Passivhaus Tenement by Lilia Obletsova

Passivhaus Tenement Potential of Affordable Multi-family Passivhaus Housing in Urban Glasgow

The Case of Pre-fabricated Massive Timber Construction

A Research Project by: Lilija Oblecova

Submitted for: Bachelor of Architecture (Honours)

Mackintosh School of Architecture Glasgow School of Art April 2012

Acknowledgements I am sincerely grateful to my research project supervisor, Dr. Filbert Musau, for his insightful advice throughout the course of the project. My thankfulness extends also to Alexander Romanov for his knowledgeable comments and continuing encouragement.

Contents List of Illustrations List of Abbreviations Executive Summary

Introduction 1. Context 1.1. Affordable Housing in Glasgow 1.1.1. Affordable Housing Typologies ....................................... 8 1.1.2. Affordable Housing Provision Trends ............................ 12 1.2. Sustainable Housing 1.2.1. Scotland: Standards and Codes .................................... 17 1.2.2. Passivhaus Standard 1.2.2.1. Requirements / Definition .................................. 20 1.2.2.2. Applicability to the Tenement ............................. 22 1.2.2.3. Passivhaus in the UK ......................................... 24

2. Construction 2.1. Timber Construction 2.1.1. Advantages ................................................................ 26 2.1.2. Timber Construction in Scotland ................................... 27 2.3. Modern Methods of Timber Construction 2.2.1. Applicability to Affordable Housing ............................... 28 2.3.1. Engineered timber: Cross-Laminated Panels 2.3.1.1. Properties and Features .................................... 30 2.3.1.2. Suitability for Passivhaus Construction................. 32 2.3.1.3. Procurement .................................................... 33

3. Case Studies 3.1. M端hlweg Street, Vienna, Dietrich I Untertrifaller Architekten, 2006 3.1.1. Background to the Project ........................................... 35 3.1.2. Construction ............................................................... 37 3.1.3. Environmental Systems and Performance ..................... 38 3.2. Passivhaus and Massive Timber in the UK ............................... 39 3.3. Conclusions .......................................................................... 43

4. Simulation 4.1. Description of Method & Scenarios 4.1.1. Method ...................................................................... 45 4.1.2. Scenarios 1 & 2 - Original & Refurbished Tenements ..... 50 4.1.3. Scenario 3 - Building Standards + CLT .......................... 51 4.1.4. Scenario 4 - Building Standards + CLT + Passivhaus ..... 53 4.2. Simulation Results and Analysis 4.2.1. Compliance Check ...................................................... 56 4.2.2. Specific Annual Heating Demand .................................. 59 4.2.3. Effect of Urban Configurations 4.2.4.1. Effect of Terracing ............................................ 63 4.2.4.2. Effect of Hillside Terracing ................................. 64

5. Discussion ................................................................................ 65 Appendices Bibliography

List of Illustrations*

Fig.1. Plan of a typical tenement ........................................................... 8 Fig.2. Map of Glasgow showing the ratio of dwellings to the acre (height represents density) and tenure profile of dwellings (2008) by neighbourhoods ....................................... 16 Fig.3. Cross-Laminated Timber panel: pre-fabricated, fire resistant, air-tight .................................................... 30 Fig.4. External view of Mühlweg Street housing ..................................... 35 Fig.5. Typical Plan of Mühlweg Street housing ....................................... 36 Fig.6. Detail of exterior wall of Mühlweg Street housing ......................... 37 Fig.7. External view of Nash Terrace .................................................... 39 Fig.8. Model of the completed CLT shell of Bridport House ..................... 40 Fig.9. Perspective section through the Stadthaus ................................... 41 Fig.10. Diagram of a typical tenement with assumed external dimensions ............................................................... 46 Fig.11. Diagram of the thermal envelope modelled in this study ............. 47 Fig.12. Achieving Building Standards compliance in the worst case scenario: DER, TER and % Reduction .............................. 52 Fig.13. Effect of terracing on PH compliance of a tenement designed to guideline specifications ..................................... 53 Fig.14. Development of Passivhaus-compliant prototype using PHPP ........................................................................... 54 Fig.15. Dwelling Emission Rate (DER), Target Emission Rate (TER) and % Reduction ........................................ 56 Fig.16. Total CO2 Emissions Equivalent (no household applications) – comparison of SAP (DER) and PHPP results ...................... 57 Fig.17. Heat Loss Parameter and EcoHomes Ene 2 Credits (based on SAP calculations) .................................................................. 58

Fig.18. Specific Annual Space Heating Demand and Fabric Energy Efficiency (Comparison of SAP and PHPP results) ............. 59 Fig.19. Specific Annual Space Heating Demand Variations (per flat type as modelled in SAP) ....................................................... 60 Fig.20. Specific Annual Space Heating and Auxiliary Electricity Demand (comparison of SAP and PHPP) .............................. 61 Fig.21. Difference in Specific Annual Heating Demand Depending on Orientation and Street Width (based on PHPP results ...................... 62 Fig.22. Effect of terracing on the performance of PH Tenement (as modelled in PHPP) .................................................. 63 Fig.23. Effect of hillside terracing on the performance of PH Tenement (as modelled in PHPP) .............................................. 64

* The source of illustrations is acknowledged in the text.

List of Abbreviations

BRE

Building Research Establishment

CLT

Cross-laminated timber

DER

Dwelling Emission Rate

FEES

Fabric Energy Efficiency Standard

GHA

Glasgow Housing Association

LZCGT

Low and zero carbon generating technology

MMC

Modern Methods of Construction

MVHR

Mechanical Ventilation with Heat Recovery

Passivhaus or Passive House

PHPP

Passive House Planning Package

SAP

Standard Assessment Procedure

TER

Target Emission Rate

Executive Summary

Focus

The focus of this project was to test the hypothesis that housing constructed to the Passivhaus standard from pre-fabricated massive timber panels and taking precedent from the Glasgow tenement in its urban form is a suitable affordable housing prototype for Glasgow in terms of construction feasibility and environmental performance.

Context

The hypothetical Passivhaus Tenement was tested against the climatic, social and economic conditions found in Glasgow, including a range of applicable policies.

Pre-fabricated massive timber construction was chosen for its potential to be manufactured in Scotland and quick erection on site.

Passivhaus is a proven standard that provides a good starting point for achieving zero-carbon buildings through the adoption of a fabric-first approach, while also dramatically reducing operational costs.

Significance

The research project was triggered by the recognition of the necessity to develop feasible and publicly attractive alternatives to suburban living because the latter is unsustainable its use of resources and is contrary to the principles of green urbanism. 1 This study examines whether multi-storey timber tenements constructed to the Passivhaus standard could provide affordable accommodation for the growing number of households in Glasgow without advanced component specification.

Method

A brief historical overview of housing typologies in Glasgow is followed by an analysis of Glasgow's affordable housing provision trends, drawing a connection between areas with identified housing need, density and traditional tenement districts. Legislative context applicable to sustainable housing is described, and advantages of Passivhaus are outlined, together with obstacles to the standardâ&#x20AC;&#x2122;s adoption in the UK.

An overview of massive timber construction focuses on its suitability for lowenergy multi-storey housing and highlights the materialâ&#x20AC;&#x2122;s sustainability.

Lehmann, S., The Principles of Green Urbanism. Regenerating the Post-Industrial City, (Earthscan, London 2010)

An example of a successful scheme is presented, which is social housing on Mühlweg Street in Vienna by Dietrich I Untertrifaller Architekten. Several case studies in the UK are also analysed to assess feasibility.

Passive House Planning Package (PHPP) was used to establish that a detached north-facing tenement constructed to minimum specifications would not be Passivhaus-compliant in overshadowed conditions. To ensure that the proposed prototype retains the adaptability of its traditional predecessor, the components were upgraded to ensure performance in the worst-case scenario.

The prototype’s energy demands were compared to several alternatives. All sharing the same exterior dimensions, the original and refurbished tenements, Building Standards version and the prototype Passivhaus – were modelled in PHPP and FSAP 2009 to obtain comparable figures. The prototype was further evaluated in terms of the effect of orientation, overshadowing and terracing.

Contribution

The research demonstrates the suitability of cross-laminated timber for the use as the primary construction material for multi-storey Passivhaus housing. An insight is provided into the advantages and possible obstacles to adopting the Passivhaus Tenement prototype as Glasgow’s affordable housing model for the future.

Introduction

Passivhaus Tenement is an adaptable housing unit that can fill the gaps in the fabric of the city, increasing the density and attractiveness of existing neighbourhoods. It can provide accommodation that takes into account the needs of the growing proportion of small households and that is affordable in that it costs no more than 25% of the householdâ&#x20AC;&#x2122;s chief earnerâ&#x20AC;&#x2122;s income to rent. 2 It uses a construction system that is quick, sustainable and with components that could be produced locally. Chapter 1 focuses on the context in which the prototype is set, and cross-laminated timber construction is described in Chapter 2. Relevant case studies are presented in Chapter 3.

The prototype is based on Package 1 described in clause 6.1.2 of the Building Standards (Scotland), but the design was updated to bring the performance of its components to the standards defined by the Passivhaus Institute. Only the minimum targets were set, so as to avoid high construction costs. Whether this yields a working Passive House in the worst case of orientation and overshadowing and how well it performs in comparison to the alternatives is investigated in Chapter 4.

Paul Balchin and Maureen Rhoden, Housing Policy: An Introduction, 4th Edition, (Routledge, London, 2002), p.253

1. Context 1.1. Affordable Housing in Glasgow 3 1.1.1. Affordable Housing Typologies

A close-knit pattern of vertical flatted housing units has been a common feature of Scottish urban life from the earliest of times, and Glasgow is no exception4. The possibility of full and separate ownership of a flat in a block, a unique feature of Scots Law, has enabled this typology to flourish and to develop into the basic housing unit for the working classes - the Glasgow Tenement. It is a 3-4 storey block with a variety of one- and two-room flats at each landing (Fig.1).

Fig.1. – Plan of a typical tenement 5 3 4

The meaning of “affordable” is defined in the Introduction Douglas Niven, The Development of Housing in Scotland, (Croom Helm, London, 1979), p.22 John Gilbert, The Tenement Handbook, (RIAS, Edinburgh, 1993), Fig. 16.1, p.85

Before the interest waned in the early 20th century, affordable housing demand was met by private speculative developers, who used local materials and subjected the tenement to countless refinements.6 The resulting districts retain a balanced social mix owing to the strategy of selling land in small plots to a variety of developers. 7 The ‘way of life’ characteristic to historic tenements is described in a book by Worsdall.8

In spite of various incentives, private speculation ceased being able to meet the housing needs of the working classes, so the government had to rise to the challenge. However, due to the lack of funds, it was forced to reduce design standards to the bare minimum, resulting in segregated peripheral developments of ‘dreary boxes’ on Garden City-inspired layouts.9

Housing has been a highly political matter since the 1920s, and the advent of time-saving pre-fabricated technologies gave it a new force. "Multi" was a word particularly attractive to politicians and the government introduced a subsidy for system-built high-rise blocks in blind belief that this typology would deliver a long-lasting improvement in the quality of life for the masses.10

Niven, p.21 Ibid., p.70 8 Worsdall, F., The Tenement : A Way of Life : a Social, Historical and Architectural Study of Housing in Glasgow, (W. and R. Chambers, Edinburgh, 1979) 9 Niven, pp.28,72 10 Ibid., p.76 7

Even though Scotland was numerically unmatched in its public sector housing provision at the time, 11 public disillusionment came soon after, because quality was not on the agenda. The main causes of tenantsâ&#x20AC;&#x2122; dissatisfaction12 could have been eradicated through effective management, but the public was unwilling to see beyond the surface of deterioration and was led to believe that 'houses not flats'13 was the way forward.

Unable to find an alternative solution, Scotland launched a vast demolition programme aimed at the legacy of the high-rise era, which means that the majority of affected buildings are razed, most likely before having their cost paid off by the taxpayer.

