Passivhaus: Is it Worth it? An Investigation into the feasability of building to the Passivhaus standard. By Sophie Craven
History and Theory 4 | Issues in Contemporary Architecture
PREFACE:
My interest in this field originates from participating in a week long intensive course and qualifying as a certified Passivhaus consultant. Whilst on the course, I was made aware of the extreme lengths that are taken in order for a building to achieve certification. This left me unsure as to whether reaching the standard is worthwhile. When focused so closely on the environmental design of a building, are other aspects overlooked?
BSc Architecture Year 4 | AR30039 | 2014/15
Contents 1. INTRODUCTION - - - - - - - - - - - - - - - - - - - - - - - - - - - -5 Background
6-9
2. INVESTIGATION - - - - - - - - - - - - - - - - - - - - - - - - - - - 10
10-19
Case Study: Ebbw Vale Lime House
20-23
Personal Experience: Passivhaus B&B
24-25
10 Important Points in Considering Passivhaus
3. CONCLUSION - - - - - - - - - - - - - - - - - - - - - - - - - - 26-27
Notes and Bibliography
29-31
History and Theory 4 | Issues in Contemporary Architecture
BSc Architecture Year 4 | AR30039 | 2014/15
1
Introduction
One of the main issues surrounding contemporary architecture is the objective to reduce energy consumption and carbon emissions, and to eliminate wastage. This has led environmental design to become a major part of the construction industry. Targets brought in by the government give incentive for architects, developers and contractors to brand themselves and their buildings with energy efficiency standards and labels. In this essay I seek to establish the feasibility of building to the Passivhaus standard. Due to its highly regarded reputation and rigorous guidelines, it has seldom been criticised. However there are many aspects of the standard that are problematic, and in some cases it may not be a suitable environmental strategy. The method through which I will investigate this issue will be firstly by looking into various issues raised in the verbal manifesto: Roger Hawkins’ talk ’10 Things I Didn’t Know About Passivhaus’ at the AJ Footprint Live 2014. This will allow me to explore the pros and cons of the design method. I will then judge the quantitative performance of the standard through the comparison of a built example to an equivalent house that reaches part L of the 2010 building regulations. In order to judge the qualitative performance of the standard and experience it first hand, I will be spending a weekend at the Passivhaus B&B near Totnes, Devon. Through this study, I hope to question all areas of the design method and evaluate what improvements could be made to the certification.
History and Theory 4 | Issues in Contemporary Architecture
Figure 1: Historic U Values and Air Permeability Targets Building Standard
Wall U value (W/m2K)
Roof U value (W/m2K)
Floor U value (W/m2K)
Window U value (W/m2K)
Air Permeability (ach)
1976 1982 1990 1995 2000 2006 2010 Retrofit Passivhaus
1 0.6 0.45 0.45 0.35 0.35 0.28 0.15 0.15
0.6 0.35 0.25 0.25 0.25 0.16-0.25 0.16-0.18 0.12 0.15
N/A N/A 0.45 0.35 0.25 0.25 0.22 0.15 0.15
N/A N/A 3.3 3.3 2.2 2.0-2.2 1.6 0.8 0.8
N/A N/A 10 10 10 10 10 1 0.6
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Background: When faced with an energy crisis in 1973, building regulations were revised to include directions for the fabric of buildings and minimum U values. Periodical revisions have since been made. In 1982, U values were reduced and in 1990, air permeability and window U values were primarily introduced. This ensured less draughty homes, though it could also increase bad air quality and condensation due to lack of ventilation. In 1995, 2000, 2006, and 2010 further improvements and calculation methods to measure efficiency were made in order to reduce carbon emissions [1]. Regardless of this effort the thermal performance and air quality of most buildings is still low. The government has committed to a target for most new homes in the UK to be ‘Zero Carbon’ by 2016 [2]. This may include some off site measures and may be misleading as a zero carbon building does not necessarily have zero carbon emissions itself. For this reason there is still an increased need for highly insulated and efficient buildings. With another target set in the Climate Change Act 2008, to reduce carbon emissions by 34% by 2020 and 80% from the 1990 base line by 2050 [3], millions of poorly insulated existing buildings will need to be improved considerably in terms of their thermal performance, as a large percentage of them will still be in use [4]. Passivhaus is a voluntary energy efficiency standard for the construction of all types of buildings. The concept was co-developed in 1988 by Professors Bo Adamson of Lund University, Sweden, and Wolfgang Feist of the ‘Institut für Wohnen und Umwelt’ in Darmstadt, Germany [5]. It has since become an increasingly popular method of construction.
