Dwelling Ventilation and Airtightness for PAS 2035

One thing to remember with Ventilation and airtightness is they are always co-dependent when it comes to PAS2035  doesn’t recommend to make a building airtight without allowing for adequate building ventilation.

Having undertaken thousands of air tightness tests, we often see dwellings with expensive ventilation systems such as MVHR systems. it s worth noting that its not worth incorporating expensive ventilation systems such as MVHR if the building envelope is riddled with air leakage paths as it will not work properly.


This was evident on one recent retrofit project where the M&E design was built around an air leakage rate between 3-5m3/hr/m2; however, when tested the building achieved an air leakage rate in excess of 15 m3/hr/m2! We then carried out a blower door smoke leakage surveys and issued a report highlighting all the air leakage paths. Thereafter,  once the remedial sealing works had been completed the building was retested and achieved an air leakage rate below 5m3/hr/m2, which worked perfectly with the new MVHR ventilation system.

PAS2035 recognises this co-dependency by stating the following:

            • If the post-retrofit air leakage rate is better (more air tight) than 5m3/hr/m2 then continuous running ventilation (such as MVHR or MEV) is recommended.
            • If post-retrofit ir leakage rate is worse (i.e. leakier) than 5 m3/hr/m2, trickle vents with intermittent or passive ventilation are permitted.

So, as the PAS 2035 air tightness test can be carried out quickly and easily, it makes logical sense to measure all retrofit buildings, both before (pre-works) and after the retrofit (post-works). Using this information, stakeholders can work from an informed position and risks can be more readily managed with M&E design etc.

Call us if you require an air tightness test for PAS 2035

We have large amount of experience in understanding the requirements of Approved Document L and PAS 2035, along with extensive experience of carrying out thousands of successful air tightness tests on a wide range of developments across London and the UK.

You can rest assured that we provide the highest quality service for all your air tightness testing and reportage. We are a UKAS accredited laboratory, as well as being certified to ATTMA Level 2.

If you would like more information in for our PAS 2035 air tightness testing services, please contact us at info@airpressuretesting.net  or visit our call us on 01525 303905. Alternatively, please see a copy of our air leakage checklist to help you prepare for your PAS2035 Air Test.