Passivhaus Tenement
-
Upload
lilia-obletsova -
Category
Documents
-
view
223 -
download
4
description
Transcript of Passivhaus Tenement
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. Mühlweg 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
1
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
2
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.
3
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
PH Passivhaus or Passive House
PHPP Passive House Planning Package
SAP Standard Assessment Procedure
TER Target Emission Rate
4
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.
5
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 standard’s adoption in the UK.
An overview of massive timber construction focuses on its suitability for low-
energy multi-storey housing and highlights the material’s sustainability.
1 Lehmann, S., The Principles of Green Urbanism. Regenerating the Post-Industrial City,
(Earthscan, London 2010)
6
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.
7
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 household’s chief earner’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.
2 Paul Balchin and Maureen Rhoden, Housing Policy: An Introduction, 4th Edition, (Routledge,
London, 2002), p.253
8
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 The meaning of “affordable” is defined in the Introduction 4 Douglas Niven, The Development of Housing in Scotland, (Croom Helm, London, 1979),
p.22 5 John Gilbert, The Tenement Handbook, (RIAS, Edinburgh, 1993), Fig. 16.1, p.85
9
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
6 Niven, p.21 7 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
10
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 tenants’ 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
11 Ibid., p.34 12 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
11
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.
16 Niven, p.108 17 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
12
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
22 John English, (ed.), The Future of Council Housing, (Croom Helm, London, 1982), p.37 23 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
13
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 Ibid., p.43 28 Lehmann, p.221 29 ‘The Development Plan for Glasgow - Main Issues Report’, p.44 30 ‘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-for-industry-awards/>, [Accessed on: 11 February 2012]
14
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 in 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, 35 which is in line with the
“decentralised concentration” discussed earlier.
33 ‘The Development Plan for Glasgow - Main Issues Report’, p.44 34 Ibid., p.45 35 Ibid., p.77
15
The areas with the highest identified need happen to be the densest ones
(Fig.2) and feature traditional tenement districts36. 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 single-
people households. The proposed Passivhaus Tenement is a possible solution
to the problem.
36 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]
16
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., ‘People and Households in Glasgow. Current Estimates and Projected Changes 2008-2028. Demographic Change in Glasgow City and Neighbourhoods’, [Briefing Paper by Director of Development and Regeneration Services, 7 March 2011], (Glasgow City Council, 2011)
39 Adapted from Freeke, p.16
17
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
40 ‘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)
18
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
42 ‘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 2010-
2011’, (Scottish Government, Edinburgh, 2011), p.8 47 ‘Conserve and Save’, 2009, Annexe F
19
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
48 ‘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]
49 Melissa Taylor, and Neil Cutland, ‘Passivhaus and Zero Carbon’, [Technical briefing document], (Passivhaus Trust, 2011), p.2
50 ‘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]
20
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 54
51 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]
53 Ibid. 54 Taylor and Cutland, p.2
21
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. 57 Only upon final
certification can the building claim the Passivhaus standard, provided that all
criteria are satisfied.58
55 Mead and Brylewski, p.3 56 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
22
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 single-
family 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
59 See Appendix 6.2. for calculation 60 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
23
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 Mühlweg Street case study described in Chapter 3, so a
centralised MVHR system located in the attic is proposed for the prototype.
63 Mead and Brylewski, p.9 64 Feist, 2009 65 ‘Design Guidelines: Non-Domestic Passive House Projects’, p.56 66 Ibid., p.57
24
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.
67 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
25
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 Passivhaus-
certified 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.
71 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
72 Neil Cutland, ‘Passivhaus Trust Outline Position Re. 2013 Domestic Regulations’, (Passivhaus Trust, May 2011)
26
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.
73 Robert Hairstans, Off-site and Modern Methods of Timber Construction: a Sustainable
Approach, (TRADA Technology, UK, 2010), p.54 74 Jill Burnett, ‘Forestry Commission Scotland Greenhouse Gas Emissions Comparison -
Carbon Benefits of Timber in Construction’, (Edinburgh Centre for Carbon Management Ltd., Edinburgh, 2006)
27
2.1.2. Timber Construction in Scotland
Timber frame is the most common house construction system in Scotland,
accounting for 65% of the market. 75 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 re-
engineering 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.