History and Theory 4 | Issues in Contemporary Architecture
THE PASSIVHAUS REQUIREMENTS [6]: 1. The building must not use more than 15 kWh/m² per year in heating or cooling energy. 2. The building must not leak more than 0.6 times the volume of air in the house per hour. (At a test pressure of 50pa) 3. The total primary energy consumption must not be more than 120 kWh/m² per year.
BSc Architecture Year 4 | AR30039 | 2014/15
The main objective of Passvihaus is to reduce energy consumption through designing carefully the form and fabric of the building, as an alternative to employing expensive ‘active’ systems such as photovoltaics. This results in a high level of insulation, avoidance of thermal bridging and careful positioning and sizing of openings. The buildings are also built to be extremely airtight, and a mechanical ventilation heat recovery system is used to supply and maintain air quality. Only a small amount of auxiliary heating is required as heat is mainly generated from other sources. The occupants, lighting and other appliances are usually sufficient to maintain a comfortable room temperature. In order to be certified, a Passivhaus must meet the rigorous levels of maximum heating/cooling demand for the specific floor area, per year. The method of assembly is documented at each stage in order to ensure quality of construction. Pressure tests and thermal images are used prior to completion in order to test for inaccuracy and air leakage before the final finishes of the interior are added. Once the building has been completed and the final tests have been made, the results are compiled into the Passivhaus planning package spread sheet and final gains and losses are calculated. Assuming a pass is achieved, certification is provided through the Passivhaus Institut. Passivhaus can also be achieved in retrofit situations, where the standards will inherently be slightly lower. There is an allowance for an extra 10 KWh/m2 per year in this case. However, this is still a high standard and the airtightness of the building must be a maximum of 1 Ach - up to 10 times lower than a typical building reaching part L of the 2010 regulations [7].
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History and Theory 4 | Issues in Contemporary Architecture
Figure 2: Agar Grove Passivhaus Housing Development, Camden: Hawkins Brown
‘10 Things I Didn’t Know About Passivhaus’ - Roger Hawkins 1. Passivhaus is not just for ‘Grand Design’ houses. 2. Passivhaus tackles fuel poverty. 3. There is design choice. 4. It is difficult to apply Passivhaus retrospectively. 5. There is a large volume of detailing and thought required in advance of commencing on site. 6. It is not just about filling in a spread sheet. There must be design team collaboration. 7. Non standard, specialist products need to be researched and specified. 8. External walls really do get thicker! 9. There is an increased cost. 10. The certification process can be challenging. BSc Architecture Year 4 | AR30039 | 2014/15
2
Investigation
There are various benefits but also some compromises to be made in building to such a high standard of thermal performance as Passivhaus. Hawkins Brown are in the process of designing to the Passivhaus standard in 349 new build units as well as 144 retrofit units, in Agar Grove, Camden. If completed successfully, this will be the largest Passivhaus development in the UK [8]. In Roger Hawkins’ talk ’10 Things I Didn’t Know About Passivhaus’ at the AJ Footprint Live 2014, he identifies various pros and cons of the building standard, given by his first hand experience. This presents an insight into whether such high standards are worth applying. As demonstrated in the project at Agar Grove, it is conceivable to achieve Passivhaus in affordable housing. The standard can be implemented in a range of situations and it is more of a flexible design method than has been widely recognised. One of the main benefits of the standard is the displacement of high fuel bills, creating an ideal long term opportunity for social housing. Fuel The way the standard could improve the quality of lives of the inhabitants is a major asset. However, it is often overlooked when focusing on the quantitative aspect of preserving resources. Passivhaus buildings are built without the need for ‘bolt-on’ technology, yet a common misconception of the standard is that there is no design choice for the architect and a distinctive style must be followed. Domestic Passivhaus buildings are often vernacular in style, presumably for the reason that this naturally follows the approach of designing a functional building with a low form factor and minimal energy usage. However, there are other built examples of a more expressive form, and the style of the building is often limited by the budget more than it is defined by the standard. 11
