Description

Part L requires new dwellings, new buildings other than dwellings and 'large' extensions to non-dwellings to achieve reasonable levels of air permeability as part of minimising heat loss through the building fabric. Performance is proven through on-site pressure testing.

The test measures the amount of heated/cooled air escaping through gaps, cracks, holes etc. Buildings must demonstrate that they are not losing more than 10m3 of air every hour accross every sqaure meter of the 'envelope' when pressurised to 50Pa. This should be a relatively attainable target, but lower figures may be required as part of the overall emission rate requirements for the building.

The regulatory requirements are covered in more detail in the Technical Information Sheet TI-0808 - Air tightness testing.