Thread: Insulating a brick wall lined with plaster

Any chance of some photos first please before comment

20mm of still air has an R value of about 1 in winter

the 10mm plaster board has an R value of about 0.4

will you really need much more?

If yes consider foil between the batterns and the Gyprock, which would lift the R value to >2

Originally Posted by Jesspet

Hi all,

i am lining my garage with 10mm plaster, on 20mm thick pine batterns, and want to stop heat convection through the plaster. I have a 20mm cavity for insulation. There will be heat transfer through the batterns but pine's r value is about 1, so I'm not too concerned about this. I was thinking of maybe 15mm polystyrene sheets, or spray foam. I can't use foil board or corrugated foil, as this cannot be in contact with the brickwork. Standard batts are way too thick. Any suggestions ? Cheers. Pete.

Convection is a heat transfer term applied to fluids so I think you mean "conduction" rather than convection.

Inside the cavity, conduction of heat from a brick wall may be less of a problem than radiant heat transfer from the brick to the plaster, in which case something like a bubble foil layer bubble foil will reduce the radiant heat transfer from the brick wall to the plaster -and will be suitable to act as a vapour barrier as well.

BTW When using bubble foil it gets stretched over (not in between) and stapled to the battens and then the plaster board goes over that.

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Originally Posted by rwbuild

Any chance of some photos first please before comment

When you say 'double brick do you mean a 230mm thick wall or a cavity brick wall of 270mm?

If its a solid 230 wall you will need to put a vapour barrier on the brick first then your battens then foil backed plaster board or bubble foil insulation as suggested.

If its a cavity wall, no need for insulation as the timber battens are creating another cavity which will more than adequately give you a higher R value again and timber is a very poor conductor of heat. Use treated pine battens and you won't have to worry about the termites.

You can also increase the R value by using 13mm board or even 16mm fire check which by its very name is a poor conductor of heat.

BobL is on the right track.

the 20mm cavity is too narrow to act as a true cavity, but will have some benefit. as long as the battons are place verticaly and the plasterboard horazontaly and the cavity is open at the top and bottom to allow hot air to rise.
some wall wrap, (sarking) will give the best radiant protection from the brick heat.

easyiest solution will be the cheapest and will be effective. That is battons (think studs) glued/nailed/screwed to bricks. wall wrap. 13mm plasterboard (and if you have a look at the different plasterboards there are impact resistant tough boards out there that will be welcome in a garage.

godo luck.

impacheck plaster board linky