The density of the high-rise estates as a whole was considerably lower than traditional tenement districts. It was overcrowding and unsanitary conditions that should have been tackled, as high density was shown to be beneficial to the quality of urban life. 14 However, by the time it was realised that the Victorian housing legacy was not devoid of its advantages and redevelopment was accepted as an alternative to demolition, a lot of the tenements were already gone.15

Ibid., p.34 Pearl Jephcott, and Hilary Robinson, Homes in High Flats (Oliver and Boyd, Edinburgh, 1971), [cited in Alice Coleman, Utopia on Trial - Vision and Reality in Planned Housing, (Shipman, London, 1985)] 13 Alice Coleman, Utopia on Trial - Vision and Reality in Planned Housing, (Shipman, London, 1985 14 Jane Jacobs, The Death and Life of Great American Cities, (Modern Library ed., New York, 1993), pp.262-265 15 Niven, p.78 12

The fixed-price contracts typical for public housing procurement meant that contractors’ profits depended on the absence of delays and low inflation. 16 Unwilling to take risks, they turned back to the private sector, producing, among other things, a number of developments in the tenement tradition,17 verifying that this typology is in demand even with home-owners.

Having a high dwelling/acre ratio, tenement streets can accommodate enough people to form a basis of a lively community. When supplemented by additional functions, non-residents start visiting the area, increasing passive surveillance. Defensible space issues 18 are resolved through a small front garden demarcated by an iron fence. As a result, typical features of successful streets are achieved.19 Furthermore, the tenement perimeter block uses urban resources more intensively compared to suburban alternatives. No matter how sustainable individual houses are, suburbia encourages further sprawl and causes pollution through increased transport.20 The majority of theories concerning sustainable urban design seem to agree on the need for “decentralised concentration”,21 so it is suggested that Passivhaus Tenements are added to areas that lack the density to achieve their full potential, preventing social segregation by the modesty of interventions.

Niven, p.108 Natalie Marie Trotter, ‘The revival of the tenement tradition in Glasgow’, [Dissertation], (Mackintosh School of Architecture, Glasgow, 1996) 18 Oscar Newman, Defensible Space: People and Design in the Violent City, (Architectural Press, London, 1973) 19 Jacobs, p.44 20 Lehmann, p.78 21 Hildebrand Frey, Designing the City. Towards a More Sustainable Urban Form, (Spon Press, London, 1999), p.39 17

1.1.2. Affordable Housing Provision Trends

In belief that owner occupation was the norm, the Conservative government introduced the right to buy council housing in 1980, which redistributed housing resources in the interest of the working class. This, however, led to wealth accumulation only for the selected few, while others suffered increasing inequality, leading to problems such as homelessness.22

The coalition of interests that supported the growth of public sector housing no longer existed and what was left in stock were the least desirable properties.23 The local authorities acted on the majority vote of their tenants and transferred all of their remaining stock to housing associations. The latter, together with a number of Registered Social Landlords currently own around 110,000 properties in Glasgow, which, being 37% of the total stock, is what constitutes the majority of affordable housing in the city.24

Glasgow’s population is anticipated to rise from 584,240 in 2008 to 614,795 in 2025,25 with number of households projected to increase due to the loss of families from the city and the ageing population.26

John English, (ed.), The Future of Council Housing, (Croom Helm, London, 1982), p.37 English, p.36 24 ‘Housing Stock by Tenure for Glasgow's Wards’ (Glasgow City Council, Development & Regeneration Services, 2011) <http://www.glasgow.gov.uk>, [Accessed on: 4 April 2012] 25 ‘The Development Plan for Glasgow - Main Issues Report’, (Glasgow City Council, 2011) <http://www.glasgow.gov.uk>, [Accessed on: 11 February 2012], p.11 26 Ibid., p.77 23

The figures representing Glasgow's social rented stock are expected to decrease from 109,756 in 2008-09 to 96,754 in 2024-25 – which is a 12% drop.27 This will take Glasgow to the minimum proportion of social housing that still ensures an effective social mix,28 but it will still have to be supported by new additions to the stock due to deterioration.

Although these estimated figures are yet to be corroborated through ongoing work with the Local Housing Strategy, a £410m grant has been made to housing associations to support the delivery of around 5,400 units.29

Glasgow Housing Association (GHA) is the biggest one in the city. Its aim is to deliver 750 new homes by 2014 and to support Glasgow's target of cutting its carbon footprint by 30% by 2020.30 One of the major steps in that direction is the 'Glasgow House' – family accommodation with a £100 annual heating bill, which is the first sustainable housing prototype for Glasgow.31 The feasibility of the project is ensured by involving local suppliers, and most importantly, City Building, a construction company who are eager to invest time in developing the skills necessary to achieve the challenging specification.32

27 28 29 30

Ibid., p.43 Lehmann, p.221

‘The Development Plan for Glasgow - Main Issues Report’, p.44

‘Our Corporate Strategy. The next three years (2011-2014)’, (Glasgow Housing Association, 2010), p.26 31 Sneddon, J., ‘The Glasgow House - It's Already Happening’, (Glasgow Housing Association, 2010) 32 ‘City Building - Glasgow House Shortlisted for Industry Awards’ , (City Building, 16 May 2011), <http://www.citybuildingglasgow.co.uk/2011/glasgow-house-shortlisted-forindustry-awards/>, [Accessed on: 11 February 2012]

Land availability is crucial to providing affordable housing and the Council has identified ways of optimising the use of this resource. Particular need for affordable housing has been identified in the West and South of the city, so releasing greenbelt land is not a solution. An obligation for private housing developers to provide a portion of affordable homes is believed to become effective after the economic recovery, and employing some of the land dedicated to the private sector, e.g. the Community Growth Areas, might be beneficial in the meantime.33

While new districts require additional investment into infrastructure, urban infill and post-demolition sites are usually well-serviced and, unless they require expensive de-contamination, it makes sense for affordable housing to be constructed there.

The Development Plan discusses urban density policy for its advantages of creating

sustainable

communities

and

attracting

investment

local

infrastructure by creating higher demand.34 Although it suggests that higher densities are mainly appropriate for traditional inner-city locations, it speculates that densifying locations near important transport nodes outside the centre would also be advantageous,

which is in line with the

“decentralised concentration” discussed earlier.

33 34 35

‘The Development Plan for Glasgow - Main Issues Report’, p.44 Ibid., p.45 Ibid., p.77

The areas with the highest identified need happen to be the densest ones (Fig.2) and feature traditional tenement districts 36 . GHA acknowledges the importance of providing a choice in the type of affordable accommodation and not just in terms of location, but also typology.37 While there is already an initiative that deals with sustainable suburban family housing, no comparable projects have been developed to actually meet the identified need in the city and to suit the requirements of the growing number of singlepeople households. The proposed Passivhaus Tenement is a possible solution to the problem.

McKenna, M., Typology Project: Tenement [A Record of Buildings in Glasgow: Volume One: October 2011], (Dress for the Weather Limited, SUST, 2011) 37 Glasgow Housing Association: Homechoice, (GHA, 2009), <https://homechoice.gha.org.uk/>, [Accessed on: 16 February 2012]

Fig.2. - Map of Glasgow showing the ratio of dwellings to the acre (height represents density) 38 and tenure profile of dwellings (2008) by neighbourhoods 39 38

Density calculated by the author using Key Facts, (Glasgow City Council, 2010) <http://www.glasgow.gov.uk >, [Accessed on: 18 February 2012] and housing unit information from Freeke, J., â&#x20AC;&#x2DC;People and Households in Glasgow. Current Estimates and Projected Changes 2008-2028. Demographic Change in Glasgow City and Neighbourhoodsâ&#x20AC;&#x2122;, [Briefing Paper by Director of Development and Regeneration Services, 7 March 2011], (Glasgow City Council, 2011) Adapted from Freeke, p.16

1.2. Sustainable Housing 1.2.1. Scotland: Standards and Codes Around 29% of all energy consumed and 30% of all greenhouse gas emissions in Scotland derive from the domestic sector. Numerous initiatives have been supported by the Scottish Government in order to reduce this impact.40

The main driving force for sustainability in Scottish housing is The Sullivan Report, which recommended a set of energy improvements on 2007 standards:  30% by 2010 (already incorporated in the Building Standards from October 2010)  60% by 2013  Net zero carbon by 2016  Total life zero carbon domestic standard by 203041

The latest amendment of the Building Standards featured an introduction of Section 7 (Sustainability), which further encourages sustainable construction by introducing three levels – Bronze/Bronze Active, Silver/Silver Active and Gold. While Bronze Active can be achieved by complying with Sections 1-6

‘Conserve and Save - A Consultation on the Energy Efficiency Action Plan for Scotland’, (Business, Enterprise and Energy Directorate, Scottish Government, 2009) 41 Sullivan, L., ‘A Low Carbon Building Standards Strategy For Scotland’, [Report of a panel appointed by Scottish Ministers], (Chaired by Lynne Sullivan from Scottish Building Standards Agency (SBSA), 2007)

and utilising low and zero carbon generating technology (LZCGT), the other levels are more challenging.42

The Climate Change (Scotland) Act requires a 42% reduction in greenhouse gas emissions by 2020 and 80% by 2050. It also brings amendments to the Town and Country Planning (Scotland) Act 1997, requiring that all new buildings minimise their environmental impact through the use of LZCGT.43

A standard imposed on large-scale residential developments in Glasgow is EcoHomes "Very Good". 44 EcoHomes is a flexible system, which assesses environmental performance with general lifestyle issues. EcoHomes standard was replaced by the Code for Sustainable Homes in the rest of the UK in 2007, together with a set of increasing targets set specifically for social housing.45

A Strategy for Sustainable Housing in Scotland, which is currently being developed, will tackle energy efficiency issues affecting both new and existing housing stock.46 Among the difficulties of achieving cost-effective retrofits in Scotland is a relatively high proportion of flats - 36%.47 Increased costs could be linked to ownership issues and also the necessity for more complex

‘Building Standards Domestic 2011 Technical Handbook’, (Scottish Government, 2011) <http://www.scotland.gov.uk/> [Accessed on: 16 March 2012] 43 The Development Plan for Glasgow - Main Issues Report’, 2011, p.80 44 ‘City Plan 2 - Part 3: Development Policies and Design Guidance’, (Glasgow City Council, 2009), <http://www.glasgow.gov.uk/>, [Accessed on: 11 February 2012], p.119 45 ‘BREEAM: EcoHomes’, (Building Research Establishment, 2012) <http://www.breeam.org>, [Accessed on: 8 April 2012] 46

‘Conserve and Save - The Energy Efficiency Action Plan for Scotland - Annual Report 20102011’, (Scottish Government, Edinburgh, 2011), p.8 47 ‘Conserve and Save’, 2009, Annexe F

solutions. This fact only stresses the importance of constructing the flatted accommodation to the highest standards in the first place.

A 'Zero Carbon' home - compulsory from 2016, must also meet the Fabric Energy Efficiency Standard (FEES). This has been set as a limit for energy demand for space heating and cooling of 39 kWh/m2/a for flats and terraced houses, and 46 kWh/m2/a for detached and semi-detached houses.48

A way to exceed these requirements and to come close to meeting the ‘Carbon Compliance’ element of the 'Zero Carbon' definition without additional renewable energy devices is opting for the Passivhaus standard.49 AECB, an independent UK-based organisation with an aim of developing sustainable building guidance, recognises the virtues of Passivhaus by making it a reference point for its own set of voluntary standards developed within the CarbonLite programme.50

‘Defining a Fabric Energy Efficiency Standard for Zero Carbon Homes: Task Group Recommendations’, (Zero Carbon Hub, London, 2009), <www.zerocarbonhub.org>,

[Accessed on: 1 April 2012] Melissa Taylor, and Neil Cutland, ‘Passivhaus and Zero Carbon’, [Technical briefing document], (Passivhaus Trust, 2011), p.2

‘AECB CarbonLite Programme: Delivering buildings with excellent energy and CO2 performance: Volume Three: The Energy Standards: Prescriptive and Performance versions’

[version 1.0.0] (Carbon Literate Design and Construction, Sustainable Building Association 2007) <http://www.aecb.net > [Accessed on: 23 February 2012]

1.2.2. Passivhaus Standard 1.2.2.1. Requirements / Definition Passivhaus (PH) is a holistic approach that produces buildings in which comfortable temperature can be achieved with minimal energy consumption51 through pre-heating or pre-cooling of the fresh air mass required to sustain indoor air quality.52 Being more challenging compared to traditional buildings at all stages of procurement, they require an alternative approach to design, one that considers small details along with initial concepts.

