Air Tightness Testing

Aurora is able to offer air tightness testing in Harrogate and North Yorkshire in line with Part L of the Building Regulations.

Air tightness testing is mandatory for all single dwelling builds and should be carried out for a sample of new builds on larger developments. The air tightness test is fairly simple. So it shouldn’t take too long to perform.

Aurora will be able to assist you throughout the process. If your building fails the test we are able to help you to fix the problem too.

What is Air Tightness Testing and why is it needed?

Simply put, air tightness testing is a way to measure how efficient the building is at preventing air leaks. These air leaks allow cold draughts into the building and heat to escape from the building. The fewer leaks, the less energy that is required to heat it.

With up to 40% of heat loss coming from air leaks, air tightness testing is an important way to measure the efficiency of your building and reduce your energy usage. This is particularly true when used in conjunction with other energy usage reduction measures. These include efficient insulation, micro generation (solar PV or solar thermal) or an efficient boiler.

Under Part L of the Building Regulations a figure has been set for the maximum air permeability allowed. If the test shows that your building exceeds that figure it will fail the air tightness test.

In practical terms the test is fairly straightforward. Our engineer will need to visit site, usually for no more than a couple of hours to perform the test. You will just need to provide a full set of architect’s plans for your building.

Aurora is able to perform air tightness testing throughout the Yorkshire, Humberside and North East regions, and if your building doesn’t pass the test we are able to help you with further testing and practical advice to show you any areas which need to be addressed.

What to do if your building fails the Air Tightness Test

Fortunately there is often a simple fix when a building fails an air tightness test. The first step is to find out where there is a leak. Aurora are able to perform a number of tests to find these leaks:


  • Depressurisation – during the air pressure test the building will be pressurised. Once the test is complete the building begins to depressurise. As this happens draughts can be felt as the air comes back into the building. Any large draughts felt at this time are likely to indicate areas that will need to be addressed.
  • Smoke Testing – Aurora can either use smoke pencils, or fill the building with a harmless smoke and the pressurise the building again. The smoke will be seen as it escapes through any gaps. This hows exactly where leaks need to be stopped.
  • Thermography – we can use infrared technology to show hot and cold spots in the building and identifying leaks. It is easier to complete these test at night though as this is when the difference between the indoor temperature and the outdoor temperature is at its greatest.


Once the source of the air leakage has been found the leaks can be sealed or remedial works carried out. Then the building can be retested. There are a number of common areas where leaks can occur. It is always worth paying special attention to these areas before your first air tightness test is carried out or if your building fails its air tightness test. See more information on common problem areas when conducting air tightness testing.

Common Problem Areas

Check for gaps where services enter and leave the building – especially in bathrooms and kitchens including hidden areas such as behind the bath panel, in a service box or behind kitchen units.

Look at areas where walls, floors and ceiling meet, especially around suspended floors.

Check door and window surrounds and light fittings.

Ensure loft hatch is a snug fit and has been sealed.

Check that sealant has been used in all relevant areas such as around sockets and skirting boards.