2 0 Conference 139,1 0, ,07 0, no people Café 295,9 0, ,07 0,03 4,1 1,2 0 Café no 295,9 0, ,07 0, people Stairs/elevator 154, ,07 0, Toilets 129, ,07 0,03 4,1 0 0 Installation ,07 0, shafts Cell offices 896, ,07 0,03 4,6 1,2 0,6 Landscape 979, ,07 0,03 3,1 1,2 0,6 office Meeting room 121,9 0,3 18 0,07 0,03 4,6 1,2 0,6 Meeting room 121,9 0,7 18 0,07 0, Internal heat supply Zone Whole building Zone Area (m²) Persons (W/m²) App. (W/m²) App,night (W/m²) Area (m²) Lighting General (W/m²) Lighting (lux) DF (%) Control (U, M, A, K) Fo (-) Work (W/m²) Conference 139, K 0,8 0 Toilet 129, A 0,3 0 Stairs/corridor 154, A 0,7 0 Installation shafts U

80 Cell offices 896, K 0,7 0,5 Landscape 979, K 1 0,5 office Café 295, K 1 0 Canteen 231, K 0,3 0 meeting 121, A 0,7 0 rooms Domestic hot water Description DHW Hot-water consumption, average for the building 100,0 litres/year per m² of floor area Domestic hot water temp. 55,0 C Solar cells Area 290,0 m² Orientation Slope 10,0 S Horizon 0,0 Left 0,0 Right 0,0 Additional Peak power 0,150 kw/m² Efficiency 0,80 80

81 Appendix B B.1 The cell office facing north annual glare The annual glare analysis for the cell office facing north, where the x-axis represents different months of the year and the y-axis presents the time of day. B.2 The cell office facing east annual glare The annual glare analysis for the cell office facing east, where the x-axis represents different months of the year and the y-axis presents the time of day. 81

82 B.3 The landscape office facing west annual glare The annual glare analysis for the cell office facing west where the x-axis represents different months of the year and the y-axis presents the time of day. 82

83 Appendix C C.1 Parametric study plan for the thermal comfort and energy use Detailed parametric study plan for the thermal comfort and energy use analyses. 83

84 C.2 Parametric study plan for the visual comfort Detailed parametric study plan for the visual comfort. 84