75 ‘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, (Birkhauser, Germany, 2010), pp.77-82, p.77
79 Hairstans, p.73
28
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 – 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 Ibid., p.10 81 Ibid., p.12 82 Ibid., p.14
29
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 cost-
effective 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 Ibid., p.27 84 Ibid., p.53
30
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
85‘Cross-Laminated Timber: Introduction for Specifiers’, [TRADA Wood Information Sheet,
WIS 2/3-61], (TRADA Technology, 2011) 86 Author
31
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
87 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
32
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 Thompson et al., p.12 93 Ibid., p.77 94 Hairstans, p.14 95 Ibid., p.14 96 Thompson et al., p.34 97 ’Cross-Laminated Timber: Introduction for Specifiers’, p.8
33
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
98 Ibid., p.8 99 Ibid., p.2 100 Ibid., p.5
34
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]
35
3. Case Studies
3.1. Mühlweg Street, Vienna,
Dietrich I Untertrifaller Architekten, 2006
Fig.4. External view of Mühlweg 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
36
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
37
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 It 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 At a Euro/Pound conversion rate 0.83 112 Gauzin-Muller in Zshokke, p.291 113 ‘10 years of the program Building of Tomorrow 1999-2009’ 114 Gauzin-Muller in Zshokke, p.290 115 Zschokke, p.293
38
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 17°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 -3°C.116
The building’s annual heating demand is under 10 kWh/m2 and an air-
tightness 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 Ibid., p.290 117 Ibid., p.290 118 [Results of a survey, 2007], Ibid., p.292
39
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 £80, 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]
40
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)
41
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.75 124 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]
42
Summary of Case Study Data
No of Storeys
Total area CLT No of units
Size of units m2
Affordable Case Study Year Development Erection housing
m2 time (w) ratio Mühlweg 2006 4 6,750 1x4 70 96 100% Aubert Park 2010 5 2,328* 5 8 291 0% Bridport 2011 5 - 8 4,220 12 41 103 100% Stadthaus 2009 9 2,750 9 29 95 46%
Case Study Total budget
Cost per m2
Cost per Price per Dwelling
Specific Space Heating Demand kg/m2 CO2
Dwelling
Mühlweg 5,966,663 884** 85,238 - 10 - Aubert Park - - - 2,500,000 11 - Bridport 6,000,000 1,422 146,341 - - *** Stadthaus 3,800,000 1,400127 131,034 - - 28.69128
U-value (W/m2K) Air tightness
ac/h
Air perm.
m3/h/m2 MVHR
CLT produced
by
Case Study
wall roof window Mühlweg 0.145 0.075 0.74 0.3 - 83% KLH129 Aubert Park 0.15 0.17 0.7 0.5 - - Kaufmann Bridport 0.13 0.12 1.37 - 3 - StoraEnso Stadthaus 0.27130 - - - 3 70%131 KLH
Case Study Green features & technologies / Achieved code levels
Mühlweg 60m2 of solar hot water collectors per block Aubert Park Rainwater harvesting, GSHP for heating and DHW 132 Bridport Brown roof, photovoltaic panels; Code for Sustainable Homes (CSH) Level 4. 133 Stadthaus EcoHomes Very Good
* 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.36 128 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
43
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
44
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 pre-
defined 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 See Appendix 6.1 138 Lehmann, pp.335-346
45
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>
46
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
47
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 600mm146 , 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 Feist, 2010, p.38 144 ‘The Government’s Standard Assessment Procedure for Energy Rating of Dwellings’, p.7 145 Author 146 ‘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]
48
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 in 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.16 148 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
49
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.
50
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)
151 Baker, Table 2, p.16 152 ‘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
51
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 Ibid. 156 See Appendix 6.6. for wall construction
52
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).
21.31
19.15(3%)
21.18
19.90
20.79
19.24(2%)
16.91(14%)
14.00
15.00
16.00
17.00
18.00
19.00
20.00
21.00
22.00
BS (Guide
lines)
(little
ove
rshad
owing
)
g-va
lue =
0.7
2
y-va
lue =
0.0
2
air p
ermea
bility =
5
Building
Stand
ards
(little
ove
rshad
owing
)
kg
/m2 /a
TER
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 (‘Building Standards
Domestic 2011 Technical Handbook’, Clause 3.14.10) 158 Author
53
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.
2522
11 10 9
8177
73
18
0
10
20
30
40
50
60
70
80
90
Passivhaus Tenement(Guidelines)
Adjacent to 1 Terrace
Specific Space Heating Demand (kWh/m2/a)
Heating Load (W/m2)
Specific Primary Energy Demand (kWh/m2/a)
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 160 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.
54
To ensure performance in all configurations, improvements had to be sought.
25 24 25 2320
11 11 11
81 80 78 79 79
73
23
91010
0
10
20
30
40
50
60
70
80
90
Passivhaus(Guidelines)
Higher g-value(0.68)
Better MVHREfficiency
(85%)
Lower SpecificFan Power (1)
Better Air-tightness (0.3)
Passivhaus
Specific Space Heating Demand (kWh/m2/a)
Heating Load (W/m2)
Specific Primary Energy Demand (kWh/m2/a)
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 Author 162 ‘Energy Efficient Ventilation in Dwellings – a Guide for Specifiers’, [GPG268], (Energy
Saving Trust, 2006), <http://www.energysavingtrust.org.uk>, [Accessed on: 30 March 2012]
55
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.
56
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.
