WHAT IS AIR TIGHTNESS TESTING?
Air tightness testing aka air leakage testing is the measurement of the total area of air gaps in a building’s external fabric. Nearly all new build dwellings and the majority of new comercial developments require an air tightness test.
Why is air testing important?
The larger the area of air gaps the more hot air that will escape and the more cold air that will get in (draghts). The less heated air that escapes a building the less heating that is required to compensate for the heat loss.
Residential Air Tightness Testing
All new dwellings require an airtightness test result to calculate the Dwelling Emission Rate in the SAP calculation which produces the Energy Performance Certificate. The airtightness test is usually done just before practical completion. The result is then put into the SAP calculation to determine the final EPC rating of the building.
If you are building multiple identical or similar dwellings you can choose to do sample testing, however, a confidence factor of +2 m3/(m2.hr)@50Pa will be applied, which makes the SAP calculation harder to pass.
Commercial Air Tightness Tests
All new commercial buildings require an air permeability socre to Calculate the Building Emission Rate in The SBEM calculation which is used to calculate the EPC rating.
Commercial buildings below 500m2 have the option of using a default Air tightness value of 15m3/(m2.hr)@50Pa however this will negatively impact the SBEM (EPC) performance. If a value <15m3/(m2hr)@50pa is used in the SBEM to improve the EPC then an air tightness test is required.
Air Testing FAQs
Can I make a building too air tight?
Yes and no, if there is a MVHR (Mechanically Ventilated Heat Recovery) system installed correctly then the more airtight the better.
For buildings without an MVHR or mechanical ventilation system that score less than 3 m3/(h m2)@50pa there is a significant risk of condensation and black mould.
To be sure a building has enough controlled ventilation Part F Ventilation Testing should always be carried out.
Do all of the dwellings need an air test?
If there are multiple dwellings of the same design type then sample testing can be used. In which case an air pressure test should be carried out on three units of each dwelling type or 50 per cent of each dwelling type, whichever is less.
However dwellings that are not air tested must use the average score of all of the dwellings of that type with a penalty or +2 m3/(h m2)@50pa per dwelling. This means if you are using a design air permeability of 5 m3/(h m2)@50pa the dwellings must achieve an air tightness test value of 3 m3/(h m2)@50pa so that 5 m3/(h m2)@50pa can be used in the SAP calculation. If a dwelling achieves <3 m3/(h m2)@50pa there is a significant risk of condensation and black mould if there is no MVHR (Mechanically Ventilated Heat Recovery)