Pir vs loft insulation
Discussion
I would always choose mineral wool for a loft, as it’s cheaper and much easier to get a good fit between joists.
The benefit of PIR is the reduced thickness, which isn’t such an issue for most loft installs, even if you want to store stuff above it you can just use loft legs or a similar solution.
The previous owner of our house had somebody insulate part of it with PIR and there are loads of gaps you can get your hand into, which rather defeats the object…
The benefit of PIR is the reduced thickness, which isn’t such an issue for most loft installs, even if you want to store stuff above it you can just use loft legs or a similar solution.
The previous owner of our house had somebody insulate part of it with PIR and there are loads of gaps you can get your hand into, which rather defeats the object…
Yes the insulation value of 100mm celotex vs 200mm Rockwool
Is about the same.
As has been said above the main issue with celotex is that it is flammable, and also you need to ensure you get a good airtight seal again the rafters / joists. You will need to seal all edges and joints with aluminium foil tape. If you are laying it over the rafters then ideally use whole sheets and cut it accurately to size to reduce time fitting and the number of edges to seal.
The issue with rockwool is that it can be tricky to maintain a regular thickness across the whole roof area, but the benefit is that its flame resistant and it s easier to squeeze into odd shapes and sizes and providing you pack it well (no gaps but not too tight) and there is no need to seal the edges as it self seals due to its spongy nature.
Is about the same.
As has been said above the main issue with celotex is that it is flammable, and also you need to ensure you get a good airtight seal again the rafters / joists. You will need to seal all edges and joints with aluminium foil tape. If you are laying it over the rafters then ideally use whole sheets and cut it accurately to size to reduce time fitting and the number of edges to seal.
The issue with rockwool is that it can be tricky to maintain a regular thickness across the whole roof area, but the benefit is that its flame resistant and it s easier to squeeze into odd shapes and sizes and providing you pack it well (no gaps but not too tight) and there is no need to seal the edges as it self seals due to its spongy nature.
Edited by AdamV12V on Saturday 17th January 17:25
megaphone said:
I have Rockwool between the joist and have laid Celotex on-top across the joists. This allows me to store crap on top. Had to cut the Celotex down the middle to get it up through the loft hatch.
I’m self-building an extension and I proposed this solution to my helpful building regs guy and he advised against it due to the mix of breathable and non-breathable potentially leading to condensation issues. I say ‘advised’ and potential’ because he didn’t rule it out, but he was not in favour. Gassing Station | Homes, Gardens and DIY | Top of Page | What's New | My Stuff