Air Permeability Testing - The Info

This testing process is also described as Air Pressure Testing, Air Leakage Testing, Air Tightness Testing or just Air Testing. Whichever name it goes by, Air Permeability Testing is designed to measure uncontrolled air flows through gaps or cracks which exist in the fabric of the build. This gives a good indication as to the quality of the build and is designed to minimise heat lost through the fabric envelope of the building.

Regulations get tougher all the time and Air Permeability Testing is a key focus. This testing procedure plays a vital role in determining the energy efficiency of your build, so we would stress the importance of designing for air tightness right from the start of your project.

When Does Air Permeability Testing Take Place?

This happens late on in the process, once the build is complete. The test measures whether or not your air leakage strategy is successful by seeking out leakage routes in the build envelope.

At Hilsdon Holmes our test engineers are highly qualified. If your build fails its Air Leakage Test, or if the air leakage exceeds expectations, our engineers will always discuss the results, and advise on remedial actions.

Will I Need an Air Permeability Test?

The number of residential builds requiring testing has increased due to the Part L1 2010 changes,(and continues under Part L1 2013), so it is becoming more and more likely that you will need an Air Permeability Test. Should you decide against it, the value taken as an Air Permeability figure has not changed and worsens the SAP performance markedly.

How Many Air Permeability Tests Should I Schedule?

  • All developments: an air pressure test should be carried out on three dwellings of each type or 50%, whichever is the lesser
  • Untested dwellings: the as-built air permeability must be taken as the average of the test results for tested dwellings of the same type plus a margin of +2.0m³/hm²@50Pa.

Unless all dwellings are to be tested, to ensure that all dwellings meet the as-built air permeability limit of 10m³/hm²@50Pa, the design air permeability (DAP) should be no greater than 8m³/hm²@50Pa

Hilsdon Holmes works across the UK with clients involved in a variety of builds, from small to large, simple to complex.  Our team includes qualified and experienced Air Permeability Testers, and we are also happy to test non-domestic buildings.

Our ATTMA accredited testers comply fully with Building Regulations requirements, applying ATTMA TS1 standards with UKAS calibrated equipment.


Need to discuss your Air Permeability Testing requirements? Just give us a call on 01579 382202, or email us at info@hilsdonholmes.co.uk