45.42
34.84
19.24(2.4%)
14.33(24.7%)
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
45.00
50.00
Original Tenement RefurbishedTenement
Building Standards Passivhaus
kg
/m2/a
TER
Fig.15. Dwelling Emission Rate (DER), Target Emission Rate (TER) and % Reduction 164
163 values taken from FSAP 2009 164 Author
57
The DER taken from SAP was then evaluated against comparable CO2
emissions estimated by PHPP165.
45
35
1914
76
54
24
9
0
10
20
30
40
50
60
70
80
90
100
Original Tenement RefurbishedTenement
Building Standards Passivhaus
kg
/m2/a
SAP
PHPP
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 Taken from ‘PE Value’ worksheet 166 Author 167 Reason and Clarke, p.31 168 ‘EcoHomes 2006: The Environmental Rating for Homes. The Guidance 2006’, Issue 1.2,
(Building Research Establishment, Watford, April 2006), p.6
58
EcoHomes category Ene 2 credits are assigned for low heat loss
parameters 169 , and again, Passivhaus would have gained more credits
(Fig.17).
2.67
3.41
1.29(1)
0.60(2)
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
OriginalTenement
RefurbishedTenement
BuildingStandards
Passivhaus
W/m
2 K
Heat Loss Parameter
Ene 2 - 1 Credit
Ene 2 - 2 Credits
Fig.17. Heat Loss Parameter and EcoHomes Ene 2 Credits (based on SAP calculations) 170
169 Ibid., p.11 170 Author
59
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.
157
55
13
246
183
77
20
168
136
6345
126
0
50
100
150
200
250
300
Original Tenement RefurbishedTenement
BuildingStandards
Passivhaus
kW
h/m
2 /a
SAP PHPP FEE
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, ‘Benchmarking Scottish energy standards: Passive
House and CarbonLite Standards: A comparison of space heating energy demand using SAP, SBEM, and PHPP methodologies’, [Report commissioned by the Directorate for the Built Environment, Scottish Government], (ESRU, University of Strathclyde, 2009), p.20
172 Author
60
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 flat’s
demand (Fig.19).
p p g (p yp )
64
50
49
20
8
7
1658
0 10 20 30 40 50 60 70
Ground Floor
First Floor
Second Floor
Third Floor
kWh/m2/a
Passivhaus
Building Regulations
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
61
Building S
tandard
s (PHPP)
Building S
tandard
s (SAP)
Passivh
aus (PHPP)
Passivh
aus (SAP)
1.6
77.0
1.9
55.1
2.4
20.0
9.8
12.60.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
kW
h/m
2 /a
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
62
246
183
77
20
246
182
77
19
246
183
77
20
246
183
78
20
0
50
100
150
200
250
300
Original Tenement RefurbishedTenement
Building RegulationsTenement
Passivhaus Tenement
kW
h/m
2 /aNorth-facing South-facing West-facing East-facing
241
179
73
19
240
178
72
15
244
181
75
18
244
181
75
18
0
50
100
150
200
250
300
Original Tenement RefurbishedTenement
Building RegulationsTenement
Passivhaus Tenement
kWh
/m2/a
North-facing (little overshadowing) South-facing (little overshadowing)
West-facing (little overshadowing) East-facing (little overshadowing)
Fig.21. Difference in Specific Annual Heating Demand Depending on
Orientation and Street Width (based on PHPP results) 175
175 Author
63
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.
2017
9 8 7
7369
65
13
0
10
20
30
40
50
60
70
80
Passivhaus Tenement Adjacent to 1 Terrace
Specific Space Heating Demand (kWh/m2/a)
Heating Load (W/m2)
Specific Primary Energy Demand (kWh/m2/a)
Fig.22. Effect of terracing on the performance of PH Tenement (as modelled in PHPP) 176
176 Author
64
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.
2017
14
9 8 8 7
7369 69
65
17
0
10
20
30
40
50
60
70
80
Passivhaus Tenement Adjacent to 1 lower Adjacent to 1 higher Hillside Terrace
Specific Space Heating Demand (kWh/m2/a)
Heating Load (W/m2)
Specific Primary Energy Demand (kWh/m2/a)
Fig.23. Effect of hillside terracing on the performance of PH Tenement (as modelled in PHPP) 177
177 Author
65
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
66
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.
