What air test score do I need to achieve for a new build?

The standard set out in Approved Document Part L 2021 is a maximum air permeability of 8 m3 /(h·m2 ) @ 50Pa.

However, the air test target will vary between different dwellings & is often lower than the maximum set out above in Part L.

This is determined by the dwellings SAP Calculations. A better SAP specification e.g. more insulation, minimal thermal bridging, renewable technologies etc… will give more leeway on the air test target.

Most dwellings tend to have an air test target of around 5 m3 /(h·m2 ) @ 50Pa. This is widely considered to be an ‘average’ & achievable score within the industry.

A target of below 5 would be increasingly difficult to achieve. Any result below a 3 would require whole house mechanical ventilation due to being too airtight & the potential issues this could cause with mould.

UKBC offer diagnostics and assistance on how to achieve a pass as a standard part of our Air Tightness Testing service.

Check out our guide to air testing page for more information on this.