There are around 30,000 Passivhaus buildings built since the first experiments in Darmstadt in 1991.53 It is proven that they are generally: 

Efficient, using 10% of the energy used by an average building



Quality assured to deliver proven performance



Comfortable - warm, no draughts or cold surfaces



Healthy - good internal air quality



Affordable in the long-term through reduced running costs

Dr, Wolfgang Feist, ‘Certification as "Quality approved Passive House" Criteria for Residential-Use Passive Houses’, (Passivhaus Institut, Darmstadt, 2009) 52 Kym Mead, and Robin Brylewski, ‘Passivhaus Primer: Introduction: An Aid to Understanding the Key Principles of the Passivhaus Standard’, (Building Research Establishment, Watford, 2011), <http://www.passivhaus.org.uk/page.jsp?id=73>, [Accessed on: 12 February 2012] Ibid. 54 Taylor and Cutland, p.2 53

In return for these results, the design is required to achieve the following criteria: 

Specific Heating Demand

≤ 15 kWh/m2/a



(or) Specific Heating Load

≤ 10 W/m2



Specific Cooling Demand

≤ 15 kWh/m2/a



Specific Primary Energy Demand

≤ 120 kWh/m2/a



Air tightness

≤ 0.6 ach @ 50pascals (n50)

A way to achieve these criteria is to use the guideline targets of the building's components’ performance as a start: 

U-values for opaque fabric of ≤ 0.15 W/m2



U-values for windows and doors (frame + glazing) ≤ 0.8 W/m2K



Thermal bridging minimised (psi (y) value of < 0.01 W/m2K)



Whole house mechanical ventilation with heat recovery (MVHR) with efficiency ≥ 75%55 and specific fan power ≤ 0.45 Wh/m3. 56

Passive House Planning Package (PHPP) software should be used to verify the predicted performance of the design at all stages.

Only upon final

certification can the building claim the Passivhaus standard, provided that all criteria are satisfied.58

Mead and Brylewski, p.3 Dr Wolfgang Feist, Passive House Planning Package, PHPP 2007, 2nd Edition, [Technical Information PHI-2007/1 (E)], (Passive House Institute, Darmstadt, 2010), p.14 57 Passive House Institute, Passive House Planning Package 2007 [Computer Programme], Available from BRE, <http://www.passivhaus.org.uk/page.jsp?id=25> 58 Feist, 2010, pp.24-30 56

1.2.2.2. Applicability to the Tenement

Area to Surface (A/V) ratio is used as a measure of the building's compactness and 0.7 or less is considered favourable for Passivhaus. The A/V ratio of the tenement as a whole is 0.38, and it is 0.49 if you consider the common close external,59 which gives it a considerable advantage over singlefamily houses.60

The common close of the tenement – either heated or not, is not considered in Standard Assessment Procedure (SAP) calculations. 61 In contrast, only when falling outside of the thermal envelope can it be omitted from PHPP simulation. It saves energy to leave the stairwell out, and, due to the compactness of apartment blocks, these unheated spaces can serve as acceptably warm buffer zones. 62 This is the strategy proposed for the prototype.

When a flatted block has a non-residential use, it can only be excluded if there is sufficient thermal separation between them. Same logic applies to buildings forming a terrace - they will also be considered as one unit, unless

See Appendix 6.2. for calculation Rob McLeod, Kym Mead, and Mark Standen, ‘Passivhaus Primer: Designer’s Guide: A Guide for the Design Team and Local Authorities’, (Building Research Establishment, Watford, 2011), <http://www.passivhaus.org.uk/page.jsp?id=73>, [Accessed on: 12 February 2012] 61 ‘The Government’s Standard Assessment Procedure for Energy Rating of Dwellings’, [2009 edition, version 9.90], (Building Research Establishment, Watford, 2011), p.15 62 ‘Design Guidelines: Non-Domestic Passive House Projects’, (Sustainable Energy Authority of Ireland Renewable Energy Information Office and MosArt Architecture, 2010), p.59 60

thermal resistivity of party walls is sufficient to act as a barrier.63 It is also worth noting that, unlike SAP, which assesses individual dwellings, whole buildings are assessed in PHPP, as flats can not be certified separately.64

There are two options for services distribution in apartment blocks centralised and decentralised. Although the decentralised distribution system is more commonly used for MVHR, the alternative has its advantages if installed in a suitable project. First, it can be centrally managed, which is especially relevant in subsidised housing. Second, centralised positioning of the MVHR can deliver small space savings in individual apartments. Lastly, a central MVHR is more energy efficient, especially when the served individual units are quite small.65

Among the disadvantages are having to deal with fire compartmentalisation issues, sound attenuation challenges and the complexity of providing individual controls. 66 However, all of these can be overcome, as was demonstrated by the MĂźhlweg Street case study described in Chapter 3, so a centralised MVHR system located in the attic is proposed for the prototype.

63 64 65 66

Mead and Brylewski, p.9 Feist, 2009

â&#x20AC;&#x2DC;Design Guidelines: Non-Domestic Passive House Projectsâ&#x20AC;&#x2122;, p.56 Ibid., p.57

1.2.2.3. Passivhaus in the UK

In Germany, Passivhaus construction costs around 3%-8% extra compared to conventional alternatives.67 One of the first PH projects in the UK was 14% more expensive to construct than a house built to 2010 Building Regulations. However, due to reduced operational expenditure and the benefits of the feed-in tariffs, it was predicted that the payback period would be 17 years.68 This was a one-off project and did not benefit from the economies of scale.

Adopting Passivhaus in the UK is a challenge, since an average consumer 'expects central heating and wants a fireplace'.69 Among the main reasons for the standard’s slow adoption in the UK is the strong tradition of masonry construction, which poses challenges in terms of detailing for air-tightness and minimisation of thermal bridges. A lack of a developed market and suitable locally-produced building products is another reason, but it is likely to change when the demand increases. 70 In the meantime, savings can be achieved by simplifying building procedures and rethinking details.

Jon Bootland, ‘Passivhaus Principles’ , (EcoBuild presentation from Passivhaus Trust, 01 March 2011) <http://www.passivhaustrust.org.uk/UserFiles/File/Jon%20Bootland%20Ecobuild%20Passivhaus%20Principles.pdf>, [Accessed: 11 February 2012] 68 Nick Newman, ‘Payback: Applying Passivhaus Research to the Cost-Driven World of Construction’, (Presentation from bere:architects at the Student Passivhaus Conference, 10 October 2010) 69 Isolda Strom, Loes Joosten, and Chiel Boonstra, ‘Passive House Solutions’, (Promotion of European Passive Houses, 2006), p.42 70 Strom et al., p.5

All buildings need to be modelled in SAP to demonstrate compliance, and Passivhaus is no exception. Research by AECB into the differences between PHPP and SAP highlighted the fact that SAP underestimates the benefits of high insulation and air-tightness in low-energy houses.71 For developers eager to obtain high environmental ratings Passivhaus might not be the most attractive choice, as alternatives might deliver greater DER/TER percentage reductions.

A report by the UK-based Passivhaus Trust recommends that Passivhauscertified dwellings are granted a "deemed-to-satisfy" status for Part L 2013.72 However, as long as Passivhaus remains unrecognised as an alternative route to compliance, it will be up to the clients and the architects to transform the market.

Liz Reason, and Alan Clarke, ‘Projecting Energy Use and CO2 Emissions from Low Energy Buildings. A comparison of the Passivhaus Planning Package and SAP’, (AECB, 2008), <http://www.aecb.net/> [Accessed on: 1 April 2012], p.31 Neil Cutland, ‘Passivhaus Trust Outline Position Re. 2013 Domestic Regulations’, (Passivhaus Trust, May 2011)

2. Construction 2.1. Timber construction 2.1.1. Advantages Trees absorb carbon dioxide during their growth and store it within until they decay or are burned, making timber a highly sustainable material. Furthermore, wood consumes 50% of the energy required to produce concrete and 1% of that needed to produce steel.73

An estimated saving of 83% on embodied carbon emissions can be achieved by increasing timber content in the build-up of a 4-storey block of flats compared to traditional construction methods. 74 This figure can be further increased if timber is locally produced. Furthermore, buildings with increased timber content are generally lighter, which alleviates pressure on foundations and means that savings can be made by reducing their size.

Robert Hairstans, Off-site and Modern Methods of Timber Construction: a Sustainable Approach, (TRADA Technology, UK, 2010), p.54 74 Jill Burnett, â&#x20AC;&#x2DC;Forestry Commission Scotland Greenhouse Gas Emissions Comparison Carbon Benefits of Timber in Constructionâ&#x20AC;&#x2122;, (Edinburgh Centre for Carbon Management Ltd., Edinburgh, 2006)

2.1.2. Timber Construction in Scotland Timber frame is the most common house construction system in Scotland, accounting for 65% of the market.

Pre-fabricated kits are also available. A

system developed by the now defunct ‘RTC Timber Systems’ was capable of meeting the Passivhaus standard, but was only appropriate for low-rise housing.76

The most common structural grading for local timber is C16. Although perfectly suitable for timber framing, it is usually avoided in favour of the stronger (C24) imported timber, less of which is required. While there are some supply chain issues preventing the wide-spread use of local timber, past prejudices are the main obstacle, as it is still perceived to distort easily and to be full of knots.77 Cutting-edge multi-storey timber construction is not about linear elements; rather its basic unit now is a slab,78 which means that there are ways in which Scottish timber can become highly competitive. By reengineering the natural product into a homogenous material improved performance can be achieved, while also optimising the use of resources and minimising waste. 79 This might enable local timber to be used not only in single-family houses, but in larger residential schemes as well.

‘Designing Housing with Scottish Timber - a Guide for Designers, Specifiers and Clients: Case Studies’, (John Gilbert Architects, Forestry Commission Scotland, 2005), p.3 76 ‘Pioneering Passivhaus Timber Frame Firm Falls Victim’, Timber and Sustainable Building, 15 July 2011, <http://www.timber-building.co.uk/>, [Accessed on: 2 April 2012] 77 ‘Designing Housing with Scottish Timber…’, pp.32-33 78

Andrea Deplazes, ‘Wood: Indifferent, Synthetic, Abstract - Plastic’, in (ed.) Deplazes, A.,

Constructing Architecture: Materials, Processes, Structures - a Handbook, 2nd Edition, 79

(Birkhauser, Germany, 2010), pp.77-82, p.77 Hairstans, p.73

2.3. Modern Methods of Timber Construction 2.3.1. Applicability to Affordable Housing

In his book on the subject Robert Hairstans argues that the application of the both efficient and effective "modern methods" to off-site timber construction can lead to a more socially, economically and environmentally sustainable industry, and that only a step change such as this will enable Britain to overcome the shortage of housing.80

Within the Modern Methods of Construction (MMC) there are four product sectors: panelised units; volumetric construction; hybrid techniques, and other components.81 All of these construction systems offer quick erection on site, which is not only advantageous for rural locations, where workforce is limited, but also for urban areas - where neighbours will appreciate the reduced noise and disruption.

To gain the numerous benefits associated with the MMC, one has to take certain risks â&#x20AC;&#x201C; such as the difficulty of absorbing late design changes, the necessity to work to tight tolerances and the possibility of severe delays due to problems in the supply chain.82

80 81 82

Ibid., p.10 Ibid., p.12 Ibid., p.14

With the increasingly individualistic society, it is important to offer variety. By achieving a large degree of flexibility in a mass-production environment, one can achieve mass-customisation, allowing a set number of designs to be produced from range of standard component parts.83 This can only be costeffective when a large volume of houses is being built, and is especially relevant for affordable housing. In the Passivhaus Tenement variety can be introduced not only by removing load-bearing functions from internal walls, but also by developing a set of fenestration alternatives.

For construction to be sustainable, it has to provide a "service", rather than a finished "object",84 and breaking up the design into smaller components that, in the end of the building's life, can be rearranged without losing their value (rather than being demolished) can be an important step towards greater environmental responsibility and towards a more flexible affordable housing stock.

