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Video: Designing for airtightness

The Building Regulations are a key tool in the UK strategy for cutting carbon emissions by 20% by 2010. The revisions to Part L of the regulations, which came into force in 2006, aim for a 25% improvement in the energy efficiency of new buildings. Minimum acceptable standards are imposed upon the designer. For airtightness, Part L stipulates a requirement to declare the air permeability target figure you've used in the design process, a requirement to test the building, to demonstrate that the air permeability is less or equal to that figure. If you exceed the target performance figure you'll be required to compensate in other areas, or carry out remedial sealing work. It's worth noting that Part L very much sees air permeability as a proxy for build quality. So what are the secrets for designing and constructing for airtightness?

Airtightness increases the efficiency of the building; it ensures that you don't get cold drafts. It makes sure that the energy input that heats the internal space is used to the greatest effect.

The carbon dioxide (CO₂) savings for an airtight building can be significant. Looking at housing, by reducing air permeability down from the current worst acceptable standard of 10m³ per hour down to a reasonably good standard of 7, about 90kg of CO₂ per year can typically be saved for each dwelling. With approximately 130,000 dwellings built per year, this gives a combined saving of about 12,000 tonnes of CO₂.