Soldato
The house we've bought has a flat roof (mid 60s built) and I've finally had time to investigate a bit. We're hoping to add any insulation that's possible - depending on how cold it gets this winter it might be a priority, or might just be common sense as we're renewing ceiling boards.
The roof was replaced 2 years ago (with bitumen felt), not much info on the invoice but it does mention adding insulation. From what I can tell it's a warm roof construction - it looks much like the ceilings between floors i.e. plasterboard then cavity with wooden joists. Above this is some kind of fibre insulation, but it's formed into blocks/sheets and is rock hard? Never seen this stuff before.
So the question is, can I put either rockwool or celotex/PIR board into the gaps between joists? If I can, do I need to leave a gap above/below? FWIW it felt reasonably draught free and dry up there but didn't exactly spend a long time taking readings. Don't want to add insulation and cause condensation or air flow issues.
There's a full 17cm of joist height so could easily get 100mm board in there if permitted and still leave an air gap. Ceilings are only 235cm high so rather not lose any height with adding insulation board below the joists, but if it helps...
The roof was replaced 2 years ago (with bitumen felt), not much info on the invoice but it does mention adding insulation. From what I can tell it's a warm roof construction - it looks much like the ceilings between floors i.e. plasterboard then cavity with wooden joists. Above this is some kind of fibre insulation, but it's formed into blocks/sheets and is rock hard? Never seen this stuff before.
So the question is, can I put either rockwool or celotex/PIR board into the gaps between joists? If I can, do I need to leave a gap above/below? FWIW it felt reasonably draught free and dry up there but didn't exactly spend a long time taking readings. Don't want to add insulation and cause condensation or air flow issues.
There's a full 17cm of joist height so could easily get 100mm board in there if permitted and still leave an air gap. Ceilings are only 235cm high so rather not lose any height with adding insulation board below the joists, but if it helps...
