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Re: New Workshop / Garage renovation.

PostPosted: 22 Oct 2019, 20:51
by 9fingers
The cold side of the compsite wall needs to breathe.

Bob

Re: New Workshop / Garage renovation.

PostPosted: 22 Oct 2019, 21:07
by bulla
9fingers wrote:The cold side of the compsite wall needs to breathe.

Bob


Thanks Bob, that makes sense.

Re: New Workshop / Garage renovation.

PostPosted: 22 Oct 2019, 21:30
by Mike G
bulla wrote:
Mike G wrote:You don't put a vapour barrier on the wrong side of the insulation.


I was wondering more why in this case the Kingspan being foil backed, and foil taped doesn't act as the vapor barrier ?


It isn't continuous. It stops and starts at each stud, and around the edges. Each of those joins is a place for air, with its water vapour, to penetrate the structure. You would then have warm moist air meeting the cold impermeable inside face of the OSB, where it would condense. Those damp patches would allow the growth of mould, and in the end, rot.

Re: New Workshop / Garage renovation.

PostPosted: 22 Oct 2019, 21:37
by bulla
Mike G wrote:
bulla wrote:
Mike G wrote:You don't put a vapour barrier on the wrong side of the insulation.


I was wondering more why in this case the Kingspan being foil backed, and foil taped doesn't act as the vapor barrier ?


It isn't continuous. It stops and starts at each stud, and around the edges. Each of those joins is a place for air, with its water vapour, to penetrate the structure. You would then have warm moist air meeting the cold impermeable inside face of the OSB, where it would condense. Those damp patches would allow the growth of mould, and in the end, rot.


Thanks Mike, clear as day when you put it like that :D OSB internally it is !

Re: New Workshop / Garage renovation.

PostPosted: 22 Oct 2019, 22:00
by RogerS
Mike G wrote:
bulla wrote:
Mike G wrote:You don't put a vapour barrier on the wrong side of the insulation.


I was wondering more why in this case the Kingspan being foil backed, and foil taped doesn't act as the vapor barrier ?


It isn't continuous. It stops and starts at each stud, and around the edges. Each of those joins is a place for air, with its water vapour, to penetrate the structure. You would then have warm moist air meeting the cold impermeable inside face of the OSB, where it would condense. Those damp patches would allow the growth of mould, and in the end, rot.


When we did our house, we put foil tape over those joins. Was that the wrong thing to do ?

Re: New Workshop / Garage renovation.

PostPosted: 22 Oct 2019, 23:22
by Mike G
No, that's fine, Roger. That's not the issue. The issue is where the vapour barrier is in relation to the insulation..............and it must be on the inside (in our climate).