Garage conversion insulation?

[simonb88]

My 1930s house has a flat roofed garage converted into a bathroom and bedroom. Both cold rooms. I need to insulate the bedroom first but don't know what the best option is?
Thinking of using thickest kingspan type material on the ceilings but do you attach it with wooden bats? And can you plaster it?
Also seen this wallpaper foam insulation rolls which you glue to the walls/ceilings. It also looks good and could do the walls as well.

Does anyone know the best option?

 

[foxhole]

Insulation should have been do at conversion stage. Retro fitting insulation will not be as effective.You need to timber baton the ceiling and walls if possible and insert insulation between, then plasterboard and skim or dryline.

 

[simonb88]

Thanks. Thats what I thought would be the best option as the ceiling is high. The original isolation was quite thin rockwool I think under the felt?

Do I need to leave an air gap between the kingspan and the original painted ceiling? Or can it be flush? Would using isulating plasterboard as well be better or is this going OTT?

Cheers.

 

[foxhole]

No gap required, you can use insulated palsterboard but someone here said it's cheaper to increase the insulation and use standard board.