What Happens If Your House Fails an Air Permeability Test?

Although proper sealing should take place during the building stage of a house, your home may still have air leakage issues that could lead to an air permeability test failure. In this blog, we have provided common reasons why houses fail the air permeability test and how you can minimise air leakage and receive a pass.

So what happens if your house fails an air permeability test? If your house fails an air permeability test, the air tester will provide a report with the locations of any major leaks so you can resolve them. The test will then be performed again to see if your house passes. A passable score for air permeability is 3 – 5 m3h-1m-2, any less being too airtight.

Read on to find out the common reasons for failing air permeability tests and how you can improve your result.

What Happens If Your House Fails an Air Permeability Test?

If your house fails the air permeability test, the air tester will locate the sources of air leakage and seal them with foam, mastic, or caulk if it’s available. If multiple leakage issues are found that cannot be sealed immediately, the air tester will provide a technical report listing the problems. They will then return to the house and retest once the problems are resolved. 

The purpose of an air test is to determine the total amount of air loss through leaks in the building’s structure. It is a legal requirement according to Part L of the building regulations to monitor the conservation of fuel and power. It is important to make sure every floor of the building meets the expected standard, including any access below ground level and attic. 

This can be achieved by ensuring that thermal bridging details have been followed correctly so that there are no gaps in insulation. However, you must balance an appropriate airflow level to allow for ventilation for the building’s inhabitants. For more information on how to pass an air permeability test, read our recent blog.

Common Reasons for Failing Air Permeability Tests

There are a number of common reasons houses fail air permeability tests, usually related to sealing. Here are some reasons and how to resolve them:

Too Air Tight

Although this may seem contradictory to the purpose of an air permeability test, a common reason for failure is a building being too air tight. In an attempt to avoid failure, builders may overcompensate by sealing every possible gap. However, this doesn’t allow for an appropriate amount of natural ventilation in the home, making it unlivable for occupants without additional ventilation. A reading of less than 3 m3h-1m-2 could mean that your home is too air tight.

Leaks Around Skirting

Air leaks at floor level are very common due to skirting boards not being sealed properly, this is another common reason why your house may not pass an air test. You can seal gaps in skirting boards by using caulk and smoothing it with a silicon spreader. Before you apply caulk make sure the nozzle is the correct size for the gap and fill the gap up completely. Then use a damp cloth to clean off any excess caulk to create a clean finish.

Leaks From Penetrations

Air permeability tests can also fail due to unsealed areas around toilets, chimneys, cabling, and pipes as these can result in significant air leakage from a house. 

  • Gaps around pipes: Pipes leading to the exterior of the house or under sinks should be sealed around where they penetrate the building fabric. 
  • Eaves cupboard doors and loft hatches: Treat hatches and cupboard doors the same at any doors leading to the exterior of the house and seal them well. 
  • Fitted units: In any room that contains fitted units such as kitchens and bathrooms, the area where the unit meets the wall should be sealed prior to installation. 
  • Light fittings & Plug sockets:  Any light fittings, pull cords and plug sockets need to be sealed.

What is a Good Air Permeability Test Result?

In the UK the Maximum Air Permeability is 10 m3h-1m-2. A good air test result for a new build is between 3 – 5 m3h-1m-2, usually accepted by building control and your SAP assessor. A reading of less than 3 m3h-1m-2, or more than 10 m3h-1m-2 is unlikely to be accepted as extra measures would need to be taken, such as ventilation systems, to ensure the correct airflow through the building.

Air Permeability Tests at RS Energy

At RS Energy we determine the amount and costs of energy required for your build. While we work with you, our SAP assessors will take into consideration air permeability and ventilation during the design stage of your build. 

Contact us today to receive a free air permeability test quote.