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AIRTIGHTNESS OF BUILDINGS – Towards Higher Performance
Domestic Sector Airtightness
(ref C1 61/6/16 BD2429)


Airtightness is crucial to improving the energy performance of buildings. This was recognised in Approved Document Part L of the 2002 Building Regulations, which, for the first time, included a maximum air leakage target for both domestic and non-domestic buildings. This Department of Communities & Local Government funded project considered the overall conclusions and key messages obtained through design assessments, construction observations, discussions with developers and pressurisation test results. The project analysed the airtightness performance of current UK housing, the implementation and impact of current and future legislation and identified potential areas for future work.

Following an initial literature review, the project adopted an action research methodology that involved the research team working very closely with 5 developers to investigate the practical design and construction issues that arise in making improvements to the airtightness of speculatively built mainstream housing. The research was carried out in three phases. Phase 1 sought to track in detail the design and construction of 25 dwellings (5 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. 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 processed they were adopting. The feed back phase was followed by a further construction phase (phase 3) in which the design and construction of a further 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.

The project highlighted a number of issues that need to be considered when constructing dwellings to meet a particular airtightness target. Suggesting that certain construction types appear to be intrinsically more airtight than others, complexity of the design can have a significant effect on airtightness, certain approaches to improving airtightness are likely to be both more successful and more robust than others and that achieving consistently high levels of airtightness in dwellings may prove difficult within existing design and construction cultures.

Final Report on Domestic Sector Airtightness
Appendix 1 : Literature Review and Built Examples
Appendix 1A : Literature Review and Built Examples
Appendix 2 : Developers, Sites and Protocols
Appendix 3 : Assessments of Design and Pilot Site Data
Appendix 4 : Airtightness Results from Phase 1
Appendix 5 : Site Assessments and Feedback Material
Appendix 6 : Seminars and Developer Feedback
Appendix 7 : Design Assessments
Appendix 8 : Site Assessments and Test Results
Appendix 9 : Discussion Paper 1: Performance and Implementation

Appendix 10 : Discussion Paper 2: Impacts of Pressure Testing