Air Tightness Testing

APT Sound Testing provides air tightness testing throughout the United Kingdom. We undertake air testing on all types of projects from single dwelling to the largest commercial buildings. We are one of the few companies that are UKAS accredited to undertake both Air & Sound testing in compliance to Building Regulations and Standards. This means we can undertake Air, Sound and Vent Testing Packages during the same visit which provides our clients with cost savings and improved on site co-ordination. Unlike many companies we do not subcontract our works.

Air testing to achieve satisfactory levels of air tightness became a legal requirement in 2006 in England and Wales, under Building Regulations Part L and is becoming increasingly important to help produce greener buildings, via reducing carbon emissions due to the fact that energy is not being needlessly lost from residences via large air leakage paths etc. Building Regulation Part L defines ‘air leakage’ as the uncontrolled flow of air through gaps and cracks in the fabric of a building. The general public recognise it as draughts.

When you lose energy through the building fabric this is known as the building emission rate. New projects/developments must meet specific requirements for air testing and emission rates. The usual target for a standard dwelling is 5.0m3/hr/m2; however for commercial buildings the target rate is often much lower – around 3.0m3/hr/m2

Wherever air infiltration occurs, there is usually exfiltration somewhere else in the building. During the summer, infiltration can bring humid, outdoor air into buildings. In winter, exfiltration can result in moist indoor air moving into cold wall cavities and may result in condensation and mould and/or rot which could result in serious damage to the property.

We undertake air tightness consultancy and design reviews to help support our clients from the design stage of the project through to the precompletion air testing to achieve building control signoff. If you need to undertake your testing on Saturdays or Sundays, we offer an ‘out of hours testing’ service to help reduce the impact of testing during working hours.

We also offer substantial cost savings for combined air and sound testing packages. This is due to our multi skilled engineers being UKAS accredited to carry out the Air & Sound Testing, in fact most of our clients now use our ‘3 step’ precompletion package as it negates the need to employ multiple companies.

On site co-ordination is also improved, with both tests being undertaken on the same day in a planned methodical manner. We can also provide out of hours testing (if required) to help reduce the impact of testing during working hours.

We provide a friendly expert advice for helping properties achieve required emission rates for air testing. Simply the use our contact form on this page, or call our offices, to chat about your specific air testing requirements with our knowledgeable team of air tightness consultants.

Air tightness testing is carried to check the air leakage that occurs through a buildings envelope. The air test checks amount of conditioned air that escapes or gets wasted through gaps or air leakage paths through the building fabric. If the building is more air tight, less energy will be being needlessly lost, thus lowering the carbon emissions of the building. Air tightness testing also shows how efficient a building is at retaining conditioned air which will also put less straight on your mechanical and ventilation system. Failing to maintain adequate air tightness can lead to up to 50% of heat loss from within a building to the outside atmosphere.

Air testing is mandatory in the United Kingdom and is governed by Part L of the Building Regulations, this split into two parts; for domestic properties Part L1A should be used and for commercial properties Part L2A should be referenced.

Most air tests can be completed in 1-2 hours although some can take much longer, if low air leakage rates are required to comply with Passivehaus standards etc. Also other factors such as the size of the property, how many apertures need to be taped over; however even on very large dwellings the duration of the actual air test should take no longer than 2 hours if the building has been adequately prepared.

We also offer a smoke testing service to locate the air leakage paths within a building envelope which can also take extra time; however this often allows our clients to seal and pass their building at the first attempt even if their building initially fails the air test.

It depends on the location and the number of tests that are required on each site; it can be as low as £75 plus VAT per unit if we are undertaking multiple tests. Please contact us at to obtain a no obligation quote along with some friendly advice for you project.

As a general rule, the nature of the current building regulations requires that all new dwellings achieve an air leakage of 5m3/hm2 or less. That is the air leakage rate per hour, per square metre of envelope area. An air test results between 3 – 5m3/hm2 would usually be acceptable by building control and your SAP assessor as a good and acceptable result, although you need to check each your designed SAP Assessment as there may be items within your buildings design that that may affect this figure as the dwelling may be struggling to meet its emissions targets and a low air leakage may compensate for other areas, either arising from poor design, or factors beyond the developer’s control.

The air tightness test is undertaken in-line with Part L and the ATTMA standard. The pressure differential is measured across the envelope of the building by means of the temporarily installation of a large fan inside a door panel. Thereafter, a range of static pressures and environmental readings are taken. The fan is switched on and the air pressure in the property is gradually increased or decreased and the differential pressure is recorded at each step. The total air flow required to achieve a pressure differential of 50 Pa is calculated and divided by the total building envelope area to provide the leakage rate in m3/h.m2@50Pa.

In all cases the more complete a development, the more likely it is to meet air testing requirements. When we send out our quotation we also forward a specific air leakage checklist to help our client prepare for the testing.

Basically if you meet the following criteria will generally have a much better chance of passing the testing at the first attempt.

a. The building envelope should be fully complete; this includes walls, floors and ceilings.
b. All doors and windows must be fully fitted and able to shut tightly against their seals.
c. All electric fittings must be installed and functional.
d. All mechanical fittings must be installed and functional.
e. Gaps within walls and floors must be sealed.
f. All service penetrations must be fully sealed through the building envelope.
g. Bathrooms and kitchens must be fully fitted and all service penetrations sealed.
h. All mechanical ventilation turned off with grilles sealed.
i. All trickle vents to windows and doors must be sealed.
j. All fireplaces must be sealed.
k. Ensure water is present in soil pipes.
l. 240v power must be available on site.