Looking Towards Passivhaus Standards for Tall Buildings The Application of the Passivhaus Standard for Tall Buildings in a Temperate Climate in the Context of Climate Change.
Grace-Marie Spencer Technology 4 AR546 April 2020
Contents
Introduction
3
Literature Introduction
4
Fabric-First” Approach
4
FXCollabroative
5
PassivTower
7
Raiffeisen (RHW.2) Tower Case Study
8
Analysis
10
Energy
10
Surface Area, Heating and Cooling
10
Lack of Familiarity and skill Level and Cost
12
Effects of Wind
13
Airtightness and thermal envelope
13
MHVR
18
Glazing
19
Discussion
20
Conclusion
21
Bibliography
22
Figures/Tables
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Looking Towards Passivhaus Standards for Tall Buildings The Application of the Passivhaus Standard for Tall Buildings in a Temperate Climate in the Context of Climate Change.
Introduction
Figure 1- Climate areas on map.
The building industry is a large contributor to climate change, therefore reducing the impact of the building industry will reduce the severity of future changes to the climate. Energy use in buildings can increase if a building is poorly designed and lead to the use of energy utilizing services like artificial heating and cooling to adjust the thermal comfort, contributing to climate change. (Pelsmakers, 2015) The Passivhaus standard is a set of rules through the building fabric and services, which can be applied to new build and retrofit buildings to accomplish reduction of Carbon and aims to achieve zero carbon buildings. Using the standards, the buildings require less energy by improving comfort and indoor air quality therefore achieving their aims. The standards were developed by the Passivhaus Institut (PASSIVHAUSI) in Germany in the early 1990s by Professors Bo Adamson and Wolfgang Feist. (Passivhaus Trust, 2013) The design process when attempting to achieve Passivhaus Standard is different to the original design process. With designing to meet Passivhaus Standard, the energy use limit is set at the start, looking at how the building will perform thermally. (Wilson, 2018) An “intergovernmental panel on climate change regards Passivhaus standards among a few whole-building strategies capable reducing building energy use sufficiently to help limit global warming.” (FXCollabroative, 2017) The research topic that will be investigated will be the application of the Passivhaus standard for tall buildings in a temperate climate in the context of climate change. There are many tall sustainable buildings however only a few that are to the Passivhaus standard. Specific details and construction arrangements have to be specially designed for a high rise building meeting Passivhaus standards as the standard was made for low rise and dense building, and due to it not being applied in many high rise buildings, there is a lack of knowledge. Figure 3- Main design features for Passivhaus.
Figure 2- Criteria for Passivhaus. The sub objectives which will be covered are: • • •
The design considerations to incorporate the Passivhaus standard in high rise buildings. An investigation of details to achieve these standards for high rise buildings. Looking at the cost implications to achieve the environmental performance in high rise buildings.
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Looking Towards Passivhaus Standards for Tall Buildings The Application of the Passivhaus Standard for Tall Buildings in a Temperate Climate in the Context of Climate Change.
An evaluation of the key features of the Passivhaus strategies for tall buildings as well as issues will be discussed based on the findings that have been covered in the sources that have been examined. Each area will be analysed in the context of climate change and the difference between building to achieve Passivhaus standard in a low rise and high rise will be highlighted in each area. The main data collected will be from a qualitative approach from the case study, literature and an interview with an architect, Ciaran Garrick, who worked on the literature by Allies and Morrison and worked with the Passivhaus standards on tall buildings. Three key literature sources were looked at when conducting research on this topic, two are research articles investigating how tall buildings could be adapted to achieve Passivhaus standard and to do this they used the Passive House Planning Package. The other was an investigation of the building fabric to allow it to achieve Passivhaus in tall buildings. Additional sources were looked at as a knowledge source for wind effects, airtightness and information on the case study. The Passive House Planning Package (PHPP) is a planning tool to help buildings achieve Passivhaus standards and low energy and has been used in the research discussed in the report. It calculates the annual energy demand of the building based on data inputted into the system. The level of detail the package goes down to for the data, the user inputs suggests that the readings are accurate and reliable , however it is still questionable whether one can rely solely on these readings as an accurate report especially when the package is pushed to the limits that Garrick admits (Garrick, 2020). The true behaviour of the buildings is only discovered when it has been built and left after a year to settle.
Literature Introduction A “Fabric-First” Approach to Sustainable Tall Building Design -Philip Oldfield This research paper discusses the most appropriate methods of achieving sustainable design by looking at a fabric first (Passivhaus) approach and how to efficiently achieve this in tall buildings. Oldfield primarily uses heat demand for comparative in this study due to it being the source for the most energy usage in temperate climates, equating to 70% energy use in Europe. Oldfield then goes on to examine the impact of the form and typology with the scenarios of location, orientation, glazing, shading and ventilation that are kept the same. Ten buildings with different scenarios and standards were used to complete a comparative study, the first 3 met the UK building regulations part L, scenarios 4-6 used Passivhaus characteristics, 7-9 used Passivhaus standard but with additional shading elements, and the 10th scenario attempted to use minimal acceptable building fabric characteristics necessary to achieve Passivhaus standards of heating demand. (Oldfield, 2017)
Figure 4- Two tables showing the performance of Olfields buildings for his study. 4
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Looking Towards Passivhaus Standards for Tall Buildings The Application of the Passivhaus Standard for Tall Buildings in a Temperate Climate in the Context of Climate Change.
Feasibility Study to Implement the Passivhaus Standard on tall Residential Buildings – FXCollabroative • • •
A 26-storey New York Exceeds the requirements of ASH RAE 90.1-2007 by 20% and targets LEED silver rating,
The research of this project highlights possible solutions to achieve Passivhaus standard in a high-rise residential building and the study experiments the ability to achieve this in mixed-use high-rise buildings located in New York. The aim was to produce a feasible Passivhaus building model whilst addressing the lack of familiarity with the standard. The changes were then evaluated and concluded the successes of the study “from architectural enclosure detailing, mechanical design, constructability, resiliency, zoning and cost among other perspectives. Cost impacts and marketability are also reviewed whilst addressing multiple and real perceived barriers implementing the standard at a large scale in New York City and how these barriers can be overcome.”
Figure 5- Model of FXCollabroative building to be analysed.