67
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
68
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., ‘Glasgow tenements: Past, Present and a Sustainable Future?’ [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]
69
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
product’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]
70
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.262 189 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
71
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 Incentive194 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
72
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 pre-
fabrication, 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 Rudlin and Falk, pp.113, 116 201 Ibid., p.16
Bibliography ‘10 years of the program Building of Tomorrow 1999-2009’ (Federal Ministry of Transport, Innovation and Technology, Austria, 2009) About the AECB (Sustainable Building Association, Llandysul) <http://www.aecb.net/about_us.php> [Accessed on: 16 February 2012] ‘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] ‘Air tightness in UK dwellings’, [BRE Information Paper: IP01/00], (Building Research Establishment, January 2000) Baker, P., ‘U-values and Traditional Buildings: In Situ Measurements and Their Comparisons to Calculated Values’, [Historic Scotland Technical Paper 10], (Glasgow Caledonian University, 2011) Balchin, A., ‘Massive Timber - Why Aren't We Using It More?’, (Unpublished BSc dissertation, University of Strathclyde, 2009) Balchin, P. and Rhoden, M., Housing Policy: An Introduction, 4th Edition, (Routledge, London, 2002) Binder-Jones - Press Release (Binder-Jones, 2012) <http://www.binder-jones.co.uk/> [Accessed on: 16 February 2012] Birch, A., 'Technical: Timber Structures: Bridport House', BD Online, 24 Jun 2011, <www.bdonline.co.uk>, (pp.16-17) ‘Building Standards Domestic 2011 Technical Handbook’, (Scottish Government, 2011) <http://www.scotland.gov.uk/Topics/Built-Environment/Building/Building-standards> [Accessed on: 16 March 2012] Burnett, J., ‘Forestry Commission Scotland Greenhouse Gas Emissions Comparison - Carbon Benefits of Timber in Construction’, (Edinburgh Centre for Carbon Management Ltd., Edinburgh, 2006) Bootland, J., ‘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]
‘BREEAM: EcoHomes’, (Building Research Establishment, 2012) <http://www.breeam.org>, [Accessed on: 8 April 2012] ‘Business Plan 2008/09. Better Homes, Better Lives’, (Glasgow Housing Association, 2007) < http://www.gha.org.uk/>, [Accessed on: 3 April, 2010] ‘City Building - Glasgow House Shortlisted for Industry Awards’ , (City Building, 16 May 2011), <http://www.citybuildingglasgow.co.uk/2011/glasgow-house-shortlisted-for-industry-awards/>, [Accessed on: 11 February 2012] ‘City Plan 2 - Part 3: Development Policies and Design Guidance’, (Glasgow City Council, 2009), <http://www.glasgow.gov.uk/>, [Accessed on: 11 February 2012] ‘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] ‘Code for Sustainable Homes: Technical Guide’ , (Department for Communities and Local Government, London, November 2010) Coleman, A., Utopia on Trial - Vision and Reality in Planned Housing, (Shipman, London, 1985) ‘Conserve and Save - A Consultation on the Energy Efficiency Action Plan for Scotland’, (Business, Enterprise and Energy Directorate, Scottish Government, 2009) ‘Conserve and Save - The Energy Efficiency Action Plan for Scotland - Annual Report 2010-2011’, (Scottish Government, Edinburgh, 2011) Cook, S., ‘Bridport House – The Contractor’s View’ [Presentation] (Wilmott Dixon Group, 2011), <www.buildingcentre.co.uk>, [Accessed on: 1 April 2012] ‘Cross-Laminated Timber: Introduction for Specifiers’, [TRADA Wood Information Sheet, WIS 2/3-61], (TRADA Technology, 2011) Cutland, N., ‘Passivhaus Trust Outline Position Re. 2013 Domestic Regulations’, (Passivhaus Trust, May 2011) ‘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] Deplazes, A., ‘Wood: Indifferent, Synthetic, Abstract - Plastic’, in Deplazes, A. (ed.), Constructing Architecture: Materials, Processes, Structures - a Handbook, 2nd Edition, (Birkhauser, Germany, 2010), pp.77-82
