waddycall
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I’d appreciate some sensible suggestions as to how I could permanently and effectively insulate the flat roof without spending a fortune or having to do any rewiring etc.
Cheers, Pete
Rockwall between. Vapour barrier then kingspan over the lot. Not between.Use rockwool and thin ply on or between your joists, I did my old garage, the larger part with kingspan and smaller with rockwool, the rockwool was better it also had far better noise deadening properties, could hardly hear the rain with the rockwool but it was fairly loud with kingspan
Cover the polystyrene up with plasterboard.I thought of using polystyrene for roof insulation,but the risk of fire when welding,grinding etc led me to get a better heater instead.
Cover the polystyrene up with plasterboard.
Only short term. Heater running costs add up over timeBetter heater was cheaper too unless I spent more time in there.
its a garage, there is no standard to achieve.
It's easy, use a hand saw to cut to width whilst in a roll then fix it to the ply you're putting up then fix with nail or staple gun to the roofDon't get me wrong, rockwool is good, and fireproof, but cutting it to fit between joists, and then installing it overhead? No thanks!!!
Seconded. I paid £136 to get enough 110-130mm thick to do a single garage, delivered.Look for Kingspan seconds* or damaged sheets thinner than the depth of the rafters.
Leave an air gap between the insulation and the plywood of the roof.
*many other sources!
Generally standard EPS has much lower thermal resistance than the PU of Kingspan and the like. That is unimportant if you are insulating say a loft where it doesn't matter if you need 100mm or 300mm to achieve the target thermal performance, but where your depth is limited by the depth of joists, rafters etc it matters a great deal!
Don't get me wrong, rockwool is good, and fireproof, but cutting it to fit between joists, and then installing it overhead? No thanks!!!