Insulating a wall ... again!!



Apologies if this has been covered before, I've searched the forums, and even the good old interweb, but TNA.

Our house has an integral garage. The partition wall between the garage and the house is only one brick thick. So I propose to build some studwork on the garage wall, and place insulation in the studwork voids, and cover with plasterboard.

The worry I have is that I don't want condensation to become a problem. Obviously use of a vapour barrier would be required if condensation is a consideration. The question is where should the barrier go, beneath the insulation or on top? (I guess on top) but where should the ventilation gap be? between the insulation and the membrane or between the membrane and the top plaster board covering?

Cheers guys.
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16 Aug 2005
Reaction score
West Midlands
United Kingdom
If you want to attain the 0.35 u value, your construction could be like this (from garage to house) 12.5mm Firecheck plasterboard on 100 * 50 studwork with the pvc membrane sandwiched between. 75mm kingspan insulation would then go into the void to create a 25mm airgap. It doesnt matter whether the insulation is on the brick side or the pvc side, your choice but it will be easiest to put it on the brick side! As you are not under building reg application, you could go for a lesser u value by using 50mm insulation and 75mm studs - your choice. If your garage side is not exposed to rain as it probably isn't, you dont actually need the airgap but it does help the thermal properties in this construction considerably.

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