Bristol

Air permeability testing also referred to as air tightness testing or blower door testing, determines the rate of air leakage per hour per square metre of building envelope area when exposed to a test reference pressure differential across that same envelope of 50 Pa.

Under Building Regulations Part L in the UK, new builds must undergo airtightness testing. The target for achieving an air permeability score of 5 m3h-1m-2 (air permeability rate per hour per square metre of building area at a reference pressure differential of 50 Pa) must be achieved for new buildings.