A key point highlighted by this research project was that the research may present a possible solution, however the results can’t just be copied from building to building as each project is unique with a different climates, microclimate, site, programme and construction which will affect the outcomes of the type of methods to achieve Passivhaus. (FXCollabroative, 2017)
Figure 6- Results of FXCollabroatives study with comparison.
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Looking Towards Passivhaus Standards for Tall Buildings The Application of the Passivhaus Standard for Tall Buildings in a Temperate Climate in the Context of Climate Change.
Details after adaption to meet Passivhaus Standard
Details before adaption to meet Passivhaus Standard
Figure 7- Comparison of FXCollabroative building details on base case study and Passivhaus building.
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Looking Towards Passivhaus Standards for Tall Buildings The Application of the Passivhaus Standard for Tall Buildings in a Temperate Climate in the Context of Climate Change.
PassivTower – Sustainable housing for the high-density city, by Allies and Morrison Architects. • • • •
•
44 levels 335 units Occupancy of 922. The tower achieves BREEAM Excellent, Sustainable Homes Level 4+ and exceeds the UK building regulations. Completed over the next 30 years. Considers of the rising temperatures due to climate change.
Figure 8- Model of Allies and Morrisons building to be analysed.
Working with Passive House consultants, services engineers and cost consultants, Allies and Morrison Architects undertook a research study to look at the Passivhaus Standard on a scale not yet tested on in London housing. The challenges with the housing sector in London were also identified, while reviewing costs needed as well as operational costs over the next 60 years and implications for the end user. The method used a sustainable designed tall building which has its performance reviewed and then altered to meet the Passivhaus standard using the PHPP. The Passivhaus design was then re-analysed and compared to the base case building. There were significant improvements in glazing u-values, airtightness levels and thermal bridge heat energy losses which had to be addressed to achieve the Passivhaus Standard. (Allies and Morrison, 2018)
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Looking Towards Passivhaus Standards for Tall Buildings The Application of the Passivhaus Standard for Tall Buildings in a Temperate Climate in the Context of Climate Change.
Raiffeisen (RHW.2) Tower – Case Study
Figure 9- RHW.2 building.
2014 Results
• The overall electrical consumption was 69.2kWh/m2 : 21.9kBtu/ft2 The heating consumption of 30.1kWh/m2 : 9.5kBtu/ft2 • The cooling consumption of 37.8kWh/m2 : 12kBtu/ft2.
Architect: ARGE Atelier Hayde Architekten und Architektur Maurer Building services: Vasko+Partner Ingenieure Completed in 2012, the 77.2m building with 20 storeys was the world’s tallest Passivhaus building until 2017 when the Cornell Tech building was https://cjwalsh.ie completed in New York City. This /2013/09/passivh building was the first high-rise building aus-standard-isto be certified by Passivhaus. (Toth) not-enough-inLocation: Vienna, located on the Bank new-buildingof the Donauknal, (Danube Canal) in projects/ Wien. The use of this building is an office/ unit and a treated floor area according to PHPP of 20984m2. The project aims were to use local resources optimally, reduce the consumption of energy and increase the efficiency of the facade, building component connections and the mechanical systems (Colley, 2013) with a construction budget of €84 million. The masonry construction design uses double layers which create a super insulated façade with 240m2 Photovoltaic placed on the rooftop providing 26kW. The building does have a high glazing ratio meaning that there will be more energy required. (Wilson, 2018)
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files, window strips, mullion-transom
The heat is generated by passive solar gain, equipment and occupants and specifically provided local heating surfaces / radiators. A heat pump covers 52% of the heating needs. roof windows, revolving doors A heating, cooling and power plant (CCHP), covering 48% of heating needs, is fuelled from biogas providing heating and cooling via an absorption chiller. Waste heat from a data centre that is neighbouring the building arage or basement: supplements the towers heating and cooling. Only 8% of the buildings energy requirements is for cooling; this is achieved via a mix-mode system made up form a combination of natural ventilation and mechanical cooling. The neighbouring canal is used by installing
(Toth, )
PHPP values: • Air tightness n50 = 0.39/h Annual heating demand 14 kWh /(m2a ) • Primary energy requirement 117 kWh /(m2a )
Figure 10- Design of RHW.2 building.
abs [U-value 0.108 W / (m²K)]:
geothermal probes built into the buildings trench walls. (Wilson, 2018) The ventilation is provided through eight main zones with different uses and user profiles (intermittent operation), several central ventilation units with an averaged specific heat recovery including channel losses of 79%. The hot water generation for the sanitary groups and tea kitchens takes place via an instantaneous water heater, not in a central system. To monitor 8
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Looking Towards Passivhaus Standards for Tall Buildings The Application of the Passivhaus Standard for Tall Buildings in a Temperate Climate in the Context of Climate Change. Exterior Wall: • Different structures [U values 0.17-0.6 W / (m²K)], for example component AW01 and AW 02: AW01 Element facade [average pessimistic U-value 0.595 W / (m²K)] Alu panel, 210mm Reinforced concrete, 200mm AW02 outer wall, STB + MW, ventilated [U-value 0.168 W / (m²K)] ventilated (20mm) facade panel, 10mm Mineral wool (WLS 035), 200mm Reinforced concrete, 250mm Filling different structures averaged U-value = 0.374 W / (m2K) Frame: • A combination of different window elements, permanently glazed and openable frame profiles, window strips, mullion-transom constructions, skylights, roof windows [ex: Uf values 0.62 / 0.77 / 0.95 / 1.36 W / (m²K)] over all window elements, built-in averaged U w-value = 0.73 W / (m2K) Glazing: different glazing characteristics of element facade, sun protection glass, city windows, skylights, roof windows, revolving doors •
Ug value [0.6 - 1.6 W / (m²K)] g - value [22% -52%] additional blind panels averaged U g-value = 0.7 W / (m2K) g -value = 38%
Basement Floor Slab: • Different structures [U-values 0.15-0.17 W / (m²K)], for example component 1a floor over garage or basement: Cement screed, 50mm Impact sound insulation (WLS 031), 35mm Reinforced concrete, 400mm Isover insulation (WLS 033), 160mm different components, averaged U-value = 0.318 W / (m2K) Roof: •
different structures [U-values 0.11-0.15 W / (m²K)], for example D01 warm roof concrete slabs [U-value 0.108 W / (m²K)]: Gravel layer + waterproofing, EPS-W 20 Plus (WLS 032), 260mm EPS-T 1000 Plus (WLS 032), 30mm Reinforced concrete, 220mm Filling different components, averaged U-value = 0.11 W / (m2K)
Entrance Door: • Karuselltür • U d-value = 1.64 W/(m2K)
Table 1- RHW.2 building fabric. Figure 11- Two graphs showing results of the RHW.2 building.
and control the buildings performance, an integrated automation system monitors all the components to ensure maximum efficiency. (Toth) Compared to an average tower, the heating and cooling demand has been reduced by 80%. (Wunsch, 2013) 9
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Looking Towards Passivhaus Standards for Tall Buildings The Application of the Passivhaus Standard for Tall Buildings in a Temperate Climate in the Context of Climate Change.