‘Design Guidelines: Non-Domestic Passive House Projects’, (Sustainable Energy Authority of Ireland Renewable Energy Information Office and MosArt Architecture, 2010) ‘Designed for Brettstapel - Scottish Housing Expo’, (Brettstapel, 2010), <http://www.brettstapel.org/Brettstapel/Home.html>, [Accessed on: 20 March 2012] ‘Designing Housing with Scottish Timber - a Guide for Designers, Specifiers and Clients: Case Studies’, (John Gilbert Architects, Forestry Commission Scotland, 2005) ‘The Development Plan for Glasgow - Main Issues Report’, (Glasgow City Council, 2011) <http://www.glasgow.gov.uk/en/Business/DevelopmentPlan/>, [Accessed on: 11 February 2012] Edinburgh Napier University: Wood Products Innovation Gateway (Edinburgh Napier University, 2012), <http://www.napier.ac.uk/forestproducts/pages/wood%20products%20innovation%20gateway.aspx>, [Accessed on: 15 February 2012] ‘EcoHomes 2006: The Environmental Rating for Homes. The Guidance 2006’, Issue 1.2, (Building Research Establishment, Watford, April 2006) ‘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] ‘Energy Efficient Ventilation in Dwellings – a Guide for Specifiers’, [GPG268], (Energy Saving Trust, 2006), <http://www.energysavingtrust.org.uk>, [Accessed on: 30 March 2012] English, J. (ed.), The Future of Council Housing, (Croom Helm, London, 1982) Fawcett T., Lane K. and Boardman B., ‘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] Feist, W., Passive House Planning Package, PHPP 2007, 2nd Edition, [Technical Information PHI-2007/1 (E)], (Passive House Institute, Darmstadt, 2010) Feist, W., ‘Certification as "Quality approved Passive House" Criteria for Residential-Use Passive Houses’, (Passivhaus Institut, Darmstadt, 2009) Forster, W., Housing in the 20th and 21st centuries, (Prestel, Munich; London, 2006)
Freeke, J., ‘People and Households in Glasgow. Current Estimates and Projected Changes 2008-2028. Demographic Change in Glasgow City and Neighbourhoods’, [Briefing Paper by Director of Development and Regeneration Services, 7 March 2011], (Glasgow City Council, 2011) Frey, H., Designing the City. Towards a More Sustainable Urban Form, (Spon Press, London, 1999) Gauzin-Muller, D., 'Green Building' in Zschokke, W. (ed.) Dietrich | Untertrifaller: Buildings and Projects since 2000, (Springer Wien New York, 2008), pp.284-293 Glasgow Housing Association: Homechoice, (GHA, 2009), <https://homechoice.gha.org.uk/>, [Accessed on: 16 February 2012] ‘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] Gilbert, J., The Tenement Handbook, (RIAS, Edinburgh, 1993) ‘The Government’s Standard Assessment Procedure for Energy Rating of Dwellings’, [2009 edition, version 9.90], (Building Research Establishment, Watford, 2011) Green Guide 2008 Ratings, (Building Research Establishment, 2012), <http://www.bre.co.uk/greenguide>, [Accessed on: 6 April 2012] 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/PlanningPolicy/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] Key Facts, (Glasgow City Council, 2010) <http://www.glasgow.gov.uk/en/AboutGlasgow/Factsheets/Glasgow/KeyFacts.htm>, [Accessed on: 18 February 2012] KLH: Sustainability, (KLH, 2012), <http://www.klhuk.com/sustainability.aspx>, [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 Post-Industrial 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.,
Evrard, A. (eds.) Architecture and Sustainable Development, Volume 2., pp.261-266. Nash Terrace, Aubert Park - Fact Sheet, (4orm Architects, 2010), <www.4orm.co.uk>, [Accessed on: 15 March 2012] Newman, O., Defensible Space: People and Design in the Violent City, (Architectural Press, London, 1973) Newman, N., ‘Payback: Applying Passivhaus Research to the Cost-Driven World of Construction’, (Presentation from bere:architects at the Student Passivhaus Conference, 10 October 2010) Niven, D., The Development of Housing in Scotland, (Croom Helm, London, 1979) ‘Our Corporate Strategy. The next three years (2011-2014)’, (Glasgow Housing Association, 2010) Our Portfolio, (Building Research Establishment, Watford, 2012), <http://www.passivhaus.org.uk/podpage.jsp?id=90>, [Accessed on: 12 February 2012] 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> 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] ‘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] Reason, L., and Clarke, A., ‘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] Robust Details (2012) <http://www.robustdetails.com/>, [Accessed