83 84

Ibid., p.27 Ibid., p.53

2.3.2. Engineered Timber: Cross-Laminated Panels 2.3.2.1. Properties & Features

Cross-laminated timber (CLT) is a type of MMC. It comes in panels that have an odd number of softwood plank layers stacked on top of each other at right angles and glued together under pressure (Fig.3). Walls, floors and roofs can be made out of pre-fabricated panels, reducing the time on site and delivering whole-life cost savings.85

Fig.3. Cross-Laminated Timber panel: pre-fabricated, fire resistant, air-tight86

Provided that timber comes from a certified (preferably local) source and the glue is non-toxic, CLT can be a highly sustainable material. The Passivhaus

â&#x20AC;&#x2DC;Cross-Laminated Timber: Introduction for Specifiersâ&#x20AC;&#x2122;, [TRADA Wood Information Sheet, WIS 2/3-61], (TRADA Technology, 2011) Author

Tenement can potentially store around 70 tonnes of locked-in carbon inside its structure, significantly reducing the carbon footprint of the project.87

Unlike masonry, which limits the building’s height and leads to heavy, material-intensive construction,88 12-storey buildings are possible with CLT – using 135mm internal wall, 125mm external wall and 125mm thick floor.89 In fact, to avoid over-specification of the panels, this material has to be applied to large-scale medium- and high-rise projects.90

The 9-storey high "Stadthaus" in London by Waugh Thistleton Architects was the first built example of multi-storey CLT construction in the UK. Due to the widespread lack of practical knowledge about tall timber buildings, parties such as the National House Building Council and the Building Research Establishment had to be employed by the CLT manufacturer to establish the project's feasibility.91

One of the biggest challenges for the design team was overcoming the conventional belief that timber buildings fail quicker in a fire. CLT outperforms joists and studs by relying on the fire-retarding charring of the panels. While

Based on 300m3 of CLT used in the prototype and carbon storage potential found in KLH: Sustainability, (KLH, 2012), <http://www.klhuk.com/>, [Accessed on: 9 April 2012] 88 Lehmann, p.235 89 ‘Worked Example - 12-storey Building of Cross-laminated Timber (Eurocode 5)’, (TRADA Technology, 2009) 90 Hairstans, p.86 91 Henrietta Thompson, and Andrew Waugh, Karl-Heinz Weiss, and Mathew Wells, (eds.), A Process Revealed / Auf dem Holzweg, (Murray & Sorrell FUEL / Thames & Hudson, Belgium, 2009), p.62

the three-layer lamination can deliver a fire rating of F-30, CLT used in the "Stadthaus" had 5 layers and a rating of F-60.92

It was also important to prevent the possibility of a progressive collapse. The panels can span in two directions and were designed to act as cantilevers when support is removed.93

CLT has a significantly higher density than timber frame (500 kg/m3),94 which not only provides greater thermal mass, but offers acoustic advantages as well. Although apartments and terraces built using MMC tend to suffer from acoustic transfer issues through party walls,95 CLT buildings have been shown to exceed statutory requirements.96

2.3.2.2. Suitability for Passivhaus Construction

Among the requirements for Passivhaus buildings is high performance of the building fabric – as outlined in Chapter 1.2.2. Good thermal properties of CLT (λ = 0.13 W/mK)97 help in minimising thermal bridges and enable structural elements to act as additional thermally resistant layers. However, unlike conventional timber frame, wall build-ups using CLT may lead to an increase

92 93 94 95 96 97

Thompson et al., p.12 Ibid., p.77 Hairstans, p.14 Ibid., p.14 Thompson et al., p.34

’Cross-Laminated Timber: Introduction for Specifiers’, p.8

in the overall thickness of the wall. Furthermore, substantial amounts of external insulation are likely to necessitate additional framework to support it.

With a large proportion of manufacturing carried out off-site, quality control and precision are significantly improved, which makes thermal-bridge free and air-tight construction easier to achieve. CLT panels are air-tight on their own and do not require additional measures except for the correct detailing of the junctions. 98 Furthermore, CLT panels are relatively easy to cut openings in without compromising structural properties, which helps with the integration of potentially bulky air ducts.

2.3.2.3. Procurement

Although the majority of hard work on the promotion of CLT was carried out by the design team of the "Stadthaus", there is still an obstacle - there are no current British or European standards for the material. These are likely to come in 201299 and the rise in awareness and interest is expected to increase thereafter.

The biggest producers and exporters of CLT are Austria, Switzerland and Germany, where local smallholdings supply timber such as spruce, larch and pine with strength gradings of C16 to C24.100 However, importing CLT is said

Ibid., p.8 Ibid., p.2 100 Ibid., p.5 99

to be expensive and, according to one of the first architects in Scotland to have recognised the material’s potential, John Gilbert, UK manufacture is required in order to establish a stable price appropriate to social housing.101

The type and quality of the source timber does not seem too dissimilar to what is available locally. And it probably should not be surprising to see activity aimed at establishing local manufacture to use up the vast amounts of low-grade timber available. A speaker for Wood100 announced plans for opening a factory in Scotland at a Scottish Ecological Design Association conference in 2009. 102 Binder-Jones Ltd. is another company with similar plans. Having started by supplying the UK industry with their version of the product, their ultimate goal is to manufacture CLT from British-grown wood.103 To establish the feasibility of this, structural testing of CLT from local timber is currently being carried out by the Wood Products Innovation Gateway at the Edinburgh Napier University.104

101

‘Designed for Brettstapel - Scottish Housing Expo’, (Brettstapel, 2010), <http://www.brettstapel.org/Brettstapel/Home.html>, [Accessed on: 20 March 2012] 102 Miles Montgomery cited in Balchin, A., ‘Massive Timber - Why Aren't We Using It More?’, (Unpublished BSc dissertation, University of Strathclyde, 2009), p.9 103 Binder-Jones - Press Release (Binder-Jones, 2012) <http://www.binder-jones.co.uk/> [Accessed on: 16 February 2012] 104 Edinburgh Napier University: Wood Products Innovation Gateway (Edinburgh Napier University, 2012), <http://www.napier.ac.uk/ >, [Accessed on: 15 February 2012]

3. Case Studies 3.1. M端hlweg Street, Vienna, Dietrich I Untertrifaller Architekten, 2006

Fig.4. External view of M端hlweg Street housing 105

3.1.1. Background to the Project Vienna's municipal policy in the beginning of the 1920s was highly social, to the extent that industrialised building methods were avoided in the construction of new dwellings in favour of local craftsmanship - as it provided more jobs.106 It seems that Austrian construction industry has maintained a meticulous attention to detail even as the new methods of construction took over. 105

Walter Zschokke, (ed.) Dietrich | Untertrifaller: Buildings and Projects since 2000, (Springer Wien New York, 2008), p.210 106 Wolfgang Forster, Housing in the 20th and 21st centuries, (Prestel, Munich; London, 2006), p.29

Austrian nationwide programme "Building of Tomorrow" supported research and development in sustainable construction and provided partial grants for the erection of demonstration projects, one of which was a housing scheme designed by Dietrich I Untertrifaller Architekten.107 Being the first of its kind in Europe, it required dedication on the part of all the parties involved in its delivery.108

The scheme provides 70 affordable flats for approximately 200 residents to be rented within four Passivhaus-certified 4-storey blocks with A/V ratio of 0.44. Every single apartment has a flexible plan which includes an outdoor seating area. 109

Fig.5. Typical Plan of Mühlweg Street housing 110

107

‘10 years of the program Building of Tomorrow 1999-2009’ (Federal Ministry of Transport, Innovation and Technology, Austria, 2009) 108 Dominique Gauzin-Muller, 'Green Building' in Zschokke, W. (ed.) Dietrich | Untertrifaller: Buildings and Projects since 2000, (Springer Wien New York, 2008), pp.284-293, p.289 109 Ibid., p.290 110 Zschokke, p.292

This 6,750 m2 development was delivered at 1,065 EUR/m2 (884 £/m2)111 and demonstrated that sustainable buildings were possible in the affordable housing

sector.

112

was

established

that

further

environmental

improvements could have been made at little extra cost had they been included in the original tender documents.113

3.1.2. Construction Reinforced concrete was used to construct basements, ground floor walls and stair cores, with the rest constructed from pre-fabricated CLT in a week’s time. The exterior walls achieve a U-value of 0.145 W/m2K. The roof has a U-value of 0.075 W/m2k by having 400mm of insulation on top of 146mm-thick CLT panels. Triple-glazed windows have a U-value of 0.74 W/m2K.114

Fig.6. Detail of exterior wall of Mühlweg Street housing 115

111 112 113 114 115

At a Euro/Pound conversion rate 0.83 Gauzin-Muller in Zshokke, p.291 ‘10 years of the program Building of Tomorrow 1999-2009’ Gauzin-Muller in Zshokke, p.290 Zschokke, p.293

3.1.3. Environmental Systems and Performance All apartment blocks have an 83% efficient centralised MVHR system located on the roof, supplying 1800 m3 of air per hour. The air is delivered at 17Â°C, and all flats have small space heaters in each room. Hot and cold water meters are located within each flat. Although each block has 60m2 of solar hot water collectors, they are not enough to meet the total demand, so the basement accommodates two gas tanks feeding a boiler and supplying energy for the pre-heating of the air when the outside temperature falls to -3Â°C.116

The buildingâ&#x20AC;&#x2122;s annual heating demand is under 10 kWh/m2 and an airtightness test revealed an air exchange rate n50 below 0.3 1/h.117

The overwhelming majority of residents highly rate the quality of accommodation and attribute this to the use of wood as a construction material and the adherence to the Passivhaus standard.118

116 117 118

Ibid., p.290 Ibid., p.290 [Results of a survey, 2007], Ibid., p.292

3.2. Passivhaus and Massive Timber in the UK Although the adoption of both Passivhaus and solid timber construction in UK has been slow due to the reasons outlined in Chapters 1.2.2.3 and 2.3.2.3, there are some relevant case studies to refer to. A short description is followed by a comparative table. Nash Terrace, Aubert Park, 4orm Architects, London

Fig.7. External view of Nash Terrace 119 This Passivhaus terrace was erected in 5 weeks using DubelHolz solid timber panels. Each house has a double height living cube, four double bedrooms with en suites, a cinema room, a games room and two roof terraces. Each house collects rainwater for WCs and laundry; each has whole house MVHR and a ground source heat pump providing heating and domestic hot water. The annual energy bill is ÂŁ80, 120 which is still unlikely to compensate for the exuberant price charged for apartments.

119

(Nash Terrace, Aubert Park (2010) Fact Sheet. 4orm Architects. Available at: www.4orm.co.uk (Accessed 15 March 2012) 120 Our Portfolio, (Building Research Establishment, Watford, 2012),

<http://www.passivhaus.org.uk/podpage.jsp?id=90>, [Accessed on: 12 February 2012]

Bridport House, Karakusevic Carson Architects, London, 2011

Fig.8. Model of the completed CLT shell of Bridport House 121

This affordable apartment block was developed for The Homes & Communities Agency for a total budget of £6,000,000. As the building sits on top of a sewer, care had to be taken not to overload it, so CLT was chosen for its light weight and ability to deliver an increase in the number of units. Engineered brick was nevertheless adopted as external finish. Structure was built in 10 weeks and cores were also made from CLT to eliminate movement joints. Internal walls are non-load-bearing to increase flexibility. Acoustic performance of party elements exceeds the Building Regulations by 5dB. The project also features a brown roof and photovoltaic panels, achieving the Code for Sustainable Homes Level 4.122

121

Cook, S., ‘Bridport House – The Contractor’s View’ [Presentation] (Wilmott Dixon Group, 2011), <www.buildingcentre.co.uk>, [Accessed on: 1 April 2012] 122 Amanda Birch, 'Technical: Timber Structures: Bridport House', BD Online, 24 Jun 2011, <www.bdonline.co.uk>, (pp.16-17)

Stadthaus, Waugh Thistleton Architects, London, 2008

Fig.9. Perspective section through the Stadthaus 123

This block of 29 apartments on a tight 17m x 17m site was the first project in the UK to have used CLT. The challenges the design team faced are described in Chapter 2.3.2.1.

