Frequently Asked Questions
What is an air leakage test for?
The test shows how much air leaks from your building. As the air escapes it takes heat with it. The heat was likely created by burning a fossil fuel. The more air leaks the more fuel needs to be burned, and the more CO2 is produced.
Is there any difference between the terms "air leakage test", "air test" or "air permeability test"?
No. They all mean the same thing. People just refer to them differently. We use all three descriptions throughout this website.
Do industrial buildings need an air leakage test?
Yes, if the floor area is more than 500m2. Floor area is calculated as the ground floor area (footprint) plus the area of any additional floors.
Do houses need an air test?
Yes. A representative sample of a development need testing, this is determined by the number of dwelling types as the lesser of 3 or 50% of a dwelling type need to be tested. In the case of blocks of flats, each block constitutes a separate development. This means that on a housing development of say 10 identical houses you would have to test only 3 of them not 5. However with a development of 4 houses you would have to test 2 of them (i.e. 50%).
Can I use any air testing company?
Yes and No! To comply with current Building Regulations and to avoid any possible problems with Building Control rejecting your air test certificate, you should ensure that the company you use are ATTMA or BINDT accredited. Remember though BINDT members can ONLY test dwellings, whereas ATTMA members can test BOTH dwellings and non-dwellings. Air Leakage Testing Limited is a member of ATTMA and are fully UKAS accredited to ISO/IEC 17025 (testing) and BS EN 13829. We are also registered with CHAS scheme for Health and Safety.
Are any types of building exempt from having an air test?
Yes. Details can be found in Building Regulations Approved Document Part L.
Why bother with an air permeability test?
1. Minimising air loss will reduce heat loss and will save you money.
2. Reducing CO2 emissions is good for the planet.
3. It is a Building Regulation Requirement.
How is an air leakage test conducted?
In simple terms, we set up pressure testing and temperature recording equipment in the building to be tested. We then attach an electrically driven door-mounted blower unit - a large fan - to a suitable opening in the building envelope having first ensured that all the external doors, windows and ventilation openings are closed. We then start the fan and pressurise the building.
How much is a building "pumped up" in a test?
The pressures involved aren't that great. Visions of roof sheets popping off and windows blowing out are unfounded. The pressures we work with are normally in the 55-60 Pascals (Pa) range, although in certain conditions this may be increased to 100Pa (see - What is a Pascal? below). What we do need is lots of air. We use sets of fans capable of delivering 30m3 of air per minute.
What is a Pascal?
A Pascal (Pa) is a metric unit of pressure. As guidance 1psi is roughly 6,900Pa, so even 100Pa is a still a very low pressure. Atmospheric pressure is about 100,000Pa, or about 14.5psi.
How much do the regulations allow a building to leak?
The general requirement for dwellings and non-dwellings is to achieve maximum air permeability of not greater than 10m3 per hour per m2 at 50Pa applied pressure. However, in order to comply with the carbon emission target, a lower permeability may have been specified by the designer. This might be considerably lower than the 10m3/hr@50pa that the Buildings Regulations allow. The lower the design air permeability the better you have to build the building!
What air permeability figures do buildings generally achieve?
We find that most houses, if well built, achieve between 5-7m3 per hour per m2 at 50Pa. Industrial units generally achieve between 7-10m3 per hour per m2 at 50Pa. In both cases however, we've seen buildings that outperform that.
What's the best result you've measured?
We tested one house which achieved 0.5m3 per hour per m2 at 50Pa, which is exceedingly good! The best industrial unit we've tested was just over 3m3 per hour per m2 at 50Pa.
What do I have to do to prepare for an air test?
Have a look at our air leakage test picture gallery to see the items you should seal or make sure are finished prior to the test. Common sense detailing at the eaves, verges, around windows/doors and other junctions will effectively block all gaps. Most buildings that fail do so because of poor workmanship and site supervision, rather than design faults. Once you have booked your air test with us we will provide you with a full list of what you can and can't seal up, what has to be open and closed, and what you may need to remove before we can carry out a test. A contractor's representative should be on site throughout the test. We can also review your drawings to help you avoid costly problems before building commences.