History and Theory 4 | Issues in Contemporary Architecture
Figure 3 : Princedale Road Retrofit, Octavia Housing
BSc Architecture Year 4 | AR30039 | 2014/15
In a situation with demands for vast expanses of glass and North views, or a lightweight steel and glass structure, Passivhaus is unlikely to be achieved due to heating and cooling load requirements. In other cases it is possible to acquire the majority of characteristics desired. The design must however relate to its climate, location and orientation, with appropriate constraints given to the plan. This does not necessarily compromise beauty and it may even be derived from the intricacy of the detail, high quality of materials and environmental concerns in awareness. Due to restraints in terms of orientation, space and planning restrictions, retrofit projects do pose a significant challenge. Passivhaus is a concept designed for new buildings and to apply it retrospectively opposes many of the initial principles. However, around 30% of carbon emissions come from the energy use in the existing building stock, and around 75% of this building stock may still be in use in 2050 [4]. This indicates that unless action is taken now to improve the situation, we are unlikely to meet the targets set out in the Climate Change Act 2008. As it is impractical to demolish and rebuild most existing buildings without causing significant disruption, retrofitting them to a higher standard would be the preferred option. One of the major barriers to retrofitting is the possibility that improvements will be inhibited by planning restrictions, where both the internal and external appearance of the building cannot be changed. Even so there have been some very successful retrofit projects undertaken in the UK, such as Princedale Road [See Fig. 3]and Lena Gardens, in London. As part of Victorian terraces, the buildings prove that if implemented with care, retrofit can be achieved without interfering with a traditional aesthetic. 13
History and Theory 4 | Issues in Contemporary Architecture
BSc Architecture Year 4 | AR30039 | 2014/15
Additional design time required by the designer or architect is inevitable when aiming for such a high standard. Collaboration with specialist consultants is also recommended throughout the project and this must be taken in to account in the budget. A key disadvantage apparent in Passivhaus design is the additional cost involved, as it does impact at every stage of the project. This may intimidate prospective developers, as it is ambiguous as to whether building to the standard has a sufficient return on investment. There are numerous products used in a Passivhaus such as triple glazed windows, high performance and structural insulation materials, air tightness tapes and the mechanical ventilation heat recovery system with insulated ducting, filters and noise attenuation. The MVHR system is one of the main additional products that wouldn’t be required in a standard house. In Hawkins Brown’s large housing project – Agar Grove, the price of each housing unit was raised by £10-15k to achieve Passivhaus standards. £5700 of this was spent by the 3m2 extra plant space required for the MVHR in each unit. The filters for each ventilation system need changing every year which adds up to £300 to the annual costs, as part of the general upkeep [8]. The triple glazed windows, increased quantity of insulation and thermal breaks are not only costly additions in themselves, but also diminish useable floor area. A typical wall depth for a Passivhaus may reach 600mm. This consumes valuable space, especially in small sites and where land is expensive.
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History and Theory 4 | Issues in Contemporary Architecture
Figure 4 Passivhaus Church, Sheffield: Architype
Figure 5: Table to show reduction in savings at higher levels of insulation. Insulation Capital Annual Life Lifetime Return on Added: Cost: Saving: Span: Saving: Investment: (mm) (£) (£) (years) (£) (£) 0+300 50+250 100+200 150+150 200+100
273 254 211 199 170
86.2 38.2 11.3 5.4 2.7
30 30 30 30 30
2587 1146 338 162 81
2314 892 127 -37 -89
Data from Retrofit Passivhaus measures applied to a typical 3 bedroom house.