on: 4 April 2012] Rudlin, D. and Falk, N., Building the 21st Century Home. The Sustainable Urban Neighbourhood, (Architectural Press, Oxford, 1999) ‘Saving 120 tonnes of CO2’, Detain Green, 02/2009, (p.2) Smith, S., Wood, J.B. and Mackenzie, R., ‘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] Sneddon, J., ‘The Glasgow House - It's Already Happening’, (Glasgow Housing Association, 2010) ‘Stadthaus, 24 Murray Grove, London’, [Case Study], (TRADA Technology, 2009) Strom, I., Joosten, L., and Boonstra, C., ‘Passive House Solutions’, (Promotion of European Passive Houses, 2006) Stroma Certification, FSAP 2009 (1.4.0.63), [Computer Programme], (2009) Available at: <http://www.stromamembers.co.uk/SAPUser.aspx> 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) Tariff level tables, (Renewable Heat Incentive, 2012), < http://www.rhincentive.co.uk/eligible/levels/>, [Accessed on: 10 April 2012] Tariffs payable per kWh of electricity produced, (Feed-in Tariffs, 2012), < http://www.fitariffs.co.uk/eligible/levels/>, [Accessed on: 10 April 2012] Taylor, M., and Cutland, N., ‘Passivhaus and Zero Carbon’, [Technical briefing document], (Passivhaus Trust, 2011) The Concrete Centre, Dynamic Thermal Property Calculator Tool (v.1), [Computer programme], (Developed by Arup, 2010), Available at: <http://www.concretecentre.com/> Thompson, H. and Waugh, A., Weiss, K., and Wells, M. (eds.), A Process Revealed / Auf dem Holzweg, (Murray & Sorrell FUEL / Thames & Hudson, Belgium, 2009) Trotter, N.M., ‘The revival of the tenement tradition in Glasgow’, [Dissertation], (Mackintosh School of Architecture, Glasgow, 1996) Tuohy, P. and Davis Langdon LLP, ‘Benchmarking Scottish energy standards: Passive House and CarbonLite Standards: A comparison of space heating energy demand using SAP, SBEM, and PHPP methodologies’, [Report commissioned by the Directorate for the Built Environment, Scottish Government], (ESRU, University of Strathclyde, 2009)
Worsdall, F., The Tenement : A Way of Life : a Social, Historical and Architectural Study of Housing in Glasgow, (W. and R. Chambers, Edinburgh, 1979) ‘Worked Example - 12-storey Building of Cross-laminated Timber (Eurocode 5)’, (TRADA Technology, 2009) Zschokke, W. (ed.) Dietrich | Untertrifaller: Buildings and Projects since 2000, (Springer Wien New York, 2008)
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 –
rendering, rain-screen cladding and brickwork – 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
Difference with Rendered n/a 8.55 26.64
U value = 0.15 Rendered Rain-screen Brickwork
Wall thickness (mm) 0.37 0.405 0.485
Treated Floor Area (m2) 689.73 682.28 665.42
Difference with Rendered n/a 7.45 24.31
The comparison of the treated floor area achievable for the two scenarios
6.2 External Dimensions Wall height - front (m) 17.6 Wall height - rear (m) 17.8
Roof surface area (pitched) (m2) 267.93 Roof pitch (degrees) 30.00
External Wall - Side (1 of 2) (m2) 248.69
External Wall - Side - top triangle (1 of 2) (m2) 28.07
Stairwell within thermal envelope? Yes No
External Wall (Front) (m2) 304.00 299.39
Opening area (m2) 64.15 64.15
External Wall (Front) - excl. openings (m2) 239.85 235.24 Opening/façade ratio 21.10% 21.43%
External Wall (Back) (m2) 289.00 239.94
Opening area (m2) 57.54 42.78
External Wall (Back) - excl. openings (m2) 231.46 197.16 Opening/façade ratio 19.91% 17.83%
Footprint - Roof level (m2) 232.49 214.58
Footprint - Foundation level (m2) 232.49 205.12
Gross volume (excl. cold roof space) (m3) 4091.82 3610.11 Surface to volume ratio 0.38 0.49 Perimeter - Roof level - external (m) 61.75 57.75 Perimeter - Roof level - total (m) 61.75 74.83 Perimeter - Foundation level - external (m) 61.75 57.75 Perimeter - Foundation level - total (m) 61.75 87.48
Close wall (Average) (1 of 2) (m2) x 137.00
Opening area (m2) x 14.80
Close wall (1 of 2) excl. openings (m2) x 122.20
Close wall (Back) (m2) x 41.88
Close soffit (Corridor) (m2) x 8.77
Total external envelope area (incl. pitched roof) (m2): 1646.94
Total close wall area (m2): 324.65
Total thermal envelope area (m2): 1555.36 1781.06
6.3 Description of Scenarios (PHPP)
Original Tenementlittle
overshadowing
Refurbished Tenement
little overshad
owing
Building Standards
(Guidelines)
little overshad
owingg-value
