Which insulation?

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mikeadams1985

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I've got a flat fibreglass roof to insulate and I'm unsure which insulation to go for? Rigid foam style like celotex or the fibreglass roll stuff? The house gets freezing so I'm happy to spend the dosh on whatever is best. Suggestions? The size is about 24ft x 12ft
 
100mm celotex nothing to hand but I was under the impression celotex is a much better insulator when compared with the same thickness loft roll.
 
Yeah it is something like that beddy , as mentioned 100mm long as they are 6 in joists , then for the sake of it go over with 25mm to stop cold spots where the timber is
 
Would need to batten on top of the foil to keep the air gap same with kingspan can be a pain when retro fitting sometimes!
 
Good point. Last winter I insulated a ceiling only inbetween joists and skimmed it. a week later there was icicles hanging where the joists were.
 
I've seen a silver foil bubble wrap used instead of celotex when overdrawing ceilings. 2 layers of approximately 2mm thick wrap has the same U value as 50mm celotex. Easy to use with a staple gun. Think its called something like 'Airtec'
 
That silver foil bubble wrap TLX silver or similar has been specced on the last few loft conversion I worked on. It is easier then fixing celotex onto the joists but it still needs battening on top before fixing boards to retain the air gap.
 
100mm between timbers with air gap and 50mm over timbers and sometimes building control want duplex board over that . building controls regs vary from 1 city to the next but this is the most I have had to do in any area so would be a safe bet.hope this helps:RpS_thumbsup:
 
Hi, the easiest way is to do a warm roof system which is say a 100 mm pir insulation board layer run over the top of the joist (and furrings) then just ply straight on top and fixed with long fixings into the joists, then your new roof covering applied .
 
I've seen a silver foil bubble wrap used instead of celotex when overdrawing ceilings. 2 layers of approximately 2mm thick wrap has the same U value as 50mm celotex. Easy to use with a staple gun. Think its called something like 'Airtec'

I read somewhere that the U value figures for that bubble wrap gear had been incorrectly calculated. I mean think about it both the bubble wrap gear and Celotex have two layers of foil, the bubble wrap has air pockets about 4mm deep surrounded by areas of just foil whereas Celotex has a decent thickness of expanded foam between it's foil.
 
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