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In advance of commencing construction on site, proposals for a Passivhaus must be checked by an approved certifier. The building contractor must also be carefully selected as the unusual details and specific procedures may not be part of the repertoire of the typical builder. It is critical that all drawings and specification are comprehensively annotated up to precise details in order to explain to the contractor the requirements of the certification. Considering so much additional time and expense goes into the act of reaching certification, it is unclear whether or not it might be worth aiming slightly below the Passivhaus standard. When for example adding each additional layer of insulation, the energy saving in relation to capital cost is reduced as the standard is raised [See Fig. 5]. Once a certain level of insulation is reached, the energy savings made over the lifetime of the product will not justify the capital investment. Perhaps in some cases where other restraints such as the form factor take precedence it may not be economical during the life span of a building to reach Passivhaus certification. In public buildings where the external doors are consistently open, it may not even be possible to achieve Passivhaus standards in reality. Opening external doors and windows is not considered in calculations for Passivhaus, nor during the final air pressure tests. Although performance appears adequate on paper, this is a case where the concept of sealing a building tightly and ventilating mechanically is irrational. This also highlights a flaw in the certification process. Offices, schools, and churches have been certified as Passivhaus, yet the method of measuring their efficiency as well as the whole building concept is not necessarily suited to the typology.
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History and Theory 4 | Issues in Contemporary Architecture
BSc Architecture Year 4 | AR30039 | 2014/15
Again, where a building is used only a small percentage of the time it is not necessary to heat it for the whole year. In the situation of a school, the classrooms may only be used approximately 14% of the time [9]. It may be more logical economically and ecologically, during the life span of the building, to only produce and use energy when the building is actually occupied. For buildings in this situation, another type of standard and a whole different environmental strategy might be more practical. In the assessment process and the Passivhaus planning package, two other important aspects are overlooked. At the outset, the embodied carbon and energy of the building are not considered. It would be reasonable in this case to enforce a limit, just as strict as the energy usage limits, on distance for the sourcing of materials and transport, as well as use of environmentally sustainable and renewable materials. Additionally, when calculating the peak heat load and primary energy used per year, renewable sources of energy are not considered. A Passivhaus may utilize these sources, yet it would not help the designer in the certification process. Renewable sources may not be part of the concept behind Passivhaus, but would help reduce the primary energy load of appliances. The Code for Sustainable Homes levels 5 and 6 and the BREAAM rating standards address these issues of carbon emissions in a way Passivhaus does not, as well as other factors such as correct methods of waste disposal and flood prevention [10][11]. Encouraging a ‘zero carbon’ approach in the assessment of Passivhaus would combine the two concepts and create the optimum building standard in terms of energy usage and sustainability.
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History and Theory 4 | Issues in Contemporary Architecture
Figure 6: The Lime (left) and Larch (right) houses, Bere Architects
BSc Architecture Year 4 | AR30039 | 2014/15
Case Study: The Lime and Larch Houses in Ebbw Vale in Wales [See Fig. 6], were completed in 2011 by Bere Architects, and are both Passivhaus certified. They were built as a prototype for low cost social housing and the performance of the houses has been monitored since, with government funding. Test results show that the houses are performing in line with the predictions that were made in the Passivhaus planning package spread sheet [12]. In order to judge the value of the Passivhaus standard, I will compare the data sets retrieved from the 2 bedroom detached Lime House to a similarly sized house in Manchester that meets the minimum values for Part L of the 2010 building regulations. Tests for this house have already been carried out, and the test results from the Passivhaus have been adjusted according to the corresponding climate data value [13]. The initial building cost value of the Passivhaus was 15% more than the Manchester house, with £5315.56 additional cost incurred by the ventilation system, £5210.22 by the external doors and windows, £3551.42 by the external walls, £3023.65 by the ground floor construction and £738.02 by the building frame [14]. Additional expense is to be expected, although it is quite high for this project. This could be a consequence of the fact it was publicly funded or that it is a small detached house. When building on a larger scale such as in multiple terraced houses or apartments, some of the costs of the fabric could be reduced. On a larger scale the additional cost would appear a lesser percentage of the whole project cost value.
