Hi to group - how much polystyrene foam board in studded walls & between roof timbers (warm roof) to satisfy building regs. for attached garage conversion to habitable space - garage is single skinned brick building with pitched tiled roof (has concrete tiles over sarking felt). Also do I need to insulate timber joist and chipboard foor over concrete raft if so to what thickness of polystyrene board. Hope you can help - Bldg. Insp. on war path!. THANKS.
What about any cold bridges, have they been designed out?
Have you also considered the prevention of the passage of moisture through the single skin?
Is the average thermal efficiency of the rest of the house such that you could have less insulation in the new room?
No you may not need to insulate the floor if you can prove increased thermal efficiency elsewhere
If you are doing this all yourself under a building notice, then I would just ask the BCO what he wants, else look at the LA website (or a neighbouring council)which normally has a guidance note published by Local Authority Building Control
According to the manufacturers of Wickes polystyrene insulation and Jablite, it's also fine for installation under ground-floor suspended wooden flooring.
I had concerns about installing it in such a situation, Wickes were unable to tell me whether it's flame retardant or not, so they gave me the number of Vencil, who manufacutre the stuff. It isn't flame retardant, incidentally, and neither is Jablite, but the do conform to various applicable BS standards for manufacture and usage.
Their technical dept reckoned that in the cases that they know about where houses have been completely burnt out, the fire investigators had lifted the floorboards to find completely intact insulation.
Of course, adequate separation has to be ensured for cables, but that shouldn't be a problem if you have the whole cavity to play with, and you don't need to worry about cable current capacity derating issues.
However, I wouldn't use it in walls, under upper floors (not necessary anyway) or the loft.
However, I was concerned that I shouldn't install an inappropriate product under wooden flooring if it had been designed for installation only under concrete screed.
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