Do I need an air tightness test??

[selfbuildrookie]

This is probably a stupid question but... I assumed an air tightness test would be the norm at the end of our new build project, but both builder and architect seem to think not. Google suggests it *is* a requirement on new builds. Can anyone advise if it’s a standard requirement for building regs or not?

[ADLIan]

Air pressure test can be avoided for a single house but the SAP assessment must use the default air infiltration rate of 15 - unless accounted for at the design stage this will probably result in Building Reg failure (CO2 emissions and fabric efficiency). Compare this value to some of the numbers achieved by members on here of 3 or lower! I regularly see values of about 7 with masonry construction and standard levels of workmanship/detailing.

[Jeremy Harris]

There are only two cases where you don't need to do an airtightness test:

 

The first is if the house is part of a small development where no more than two houses are to be built, and where the builder has demonstrated compliance on another house of the same type, with a pressure test, within the preceding 12 months.

 

The second is if a default value of 15m³/h.m² at 50 Pa is used when calculating the DER.

 

The first case almost certainly doesn't apply to most self-build, I suspect, and the second case will be challenging to meet, as it implies a pretty dreadful air permeability level.

Edited February 20, 2020 by Jeremy Harris
Cross-posted. . .

[MikeSharp01]

6 minutes ago, Jeremy Harris said:

challenging to meet

By challenging I guess you mean easy to achieve such a leaky building if you were trying but with this level of leakiness other things around building regs etc fall out of bed?

[Jeremy Harris]

6 minutes ago, MikeSharp01 said:

By challenging I guess you mean easy to achieve such a leaky building if you were trying but with this level of leakiness other things around building regs etc fall out of bed?

 

 

Yes, challenging in the sense of the impact it will have on meeting the overall requirements in Part L1a. 

[Simon Brooke]

Yes you will need a test. But look at this as a positive. If you choose a sensible person to do the test they will do it in two steps. In our case this flagged up leaks which I had not spotted but could be fairly easily resolved before a second, final test. That being said we didn't achieve quite what we wanted.

[ADLIan]

What value was assumed at the design stage SAP assessment to show Part L1A compliance? This, or better, will be your target for the test.

[Critical Path]

What sort of cost are you looking at for an Air Test on a single house?

Am I correct to think you need below 10m3/hr/m2

for a building regulation pass?

[nod]

Most will work the air test around your sap 

Especially the cheaper online ones 

I’m not sure why BC insist on an air test Most are meaningless 

[joe90]

I paid £250 for my air test but others here paid less I think ?

[PeterW]

There is a third case where you do not need a test and that is for a conversion from an existing building. 

[selfbuildrookie]

Thanks all. As I thought, yes we do need a test - and I'm very happy about that as we are seeking to achieve 2m3/hr/m2. The builder's reluctance is a slight red flag, but we are very early doors with the build so plenty of time to make it clear that we certainly will be having a test at the end, and I am looking forward to seeing what we will have achieved!

[Jeremy Harris]

Our build company provided a guarantee that the house would be 0.6 ACH at 50 Pa or less ( they actually achieved 0.43 ACH @ 50 Pa when the house was tested).  The final payment of 20% of the total contract price was dependent on them meeting this requirement.

 

I'd be inclined to try and get a builder to contract to meet the spec you want, TBH, just to save pain and grief down the line. 

[jen and mark]

Hi Jeremy,

 

I cant find your blog, could you paste a link?

[ProDave]

Jeremy has not been on the forum for a while now, and the EU made him surrender that domain name after Brexit.

[joe90]

Here it is.   https://web.archive.org/web/20200923193339/http://www.mayfly.eu/

[jen and mark]

Thanks @ProDave. What a shame! I will check yours out - thanks again

 

[jen and mark]

Brilliant - thank you @joe90

[IainH]

On 20/02/2020 at 15:30, PeterW said:

There is a third case where you do not need a test and that is for a conversion from an existing building. 

Is there a link to where I can find this in the regulations please?

 

Thanks in advance.

[JohnMo]

Building Regs applicable to the area of the UK you live, should all the info you need.