Air Tightness Testing – Low Energy

PassivHaus, EnerPHit, and similar low energy schemes prioritise the importance of the building fabric being well insulated and airtight so that other energy saving measures/design can be fully effective.



Passive House requires certified properties to achieve less than 0.6 air changes per hour which is the equivalent of less than 1 m3.h-1.m-2 @50Pa, which is tight but the design also incorporates suitable ventilation strategies.


We undertake air tightness testing of PassivHaus houses, apartment blocks and commercial properties.

Testing typically involves preliminary tests and identification of leakage paths to confirm performance at an earlier stage ahead of a test on completion to confirm the final air tightness performance. The result is based on the average of negative and positive pressure tests.

Our test engineers are ATTMA registered for Low Energy Scheme air testing to TSL4. For more information on air tightness and the testing, please visit our FAQ


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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.


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.

For PassivHaus and similar it is advisable to undertake preliminary testing at key stages in the formation of the air seal barrier to confirm the build is on track to meet these demanding targets ahead of a final air test:

  1. Air barrier complete
  2. Services installed
  3. Practical completion
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.

4. On the day of testing

We would talk you through what would need temporary sealing would need to be done in advance of our arrival.

We conduct the test. Testing is done through negative and positive pressure tests 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 move air and/or smoke to identify the leakage paths. If these can be addressed relatively quickly, then we can repeat the test on the same day.

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).

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!”

Established in 2002

5 Star Google Reviews


why choose alt?

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 all our test engineers have a vast amount of experience.

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.