Analysis of the literature and case study (key points raised on building to meet Passivhaus standard in high-rise.) Energy Compared to a smaller building, a taller building uses significant more energy which needs to be accounted for when designing to meet the Passivhaus standard. This relates to the use of the building per square metre. In a high rise building the use is more compact and dense meaning that more energy is used per m2. Although the Passivhaus Standard does not change the use of buildings, the user behaviour can alter the required energy. In office design or buildings that require high software usage, there is a high energy demand peaking during the working hours of the day with occupancy fluctuations and more heating and lighting required, primary energy creating additional difficulty to achieve Passivhaus Standard which is the reason why there are not many Passivhaus office buildings according to Ciaran Garrick. He believes it is possible to achieve but a lot more difficult. (Garrick, 2020) To help with this issue, renewable solutions could achieve this like the RHW.2 building, which is an office-based building, that uses photovoltaics as an additional renewable energy source providing an additional 26kW. (Toth) Garrick adds to his point by stating that residential energy use is much more even, however the energy requirements can also be demanding in a tall residential building.(Garrick, 2020) For example, student residence has smaller units, requiring more air changes per hour due to additional units, therefore greater energy demand for ventilation. With the RHW.2 building, the use was for offices so when designing the building, energy use had to be considered from the start to be able to meet the Passivhaus standard however, the architects did not want to compromise on user satisfaction. Not only was the building an office, it was used as a bank meaning further energy is needed for meeting certain strict heating and humidity requirements. The buildings design was based on two principles; firstly a reduction of energy demand through equipment and creating an envelope with low air-leakage and secondly, the energy sources used were to be integrated and make the most out of the site. During the hours with no occupancy, the plant is put out of operation or the air flow kept minimal to help reduce energy, as well as this the light fittings that on standby looses 6kW of energy have installed switching mechanisms to switch off during periods that are not required saving additional energy. Having energy efficient design substantially reduced the energy demand of the office helping it meet to the Passivhaus standard. (Stendnger, Toth, 2016) The redesigned model in Allies and Morrison’s research also used low energy appliances which would save energy. (Allies and Morrison, 2018)
Surface Area, Heating and Cooling
Figure 12- Graphs showing the relationship between surface area and heat demand
A finding Oldfield discovered from his study was that the surface area to volume ratio has an impact on the energy use in tall buildings, where a lot less surface area can lower the annual heating demand considerably at a linear relationship. He discovered that the heating demand was so low he stated that double glazing alongside thinner insulation could work in a tall building whilst still meeting Passivhaus standard creating savings in cost and space and simplifying detailing. (Oldfield, 2017) This is a huge difference when designing to meet Passivhaus standard between high rise and small buildings. The smaller buildings being less dense means it requires more emphasis on heating requirements rather than in a taller building where the heating demand is easily met by its surface area; however, there is more demand on cooling. Oldfield then suggests as a result of this scenario, architects can explore more exciting forms within tall buildings because the the surface area to volume ratio can be increased slightly whilst still performing to the Passivhaus standard. (Oldfield, 2017) 10
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Looking Towards Passivhaus Standards for Tall Buildings The Application of the Passivhaus Standard for Tall Buildings in a Temperate Climate in the Context of Climate Change.
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Figure 13- FXCollabroative building heating and energy results comparrison before and after redesign. Figure 14- Allies and Morrison building heating and energy results comparrison before and after redesign.
This however has its disadvantages on unwanted heat in the summer months in a temperate climate, this alongside the predicted rising temperatures would lead to the tall buildings significantly overheating in the summer months. This is a key concern for Passivhaus design of tall buildings and can cause significant health and potential morality implications affecting the comfort of the building. (Oldfield, 2017) The Allies and Morrison Passivhaus building showed 50% of the heat energy requirements would be achieved through uncontrolled internal sources generating heat in the apartments. (Allies and Morrison, 2018) Garrick adds trying to mitigate overheating was the biggest problem, without opening windows and without the active cooling installation providing 32% of the cooling required, the building would pretty much overheat 3-4 months in the summer so passive cooling at night-time was implemented. (Garrick, 2020) Oldfield highlights using mechanical cooling systems would be an additional energy cost. (Oldfield, 2017) The windows can also be opened to provide daytime cooling and ventilation. Garrick mentioned it was important that Allies 11
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Looking Towards Passivhaus Standards for Tall Buildings The Application of the Passivhaus Standard for Tall Buildings in a Temperate Climate in the Context of Climate Change.
and Morrison study addresses the myth that you can’t open windows on a Passivhaus building where it is a key part of the working. (Garrick, 2020) Oldfield goes on to state that two buildings at height access to natural ventilation with the increased wind speeds can be achieved more successfully at height compared to smaller buildings. (Oldfield, 2017) Both agree however, that there is a risk of exposure in tall buildings when windows are open that could cause problems by the wind as buildings would perform much better in an enclosed unit due to the pressure, opening windows would also mean relying on the end user. The RHW.2 building uses a double-facade system in which the outer layer is glazed, and the inner layer is made from concrete parapets with upgraded insulation and window strip. This gives an extra layer to insulate meeting the heating requirement, reducing the heating and cooling load, and the ability to open windows to naturally ventilate the rooms without the wind compromising the feature, reducing the requirement for mechanical ventilation. (Stendnger, Toth, 2016)
Lack of Familiarity and Skill Level and Cost
Figure 15- Airtighness ability comparison of different countries.
