In April 2002 revisions to Part L of the Building Regulations were introduced, to improve the energy efficiency of UK buildings. For many housing schemes using traditional masonry cavity walls this may result in an increased cavity width and a consequent increase in the dwelling footprint. The potential impact that this may have on site utilisation, particularly in the light of planning guidance aimed at increasing site densities, has raised concern within the development community. Developers argue that even minor increases in wall thickness may reduce the number of dwellings on sites, thereby reducing overall profitability. This paper analyses these concerns by investigating the impact of increased wall thickness in the context of two developments constructed in the late 1990s. The existing site layouts were analysed under different footprint assumptions and an assessment made of the capacity of the layout to accommodate footprint increases. The theoretical analysis demonstrates that dwelling numbers are unlikely to be reduced as a result of the standards introduced in 2002. It is only when anticipated future improved standards are applied that dwelling numbers may be affected. However, the paper demonstrates also that dwelling loss is not inevitable and that it is perfectly possible to produce very low energy housing, while still achieving densities in line with planning requirements and with no reduction in the overall quality of a scheme. In the end it is not a matter of wall thickness but of good site layout and good house type design
