An Assessor’s view
Do I Need an Air Tightness Test?
The simple answer is “not necessarily”
According to Building Regulations, developments with fewer that three properties can opt out of air tightness testing.
However................
Let’s not get too excited here, there is a price to pay (isn’t there always).
If you choose the opt out, the SAP assessor has to use a default value for the predicted air tightness of your building, and it should come as no surprise that such a value will not be advantageous. The minimum requirement for a tested dwelling to pass is 10m3/hm2. The standard default value used in the case of an untested dwelling is 15m3/hm2. This gives the assessor a problem because the house still has to pass SAP, and using a factor of 15m3, the result is going to be bloody. Consequently, other elements have to be upgraded to compensate, all of which will come at a cost.
I haven’t yet come across a solution to offset a 5m3 air leakage deficit that costs less than the test itself.
Apart from anything else, a good air tightness test result is one of the best ways to improve a failing SAP and with a little forethought it is relatively painless to achieve. It will also give a real benefit to the finished property.
In my opinion as an assessor, if you’re thinking of opting out, don’t. It’s not worth the paper it is written on.
This was written by Chris, our resident SAP technician with 30 years of experience in the construction trades.
For more information or to book a test, call me on 01484 686649 or visit my website on http://www.hometestingyorkshire.co.uk/
I hope this helps,
Matt
Air tightness testing is the procedure to trace any unwanted drafts and uncontrolled airflow through the house. Too much air leakage leads to heat loss resulting in higher C02 emissions.
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