The findings have highlighted “an industry wide lack of familiarity with the Passivhaus standard.” (FXCollaborative, 2017) The Passivhaus standard is aimed for small buildings, and the familiarity is increasing within that sector is reducing the cost. Building high-rise requires different approaches as discussed, meaning the level of detail must be very accurate due to pressures on tall buildings so that the skill level must be knowledgeable. Building high-rise to meet the Passivhaus standard is a very new concept meaning that the familiarity is very limited within this sector. The more developed and recognisable the industry becomes; the cost of projects will lower. Factors which need to become more familiar within the industry will help develop cost effective designs for the future. There are also ideas that tall buildings will have a poor aesthetic design if they were to meet the Passivhaus standard as the box shape will have to be replicated; this is the reason why high-rise buildings have not been considered a feasible solution to meet Passivhaus standard compared to smaller buildings that are much easier to accomplish with a reasonable form due to the experience. FXCollabroative states many workers in the construction industry are unaware of Passivhaus standard details and instantly jump to the approach being economically infeasible and do not consider the savings in heating and cooling energy. (FXCollaborative, 2017) High density residential in Passivhaus has been built much more in different temperate climate cities compared to others. Typical air tightness levels compared to other countries in Europe showed the UK was the poorest, demonstrating the skill set in the UK is not as developed as it would be in the other countries resulting in the increase in the capital cost. A reason why the UK has a lower skill in the industry is that their regulations are carbon based rather than the building fabric so Passivhaus is not regularly practiced. Garrick discusses that if a building was started tomorrow in the UK, the capital 12
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Looking Towards Passivhaus Standards for Tall Buildings The Application of the Passivhaus Standard for Tall Buildings in a Temperate Climate in the Context of Climate Change.
cost uplift would be substantial 12.5% which 75% would be down to air tightness, in not actually achieving it but the risk associated with achieving it. He estimated that if set the air tightness levels were set as low Allies and Morrisons Passivhaus design requirements to 0.2 air changes per hour, unlike the Passivhaus required 0.6, there would not be a UK contractor to build to that type of detail and level of care. A Central European contractor then would have to be used or invest a lot in training to have the UK contractor achieve trade persons certification set by the Passivhaus which adds considerable amount of cost. (Garrick, 2020) Using the double façade system on the RHW.2 building was a clever way to address the skill level to achieve Passivhaus standard in tall buildings. This method allowed room for slip ups in the construction which wouldn’t compromise on the standard so much due to the additional façade which took away the pressure of completing the building so accurately. This could be achieved quicker than complex detailing leading to cost savings in time.
Effects of Wind
Figure 16- Wind forces on tall buildings. Torsion
Along-Wind
Cross-Wind
Tall structures must respond to the effects of the wind as the speed of the wind increases with height and is driven by pressure gradients. However, the wind pressures are not steady or uniformly distributed over the facade, which can result in fatigue damage.
Wind Direction
The taller the building, the higher the air velocity. On the ground floor, the air infiltration is only marginal but if you go above 10 storeys, the wind velocity will be much stronger therefore substantial infiltration would take place, affecting the performance of the façade and its sealant. This issue raises the question whether it is achievable for a tall building over a certain height to successfully adopt Passivhaus strategies due to the complexity of effectively sealing off the building with immense forces against it.
Attached cladding systems must be able to behave the same way the structure deforms creating deformations in the cladding itself without failure due to restraining, relief mechanisms can help achieve this. Another approach is using smaller sized cladding where the material is less ductile so deformation will be limited. The effects of the wind loading deformation must be combined with effects of gravity loading. (Mendis, 2017) The RHW.2 building uses the two-layer façade where the outer layer is a wind shield allowing the shading screens to work even on windy conditions without problems. (Stendnger, Toth, 2016) With a taller building, stronger winds are inflicted on the building at higher levels. There must be careful consideration and design of the building fabric to prevent major damage from the wind forces and pressures needed. Whereas a smaller building is not exposed to the strong wind speeds at higher levels, so the building fabric does not need to be as specially designed to meet with wind loads.
Airtightness and thermal envelope
Figure 17- Achieving airtighness.
An important feature of the standard is to make the building envelope airtight, therefore it can save the building major energy demands from heating as poor airtightness accounts for up to 50% of the energy required for heating and cooling alongside causing the most discomfort. (Writer, 2014) Air leakage can also lead to repeatedly damaging the building fabric by water through vapour condensing leading 13
The method to reduce the air leakage is to make the building as airtight as possible and to accomplish this a single continuous air barrier must be designed, this will be an airtight layer within the buildings fabric and will prevent air entering in the building if achieved successfully. There are two types of air barrier systems, firstly the exterior air barrier that is placed at the exterior side of the envelope then there is the interior air barrier placed at the interior side of the enclosure. April 2020
Looking Towards Passivhaus Standards for Tall Buildings The Application of the Passivhaus Standard for Tall Buildings in a Temperate Climate in the Context of Climate Change.
to deterioration in the U values, mould and potentially structural damage. (BRE, 2014) The most appropriate conditions for airtightness are minimal wind with a small external to internal temperature difference, therefore smaller buildings can achieve airtightness easier than taller buildings which need more work to achieve this. (Peper, 2019) Both FXCollabroative and Garrick stated that the biggest challenges that occurred were in the details which was where the most changes were made and both concluded that this was the most expensive part of the redesign and a big concern surrounding the skill set of the workers that construct the building which can leave errors in the building which affect the air tightness. (FXCollaborative, 2017) If airtightness is not achieved, air leakage will occur creating unwanted airflow within the building. (BCHousing, 2017) Air leakage is causes by different forces:
Wind blows across thecooler building’s façade causes cooler air to be ss the building’s façade causes air to be forcedthe into the in building through the gaps in the fabric under uilding through gaps the fabric under pressure fromofthe The the other side of the building, the e wind. The other side thewind. building, pressure caused by the cooler air causes the e pressureleeward caused side, by thethe cooler air causes the warmer tostronger escape on side. cape on that side. air The thethat wind the The stronger the wind the amount air is leaked f warmer greater air is leaked outofofwarmer the building. This out of the building. This generally creates the highestacross peak pressure difference across s the highest peak pressure difference the buildings envelope elope however the wind does nothowever actuallythe wind does not actually cause the mostabove air leakage. Any building above 16 floors (60m) ir leakage. Any building 16 floors (60m) has substantial affects from wind gusts and thermal effects ffects from wind gusts and thermal effects from the pressure difference between top and ground floor e difference between top and ground floor which can be stable when the wind is unstable strong. when the wind is strong.