It was delivered during a 49 week period, which

compares to the estimated 72 if the building had been in concrete. 124 The designers of the "Stadthaus" exceeded acoustic requirements125 and achieved EcoHomes “Very Good” rating.126

123

Thompson et al., p.75 Ibid., p.8 125 Ibid., p.34 126 Kucharek, J.C., ‘Process: Wood for the Hood’, RIBA Journal, 2010, <http://www.ribajournal.com/>, [Accessed on: 1 April 2012] 124

Summary of Case Study Data

Total area

CLT

Development

Erection

time (w)

2006 2010 2011 2009

4 5 5-8 9

6,750 2,328* 4,220 2,750

1x4 5 12 9

Total budget

Cost per m2

Cost per Dwelling

Price per Dwelling

Specific Space Heating Demand

kg/m2 CO2

Mühlweg Aubert Park Bridport

5,966,663 6,000,000

884** 1,422

85,238 146,341

2,500,000 -

10 11 -

***

Stadthaus

3,800,000

1,400127

131,034

28.69128

Case Study Mühlweg Aubert Park Bridport Stadthaus

Case Study

Year

U-value (W/m2K)

Case Study Mühlweg Aubert Park Bridport Stadthaus

wall

roof

window

0.145 0.15 0.13 0.27130

0.075 0.17 0.12 -

0.74 0.7 1.37 -

No of units

Size of units m2

70 8 41 29

96 291 103 95

Affordable

No of Storeys

housing ratio 100% 0% 100% 46%

Air tightness ac/h

Air perm. m3/h/m2

MVHR

CLT produced by

0.3 0.5 -

3 3

83% 70%131

KLH129 Kaufmann StoraEnso KLH

Green features & technologies / Achieved code levels 60m2 of solar hot water collectors per block Rainwater harvesting, GSHP for heating and DHW 132 Brown roof, photovoltaic panels; Code for Sustainable Homes (CSH) Level 4. EcoHomes Very Good

133

* Red denotes deduced figures; all other data comes from previously identified sources unless noted otherwise ** Euro to Pound conversion rate - 0.83 *** A 25% reduction of DER/TER 2010 can be assumed (CSH 4)134 127

Thompson et al., p.36 Lowenstein, O., ‘Towering Timber’, The Architect’s Journal, 08.05.08, pp.40-42 129 ‘10 years of the program Building of Tomorrow 1999-2009’ 130 ‘Saving 120 tonnes of CO2’, Detain Green, 02/2009, (p.2) 131 ‘Stadthaus, 24 Murray Grove, London’, [Case Study], (TRADA Technology, 2009) 132 All information from: Nash Terrace, Aubert Park - Fact Sheet, (4orm Architects, 2010), <www.4orm.co.uk>, [Accessed on: 15 March 2012] 133 All information from: Birch, 2011 134 ‘Code for Sustainable Homes: Technical Guide’ ,(Department for Communities and Local Government, London, November 2010), p.32 128

3.3. Conclusions

All projects featured short construction time, which usually entails some savings. Their acoustic performance typically exceeds recommended levels, demonstrating that traditional problems with noise transfer in flats can be minimised. 135

Typical costs vary - the only combination of Passivhaus with CLT identified in the UK is an up-market development in central London. Apart from its location, the high apartment prices could be attributed to the abundance of costly green technologies and extravagant space allowances. The average cost of affordable low-energy multi-storey accommodation made from CLT in London is around 1,400 £/m2.

The Austrian project seems to have been heavily subsidised by manufacturers interested in promoting the uptake of their products in schemes of this kind. Its affordability could be replicated if similar market conditions existed in Scotland. According to some sources, parallel tendering for the same project revealed that the “eco-desirable” version cost only 1.9% extra. 136 A factor that contributed to the low cost of construction was the large scale of the development.

135

Sean Smith, John B Wood, and Richard Mackenzie, ‘Housing and Sound Insulation: Improving Existing Attached Dwellings and Designing for Conversions’, (Scottish Building Standards Agency; Historic Scotland; Communities Scotland. Arcamedia, Edinburgh, 2006), <http://www.scotland.gov.uk/Resource/Doc/217736/0099123.pdf>, [Accessed on: 16 March 2012] 136 Lehmann, p.335

Two of the UK projects achieved comparable environmental ratings – EcoHomes “Very Good” and what it was later replaced with in England and Wales – CSH Level 4. Having done this without gaining Passivhaus certification means that the proposed prototype might even exceed these levels if similar “green” features are used.

Unlike Mühlweg Street housing, Bridport and Stadthaus had stair and lift cores made of CLT. This strategy is proposed for the prototype, as it avoids movement joints but achieves sufficient fire rating. The Viennese project is the closest to the Passivhaus Tenement in its form, so the same thickness of CLT will be used for U-value and floor area calculations.

The case studies had different approaches to cladding. While Bridport was faced in brick, Stadthaus used composite timber panels, and the walls of Mühlweg Street housing were rendered. Passivhaus does not entail a predefined aesthetic and all of these cladding options are possible. However, for the Passivhaus Tenement it is suggested that rendering is used as it minimises thermal bridging and can save an equivalent of an extra room per tenement compared to brick veneer cladding.137

Successful schemes are the key to fostering the uptake of the material and more case studies can be found in Lehmann, 2010.138

137 138

See Appendix 6.1 Lehmann, pp.335-346

4. Simulation 4.1. Description of Method & Scenarios 4.1.1. Method In order to put the proposed Passivhaus Tenement in context, several scenarios were selected for carrying out comparisons of their specific annual heating demand and their Dwelling CO2 Emission Rate (DER): 1. Original tenement 2. Refurbished tenement 3. Building Standards tenement from CLT 4. Passivhaus Tenement

This study was undertaken with the help of two software applications. Even though the author is not a certified user, best care was taken to ensure correct data entry.

The use of Passive House Planning Package (PHPP) 139 is mandatory to achieve PH certification. Developed to help architects and engineers optimise the design of passive houses, it requires the input of geometric data, occupancy and component specification in order to predict the whole building performance. 139

Passive House Institute, Passive House Planning Package 2007 [Computer Programme], Available from the Building Research Establishment, <http://www.passivhaus.org.uk/page.jsp?id=25>

FSAP 2009

140

was used to perform SAP calculations to demonstrate

compliance with the Building Standards and to determine Ene 1 and Ene 2 Credits for EcoHomes. Unlike PHPP, where the whole tenement was modelled, an area-weighted figure was obtained from separate flat simulations.

When building in existing urban fabric, the maximum building footprint is usually pre-determined. Therefore for the purposes of this study external dimensions were kept constant (Fig.10), 141 leaving internal floor areas and ceiling heights to vary depending on their construction.

Fig.10. Diagram of a typical tenement with assumed external dimensions 142

140

Stroma Certification, FSAP 2009 (1.4.0.63), [Computer Programme], (2009) Available at: <http://www.stromamembers.co.uk/SAPUser.aspxs> 141 See Appendix 6.2 for external dimensions 142 Author

In PHPP, the dimensions used are always the exterior dimensions of the thermal envelope and the treated floor area required in calculations excludes all walls. 143 In SAP, internal dimensions of walls are used and the floor area includes the footprint of partitions.144

Fig.11. Diagram of the thermal envelope modelled in this study 145

The prototype was based on the plan of a typical pre-1919 tenement (Fig.1). External wall thickness was assumed to be 600mm 146 , and the plan was scaled up to conform. As the unheated common stairwell was omitted from the thermal envelope (Fig.11), the walls and doors facing the close were considered semi-external, with a corresponding reduction factor used in

143 144 145 146

Feist, 2010, p.38 ‘The Government’s Standard Assessment Procedure for Energy Rating of Dwellings’, p.7 Author

‘Energy Efficiency Best Practice in Housing - Scotland: Assessing U-values of existing housing’, (Energy Saving Trust, 2004), <http://www.energysavingtrust.org.uk>, [Accessed

on: 16 March 2012]

calculating their U-values. 147 Further adjustments were made to the overall floor and exterior wall areas to exclude the close before supplying the figures to both SAP and PHPP.

Wall

build-ups

have

been

modelled

Dynamic

Thermal

Property

Calculator,148 arriving at kappa-values specific for the project and ready for input into SAP. Taken as a whole, the values were a little above the average thermal mass parameter. In PHPP, default values for high (Scenarios 1, 2) and medium (3, 4) were used.

An allowance for thermal bridging in SAP was based on the total exposed surface area, and in PHPP, lengths of geometric thermal bridges were kept constant, with the coefficient changing according to scenario.

For the study to cover the worst-case scenario a free-standing tenement was modelled, and in all of the SAP simulations ‘heavy’ overshadowing was assumed. In PHPP a row of tenements was placed in front of all windows at the minimum allowed distance of 18m, as defined by the Glasgow City Council.149 For the same reasons, as 60% of all glazing in the tenement is located at the front, north-facing orientation was chosen for the front façade.

147

‘The Government’s Standard Assessment Procedure for Energy Rating of Dwellings’, p.16 The Concrete Centre, Dynamic Thermal Property Calculator Tool (v.1), [Computer programme], (Developed by Arup, 2010), Available at: <http://www.concretecentre.com/> 149 ‘City Plan 2 – Development Guides Accompanying City Plan 2 – Residential’, [DG/RES1-3], (Glasgow City Council, 2009) <http://www.glasgow.gov.uk/>, [Accessed on: 1 April 2012], p.40 148

The heating system in all scenarios was based on the one described in Package 1, clause 6.1.2 of the Building Standards (Scotland). Individual flats are equipped with gas boilers for space heating and have a metered supply of hot water from a community solar hot water system, which is supplemented by a gas boiler.

Full description of parameters used in the simulation is contained in Appendices 6.3.-6.5.

4.1.2. Scenarios 1 & 2 – Original & Refurbished Tenements U-values for external walls were taken from research outcomes by Baker150 1.1 W/m2K, and are more optimistic than other sources. U-value for the close wall, 0.76 W/m2K, is an average of in-situ measurements by Baker 151 subjected to the reduction factor as described previously. U-values of the roof, floor and windows were taken as 1.6, 0.6 and 4.8 W/m2K.152

70% of air leakage through the external skin of traditional dwellings can be attributed to poor workmanship, rather than being intentional.153 Due to the lack of data regarding the actual air-tightness of the original tenement, a value of 10 m3/h*m2 at 50 Pa was assumed, which is the maximum recommended in the Building Standards.

For Scenario 2, the original tenement was subjected to a series of improvements that would take it closer to Package 1154, but that would not disturb the fabric too much. Windows were replaced with double-glazed units and draft-proofing lowered the air permeability to 7. Loft insulation helped achieve 0.13 W/m2K and the roof was fitted with 35m2 of evacuated tube collectors.

150

Dr. Paul Baker, ‘U-values and Traditional Buildings: In Situ Measurements and Their Comparisons to Calculated Values’, [Historic Scotland Technical Paper 10], (Glasgow Caledonian University, 2011) Baker, Table 2, p.16

151 152

‘Energy Efficiency Best Practice in Housing - Scotland: Assessing U-values of existing housing’ 153 ‘Air tightness in UK dwellings’, [BRE Information Paper: IP01/00], (Building Research Establishment, January 2000)

154

‘Building Standards Domestic 2011 Technical Handbook’, Clause 6.1.2

4.1.3. Scenario 3 - Building Standards + CLT The ‘whole dwelling approach’ to energy use was adopted in the Building Standards to allow greater design flexibility. It focuses on the calculated carbon dioxide emissions (DER) not exceeding the target carbon emissions (TER) for a ‘notional dwelling’.155

A simplified approach which avoids SAP calculations is designing the building to one of the ‘packages’ defined in clause 6.1.2. The first ‘package’ was selected for the purposes of this study. It specifies U-values for all building elements, an air permeability of 7 m3/m2h, y-value of 0.08 W/m2K and glazing solar energy transmittance of 0.63.

The thermal conductivity of insulation was set at 0.035 W/mK, which is achievable with both conventional insulation and also more sustainable materials. Achieving the target U-values with 96mm of CLT reduces the thickness of external walls to 315mm. However, as the common stairwell was outside the thermal envelope, close walls had to be treated as fire-rated, acoustically-isolated semi-external walls, resulting in increase in their thickness. 156 A saving of 26m2 can nevertheless be made in the total floor area compared to the original tenement.

155 156

Ibid. See Appendix 6.6. for wall construction

The simplified approach was not designed to cover the worst-case scenario. Without modifying the thickness of insulation, compliance with the Building Standards Section 6 and a 2% reduction of DER/TER could be achieved by increasing the g-value to 0.72, improving air permeability to 5 m3/m2h157 and almost eliminating thermal bridging (Fig.12).

TER 22.00

21.31

21.18

21.00

20.79 19.90

20.00

kg/m2/a

19.00

19.24 (2%)

19.15 (3%)

18.00

17.00

16.91 (14%)

16.00

15.00

nd ar (li

ttl e

ld in g

St a

y Bu i

pe rm ea bi lit

ov er sh ad ow in g)

5 =

0. 02 = yva lu e

= al ue gv

ov er sh ad ow in g)

0. 72

ai r

(li

ttl e

(G ui

de lin es )

14.00

Fig.12. Achieving Building Standards compliance in the worst case scenario: DER, TER and % Reduction 158

The tenement does not fully satisfy the Building Standards and some of the areas in which it fails to comply are identified in Appendix 6.8.