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History and Theory 4 | Issues in Contemporary Architecture
BSc Architecture Year 4 | AR30039 | 2014/15
The Lime House performed well in terms of energy efficiency. It has a heating load of 17.5% of the Manchester house and the corresponding values of final energy consumption in gas are 3489.92 kWh/a and 13438.94 kWh/a [13]. If we assume that the current price of gas is around 4.5p/ kWh [14], this gives a cost saving in the Passivhaus of approximately ÂŁ447.71 per year. This counteracts the maintenance costs of the MVHR unit, and provides a small amount of saving towards the capital cost of the build. However, if we consider that to borrow the additional 15% building cost on a typical interest rate of 4% [15] it initially costs ÂŁ521.04 per year. Therefore the energy savings do not actually counteract the cost of borrowing the original additional sum. Building to a Passivhaus standard will only give savings in the long term. This confirms the uncertainty of whether the standard is always worth reaching financially. The main motive behind aiming for the standard must therefore be for reasons of preservation of energy and reduction in carbon emissions, as well as comfort. In terms of comfort of the user, there is some debate as to whether it is pleasant to be sealed in a building and fed air through a mechanical system. However airtightness is required to reduce energy loss and a fresh air supply is required for the control of condensation, removal of odours and pollutants, removal of allergens arising from dust mites, exhaust of combustion devices and principally the health of the inhabitants [16]. The low energy costs could also improve the wellbeing of inhabitants in some cases, as fuel poverty has been shown to cause problems such as depression and underachieving in children when family life centres around one room and the television [17][18]. In helping to prevent such problems, the additional cost may be insignificant.
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History and Theory 4 | Issues in Contemporary Architecture
Figure 7: Personal photograph from the Passivhaus B&B. Wall thickness and triple glazing.
BSc Architecture Year 4 | AR30039 | 2014/15
The qualitative side to Passivhaus design is not as simple to measure as the quantitative aspects such as energy consumption. Visiting a Passivhaus at the start of the winter has been a definitive test to the physical thermal performance and comfort of the building standard. It has allowed me to sense the real worth behind the endeavour of constructing to the Passivhaus standard. I arrived at the Passivhaus on a particularly harsh day. With no dedicated heating appliances, the room temperature was still high. As well as the pleasing thermal environment the acoustic performance eliminated any perception of the weather conditions outside. The deep wall thickness gave solidity and the airtightness gave a controlled calmness. There was no noticeable mould or condensation and the air felt crisp and clean. I was surprised to discover that the B&B is a hybrid retrofit, and a full Passivhaus would perform at an even higher level. The additional construction cost was around 10% more in order to reach the retrofit standard in this case. Perhaps this near Passivhaus standard is more realistic to achieve. Having experienced it first hand, I would be keen to invest in Passivhaus. The concept of preserving rather than generating is a sensible strategy to deal with our increasingly wasteful modern lifestyles, and the side effects of such a good quality building are pleasing. As renewable energy sources are unlikely to be able to provide for all of the usage in buildings, this option may even become a necessity.
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History and Theory 4 | Issues in Contemporary Architecture
BSc Architecture Year 4 | AR30039 | 2014/15
3
Conclusion
The main problems that have been identified in Passivhaus are the additional time and cost involved, the loss of floor area, the potential for a slight impact on aesthetic and the difficulties and faults in the certification process. If these drawbacks were to be overcome, Passivhaus design could be the way forward for many new buildings as well as improving upon the existing housing stock. In order to progress with the concept, further research will need to be made into material technology, and the products used such as the MVHR. If these products were to gradually become more widely used, it would cut costs and further increase popularity of the standard. As incentives to reach the standard are increased and more take on the challenge, response to designer and occupant feedback will allow further developments. The assessment process could be improved upon by involving sustainable materials and renewable sources of energy, as in other standards. Fewer barriers to certification would also increase the appeal to all parties. In its present state, Passivhaus design is an investment. It may have additional time and cost implications, but it should be considered worthwhile in certain situations. The financial incentive may not yet be sufficient to gain wide implementation, but the qualitative aspects of the standard compensate for this. The main objective of building to the standard should be to deliver superior performing, comfortable and health conscious buildings that could limit the impact of an energy crisis, protect the occupants from fuel poverty and improve their everyday lives in the long term.