Figure 18- Damage to the building fabric if airtighness is weak.
stack effect, which is especially The stack effect, which isThe especially apparent in tall buildings, apparent in is caused by a change in the air density. During is caused by a change in the air density. During cooler periods air will typically beair less dense than outdo indoor air will typically beindoor less dense than outdoor creating a positive meaning that the air expands a positive pressure meaning that thepressure air expands which makes it gaps rise and escape the gaps in the fabric at it rise and escape from the in the fabricfrom at higher levels theis negative pressure which in is the cooler ai and the negative pressureand which the cooler air is drawn through the lower part of the building through the lower part of the building causing drafts that have causing dr consequences on the comfort of an the building and consequences on the comfort of the building and causing upward air flow pattern. upward air flow pattern.
+VE +VE
ard
-VE +VE
Leeward Windward
+VE
-VE
-VE
-VE
Leeward
Figure 19- The two types of airleakage. The barrier is normally a membrane, but the difficulty is to achieve this at certain areas:
•
The foundation to the substructure
•
Fenestration systems – around the doors and windows etc.
•
Where the wall plate meets the roof
Figure 20- Areas where airtightness is difficult. 14
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The air barrier must be able to withstand the wind and stack effects as well as structural changes from expansion and moisture absorption as well as be designed to last the entire life of the building. Sheet materials are commonly used but they can be damaged easily especially in tall building conditions, so membranes are more suitable but other materials can be used as long as it not permeable. (BCHousing, 2017) Best design methods for the difficult areas:
Roof-An exterior is the simplest approach with low slope roots because the exterior surface of the roof structure has less penetrations that the air barrier needs to address and will be able to be transferred to the exterior wall easier.
Windows-Each fenestration product has different specifications on how they are attached to the air barrier, so referring to the manufactured data will get the best information on how to accomplish this successfully. Concrete and below gradeIn buildings that use a concrete structure, the concrete itself can be used as the primary air barrier however adding an additional air barrier help with long term risks of the concrete failing lading to air barrier failure.
Figure 21- Design methods to accomplish airtighness in difficult areas. 15
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In the RWH.2 buildings, the double façade system allows the airtightness to be achieved easier than a single façade system, as the two facades will have a double air barrier so air leakage is a lot less likely, and the wind pressure does not affect the inner façade so less pressure letting air escape. (Stendnger, Toth, 2016) Airtightness is much more difficult to achieve within a tall building due to the pressure difference and the stronger winds all of which need to be considered when designing the tall building. This means the air barrier systems are more limited in choice because only a few are suitable for the pressures and wind loads at height, whereas this problem does not occur when designing a small buildings as the pressure is nowhere near as intense as a tall building and all materials are suitable.
Figure 22- Heating demand vs airtightness relationship.
Figure 23- Allies and Morrison before and after redesign, showing heat loss through building fabric. (Thermal Analysis) 16
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Looking Towards Passivhaus Standards for Tall Buildings The Application of the Passivhaus Standard for Tall Buildings in a Temperate Climate in the Context of Climate Change.
Figure 24- FXCollabroative before and after redesign, showing heat loss through building fabric. (Thermal Analysis)
Figure 25- Oldfield’s tips to design airtight in a tall building.
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Looking Towards Passivhaus Standards for Tall Buildings The Application of the Passivhaus Standard for Tall Buildings in a Temperate Climate in the Context of Climate Change.
MHVR (Mechanical heat and ventilation recovery system) There are different ways to achieve a successful mechanical heat and ventilation recovery system in a tall building to meet Passivhaus standards. The first option is to use a centralised system, or a semi centralised system and the second option is to have individual units in each apartment. Garrick worked with the Passivhaus consultants of the 26 storey Cornell Tower in New York, currently the tallest Passivhaus building, so the information was disseminated. Their ventilation method was different to Allies and Morrison’s UK Passivhaus building, as they used central and semi central units, with three central units which equated to 1 unit per 8 floors. All the ventilation was coming through the apartments from the hallway which had significant fire implications in the UK standards but still achievable with significant changes in the plans which was not feasible. Alongside this, there was a loss of the efficiency from the ductwork because they were longer. (Garrick, 2020) Allies and Morrison’s Passivhaus building put small unit by unit MHVRs in each apartment that meant the ductwork would not loose out on efficiency as it would be substantially shorter in length. However, this method meant the end user of each apartment would take over responsibility of maintaining it, not a maintenance team. The filter must be changed every 6 months which is crucial, and Allies and Morrison designed it in the ceiling on the living room instead of a utility room which meant it would be much more difficult to access. (Garrick, 2020) A reason why the location of the individual MHVR units was placed in the ceiling was to improve the efficiency. (Garrick, 2020) Relocating it to as close as possible to the façade provided an efficiency of 80%, with the length of required ductwork reduced by 3.5KM leading to cost saving implications and time savings. Extra insulation was added which halved heat energy loss as well as reducing the length. (Allies and Morrison, 2018) Figure 26- Before and after redesigning the MHVR in Allies and Morrison building showing savings in length.
Only one MHVR is needed within a small building which is a generic form of design, having no issues and clear instructions to maintain for the end user, whereas a tall building design needs to consider the best method and location to achieve the best output, multiple central units or individual units in each apartment or office space.
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Looking Towards Passivhaus Standards for Tall Buildings The Application of the Passivhaus Standard for Tall Buildings in a Temperate Climate in the Context of Climate Change.
Glazing For tall buildings, glazing is an important factor and a unique selling point, especially in residential because of the views but can contribute to major overheating. In Allies and Morrison building 25% of the heat requirements from solar gains in this building and 50% heat losses are through glazing and weakest in overall envelope performance. (Allies and Morrison, 2018) FXCollabroative states that there is a misperception that Passivhaus lacks enough glazing for views whereas their study proved that the same amount of glazing could be used whilst meeting Passivhaus standards. (FXCollaborative, 2017) Garrick said in Allies and Morrison’s research they didn’t want to compromise the architectural language due to it being one of their aims, so they used the 40% whilst playing with reveals. The windows had a two brick reveal providing shading, the north-east face had overshadowing from a neighbouring tower causing daylighting issues but was able to be incorporated within the PHPP package whilst the windows were flushed and smaller with a 30% ratio so the daily lighting levels were achieved. (Garrick, 2020) With most high-rise office buildings being totally glazed, RHW.2 wanted to incorporate this into their building but to successfully achieve that, as well as meeting the Passivhaus standard, the double façade was the method to accomplish this. The outer layer used laminated safety glass over the contour of the building whereas the inner layer was made from concrete parapets with window strips that used Passivhaus window components. The use of windows in the inside layer would allow the views and the natural daylight to penetrate the rooms but would not over-heat as it would if it was an outer layer. (Stendnger, Toth, 2016) There is more glazing per apartment and office in a high-rise building compared to any small building; views must be considered as well as providing adequate daylighting into the spaces to help with wellbeing and comfort. In a smaller building on the other hand, glazing requirement are much easier to meet without overheating issues whilst meeting requirements of daylight. Views are not a key selling point in a small building so large glazing is not needed.