157

This is the lowest limit before Mechanical Ventilation is required (â&#x20AC;&#x2DC;Building Standards

Domestic 2011 Technical Handbookâ&#x20AC;&#x2122;, Clause 3.14.10)

158

Author

4.1.4. Scenario 4 - Building Standards + CLT + Passivhaus

As a basis for the development of the prototype, guideline specifications described in Chapter 1.2.2.1 were taken. U-value for the roof and the presence of solar panels were ‘inherited’ from Scenario 3. Modelling in PHPP, assuming a total occupancy of 16 people, has demonstrated that this does not yield a working PH159 in the worst case scenario unless the tenement is adjacent to at least one other.

Specific Space Heating Demand (kWh/m2/a) Heating Load (W/m2) Specific Primary Energy Demand (kWh/m2/a) 90

81 77

70 60 50 40 30

22 18

20 10

Passivhaus Tenement (Guidelines)

Adjacent to 1

Terrace

Fig.13. Effect of terracing on PH compliance of a tenement designed to guideline specifications 160

159

See Chapter 1.2.2.1 for definition and criteria Author. Specific Space Heating Demand – amount of energy needed to heat 1 m2 of a building per year; Heating Load – maximum load on the heating system per m2; Specific Primary Energy Demand – includes DHW, Heating, Cooling, Auxiliary and Household Electricity and expresses the energy in primary units, which depends on fuel type used.

160

To ensure performance in all configurations, improvements had to be sought. Specific Space Heating Demand (kWh/m2/a) Heating Load (W/m2) Specific Primary Energy Demand (kWh/m2/a) 90

70 60 50 40

Passivhaus (Guidelines)

Higher g-value (0.68)

10 0

Better MVHR Lower Specific Better AirEfficiency Fan Power (1) tightness (0.3) (85%)

Passivhaus

Fig.14. Development of Passivhaus-compliant prototype using PHPP 161

Either the efficiency of MVHR had to be raised to the best practice standard of 85% 162 , or air-tightness had to be improved to 0.3 ac/h, as seen in the Mühlweg Street scheme. A combination of improvements outlined in Fig.14 was added to the baseline specification for the Passivhaus Tenement prototype to ensure workability at the maximum allowed U-values.

External walls ended up being 370mm thick, saving 4m2 compared to the original construction within the same external dimensions. 161 162

Author

‘Energy Efficient Ventilation in Dwellings – a Guide for Specifiers’, [GPG268], (Energy

Saving Trust, 2006), <http://www.energysavingtrust.org.uk>, [Accessed on: 30 March 2012]

Although Passivhaus demands an addition of an MVHR system, no extra space would be required within individual flats, as the vertical riser for the centralised distribution could be positioned in the storage cupboard.

The

thickness of the floors, on the other hand, had to be increased to accommodate air distribution ducts, which reduced the total treated volume.

4.2. Simulation Results & Analysis 4.2.1. Compliance Check To check the performance of the four scenarios against the Building Regulations, their DER was compared to TER163 and the results are presented in Fig.15. As could be expected, the first two scenarios are far from reaching the benchmark while the Passivhaus Tenement exceeds it.

TER 50.00

45.42 45.00

40.00

34.84

kg/m2/a

35.00

30.00

25.00

20.00

19.24 (2.4%)

15.00

14.33 (24.7%)

10.00

5.00

Original Tenement

Refurbished Tenement

Building Standards

Passivhaus

Fig.15. Dwelling Emission Rate (DER), Target Emission Rate (TER) and % Reduction 164

163 164

values taken from FSAP 2009 Author

The DER taken from SAP was then evaluated against comparable CO2 emissions estimated by PHPP165. SAP PHPP 100 90

80 70

kg/m2/a

60 50

45 35

40 30

Original Tenement

Refurbished Tenement

Building Standards

Passivhaus

Fig.16. Total CO2 Emissions Equivalent (no household applications) – comparison of SAP (DER) and PHPP results 166

Research by AECB has that SAP not only underestimates the benefits of high insulation and air-tightness in low-energy houses, as mentioned previously in Chapter 1.2.2.3., but also underestimates the efficiency of MVHR systems.167 This is a possible explanation for the shift in value domination in the last scenario (Fig.16).

While the Building Standards tenement could get 9 EcoHomes credits for Ene 1 category, Passivhaus could obtain at least 11.168

165 166 167 168

Taken from ‘PE Value’ worksheet Author Reason and Clarke, p.31

‘EcoHomes 2006: The Environmental Rating for Homes. The Guidance 2006’, Issue 1.2,

(Building Research Establishment, Watford, April 2006), p.6

EcoHomes category Ene 2 credits are assigned for low heat loss parameters 169 , and again, Passivhaus would have gained more credits (Fig.17).

Heat Loss Parameter Ene 2 - 1 Credit Ene 2 - 2 Credits 4.00

3.50

3.41

3.00

2.67

W/m K

2.50

2.00

1.29 (1)

1.50

1.00

0.60 (2)

0.50

0.00

Original Tenement

Refurbished Tenement

Building Standards

Passivhaus

Fig.17. Heat Loss Parameter and EcoHomes Ene 2 Credits (based on SAP calculations) 170

169 170

Ibid., p.11 Author

4.2.2. Specific Annual Heating Demand Due to inherent differences in the approach to internal heat gains calculations, results from PHPP tend to be higher,171 which was confirmed in this study.

SAP

PHPP

FEE

300

246

250

kWh/m /a

200

183 157

168

150

126

136

100

77 55

63 45

Original Tenement

Refurbished Tenement

Building Standards

Passivhaus

Fig.18. Specific Annual Space Heating Demand and Fabric Energy Efficiency (Comparison of SAP and PHPP results) 172

Although falling short of the 39 kWh/m2/a set by the Fabric Energy Efficiency Standard in the worst case scenario, detached north-facing Passivhaus Tenement is able of meeting it when overshadowing is removed.

171

Paul Tuohy, and Davis Langdon LLP, â&#x20AC;&#x2DC;Benchmarking Scottish energy standards: Passive House and CarbonLite Standards: A comparison of space heating energy demand using SAP, SBEM, and PHPP methodologiesâ&#x20AC;&#x2122;, [Report commissioned by the Directorate for the Built Environment, Scottish Government], (ESRU, University of Strathclyde, 2009), p.20 Author

172

The tenement has 4 flat types and their specific annual space heating demand varies considerably. This effect was extreme in the Passivhaus, where mid-floor flats required less than a half of the ground or top floor flatâ&#x20AC;&#x2122;s demand (Fig.19).

)

Passivhaus Building Regulations 16

Third Floor

58 7

Second Floor

49 8

First Floor

50 20

Ground Floor

64 0

kWh/m2/a

Fig.19. Specific Annual Space Heating Demand Variations (per flat type, as modelled in SAP) 173

This discrepancy is neutralised by the centralised MVHR, spreading the cost of heating among all the residents. Estimated increase in the non-domestic electricity usage, mainly due to MVHR, is shown in Fig.20. Estimated annual bills can be found in Appendix 6.7.

173

Author

80.0 70.0 60.0

77.0

kWh/m /a

50.0 40.0 30.0

55.1

20.0 10.0

20.0

ing ild Bu

a St

d ar nd

12.6

1.6

0.0

1.9 2.4

) PP PH ( s

in ild Bu

a St

ar nd

9.8

P) SA ( s iv ss Pa

u ha

) PP PH ( s iv ss Pa

P) SA ( s

Gas (Space Heating)

Electricity (Auxiliary)

Fig.20. Specific Annual Space Heating and Auxiliary Electricity Demand (comparison of SAP and PHPP) 174

Having ensured that the prototype works in the worst-case scenario, orientation was changed and street width was increased from 18 to 100m to determine potential savings. The results shown in Fig.21 indicate that increasing the width of the street is particularly beneficial for south-facing Passivhaus tenements, which highlights its reliance on solar gains as a source of heat.

174

Author

North-facing

South-facing

West-facing

East-facing

300

250

246 246 246 246

200

kWh/m 2/a

183 182 183 183

150

100 77

50 20

Original Tenement

Refurbished Tenement

Building Regulations Passivhaus Tenement Tenement

North-facing (little overshadowing)

South-facing (little overshadowing)

West-facing (little overshadowing)

East-facing (little overshadowing)

300

250

241 240 244 244

200

kWh/m 2/a

179 178 181 181

150

100 73

50 19

Original Tenement

Refurbished Tenement

Building Regulations Passivhaus Tenement Tenement

Fig.21. Difference in Specific Annual Heating Demand Depending on Orientation and Street Width (based on PHPP results) 175 175

Author

4.2.3. Effect of Urban Configurations 4.2.3.1. Effect of Terracing

Passivhaus Tenement was modelled adjacent to one and two other tenements, achieving respective savings of 3 and 7 kWh/m2/a (see Fig.22). No heat loss was assumed through party walls. Specific Space Heating Demand (kWh/m2/a) Heating Load (W/m2) Specific Primary Energy Demand (kWh/m2/a) 80

73 69 70

20 17

13 10

Passivhaus Tenement

Adjacent to 1

Terrace

Fig.22. Effect of terracing on the performance of PH Tenement (as modelled in PHPP) 176

176

Author

4.2.3.2. Effect of Hillside Terracing

Effects of the partially exposed party walls when the tenements are located on a hill are presented on Fig.23. A half a storey (2.2 m) change in level was assumed between adjacent buildings.

Specific Space Heating Demand (kWh/m2/a) Heating Load (W/m2) Specific Primary Energy Demand (kWh/m2/a) 80

73 69

20 17

17 14

Passivhaus Tenement

Adjacent to 1 lower

Adjacent to 1 higher

Hillside Terrace

Fig.23. Effect of hillside terracing on the performance of PH Tenement (as modelled in PHPP) 177

177

Author

5. Discussion

The Passivhaus Tenement is an urban counterpart to sustainable single-family housing already being developed in Glasgow. Not only is it perfectly suited to compliment traditional tenements in the West and South of the city (where affordable housing is in particularly high demand (1.1.2)); it could also be constructed in areas that lack density, which is in line with the “decentralised concentration” theory (1.1.1.).

The prototype addresses the need to provide accommodation for the growing number of households. As the energy consumption of households does not follow a simple geometric progression and the smaller the household, the less energy efficient it is,178 it is of special significance that the clustering of these smaller households delivers combined carbon savings. Smaller households also tend to be more vulnerable to fuel poverty, 179 but the Passivhaus Tenement is a further step towards its eradication (4.2.2.).

The Passivhaus Tenement constructed to minimum specifications outlined in Chapter 1.2.2.1 exceeds the Building Standards but is not able to meet the criteria required for Passivhaus certification in the worst-case scenario. Best

178

Tina Fawcett, Kevin Lane and Brenda Boardman, ‘Lower Carbon Futures for European Households’, (Environmental Change Institute, Oxford, 2000),

<www.eci.ox.ac.uk/research/energy/downloads/lowercarbonfuturereport>, [Accessed on: 11 February 2012] 179 ‘Glasgow’s Strategic Housing Investment Plan 2010/11 to 2014/15’, (Glasgow City Council, 10 November 2010), <http://www.glasgow.gov.uk>, [Accessed on: 5 April 2012], p.20

practice improvements introduced in Chapter 4.1.4 ensure that it not only meets PH-criteria, but also gains a minimum of eleven credits for EcoHomes Ene 1 and two for Ene 2. This simplifies the route to obtaining a “Very Good” rating.

By exceeding the TER of the current Building Standards (which is a 30% reduction on 2007 Standards) by at least 24%, the Passivhaus Tenement is in good position to achieve the 60% reduction required by 2013 and the Fabric Energy Efficiency Standard compulsory from 2016. It already achieves a DER that qualifies for the Building Standard’s Silver level.

As shown in Chapter 4.2.2, even though the heating demand varies between flats, a centralised MVHR helps redistribute solar gains and significantly cuts down the bills. High ceilings and good natural lighting levels are maintained even with bulky air ducts. A vertical riser could be placed in the storage cupboard, without encroaching on the living space.

Despite the thick walls required to achieve the Passivhaus standard, the prototype does not lose any of the floor space present in the original tenement with identical external dimensions. However, no saving of an extra room per tenement can be achieved unlike the alternative constructed to the Building Standards.

Traditional tenement configurations found in Glasgow are also beneficial for the annual heating bill of the residents and are worth replicating (4.2.3). Furthermore, they may allow down-specifying the components to the minimum (4.1.4).