thermal bridges
air tightness
Building Standard
s
little overshad
owing
Passivhaus Tenement (Guidelines)
little overshad
owingg-value
MVHR Efficiency
MVHR Specific
FP
air tightness
Passivhaus
Tenement
little overshad
owing
Spec. capacity (Wh/m2K) 204 - 132 -
DIMENSIONS
Treated Floor Area (PHPP) 685 - 705.17 689.73Average Height (PHPP) 3.95 - 4.03 3.8
Gross volume (m3) 3610.112 - - -Internal volume (m3) 2705.75 2841.84 2620.97
Number of occupants (design): 16 - - -
OPAQUE ELEMENTSExternal Ground Floor
(Slab on Grade, depth 0.3m) Ground type: silt/clay
Area (PHPP) 205.12 - - -Floor Slab Perimeter (external) 57.75 - - -
U-value 0.6 - 0.19 0.15Front
Area (PHPP) 299.39 299.29 299.57U-value 1.1 - 0.19 0.15
Thickness (m) 0.6 - 0.315 0.37Rear
Area (PHPP) 239.94 239.94 239.94U-value 1.1 - 0.19 0.15
Thickness (m) 0.6 - 0.315 0.37Sides
1/2 Area (PHPP) 248.69 248.69 248.69U-value 1.1 - 0.19 0.15
Thickness (m) 0.6 0.315 0.37Close: side 1 (out of 2)
Area (PHPP) 132.29 139.01 136.17U-value 0.76 - 0.19 0.15
Thickness (m) 0.25 0.35 0.4Close: back wall
Area (PHPP) 41.88 - - -U-value 0.76 - 0.19 0.15
Thickness (m) 0.25 0.35 0.4Close: soffit
Area 8.77 - - -U-value 0.76 - 0.19 0.15
RoofArea (PHPP) 214.58 - - -
U-value 1.2 0.13 - -
THERMAL BRIDGESy-value 0.15 - 0.08 0.02 0.02 0.02 0.01
Perimeter (ground) 57.75 - - -Floor Slab (close walls) 27.34 - - -
Perimeter (roof) 57.75 - - -External corners 70.4 - - -
OPENINGSDoors
U-value 1.4 - - 0.8Area 8x 1.85 - - -
Total Area 14.8 - - -Windows
Transmittance factor 'g' 0.85 0.63 - 0.72 0.72 0.72 0.5 0.68 0.68 0.68U-value 4.8 1.5 - 0.8
Shading22m at gable level
25 m away22; 100
-22; 100
-22; 100 22; 100
-22; 100 22; 100
Depth of reveal 0.15 - - -Frame dimensions (m) 0.14 - - -
y-value glazing edge 0.045 0.04 - 0.035y-value installation 0.15 0.08 - 0.02 0.02 0.02 0.01
North-facingBay-middle 8x 2.92 - - -Bay-side 1 8x 1.19 - - -Bay-side 2 8x 1.19 - - -
Bedroom 8x 2.69 - - -South-facing
Kitchen 8x 3.49 - - -Bathroom 8x 1.9 - - -
VENTILATIONVentilation Natural - - MVHRSpecific Fan Power W/l/s 1.5 1 1 1Electric Efficiency Wh/m3 0.41 0.27 0.27 0.27Heat Recovery Efficiency 75% 85 85 85Ducting type flexibleDuct insulation insulatedAir change rate at pressure test ac/h @ 50 Pa 6.3 4.4 - 3.14 3.14 3.14 0.6 0.3 0.3 0.3
HEATINGType Mains gas boiler - - -Efficiency (SEDBUK 2005) 90.20% - - -
WATER HEATINGHot Water System From main heating - - -
Cylinder volume 150 l - - -Insulation thickness 70 mm - - -
Average Heat Released (W) 72 - - -Length of distribution pipes 16 - - -
Length of individual pipes 16 - - -Y-Value W/mK 0.18 - - -
Solar Hot Water - evacuated tube - -Area of collector - 35 - -
Orientation - South - -Tilt - 30 - -
Overshading - 80% 100% - 100% 100% - 100% 100%Height of the collector field - 0.01 - -
Separate Storage volume - 200 l - -Losses W/K - 3 - -
Storage room temperature - 15 - -
SUMMER VENTILATIONWindows open half the time - - -Nighttime ventilation yes - - -
Low energy lights 3.1% 100% - -
ELECTRICITYCooking with: gas - - -
Clothes washing DHW connection - - -Clothes drying: clothes line - - -
6.4 Description of Scenarios (SAP – 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 – Common Parameters)
Assessment type New Dwelling Design Stage
Original Tenementlittle
overshadowing
Refurbished Tenement
little overshad
owing
Building Standards
(Guidelines)
little overshad
owingg-value
thermal bridges
air tightness
Building Standards
little overshad
owing
Passivhaus Tenement (Guidelines)
little overshad
owingg-value
MVHR Efficiency
MVHR Specific
FP
air tightness
Passivhaus Tenement
little overshad
owingThermal mass parameter Calculated - - -
DIMENSIONSTotal living area (m2) 26.4 - 28.15 27.5Height (m) 1 3.95 - 4.03 3.8
OPAQUE ELEMENTSSide
Area 51.03 - 54.41 50.88U-value 1.1 - 0.19 0.15
Thickness (m) 0.6 - 0.315 0.37Kappa 180 - 65 -
THERMAL BRIDGESy-value 0.15 - 0.08 0.02 0.02 0.02 0.01
OPENINGSDoors
U-value 1.4 - - 0.8Area 1x 1.85 - - -
WindowsTransmittance factor 'g' 0.85 0.63 - 0.72 0.72 0.72 0.5 0.68 0.68 0.68
Frame factor 'FF' 0.7 - - -U-value 4.8 1.5 - 0.8
Overshading heavy little - little - little little heavy little little
North-facingBay-middle 8x 2.92 - - -Bay-side 1 8x 1.19 - - -Bay-side 2 8x 1.19 - - -
Bedroom 8x 2.69 - - -South-facing
Kitchen 8x 3.49 - - -Bathroom 8x 1.9 - - -
