Airtightness Test Results

Putty Man

Hi,

I've just had an airtightness test done on my under construction new build and I'm concerned with the results.

The TF house is at the stage where 1st fix plumbing, electirical and HRV are in, so a good few holes in the membrane, all of which are taped.

There are still 3 air leaks tho:
1. 2-3" of blockwork showing underneath the membrane. This will be sealed when the floor screed is poured I believe?
2. Membrane cut to let 2x flue pipes into attic. No idea how I can make this airtight?
3. Air coming in thru cavity in blockwork of the foundation.

The guy who did the test said all this would roughly equate to a small window being open. He was happy we were even able to get the pressure difference up to 50pa to get a reading.

So anyway the result came in at 3.9 m3/h/m2 (not sure if my metric is correct). Should I be getting concerned that even after fixing these, the house won't reach ~1.5 or so?

Impossible for anyone to comment on no. 3 I know, but any advice or comments on points 1 or 2 would be great.

Thanks.

BryanF

who is in charge of the air-tightness? is there a clause in the contract for air-tightness performance? there's a day course ran in air-tightness that you may want to consider going on - the guys a muppet to listen to, but you'll learn a lot - sounds like 'Liga';) (type in ' air-tightness course' you'll find it) what i dont understand is why did you not go round a seal up these gapping holes while the air-tester was there??? i can recommend a couple of better testers if you want..

Putty Man

Hi Bryan,

I don't want to go down the route of contract/money arguments with the TF company, at this point anyway. They have been good to deal with up until now and to be fair the issues above (1 and 2 anyway) aren't of thier making.

As for sorting the issues at the time:
1. Can't screed the floor at this stage. Plasterboard and skim has to be up/on first.
2. We stuffed the gaps around the flues with rockwool at the time, but this wasnt perfect obviously. Taping the flues was also obviously not an option.
3. Yeah I menitoned expanding foam but they didnt have any with them (dissapointing).

I'll be getting another test done when these issues are sorted. I just really hope that when we do this the result will be much better.

PS - the air tightness test guy seemed very clued in, to me anyway.

AMG86

Was there any reference to air tightness clause in your contract with the TF company? Was there a specific number mentioned? I would have put one in. It maybe too late now

mickdw

Can you not seal around the flue with a high temperature air tightness tape. Assuming its an insulated flue anyway, the tape sholuld be perfect.

I did the airtightness course as mentioned above. Portlaoise I did it. Useful for understanding the various products the company does but nothing too special in it.

sas

Putty Man wrote: »

2. We stuffed the gaps around the flues with rockwool at the time, but this wasnt perfect obviously. Taping the flues was also obviously not an option.

I assume they are double skinned flues?

If so there are rubber gaskets that you fit over the flue (during installation) that can then be taped to the membrane.

They provide a very snug fit.

Putty Man

sas wrote: »

I assume they are double skinned flues?

If so there are rubber gaskets that you fit over the flue (during installation) that can then be taped to the membrane.

They provide a very snug fit.

I'm very interested in this idea, but I'm not sure if its possible. Would rubber not just melt when the flue became hot? Fire rope may be an option tho right enough.

Yes they are double skinned, twin wall flues. Not sure if I can mention the company name, but basically I rang them and they said SS flues cannot and should not be made airtight, saying air needs to flow around the outside of the flue to dissapate heat. They also said they did not sell anything to seal the flues to an airtight membrane.

sas

Putty Man wrote: »

I'm very interested in this idea, but I'm not sure if its possible. Would rubber not just melt when the flue became hot? Fire rope may be an option tho right enough.

Yes they are double skinned, twin wall flues. Not sure if I can mention the company name, but basically I rang them and they said SS flues cannot and should not be made airtight, saying air needs to flow around the outside of the flue to dissapate heat. They also said they did not sell anything to seal the flues to an airtight membrane.

They are rubber like but not necessarily rubber. They are good to over 100 degrees. A double skin will only ever feel warm to the touch so you are well covered.

I'll PM you the supplier details.