Construction using CLT was found to not only be highly sustainable, but also especially appropriate for multi-storey buildings (2.3.1.1). Its air-tightness and thermal mass were identified as favourable for construction of low-energy buildings (2.3.1.2). The ability of the panels to span in two directions enables the removal of load-bearing walls from the interiors of the flats, making them more flexible. Pre-fabrication of panels ensures quick erection on site and can provide economies of scale. At the end of their lifecycle, tenements could be dismantled and later reassembled in a different location or in a different manner - this type of investment should be particularly attractive for the affordable housing sector.

UK examples of CLT construction were found to exceed statutory acoustic requirements (3.3). Moreover, higher levels of air-tightness proposed are not only beneficial for energy conservation, but further contribute to noise reduction. 180 This property might overcome previous presumptions about flatted accommodation.

180

McMullan, R., Environmental Science in Building, Sixth Edition, (Palgrave Macmillan, Hampshire, 2007), p.196

To improve the performance of the prototype, the pitch of the roof could be changed to optimise the efficiency of the solar collectors, together with maximising their overall area.181 Additional LZCGT could be incorporated into the project to lower the carbon footprint even further. Some are especially efficient when they serve multiple buildings. 182 Some, like the photovoltaic panels, can be an alternative to solar thermal collectors in reducing pay-back time through the benefits of the Feed-In Tariffs.183

Treating the close walls as external and achieving the necessary U-values without applying any reduction factors (4.1.1) will deliver further energy savings and make the design more fool-proof.

When the tenement has a commercial function on ground floor, the effects of including it in the thermal envelope and connecting it to the centralised MVHR should be considered, as the benefits of any extra heat available might be balanced out by additional air extraction requirements.

181

Photovoltaic Geographical Information System - PV potential estimation utility (PV GIS, 2012), <http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php#>, [Accessed on: 1 April, 2012] 182 Mansouri, S., â&#x20AC;&#x2DC;Glasgow tenements: Past, Present and a Sustainable Future?â&#x20AC;&#x2122; [Dissertation], (Mackintosh School of Architecture, Glasgow, 2010) - looked at retrofitting exiting tenements, but the study of application of low and zero carbon generating technologies is applicable to new builds as well. 183 Tariffs payable per kWh of electricity produced, (Feed-in Tariffs, 2012), < http://www.fitariffs.co.uk/eligible/levels/>, [Accessed on: 10 April 2012]

Common barriers to achieving low carbon targets in the European construction sector were identified by Musau and Deveci. 184 One of the barriers is the split incentive - the unwillingness of owners to invest in energy efficiency when tenants pay the bills. Even though additional government funding is not available, if the developer is a social landlord acting in the interest of the tenants, they may posses this will.

The lack of locally available standard solutions was also identified as a general obstacle,185 but it is expected that with several companies already progressing in that direction, locally-produced cross-laminated timber will soon be on the market. However, there is no guarantee that this will dramatically decrease the price or reduce the carbon footprint of the product. Demand needs to be sufficient to drive the competition, foster improvement and reduce costs.

One way of increasing demand is incorporating standard details possible with CLT into the Robust Details directory 186 , which should encourage the productâ&#x20AC;&#x2122;s uptake with less adventurous practitioners. Incorporation into the Green Guide might also be beneficial, as currently a bespoke service is required to obtain a rating necessary for the EcoHomes assessment.187

184

Filbert Musau, and Gokay Deveci, 'From Targets to Occupied Low Carbon Homes: Assessing the Challenges and Delivering Low Carbon Affordable Housing' [PLEA 2011, 27th International Conference on Passive and Low Energy Architecture, Louvain-la-Neuve, Belgium, 13-15 July 2011], in Bodard, M., Evrard, A. (eds.) Architecture and Sustainable Development, Volume 2., pp.261-266., p.262 185 Ibid., p.262 186 The scheme now applies to Scotland. Robust Details (2012) <http://www.robustdetails.com/>, [Accessed on: 4 April 2012] 187 Green Guide 2008 Ratings, (Building Research Establishment, 2012), <http://www.bre.co.uk/greenguide>, [Accessed: 6 April 2012]

The collaboration between GHA and City Building on the 'Glasgow House' addresses another barrier identified in the above mentioned paper - the gap in the skills and knowledge.188 By adopting the same approach, not only can the design be improved through practical testing, but the skills required for its delivery can be sustainably disseminated. If seen as a positive tool, this should not necessarily lead to the ‘stifling of innovation’. 189 The Passivhaus Tenement could be an open-source prototype that housing associations could develop and share, contributing to affordability through directing the savings on the design fees to specifying better components.

Extra costs associated with high-performance components vary. Typical increases of 10-15% were reported in Germany and Austria in the previous decade190, with some current reports pointing to 3-8%.191 Until the demand is high enough to lower the prices in Scotland, cost-effective improvements could be pursued. Performance of cheaper windows can be optimised by ensuring that wall insulation covers much of their frame. 192 Air-tightness at junctions can be achieved through the training of the builders.193 Reduction of thermal bridging is also more a matter of careful consideration than of significant capital investment.

188

Musau and Deveci, p.262 David Rudlin and Nicholas Falk, Building the 21st Century Home. The Sustainable Urban Neighbourhood, (Architectural Press, Oxford, 1999), p.119 190 Berthold Kaufman, ‘Economics of High-Performance Houses’, in Hastings, R. and Wall, M. (eds.) Sustainable Solar Housing. Volume 1 – Strategies and Solutions., (Earthscan, London, 2007), pp. 51-62, p.60 191 Bootland, p.26 192 Kaufmann in Hastings, p.55 193 Ibid., p.59 189

Among the additions required to bring the tenement from the Building Standards level to Passivhaus are 1300m2 of 50mm thick insulation and an MVHR system. Assuming a 5% increase on the base cost of £1400/m2, ignoring the projected fuel price rise, the Renewable Heat Incentive 194 and relying on SAP calculations, the payback period would be 124 years. However, if PHPP calculations are used, which are more optimistic on the electricity needed to power the MVHR, only 35 years are required.195

Even though the time expectation of long-term oriented owners (such as housing associations) is between 50-100 years, 196 and 35 years is not too inappropriate, it is the government subsidy that determines the budget of social housing.197 The estimated £700/m2 allocated to housing associations by the Glasgow City Council198 only covers half of the predicted costs, and even the average actual price paid for social rented new builds in 2008/09 is nowhere near the required figure.

199

Unless housing associations are

particularly successful at developing their assets, they are unlikely to invest in high-performance projects as long as costs remain so high.

194

Tariff level tables, (Renewable Heat Incentive, 2012), < http://www.rhincentive.co.uk/eligible/levels/>, [Accessed on: 10 April 2012] 195 see Appendix 6.7 for calculation 196 Holger Konig, Niklaus Kohler, et al., A Life-cycle Approach to Buildings. Principles, Calculations, Design Tools, (Edition Detail Green Books, Munich, 2010), p.15 197 Rudlin and Falk, p.115 198 As mentioned in Chapter 1.1.2, 1 housing unit has a funding of around £76,000, and a tenement will receive 607,400. 199 ‘Business Plan 2008/09. Better Homes, Better Lives’, (Glasgow Housing Association, 2007) < http://www.gha.org.uk/>, [Accessed on: 3 April, 2010], p.24

Housing associations do however have the ability to make savings on the purchase of land. Not only does it account for more than a half of the cost of housing, its value tends to be the lowest in the inner city.200 This is one of the reasons dense urban developments possible with tenements are particularly appropriate for affordable accommodation.

Taking lifecycle costs rather than capital costs as a driver means including the costs of operation and deconstruction, among other aspects.201 Adopting such an approach renders the Passivhaus Tenement from cross-laminated timber a valid prototype for sustainable future-proof housing. Affordability is ensured by low operational costs, economies of scale possible with off-site prefabrication, and by the performance of its components only slightly exceeding the minimum recommended specification.

As long as SAP keeps underestimating the benefits of the key features of Passivhaus, it remains unlikely that this voluntary standard will be widely adopted. Until the market develops to offer CLT at a considerably lower price, the uptake of this material is likely to remain slow, unless the housing associations take it in their hands and drive the demand, reducing the costs through wide-scale application.

200 201

Rudlin and Falk, pp.113, 116 Ibid., p.16

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Hairstans, R., Off-site and Modern Methods of Timber Construction: a Sustainable Approach, (TRADA Technology, UK, 2010) ‘Housing Stock by Tenure for Glasgow's Wards’ (Glasgow City Council, Development & Regeneration Services, 2011) <http://www.glasgow.gov.uk/en/Business/Planning_Development/PlanningPo licy/Population_Housing>, [Accessed on: 4 April 2012] Hunter, H., ‘Tenement Adaptability’, [Dissertation], (Mackintosh School of Architecture, Glasgow, 2006) Jacobs, J., The Death and Life of Great American Cities, (Modern Library ed., New York, 1993) Jephcott, P., Robinson, H., Homes in High Flats (Oliver and Boyd, Edinburgh, 1971), [cited in Coleman, A., Utopia on Trial - Vision and Reality in Planned Housing, (Shipman, London, 1985)] Kaufman, B. ‘Economics of High-Performance Houses’, in Hastings, R. and Wall, M. (eds.) Sustainable Solar Housing. Volume 1 – Strategies and Solutions., (Earthscan, London, 2007), pp. 51-62

Kennett, S., 'Huhne Says All New Homes Should Meet Passivhaus Standard', Building.co.uk, 12/10/10, <http://www.building.co.uk/5007159.article>, [Accessed on: 11 February 12]

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[Accessed on: 9 April 2012] Konig, H., Kohler, N., et al., A Life-cycle Approach to Buildings. Principles, Calculations, Design Tools, (Edition Detail Green Books, Munich, 2010) Kucharek, J.C., ‘Process: Wood for the Hood’, RIBA Journal, 2010, <http://www.ribajournal.com/>, [Accessed on: 1 April 2012] Lehmann, S., The Principles of Green Urbanism. Regenerating the PostIndustrial City, (Earthscan, London 2010) Lowenstein, O., ‘Towering Timber’, The Architect’s Journal, 08.05.08, pp.40-42

Mansouri, S., ‘Glasgow tenements: Past, Present and a Sustainable Future?’ [Dissertation], (Mackintosh School of Architecture, Glasgow, 2010) Mead, K., and Brylewski, R., ‘Passivhaus Primer: Introduction: An Aid to Understanding the Key Principles of the Passivhaus Standard’, (Building Research Establishment, Watford, 2011), <http://www.passivhaus.org.uk/page.jsp?id=73>, [Accessed on: 12 February 2012] McKenna, M., Typology Project: Tenement [A Record of Buildings in Glasgow: Volume One: October 2011], (Dress for the Weather Limited, SUST, 2011) McLeod, R., Mead, K., and Standen, M., ‘Passivhaus Primer: Designer’s Guide: A Guide for the Design Team and Local Authorities’, (Building Research Establishment, Watford, 2011), <http://www.passivhaus.org.uk/page.jsp?id=73>, [Accessed on: 12 February 2012]

McMullan, R., Environmental Science in Building, Sixth Edition, (Palgrave Macmillan, Hampshire, 2007) Musau, F., and Deveci, G., 'From Targets to Occupied Low Carbon Homes: Assessing the Challenges and Delivering Low Carbon Affordable Housing' [PLEA 2011, 27th International Conference on Passive and Low Energy Architecture, Louvain-la-Neuve, Belgium, 13-15 July 2011], in Bodard, M.,

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Appendices 6.1. Effect of Wall Thickness on Total Treated Floor Area

6.2. External Dimensions

6.3. Description of Scenarios (PHPP)

6.4. Description of Scenarios (SAP – Geometry of Flats) 6.4.1. Ground Floor Flat 6.4.2. First Floor Flat 6.4.3. Second Floor Flat 6.4.4. Third Floor Flat

6.5. Description of Scenarios (SAP – Common Parameters)

6.6. Wall Construction 6.6.1. Scenario 3 – Building Standards 6.6.2. Scenario 4 – Passivhaus

6.7. Extra Costs Calculation

6.8. Building Standards Compliance of the Tenement

6.1 Effect of Wall Thickness on Total Treated Floor Area Three cladding options were investigated for the new-build prototype â&#x20AC;&#x201C; rendering, rain-screen cladding and brickwork â&#x20AC;&#x201C; based on the case studies described.