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History and Theory 4 | Issues in Contemporary Architecture
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Notes 1:
Dowson, M., Poole, A., Harrison, D. and Susman, G. 2012. p.295.
2:
HM Government, 2014. p.7
3:
Climate Change Act 2008.
4:
Dowson, M., Poole, A., Harrison, D. and Susman, G. 2012. p.294.
5:
Passivhaus Trust, n. d.
6:
Cotterell, J and Dadeby, A. 2012. p.18
7:
HM Government, 2010. p. 8.
8:
Hawkins, R. 2014.
9:
School hours: 6 hours per day x 5 days per week = 30 hours, x 40 weeks a year =1200 hours.
/8736 hours in a year = approximately 14% of the year.
10:
Centaur Media, 2014. p. 10
11:
BREEAM, 2014.
12:
Newman, N. 2012. p.1
13:
Ibid p.2
14:
British Gas, 2015.
15:
Bankrate, 2015.
16:
CIBSE, 2005. pp.2-28
17:
Harker L and Shelter, 2006.
18:
Pordes, A.B. and Strelitz, J. with Allen, J. and Donkin, A. 2012.
Fig. 1:
Dowson, M., Poole, A., Harrison, D. and Susman, G. 2012. Historic U values Table.
Fig. 2:
Hawkins Brown, 2014. Agar Grove Visualisation.
Fig. 3:
Passivhaus Trust, 2011. Octavia Housing, Paul Davis + Partners: Princedale Road
Fig. 4:
Architype, 2013. Christ Church Central Visualisation.
Fig. 5:
Dowson, M., Poole, A., Harrison, D. and Susman, G. 2012. Insulation and cost savings table.
Fig. 6:
Bere Architects, 2011. Lime House Passivhaus Visualisation.
Fig, 7:
Personal Photograph: The Passivhaus B&B
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Bibliography Appleby, P. 2013. Sustainable Retrofit and Facilities Management. Routledge. BREEAM, 2014. Code for Sustainable Homes [Online] Found at www.breeam.org. Acessed 15/01/2015. British Gas, 2015. Dual Fuel Tariffs. [Online] Found at www.britishgas.co.uk. Acessed 15/01/2014. Centaur Media, 2014. Passivhaus: Over Hyped? Sustainable Homes: The Homebuilding & Renovating Guide. Centaur Media. CIBSE, 2005. CIBSE Guide B. London. The Chartered Institution of Building Services Engineers. Climate Change Act 2008. (c.27). London: The Stationery Office. Cotterell, J and Dadeby, A. 2012. The Passivhaus Handbook: A Practical Guide to Constructing and Retrofitting Buildings for Ultra-low Energy Performance. Totnes, Devon. Green Books. Dowson, M., Poole, A., Harrison, D. and Susman, G. 2012. Domestic UK retrofit challenge: Barriers, incentives and current performance leading into the Green Deal. Energy Policy. Harker L and Shelter, 2006. Chance of a lifetime: the impact of bad housing on children’s lives. London : Shelter. Marmot. Hawkins, R. 2014. 10 Things I Didn’t Know About Passivhaus. Presentation and notes - AJ Footprint Live: 20 November 2014. Hawkins Brown. HM Government, 2010. The Building Regulations 2010, L1A Conservation of fuel and power in new dwellings. p. 8. [Online] Found at www.planningportal.gov.uk. Acessed 15/01/2015. HM Government, 2014. Next steps to zero carbon homes – Allowable Solutions : government response and summary of responses to the consultation. Bankrate, 2015. Mortgage Tariffs. [Online] Found at www.bankrate.com Acessed 15/01/2014 Newman, N. 2012. Passivhaus Cost Comparison in the Context of UK Regulation and Prospective Market Incentives Darmstadt, Germany. Passivhaus Institut. Pordes, A.B. and Strelitz, J. with Allen, J. and Donkin, A. 2012. An Equal Start: Improving Outcomes in Childrens Centres. UCL Institute of Health Equity. Passivhaus Trust, n. d. The History of Passivhaus. p.2 [Online] Found at www.passivhaustrust.org.uk Acessed 15/01/2015.
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