Air Tightness Testing – Residential

Air Tightness testing is a requirement for all new houses and flats. Testing must be conducted by a competent person, typically a company registered with the Air Tightness Testing & Measurement Association (ATTMA). All of our test engineers hold ATTMA L1 registration.


Air Tightness is a key factor in achieving an energy efficient building fabric in combination with insulation. The England & Wales Building Regulations require air tightness to be measured through site testing.

Testing is carried out by installing a blower door fan into the envelope of the property (typically in the front door) and using the fan to create a pressure difference. The volume of air flow required to create the pressure difference is used as the basis for calculating the amount of air escaping through holes, gaps and cracks in the building fabric that it is not intended to (i.e. not through planned ventilation, which is temporarily sealed for the test). This air flow rate is divided by the size of the building to give a measure of leakage in m3.h-1.m-2


There are different requirements for residential (dwellings – just houses and flats) and ‘commercial’ (buildings other than dwellings) which includes care homes, student accommodation and similar.

In June 2022, a revised version of Approved Document L came into force. It is divided into Volume 1 for dwellings and Volume 2 for buildings other than dwellings. There are some significant changes included in this revision in order to achieve a 31% reduction in carbon emissions from new buildings, this impacts a wide range of aspects of energy efficiency including insulation and fuel types as well as air tightness, as a stepping stone to the Future Homes Standard in 2025.

The highlights with respect to air tightness include:

  • No sampling – all units must be tested
  • Maximum air permeability reduced from 10 m3.h-1.m-2 @50Pa to 8 m3.h-1.m-2 @50Pa (i.e. less draughty)
  • A different test standard (CIBSE TM23)

The specific air permeability target for each property is determined by the design rate allowed for in the SAP energy calculation. It is important to know this figure from the outset.

Testing must be conducted by a suitably competent person, our test engineers are all registered with the ATTMA competent person scheme, as referred to in Part L.

For more information on air tightness and the testing, please visit our FAQ page.



Air Testing Process

Our air test engineers are home-based and well-placed to cover Greater London and the City, Kent, Essex, Surrey, Sussex, Hampshire, Berkshire, Buckinghamshire, Oxfordshire, Hertfordshire, Bedfordshire and Cambridgeshire, we are able to test all over the UK.

1. Answer Queries

We are happy to talk through what is involved, what to watch out for and when to test. We can provide guidance and checklists.

The below checklists can be downloaded and used to manage air testing from design/planning, through construction to preparation for the test:

Download  – Dwelling checklist

Download – Guidance for Housebuilders

2. Date & Price
We provide an indicative price based on the size of the building and location, ahead of issuing a formal quote based on PDF drawings. We can look at pencilling in dates to suit your programme, our lead times are typically 1-2 weeks but we can often fit in single tests at shorter notice.
3. Preparation

We confirm a date. Our engineer will call you ahead of the test date to talk you through the preparation and process plus agree the timings. We would also look to confirm the air permeability that has been targeted in the energy model (SAP) at this stage, if it hasn’t been discussed already. The results of the test are a key component of the calculation of the overall energy efficiency of the building and, therefore, achieving the necessary air tightness is a critical part of building control sign-off.

4. On the day of testing

On smaller houses and flats we would typically complete the temporary sealing for the test when we arrive on site.

We conduct the test. Testing is done through a pressure test whereby fans are installed into a doorway of the building and used to create a measurable difference between the pressure inside and outside of the building. The amount of air needed to maintain this difference can be used to indicate the volume of air escaping through the fabric (what would be draughts in the building’s day-to-day life).

If the building doesn’t achieve its target at the first time of asking, we can use our equipment to identify the leakage paths. If these can be addressed relatively quickly, then we can repeat the test on the same day. In order to achieve increasingly challenging energy performance targets, air tightness requirements are becoming tighter. Typically, a good level of air tightness can still be achieved with excellent attention to detail in the decorative finish but, to achieve tighter targets, consideration must be given to air permeability within the design of the fabric, including use of membranes and tapes to maintain the air barrier – please see FAQs.

5. Paperwork

We issue ATTMA certificates for each test within 24hrs of the test but we can issue them on the same day (when requested).

Established in 2002


What our clients say about us

“ALT were extremely helpful and knowledgeable. They worked with the site team to identify and resolve issues during construction.”
“I have used Air Leakage Testing Ltd on two separate occasions at my property and found them to be extremely thorough and professional at all times. The turnaround between site visit and subsequent reports was quick and efficient - making my life a whole lot easier! Would highly recommend to anyone!”


Helpful Engineers

We work with you to achieve the best result, identifying potential issues and repeating the testing once these have been addressed. We are on hand to answer any questions before, during and after the testing.

Flexible & Responsive

We try to fit in with the dates and times you need the test, we try to work around other trades to minimise disruption on site. We issue quotes and certificates within 1 working day, our lead-times are typically around a week but we will try and fit you in sooner if required.


We have been air testing since 2002 and keep pace with changing regulations. All our test engineers hold ATTMA L1 registration and have considerable experience in undertaking tests and resolving potential issues.

Great value

Our prices are very competitive but we can also undertake air and sound testing on the same visit to save you more money. If you do manage to find the testing cheaper, we will beat any quote.

Get a quote

Fill in the form at the top of this page, and we will provide an estimated cost.

Provide more information, and we will issue a formal quotation.