Figure 27- Oldfield’s glazing ratio study.
Oldfield looks at the ideal glazing ratio. At 75% of glazing ratio, this causes the highest heat demands in overheating and even with considerations of summer night-time ventilation (which has its disadvantages in Passivhaus due to reliance on openable windows creating problems with security and dust particles entering causing damage the detailing), along with passive shading solutions will still overheat 19% of the time. With a 30% glazing ratio will create the best solution with the minimal heating demands however this is not a feasible solution in tall buildings as the ratio does not take in count of views which is a requirement in these types of buildings. He then goes on to describe 50% ratio is the optimal for tall buildings as it still minimises overheating whilst incorporation the amount of glazing to provide views. Garrick however reacted to this finding saying the ratio of 50% sounded very high.
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April 2020
Looking Towards Passivhaus Standards for Tall Buildings The Application of the Passivhaus Standard for Tall Buildings in a Temperate Climate in the Context of Climate Change.
Discussion Ciaran Garrick was not very confident that office design in tall buildings can meet Passivhaus standard easily. (Garrick, 2020) However, the RHW.2 that has 80% lower energy demands than a normal tall building, a reasonable time ago, proves that it is possible. Using renewable solutions, low energy appliances, where applicable can save on the usage and will be also beneficial for the impact of global warming. Nevertheless, this is all based on the individual building, for example future surrounding buildings could alter the performance. Although the initial cost is high, the operational costs would be substantially saving tenants and owners a huge amount of money and around 40 years payback would start to happen, and the quality would mean the buildings fabric would not fail requiring replacement. With climate change predicting increased temperatures, tall buildings meeting Passivhaus standards will require greater cooling, meaning that methods must be reliable and able to withstand more pressure in the future. The ideal glazing ratio should also be agreed within the construction industry to prevent overheating, whilst more emphasis on solar shading and window reveals should be considered on each of the facades on each design. The increasing number of storms with strong winds predicted due to climate change, causing wind speeds to intensity for more days in the year meaning an increase pressure in the façade and building envelope. The cladding should be able to resist the pressures and change to the structural deformations to prevent damage to the building fabric compromising the airtightness and building behaviour, therefore failing the Passivhaus standard. Airtightness will potentially be affected with climate change weather alterations like strong winds more frequently and an increase in temperatures. The tall buildings that are designed to be Passivhaus standard in the temperate climate need to make sure airtightness is the primary issue to be able to meet the standard in the future. To achieve air tightness to eliminate thermal bridging in tall buildings will take additional time to design and construct due to the challenges of air pressure at height and the greater amount of building envelope to detail, therefore adding cost within. With an increase of knowledge for detailing to meet Passivhaus Standards within the industry, the familiarity will speed up the process of developing the details, therefore reducing cost. Another way to overcome the complexity of building envelope design is to share more knowledge and skills in the construction sector and more practice on achieving this, which would speed up the process whilst achieving accurate details without errors. Constructing off site with the prefabricated approach has been discussed widely as a feasible and financially viable solution and would leave less room for error while speeding up the process. This is the most preferred solution to achieve the standard in tall building in the future. Since publishing the report, Garrick stated if this research was to be repeated, he would look back from a more offsite construction perspective with the greater chance of achieving air tightness through a factory approach on manufacture of the façade. (Garrick, 2020) It is important that the lack of familiarity is addressed so that this standard cannot just be implemented in small buildings. This standard has been described “as among a few whole-building strategies capable reducing building energy use sufficiently to help limit global warming,” (FXCollaborative, 2017) meaning that implementing this standard in not just small buildings is a crucial way to help with climate change. To do this, the lack of familiarity needs to be reduced and an industry wide knowledge should be shared. The knowledge and skills are still lacking, however with more training and knowledge shared around the industry, the speed of construction is only likely to increase whilst keeping the skill level and quality, lowering the additional costs. A way to accomplish this is to keep the details as simple as possible to avoid build errors. As well as this simple façade solutions and double glazing could also help save costs. The data collected highlights advantages and disadvantages of both centralised and individual MHVR solutions. Having a centralised system can cause fire safety issues leading to a more challenging design approach however there is more control over humidity. The required ductwork for a centralised system is quite substantial leading to energy loss in a highrise building. The individual units have the advantage of less ductwork needed, therefore saving energy loss, however the maintenance needed to change filters is around every six months.
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Looking Towards Passivhaus Standards for Tall Buildings The Application of the Passivhaus Standard for Tall Buildings in a Temperate Climate in the Context of Climate Change.
Conclusion This report has shown that it is possible and feasible to achieve Passivhaus standard in high rise buildings in a temperate climate successfully. It is easier to meet heat requirements in high rise buildings than in a small building, to a point that double glazing is achievable therefore saving costs. The design of the aesthetics of the building does not have to be compromised and there can be good designs whilst achieving the standard in tall buildings, the issue regarding this is the lack of familiarity. The airtightness needs to be more stringent in high rise buildings but can be achieved and the ways of designing and constructing will be crucial in achieving this especially when it comes to the effects of pressure and wind which is not an issue in smaller buildings. Prefabricated approach is the best way to achieve this accurately and quickly without compromising of the quality and therefore saving costs. This approach is the future for applying Passivhaus standards on tall buildings. Although the initial cost is high in tall buildings, the overall lifecycle will lead to cost savings and pay back so this is an important point to consider when designing the initial building to the client. With time and more familiarity, the initial cost of the design and build will reduce due to processes speeding up and a wider range of Passivhaus certified components available for high rise buildings. The standard has already proven to be a contributor to help reduce climate change, so it is important that the ability to transition the standard to tall buildings is shared. The lower energy usage of tall buildings would significantly decrease the carbon impact contributing to global warming which is a major step for high energy using tall buildings. With more tall buildings being built in the temperate climate, selling the Passivhaus standard would significantly decrease the impact the buildings have on climate change. The main area of work within this subject for the future is to increase familiarity and knowledge within the construction industry which will be done over time with organisations, training, designers and construction workers and research papers sharing the knowledge. The standardised method of achieving Passivhaus needs to be adapted and publicised to meet high rise buildings so it is easily accessible and will state the cost advantages to the client becoming more enticing to invest in. More research is needed on cooling, due to the predicted pressures that it will face, energy efficiency which will help the building achieve Passivhaus standard easily, and the prefabricated approach which will be the way forward for the future.
