Air tightness test and ber

autumnbelle

Almost finished a self build. We are looking to get a ber done for final stage mortgage drawdown. Our engineer has only now told us that we will have to have air permeability test done for this. This is the first we have heard of anything like this from our engineer and we never had one done at an earlier stage. We have received almost no advice or help and done the house ourselves. Is it very difficult to pass this airtightness test? We have it booked for next week. The only airtightness we done was taped around windows. We used 150 mm insulation in the cavity wall and spray foam in the roof

sydthebeat

have the tester arranged to do a smoke test... and have a couple of tradesmen on site with caulk guns and some tape.

do the first test to find where the issues are, remedy them, then do another test after.

please post here with both results and a brief comment of works needed, if you can.

Gumbo

Joys of self building

What was the engineer engaged to do? What’s his brief?

autumnbelle

kceire wrote: »

Joys of self building

What was the engineer engaged to do? What’s his brief?[/quote

Engineer has done none of the things he was engaged to, that could be a whole separate thread. Have you any experience of this test? We are panicking now that we won’t meet whatever requirements and no funds there to rectify now until last drawdown. We have done our best regarding insulation Choices etc

Wartburg

sydthebeat wrote: »

have the tester arranged to do a smoke test... and have a couple of tradesmen on site with caulk guns and some tape.

do the first test to find where the issues are, remedy them, then do another test after.

please post here with both results and a brief comment of works needed, if you can.

I can´t understand why so many people do praise a smoke test. Coming from my own experience it does not work that great as it sounds, expect you´re using a very professional smoke generator with a high output of smoke per minute. Otherwise it´s like throwing a bucket of water into the desert and expecting recultivation of that area.

Just to clarify the formal procedure of an official air tightness test: the tester has to perform a leakage detection prior to the official measuring series.
It´s a common practise to do this leakage detection at a depressurization of 50Pa - 60Pa. As a spillover you can see the air change rate on the monitor during the blower door machine is cruising at this level, if you have the required building volumes added before. That will give you a first indication about the air tightness performance of your building. You could agree with the tester some additional time for getting some of the detected leakages sealed, which takes on average 30-60 minutes. And thereafter the AT tester can start the official testing series, consisting of at least one measuring series with depressurization of the building and another series of pressurization.
It´s hard to estimate the air tightness performance of your building upfront, because the building shape affects the air tightness in a significant way. I had buildings with the same AT strategies like yours with air permeability results - q(E50) - in the range from 1.6 up to 3.5m³/m²h. Common practice for buildings with mHRV is 3m³/m²h or less, without mHRV the limit is 5m³/m²h (poor value).

Casati

autumnbelle wrote: »

Almost finished a self build. We are looking to get a ber done for final stage mortgage drawdown. Our engineer has only now told us that we will have to have air permeability test done for this. This is the first we have heard of anything like this from our engineer and we never had one done at an earlier stage. We have received almost no advice or help and done the house ourselves. Is it very difficult to pass this airtightness test? We have it booked for next week. The only airtightness we done was taped around windows. We used 150 mm insulation in the cavity wall and spray foam in the roof

Surely you have a required air test goal already set to meet the BER requirements, this should be something discussed with the engineer in detail, along with specific best practices for airtightness for your specific build? Hopefully it’s not too low as it’s v difficult to make a house already built airtight

autumnbelle

Casati wrote: »

Surely you have a required air test goal already set to meet the BER requirements, this should be something discussed with the engineer in detail, along with specific best practices for airtightness for your specific build? Hopefully it’s not too low as it’s v difficult to make a house already built airtight

No our engineer told us nothing about the air test or ber requirements. He told us to put vents in our walls so the house was never going to be airtight

sydthebeat

autumnbelle wrote: »

No our engineer told us nothing about the air test or ber requirements. He told us to put vents in our walls so the house was never going to be airtight

Vents in the walls, and airtightness, are not mutually exclusive

Calahonda52

autumnbelle wrote: »

Almost finished a self build. We are looking to get a ber done for final stage mortgage drawdown. Our engineer has only now told us that we will have to have air permeability test done for this. This is the first we have heard of anything like this from our engineer and we never had one done at an earlier stage. We have received almost no advice or help and done the house ourselves. Is it very difficult to pass this airtightness test? We have it booked for next week. The only airtightness we done was taped around windows. We used 150 mm insulation in the cavity wall and spray foam in the roof

What exact advice or help did you ask for?
At what stage did you engage with the engineer?
What exactly did you ask the engineer to do?

In passing: what is the exact buildup of the roof that is sprayed with insulation?
Is it open or closed cell foam?