Top 3 reasons for failing an air test
The introduction of air testing in Scotland in Section 6 of the 2010 Scottish Building regs has resulted in a better build standard
The introduction of air testing in Scotland in Section 6 of the 2010 Scottish Building regs has resulted in a better build standard. Whereas previously gaps and unsealed openings which were out of sight could be ignored, the air test (or air pressure test/ air tightness test/ air leakage test as it's sometimes known) means that a minimum air tightness standard has to be achieved (10m3/h/m2). Excessive air leakage results in excessive energy costs, and the introduction of new regulations to address this can only be a good thing for homeowners and building managers. For more information click here.
So what are the top three reasons for failing an air test?
Surpringy the no.1 reason that we have experienced for failing an air test is a house being built too air tight! The builder in an attempt to avoid the house failing for being too leaky, goes too far in the opposite direction and seals up every opening and joint. As a guideline 10m3/h/m2 is the minimum standard under the new Scottish regs.
Our air testing has shown that with due care to the building process this can readily be achieved. In fact under 7 m3/h/m2 can also fairly readily be achieved if care is taken to use standard construction details and seal openings and penetrations as required.
Once a house scores between 3 & 5 m3/h/m2 then a much higher air tightness standard is being achieved. In this range, the architect must satisfy him or herself (and the verifier) that there is adequate natural ventilation provision in the house design, for example through trickle vents or include some form of assisted ventilation.
We've tested some houses which have scored 2.6 m3/h/m2 when a target of under 7 was being targeted. The builder is frustrated to realise that ironically by taking less care they would have passed the test. However in the long run (and next iteration of Building Standards) an ability to 'build tight, ventilate right' will pay off for good builders.
In cases where the house is too air tight, assisted ventilation has to be introduced - for example through changing over extractor fans to continuous running fans, or introducing humidity activated ventilation - check with your architect and Local Authority verifier for your house design. For a house scoring under 3 m3/h/m2 then some form of assisted ventilation must be included. The risks of under provision of ventilation include poor air quality and condensation.
The next most common reason we've encountered for failing an air test in Scotland is leaks around penetrations - for example unsealed areas around boiler flues, toilet waste pipes, under the kitchen sink, electricity cabling etc etc.
Cumulatively these can results in signficant losses, however the good news is if found early enough they can fairly easily be corrected.
Our third most common area for failing a house is due to leaks at floor to skirting. However these only tend to affect properties which are targeting a higher air tightness, for example under 7 m3/h/m2, and reference should be made to the architectural drawings and construction details to see what should be in place for your house.
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We are based in central Scotland and carry out air testing in Glasgow, Edinburgh, Ayr, Stirling, Perth, Dundee, Aberdeen and all across Scotland.