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Looking Towards Passivhaus Standards for Tall Buildings The Application of the Passivhaus Standard for Tall Buildings in a Temperate Climate in the Context of Climate Change.
Bibliography 1. Allies and Morrison., et al., (2018). PassivTower – Sustainable housing for the high-density city. [12 February 2020]. Available from: https://www.alliesandmorrison.com/wp-content/uploads/2017/08/Allies-and-Morrison-Passivtower-Report_for-website.pdf 2. BCHousing., et al., (2017). Illustrated guide achieving airtight buildings. [2 April 2020]. Available from: file:///E:/Downloads/Illustrated-Guide-Achieving-Airtightness.pdf 3. BRE., (2014). Passivhaus primer: Airtightness Guide – Airtightness and air pressure testing in accordance with the Passivhaus standard. [2 April 2020]. Available from: https://www.passivhaustrust.org.uk/UserFiles/File/Technical%20 Papers/BRE_Passivhaus_Airtightness_Guide.pdf 4. Colley.J., (2013). World’s first passive house office tower certified: Passive House + Sustainable Building. [2 March 2020]. Available from: https://passivehouseplus.ie/blogs/world-s-first-passive-house-office-tower-certified 5. Duncan,G., (2013). PASSIVE HOUSE OFFICE TOWERS: New York Passive House. [26 February 2020]. Available from: https://www.nypassivehouse.org/passive-house-office-towers/ 6. Futcher.J., et al., (2017). Creating sustainable cities one building at a time: Towards an integrated design framework. Cities. (Online). Volume 66, 63-71. [29 January 2020]. Available from: https://www.researchgate.net/publication/315894537_Creating_sustainable_cities_one_building_at_a_time_Towards_an_integrated_urban_design_framework 7. FXCollabroative., et al., (2017). Feasibility Study to Implement the Passivhaus Standard on tall Residential Buildings. Nyserda. [7 March 2020]. Available from: http://www.fxcollaborative.com/passivehouse/FXCollaborative_PassiveHouseStudy_033017.pdf 8. Garrick,C., 2020. Interview with Passivhaus Architect. (Interview). [20 March 2020]. 9. Mendis,P., et al., (2017). Wind Loading on Tall Buildings. Electrical Journal of Structural Engineering. Volume 7 (41)., 41-54. [10 March 2020]. Available from: https://www.researchgate.net/publication/270162977_Wind_loading_on_ tall_buildings 10. Oldfield,P., (2017). A “Fabric-First” Approach to Sustainable Tall Building Design. International Journal of High-Rise Building. Volume. 6(2)., 177-185. [10 March 2020]. Available from: https://global.ctbuh.org/resources/papers/download/3366-a-fabric-first-approach-to-sustainable-tall-building-design.pdf 11. Passive House Database., RHW.2 Building information: Passive House Database. [5 March 2020]. Available from: https://passivehouse-database.org/index.Passivhausp?lang=en#d_2860 12. Passivhaus Trust., (2013). Passivhaus- an introduction. (Online). [13 March 2020]. Available from: https://passivhaustrust.org.uk/UserFiles/File/PH%20Intro%20Guide%20update%202013.pdf 13. Pelsmakers.S., (2015). Environmental Design Pocket Book. 2nd Edition. London: RIBA Publishing. 14. Peper.S, Schnieders.J., (2019). Airtightness measurement of high-rise buildings. (Online). [13 March 2020]. Available from: https://passipedia.de/_media/picopen/airtightness_measurement_of_high-rise_buildings_guidelines_english_1.3.pdf 15. Raiffeisen-Holding., (2013). RHW.2 – The Green Office Tower in Vienna / Austria. (Online). [10 March 2020]. Available from: https://www.b2match.eu/system/building2016/files/Raiffeisen_Hochhaus.pdf?1461650687 16. Stendnger.G, Toth.R., (2016). From Design to Operation: Lessons learned from the worlds first Passive-House office tower. Expanding Boundaries, Zurich: SBE16. 17. Toth.R., RHW.2 – The Worlds First Passive House Office Tower. (Online). [2 April 2020]. Available from: https://www. innovativegebaeude.at/fileadmin/media/best_practice_objekte/RHW2_Handout.pdf 18. Wilson.J., (2018). When Passive House Goes Big. Building Green. Volume 27(2)., [7 March 2020]. Available from: https://www.buildinggreen.com/feature/when-passive-house-goes-big 19. Writer.S., (2014). BUILDING A PASSIVE HOUSE: Building Connection. [1 April 2020]. Available from: https://buildingconnection.com.au/2014/07/26/building-a-passive-house/ 20. Wunsch.B., (2013). World’s first Passive House office tower certified: Passive House Institute. [2 March 2020]. Available from: https://passivehouse-international.org/upload/2016-07-16_PR_Vienna.pdf
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Looking Towards Passivhaus Standards for Tall Buildings The Application of the Passivhaus Standard for Tall Buildings in a Temperate Climate in the Context of Climate Change.
