Morning all,
I'm considering options for internal insulation to two outside facing walls in my bedroom (external option ruled out). The walls are solid 9inch bricks with external cement render. One wall has had its plaster removed to the brick face, while the other has had cement render / plaster skin applied in the last two years. We were thinking of attaching a breathable membrane to the wall (the brick exposed wall only), followed by a treated wood batons (100mm x 50mm) screwed to the walls which would be in filled with Thermafleece (50mm or 75mm). The timber frame would be covered with a vapour barrier and then boarded up with plasterboard. This would create a 50mm gap between the Thermafleece and the plasterboard, would this act the same way as a gap between the solid wall and insulation which is normally suggested? An alternative is to use thermal phenolic laminate boards (50mm) instead of infilling between the timber but at £40 a sheet (20 sheets), it’s too expensive. Would the two approaches give similar insulation performance?

Thanks

Muhi

Why is external insulation not an option?

Buy the plasterboard and the insulation separately it is cheaper. If you want to stick them together you can but they can also be fixed separately too.

Hi Momo, try Encon Insulation, They will custom bond any suitable insulation to plasterboard and generally not insist on a minimum quantity. Prices are competitive as well.

Make sure you consider what fixings are required before buying the boards, as these can be difficult to source as thickness increases.

I agree that External is best, though would add that there are potential pitfalls with both internal and external. Lots of threads here discussing this.

Hi Momo/Chris

I noticed a new product in Travis Perkins recently for dot and dabing. It is basically expanding foam which doesn't expand very much. You can form continuous beads with it to prevent air circulation behind boards, and I imagine it would stick well to phenolic or pu boards, so you could stick the insulation board to the wall, and then stick the plaster board to the insulation. I think it costs about £10-£20/can which they say is enough for 5 8x4 boards. You also need to buy a one off applicator gun which is also about £20. If you off set this cost against the cost of timber battens/fixings and the time saved it may be worth a look.

Cheers

What were those fixings Mike? I couldn't get the link to work.

Thanks for all the suggestions, I'm still a bit wary of fixing the boards directly against the walls because the walls aren't that straight, isn't having a gap better? how do ppl fix any breathable membrane on to a brick wall, no nails glue? is it necessary to fix one? isn't infilling between batons with 50mm celotex slabs and covering with plasterboard achieve the same thing?

Momo

Paint the insulation boards with PVA glue, sprinkle coarse sand on it to give a key and use normal board adhesive. I know people who have tried this and it seems to work.

As I see it you are building in a horrid thermal bridge doing it with metal stud unless you fully insulate over them not between them.

Posted By: momo101I've decided with my builder

you mean the builder convinced you to do it his way...?

(Only joking)

J

I don't really see why you want to use studwork at all if you're using ridgid board insulation. The recommended installion meathord according to Celotex, Kingspan, Recticel, etc. is for the boards to be fitted directly to the wall and then 2x1 battens on top screwed throgh the boards into the wall and then fit plasterboards to the battens. This way you also avoid cold spots on the plaster board as the screws don't go through the insulation.

See this link for details on the performance difference between continues and between batten insulation: http://www.recticelinsulation.com/UK/EN/Application/Individual/Binnenisolatie/

These are good for fixing the Kingspan board to the wall: http://www.screwfix.com/prods/47083/Fixings/Cavity-Fixings/Fischer-Insulation-Support-45-60-8-x-85

Yes, for fixing the battens through the insulation normal frame fixings work just fine, e.g. these: http://www.screwfix.com/prods/37005/Fixings/Frame-Fixings/Frame-Screws-7-5-x-182mm-100Pk

Just an update, ending up with a timber stud wall away from the brick wall (about 2cm), the part facing the brick walls were covered in foil/polystyrene sheeting used normally under laminate floors of around 5mm (had some left over from previous work), hence there is no contact between the timber stud frame and the floor, ceiling and brick walls. The gap between the vertical studs were friction fitted with Celotex 60mm and all gaps filled with expanding foam. The studwork frame was covered with a vapour barrier and on top of that we put 12.5mm foiled backed plasterboard / plastered over. It sounds a bit over the top hopefully only doing it once and it took only 2 days for the whole job, but a bit longer to to decorate it :)