As rain-screen panels and brickwork require considerably more anchors to tie them back to primary structure and take up more space, they are less efficient than the alternative. Furthermore, a space equivalent of an extra room can be saved per tenement if brickwork is replaced by render.

U value = 0.19

Rendered

Rain-screen

Brickwork

Wall thickness (mm)

0.315

0.355

0.44

Treated Floor Area (m2)

705.17

696.62

678.53

n/a

8.55

26.64

Rendered

Rain-screen

Brickwork

0.37

0.405

0.485

689.73

682.28

665.42

n/a

7.45

24.31

Difference with Rendered

U value = 0.15 Wall thickness (mm)

Treated Floor Area (m2)

Difference with Rendered

The comparison of the treated floor area achievable for the two scenarios

6.2 External Dimensions

Wall height - front (m) Wall height - rear (m) Roof surface area (pitched) (m2) Roof pitch (degrees) External Wall - Side (1 of 2) (m2) External Wall - Side - top triangle (1 of 2) (m2) Stairwell within thermal envelope?

17.6 17.8 267.93 30.00 248.69 28.07 Yes

External Wall (Front) (m2) Opening area (m2) External Wall (Front) - excl. openings (m2) Opening/faรงade ratio

304.00 64.15 239.85 21.10%

299.39 64.15 235.24 21.43%

External Wall (Back) (m2) Opening area (m2) External Wall (Back) - excl. openings (m2) Opening/faรงade ratio

289.00 57.54 231.46 19.91%

239.94 42.78 197.16 17.83%

Footprint - Roof level (m2) Footprint - Foundation level (m2)

232.49 232.49

214.58 205.12

Gross volume (excl. cold roof space) (m3) Surface to volume ratio

4091.82 0.38

3610.11 0.49

Perimeter - Roof level - external (m) Perimeter - Roof level - total (m) Perimeter - Foundation level - external (m) Perimeter - Foundation level - total (m)

61.75 61.75 61.75 61.75

57.75 74.83 57.75 87.48

x x x x x 1646.94

137.00 14.80 122.20 41.88 8.77

Close wall (Average) (1 of 2) (m2) Opening area (m2) Close wall (1 of 2) excl. openings (m2) Close wall (Back) (m2) Close soffit (Corridor) (m2) Total external envelope area (incl. pitched roof) (m2): Total close wall area (m2): Total thermal envelope area (m2):

1555.36

324.65 1781.06

6.3 Description of Scenarios (PHPP)

little Original Tenement overshad owing Spec. capacity (Wh/m2K)

Refurbished Tenement

little overshad owing

Building Standards (Guidelines)

little overshad owing

g-value

thermal bridges

Building little air Standard overshad tightness s owing

Passivhaus Tenement (Guidelines)

204

132

685 3.95

705.17 4.03

689.73 3.8

3610.112 2705.75

2841.84

2620.97

205.12 57.75 0.6

0.19

0.15

299.39 1.1 0.6

299.29 0.19 0.315

299.57 0.15 0.37

239.94 1.1 0.6

239.94 0.19 0.315

239.94 0.15 0.37

little overshad owing

g-value

MVHR Efficiency

MVHR Specific FP

air tightness

Passivha little us overshad Tenement owing

DIMENSIONS Treated Floor Area (PHPP) Average Height (PHPP) Gross volume (m3) Internal volume (m3) Number of occupants (design): OPAQUE ELEMENTS External Ground Floor (Slab on Grade, depth 0.3m) Ground type: silt/clay Area (PHPP) Floor Slab Perimeter (external) U-value Front Area (PHPP) U-value Thickness (m) Rear Area (PHPP) U-value Thickness (m) Sides 1/2 Area (PHPP) U-value Thickness (m) Close: side 1 (out of 2) Area (PHPP) U-value Thickness (m) Close: back wall Area (PHPP) U-value Thickness (m) Close: soffit Area U-value Roof Area (PHPP) U-value

248.69 1.1 0.6

248.69 0.19 0.315

248.69 0.15 0.37

132.29 0.76 0.25

139.01 0.19 0.35

136.17 0.15 0.4

41.88 0.76 0.25

0.19 0.35

0.15 0.4

8.77 0.76

0.19

0.15

214.58 1.2

0.13

y-value

0.15

0.08

Perimeter (ground) Floor Slab (close walls) Perimeter (roof) External corners

57.75 27.34 57.75 70.4

1.4 1.85 14.8

0.8 -

Transmittance factor 'g' U-value

0.85 4.8

0.63 1.5

Shading Depth of reveal Frame dimensions (m) y-value glazing edge y-value installation

22m at gable level 25 m away 0.15 0.14 0.045 0.15

THERMAL BRIDGES 0.02

0.02

0.01

OPENINGS Doors U-value Area Total Area

Windows

22; 100

0.04 0.08

22; 100

0.72

22; 100

0.72

22; 100

0.02

0.5 0.8 0.035 0.01

0.68

22; 100

0.68

22; 100

North-facing Bay-middle Bay-side 1 Bay-side 2 Bedroom

8x 8x 8x 8x

2.92 1.19 1.19 2.69

Kitchen Bathroom

8x 8x

3.49 1.9

Natural

MVHR 1.5 0.41 75% flexible insulated

South-facing

VENTILATION Ventilation Specific Fan Power W/l/s Electric Efficiency Wh/m3 Heat Recovery Efficiency Ducting type Duct insulation Air change rate at pressure test ac/h @ 50 Pa HEATING Type Efficiency (SEDBUK 2005)

WATER HEATING Hot Water System Cylinder volume Insulation thickness Average Heat Released (W) Length of distribution pipes Length of individual pipes Y-Value W/mK Solar Hot Water Area of collector Orientation Tilt Overshading Height of the collector field Separate Storage volume Losses W/K Storage room temperature SUMMER VENTILATION Windows open Nighttime ventilation Low energy lights

6.3

4.4

Mains gas boiler 90.20%

From main heating 150 l 70 mm 72 16 16 0.18

evacuated tube 35 South 30 80% 0.01 200 l 3 15

half the time yes

3.1%

100%

gas DHW connection clothes line

100%

3.14

100%

3.14

100%

0.6

ELECTRICITY Cooking with: Clothes washing Clothes drying:

1 0.27

0.3

100%

1 0.27 85

0.3

100%

6.4 Description of Scenarios (SAP â&#x20AC;&#x201C; Geometry of Flats) 6.4.1 Ground Floor Flat

Diagram of Ground Floor Flat

6.4.2 First Floor Flat

6.4.3 Second Floor Flat

6.4.4 Third Floor Flat

6.5 Description of Scenarios (SAP â&#x20AC;&#x201C; Common Parameters)

Assessment type

New Dwelling Design Stage little Original Tenement overshad owing Calculated

Thermal mass parameter DIMENSIONS Total living area (m2) Height (m)

little overshad owing

Building Standards (Guidelines) -

26.4 3.95

28.15 4.03

27.5 3.8

51.03 1.1 0.6 180

54.41 0.19 0.315 65

50.88 0.15 0.37 -

0.15

0.08

1.4 1.85

0.85 0.7 4.8 heavy

0.63 1.5 -

Refurbished Tenement

little overshad owing

g-value

thermal bridges

little air Building overshad tightness Standards owing

Passivhaus Tenement (Guidelines)

little overshad owing

g-value

MVHR MVHR Specific Efficiency FP

air tightness

Passivhaus Tenement

little overshad owing

0.68

OPAQUE ELEMENTS Side Area U-value Thickness (m) Kappa THERMAL BRIDGES y-value

0.02

0.01

OPENINGS Doors U-value Area

0.8 -

Windows Transmittance factor 'g' Frame factor 'FF' U-value Overshading

little

0.72

little

0.72

little

0.5 0.8 heavy

0.68

little

North-facing Bay-middle Bay-side 1 Bay-side 2 Bedroom

8x 8x 8x 8x

2.92 1.19 1.19 2.69

Kitchen Bathroom

8x 8x

3.49 1.9

Natural

MVHR 1.5 75% flexible insulated 8

South-facing

VENTILATION Ventilation Specific Fan Power W/l/s Heat Recovery Efficiency Ducting type Duct insulation Wet rooms excl. kitchen Design air permeability m3/h/m2 @ 50 Pa HEATING Type Distribution

Controls Tariff Efficiency (SEDBUK 2005) Pump Boiler interlock Flue type Fan-flued Weather compensator WATER HEATING Hot Water System Cylinder volume Insulation thickness Storage losses KWh/day Cylinder in heated space Cylinderstat Primary pipework insulated Water heating timed separately Solar Hot Water Area of collector Orientation Tilt Overshading Separate Storage volume Heat loss coefficient Dedicated solar store Solar pump Zero-loss collector efficiency SUMMER VENTILATION Windows open Nighttime ventilation Effective ach Low energy lights

0.88

Mains gas boiler Radiators

Standard 90.20% in heated space yes room sealed yes yes

From main heating 150 l 70 mm 1.73 yes yes yes yes

evacuated tube 4.38 South 30 heavy 200 l 3 yes yes 0.6

half the time yes 3

3.1%

100%

Programmer, Room Thermostat, TRVs; user delayed start

1 85

0.44

1 85

0.44

little

6.6 Wall Construction 6.6.1 Scenario 3 â&#x20AC;&#x201C; Building Standards

* Adjustment: R=0.82 U1=0.227 U2=1 / ( (1/U1)+R)= 0.19

6.6.1 Scenario 4 â&#x20AC;&#x201C; Passivhaus

Internal Party Wall is identical to Scenario 3.

* Adjustment:

R=0.82 U1=0.172 U2=1 / ( (1/U1)+R)= 0.15

6.7 Extra Costs Calculation

Technical data of building

Building Standards

Passivhaus

(+5%)

(+10%)

(+15%)

Based on: PHPP Heating demand (kWh/m²a) Aux. Electricity demand (kWh/m²a) Energy saving potential (kWh/m²a)

1.6

2.4

Floor area of development (m²) Floor area of dwellings (m²)

930 720

55,440

14,400

1,152

1,728

6,930

1,800

144

216

256

275

40,464

1443.6

180

70.38%

1400 -

1400 5% 70

1400 10% 140

1400 15% 210

1,302,000

50,400 1,352,400

100,800 1,402,800

151,200 1,453,200

105

Total annual heating demand (kWh/a) Total annual electricity demand (kWh/a) Total annual heating demand per flat (kWh/a/flat) Total annual aux. electricity demand per flat (kWh/a/flat) Total annual heating cost per flat (£ / a / flat) Total annual aux. electricity cost per flat (£ / a / flat) Total bill/flat Energy saving potential (kWh/a) Cost saving potential (£ / a) Cost saving potential per flat (£ / a / flat) Percentage saving on annual bill Basic building costs (£ / m²) Extra costs % Extra costs (£ / m²) Total basic construction costs (£) Total extra costs (£) Total costs (£) Years to get pay-back

Technical data of building

Building Standards

Passivhaus

(+5%)

(+10%)

(+15%)

Based on: SAP Heating demand (kWh/m²a) Aux. Electricity demand (kWh/m²a) Energy saving potential (kWh/m²a)

1.9

9.8

Floor area of development (m²) Floor area of dwellings (m²)

930 720

39,600

8,640

1,368

7,056

4,950

1,080

171

882

183

115

205

155

25,272

406.08

27.71%

1400 -

1400 5% 70

1400 10% 140

1400 15% 210

1,302,000

50,400 1,352,400

100,800 1,402,800

151,200 1,453,200

124

248

372

6.8. Building Standards Compliance of the Tenement

According to the Building Standards, buildings with dwelling floor levels above 10m should be provided with a lift. 1 The 3rd floor level in the studied prototype is at 13.23m. If the lift is to be avoided, the best solution would be to change the number of storeys to 3 so as to maintain the generous ceiling heights and high day-lighting levels 2 , which are necessary not only for comfort, but for obtaining extra EcoHomes credits as well.

When it comes to ground floor accessibility, some further modifications would have to be made. Access to the back court lies under the staircase and sufficient headroom is ensured by stepping down, which contravenes standard 4.2. With a new corridor taking up the space of the bathroom, the affected ground floor flat could be remodelled to provide enhanced accessibility facilities.

1 2

‘Building Standards Domestic 2011 Technical Handbook’, Clause 4.2.5 Hunter, H., ‘Tenement Adaptability’, [Dissertation], (Mackintosh School of Architecture,

Glasgow, 2006), p.41