VENTILATIONVentilation Natural - - MVHRSpecific Fan Power W/l/s 1.5 1 1 1Heat Recovery Efficiency 75% 85 85 85Ducting type flexibleDuct insulation insulatedWet rooms excl. kitchen 8Design air permeability m3/h/m2 @ 50 Pa 10 7 -
5 5 5 0.88 0.44 0.44 0.44
HEATINGType Mains gas boiler - - -Distribution Radiators - - -
Controls
Programmer, Room Thermostat, TRVs; user delayed start - -
-
Tariff Standard - - -Efficiency (SEDBUK 2005) 90.20% - - -Pump in heated space - - -Boiler interlock yes - - -Flue type room sealed - - -Fan-flued yes - - -Weather compensator yes - - -
WATER HEATINGHot Water System From main heating - - -
Cylinder volume 150 l - - -Insulation thickness 70 mm - - -
Storage losses KWh/day 1.73 - - -Cylinder in heated space yes - - -Cylinderstat yes - - -Primary pipework insulated yes - - -Water heating timed separately yes - - -
Solar Hot Water - evacuated tube - -Area of collector - 4.38 - -
Orientation - South - -Tilt - 30 - -
Overshading - heavy little - little little - little littleSeparate Storage volume - 200 l - -
Heat loss coefficient - 3 - -Dedicated solar store - yes - -
Solar pump - yes - -Zero-loss collector efficiency - 0.6 - -
SUMMER VENTILATIONWindows open half the time - - -Nighttime ventilation yes - - -Effective ach 3 - - -
Low energy lights 3.1% 100% - -
6.6 Wall Construction 6.6.1 Scenario 3 – Building Standards
* Adjustment:
R=0.82 U1=0.227 U2=1 / ( (1/U1)+R)= 0.19
6.6.1 Scenario 4 – 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 Passivhaus Passivhaus
(+5%) (+10%) (+15%) Based on: PHPP
Heating demand (kWh/m²a) 77 20 20 20 Aux. Electricity demand (kWh/m²a)
1.6 2.4 2.4 2.4
Energy saving potential (kWh/m²a)
- 57 57 57
Floor area of development (m²) 930 930 930 930 Floor area of dwellings (m²) 720 720 720 720 Total annual heating demand (kWh/a)
55,440 14,400 14,400 14,400
Total annual electricity demand (kWh/a)
1,152 1,728 1,728 1,728
Total annual heating demand per flat (kWh/a/flat)
6,930 1,800 1,800 1,800
Total annual aux. electricity demand per flat (kWh/a/flat)
144 216 216 216
Total annual heating cost per flat (£ / a / flat)
256 67 67 67
Total annual aux. electricity cost per flat (£ / a / flat)
19 28 28 28
Total bill/flat 275 95 95 95 Energy saving potential (kWh/a)
- 40,464 40,464 40,464
Cost saving potential (£ / a) - 1443.6 1443.6 1443.6 Cost saving potential per flat (£ / a / flat)
- 180 180 180
Percentage saving on annual bill
- 70.38% 70.38% 70.38%
Basic building costs (£ / m²) 1400 1400 1400 1400 Extra costs % - 5% 10% 15% Extra costs (£ / m²) - 70 140 210 Total basic construction costs (£)
1,302,000 1,302,000 1,302,000 1,302,000
Total extra costs (£) - 50,400 100,800 151,200 Total costs (£) 1,302,000 1,352,400 1,402,800 1,453,200 Years to get pay-back - 35 70 105
Technical data of building Building
Standards Passivhaus Passivhaus Passivhaus
(+5%) (+10%) (+15%) Based on: SAP
Heating demand (kWh/m²a) 55 12 12 12 Aux. Electricity demand (kWh/m²a)
1.9 9.8 9.8 9.8
Energy saving potential (kWh/m²a)
- 43 43 43
Floor area of development (m²) 930 930 930 930 Floor area of dwellings (m²) 720 720 720 720 Total annual heating demand (kWh/a)
39,600 8,640 8,640 8,640
Total annual electricity demand (kWh/a)
1,368 7,056 7,056 7,056
Total annual heating demand per flat (kWh/a/flat)
4,950 1,080 1,080 1,080
Total annual aux. electricity demand per flat (kWh/a/flat)
171 882 882 882
Total annual heating cost per flat (£ / a / flat)
183 40 40 40
Total annual aux. electricity cost per flat (£ / a / flat)
22 115 115 115
Total bill/flat 205 155 155 155 Energy saving potential (kWh/a)
- 25,272 25,272 25,272
Cost saving potential (£ / a) - 406.08 406.08 406.08 Cost saving potential per flat (£ / a / flat)
- 51 51 51
Percentage saving on annual bill
- 27.71% 27.71% 27.71%
Basic building costs (£ / m²) 1400 1400 1400 1400 Extra costs % - 5% 10% 15% Extra costs (£ / m²) - 70 140 210 Total basic construction costs (£)
1,302,000 1,302,000 1,302,000 1,302,000
Total extra costs (£) - 50,400 100,800 151,200 Total costs (£) 1,302,000 1,352,400 1,402,800 1,453,200 Years to get pay-back - 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 ‘Building Standards Domestic 2011 Technical Handbook’, Clause 4.2.5 2 Hunter, H., ‘Tenement Adaptability’, [Dissertation], (Mackintosh School of Architecture, Glasgow, 2006), p.41