insulate single skin extension

[rcphwatson]

moved in to 60's bungalow last year.. damn cold.
I have a 16x9 extension on the side of the house /back of the garage, so has d/g upvc windows on 2 sides, with single skin brickwork 1/3 height underneath. this isnt exactly brickwork, more like irregular sized stone.

it will all get ripped down in 3 yrs, but am conscious it getting cold now, and its what we use for toys and a playroom (ie peace n quiet) so was thinking of anything that could make it a bit warmer.

was thinking of battening walls with 2x2, filling with celotex 50m boards, covering with insulating foil wrap, then covering with reasonably thick mdf and painting.. (not too worried about the final finish)

can anyone think of any problems with this approach?
thanks.

 

[confusedchippy]

sounds fine the only thing you might have to watch is damp, is the a damp proof in the excisting wall? it might be a idea to put membrain between the battens and the wall also wouldnt use MDF, plaster board would be fine then use plain lining paper instead of plastering it.

 

[joe-90]

4x4 would be better.