Internal wall insulation (cavity wall). Reducing U-value

[lusstor]

Hi guys, here’s the plan.

I have a ground floor north facing bathroom, it has cavity wall insulation and modern double glazing. It is built on a concrete slab.
I would like to internally insulate the north wall. I think it would be easy as there are no windows or fittings there. I would like to do this as the wall is cold, but NOT damp.

My question is how to do it?

I had assumed 50mm battens with mineral fibre and then foil backed plasterboard. I will then tile the surface.

Do I need a damp membrane or anything. I cant find any real guides for doing this. The Energysaving trusts document ce17 –GPG138 has some suggestions, but its not clear…

Is it even worth bothering?

 

[Deluks]

Worth a punt and won't cost a lot. The foil on the back of the plasterboard IS a vapour barrier. Cheaper to use normal plasterboard over vapour barrier (a sheet of polythene) You won't have to worry about gaps in the plasterboards then.

 

[lusstor]

Worth a punt and won't cost a lot. The foil on the back of the plasterboard IS a vapour barrier. Cheaper to use normal plasterboard over vapour barrier (a sheet of polythene) You won't have to worry about gaps in the plasterboards then.

cool thanks.

I had thought that the foil backed would help hold the heat (as well as the condensation); however it was just a guess. From what I understand foil stops radiant heat, but not very good at thermally bridged heat...
I suspect my biggest problem will be getting the plasterboard home!!! (too big for the car!)

 

[Deluks]

You can use the foil backed as well as the vapour barrier. It will make a minor improvement to the insulation value.