Figures/Table 1. Table 1 - Passive House Database., RHW.2 Building information: Passive House Database. [5 March 2020]. Available from: https://passivehouse-database.org/index.Passivhausp?lang=en#d_2860 2. Figure 1 - Feist. W., (2014). Map of Passive House climate regions [digital image]. [5 April 2020]. Avaliable from: https:// passivehouse-international.org/upload/download_complete_PH_Brochure.pdf 3. Figure 2 - Passivhaus Trust., (2013). The Passivhaus criteria for a central European climate [digital image]. [5 April 2020]. Available from: https://passivhaustrust.org.uk/UserFiles/File/PH%20Intro%20Guide%20update%202013.pdf 4. Figure 3 - Oldfield. P., (2017). Characteristics of Passivhaus Buildings [digital image]. [5 April 2020]. Available from: https://global.ctbuh.org/resources/papers/download/3366-a-fabric-first-approach-to-sustainable-tall-building-design. pdf 5. Figure 4 - Oldfield. P., (2017). Facade senarios for PHPP analysis and annual heat demand and frequency of overheating for ten senarios [digital image]. [5 April 2020]. Available from: https://global.ctbuh.org/resources/papers/ download/3366-a-fabric-first-approach-to-sustainable-tall-building-design.pdf 6. Figure 5 - FXCollabroative., (2017). Street level rendering of the base case buiing [digital image]. [5 April 2020]. Available from: http://www.fxcollaborative.com/passivehouse/FXCollaborative_PassiveHouseStudy_033017.pdf 7. Figure 6 - FXCollabroative., (2017). Comparison of PHPP inputs for base[digital image]. [5 April 2020]. Available from: http://www.fxcollaborative.com/passivehouse/FXCollaborative_PassiveHouseStudy_033017.pdf 8. Figure 7 - FXCollabroative., (2017). Base case vs Passivhaus proposal details [digital image]. [5 April 2020]. Available from: http://www.fxcollaborative.com/passivehouse/FXCollaborative_PassiveHouseStudy_033017.pdf 9. Figure 8 - Allies and Morrison., (2018). Tower modelled in Design PH, including adjacent shading with key building metrics [digital image]. [5 April 2020]. Available from: https://www.alliesandmorrison.com/wp-content/ uploads/2017/08/Allies-and-Morrison-Passivtower-Report_for-website.pdf 10. Figure 9 - Walsh.CJ., (2013). Recently, much ado has been made in the technical press about a New Multi-Storey Office Block in Vienna which has achieved the German ‘Passivhaus’ (Passive House) Standard [digital image]. [5 April 2020]. Available from: https://cjwalsh.ie/2013/09/passivhaus-standard-is-not-enough-in-new-building-projects/ 11. Figure 10 - Raiffeisen-Holding., (2013). Energy Concept [digital image]. [5 April 2020]. Available from: https://www. b2match.eu/system/building2016/files/Raiffeisen_Hochhaus.pdf?1461650687 12. Figure 11 - Stendnger.G, Toth.R., (2016).Overall energy consumption RHW.2 and comparison energy demand office buildings [digital image]. [5 April 2020].From Design to Operation: Lessons learned from the worlds first Passive-House office tower. Expanding Boundaries, Zurich: SBE16. 13. Figure 12 - Oldfield. P., (2017). Surface area to volume ratio [digital image]. [5 April 2020]. Available from: https:// global.ctbuh.org/resources/papers/download/3366-a-fabric-first-approach-to-sustainable-tall-building-design.pdf 14. Figure 13 - FXCollabroative., (2017). PHPP results [digital image]. [5 April 2020]. Available from: http://www. fxcollaborative.com/passivehouse/FXCollaborative_PassiveHouseStudy_033017.pdf 15. Figure 14 - Allies and Morrison., (2018). Comparison of heat loss, gains, cooling energy demand, primary energy demand and heating demand [digital image]. [5 April 2020]. Available from: https://www.alliesandmorrison.com/wpcontent/uploads/2017/08/Allies-and-Morrison-Passivtower-Report_for-website.pdf 16. Figure 15 - Allies and Morrison., (2018). Comparative review of airtightness regulation standards for new builds in European countries [digital image]. [5 April 2020]. Available from: https://www.alliesandmorrison.com/wp-content/ uploads/2017/08/Allies-and-Morrison-Passivtower-Report_for-website.pdf 17. Figure 16 - Spencer.GM., (2020). Wind forces on tall buildings. [drawing]. 18. Figure 17 - Spencer.GM., (2020). Achieving airtighness. [drawing]. 19. Figure 18 - BRE., (2014). Implications of moisture vapour ingress through a 1mm crack [digital image]. [5 April 2020]. Available from: https://www.passivhaustrust.org.uk/UserFiles/File/Technical%20Papers/BRE_Passivhaus_Airtightness_ Guide.pdf 20. Figure 19 - Spencer.GM., (2020). The two types of airleakage. [drawing]. 21. Figure 20 - Spencer.GM., (2020). Areas where airtightness is difficult. [drawing]. 22. Figure 21 - BCHousing., et al., (2017). Air barrier assemblies [digital image]. [5 April 2020]. Available from: file:///E:/ Downloads/Illustrated-Guide-Achieving-Airtightness.pdf 23. Figure 22 - BCHousing., et al., (2017). Heating energy demand changes due to improved airtightness [digital image]. [5 April 2020]. Available from: file:///E:/Downloads/Illustrated-Guide-Achieving-Airtightness.pdf 24. Figure 23 - Allies and Morrison., (2018). Thermal analysis studies [digital image]. [5 April 2020]. Available from: https:// www.alliesandmorrison.com/wp-content/uploads/2017/08/Allies-and-Morrison-Passivtower-Report_for-website.pdf 25. Figure 24 - FXCollabroative., (2017). Passivhaus Proposal—Assembled details of lightweight rain screen steel stud backup (left) and corresponding thermal bridge analyses of various junctions and Passivhaus Proposal—Assembled details of brick cavity on CMU and corresponding thermal bridge analyses of various junctions.[digital image]. [5 April 2020]. Available from: http://www.fxcollaborative.com/passivehouse/FXCollaborative_PassiveHouseStudy_033017.pdf 26. Figure 25 - Modi.A, Modi.S, Qiu.L., (2017). Facade cross-section for a Passivhaus skyscraper design and detailing to eliminate thermal bridges in a Passivhaus skyscraper design [digital image]. [5 April 2020]. Available from: https:// global.ctbuh.org/resources/papers/download/3366-a-fabric-first-approach-to-sustainable-tall-building-design.pdf 27. Figure 26 - Allies and Morrison., (2018). Change in MVHR position and reduction in insulated ductwork [digital image]. [5 April 2020]. Available from: https://www.alliesandmorrison.com/wp-content/uploads/2017/08/Allies-and-MorrisonPassivtower-Report_for-website.pdf 28. Figure 27 - Spencer.GM., (2020). Oldfield’s glazing ratio study. [drawing].
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