Airtightness of buildings — towards higher performance Final Report — Domestic Sector Airtightness Airtightness of buildings — towards higher performance Final Report — Domestic Sector Airtightness Dr David Johnston, Dominic Miles-Shenton, Prof. Malcolm Bell, Dr Jez Wingfield, Centre for the Built Environment, Leeds Metropolitan University Department for Communities and Local Government This research was commissioned by the previous government. The views and analysis expressed in this report are those of the authors and do not necessarily reflect those of the Department for Communities and Local Government. This document is being published in the interests of transparency. Department for Communities and Local Government Eland House Bressenden Place London SW1E 5DU Telephone: 030 3444 0000 Website: www.communities.gov.uk © Queen’s Printer and Controller of Her Majesty’s Stationery Office, 2011 Copyright in the typographical arrangement rests with the Crown. 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If you require this publication in an alternative format please email [email protected] DCLG Publications Tel: 030 0123 1124 Fax: 030 0123 1125 Email: [email protected] Online via the website: www.communities.gov.uk ISBN: 978 1 4098 2863 1 TABLE OF CONTENTS Executive Summary...................................................................................................................................... 4 Airtightness design and construction........................................................................................................ 4 Implementation of pressure testing........................................................................................................... 5 Logistics of pressure testing ..................................................................................................................... 6 Options for regulatory testing.................................................................................................................... 7 Further work.............................................................................................................................................. 8 Introduction................................................................................................................................................... 9 Structure of the Report ................................................................................................................................. 9 Literature Review.......................................................................................................................................... 9 Participatory Action Research — Phase 1 ................................................................................................. 10 Selection of developers, sites and house types ..................................................................................... 10 Design assessments and site surveys.................................................................................................... 11 Airtightness results.................................................................................................................................. 12 Participatory Action Research — Phase 2 ................................................................................................. 16 Participatory Action Research — Phase 3 ................................................................................................. 17 Selection of house types......................................................................................................................... 17 Design assessments and site surveys.................................................................................................... 17 Measures adopted to improve airtightness............................................................................................. 18 Airtightness results.................................................................................................................................. 18 Discussion Papers...................................................................................................................................... 23 Discussion paper 1 — Performance and implementation ...................................................................... 23 Discussion paper 2 — Impacts of pressure testing ................................................................................ 24 Suggestions for Further Work .................................................................................................................... 27 Conclusions ................................................................................................................................................ 27 Pressurisation test results....................................................................................................................... 27 Constructing dwellings to be airtight....................................................................................................... 28 The existing testing regime and the logistics of compulsory pressure testing........................................ 29 References ................................................................................................................................................. 32 Acknowledgements .................................................................................................................................... 33 List of Appendices ...................................................................................................................................... 34 Executive Summary 1 This report constitutes milestone D11 — Final Report — Domestic Sector Airtightness of the Communities and Local Government/ODPM Project reference CI 61/6/16 (BD2429) Airtightness of Buildings — Towards Higher Performance (Borland and Bell, 2003). This report presents the overall conclusions and key messages obtained from the project through design assessments, construction observations, discussions with developers and pressurisation test results. It also summarises discussion on the airtight performance of current UK housing, the implementation and impact of current and future legislation, and identifies potential areas for future work. 2 Following an initial literature review, the project adopted an action research methodology that involved the research team working very closely with five developers to investigate the practical design and construction issues that arise in making improvements to the airtightness of speculatively built mainstream housing. Two construction types were represented in the project: masonry cavity and steel frame. The action research was carried out in three phases. Phase 1 sought to track in detail the design and construction of 25 dwellings (five per developer) built to the regulatory requirements of the 2002 revision to Part L of the Building Regulations and then to measure air leakage in the completed dwellings. During this phase no attempts were made to influence the nature of the design or construction. Phase 2 involved extensive feedback to each developer on the results of Phase 1, including the analysis of detailed design drawings and observations of dwelling construction. This was used to improve the understanding of the airtightness issues and to prompt the developers into making improvements to the processes they were adopting. The feedback phase was followed by a further construction phase (Phase 3) in which the design and construction of 25 dwellings were observed and detailed feedback provided to each developer at every opportunity. Upon completion of the second cohort of dwellings airtightness was measured and the results compared with the first phase results. The data were then used to assess the impact of the different methods adopted and the implications for future regulatory policy. Airtightness design and construction 3 The key conclusions that have emerged from the pressurisation test results obtained during the course of this project are as follows: a) Although the size, structure and non-random nature of the samples preclude it being taken as fully representative of UK house production, the results obtained from Phase 1 suggest that the dwellings tested were broadly in line with the existing data on the stock as a whole and that, at least in these cases, the impact of the 2002 edition of Approved Document Part L1 on airtightness has been minimal. b) Given the qualitative nature of the project, it was not possible to extrapolate the Phase 1 results to the post 2002 new build stock with any degree of confidence. However, the results were broadly in line with the results from pressurisation tests on 99 post 2002 dwellings (also not a random sample) reported by Grigg (2004). The