Loft insualtion with celotex/kingspan
Discussion
Hi
A simple issue seems to have become a complex one
Situation before - loft was insulated with mineral fibre type stuff. Probably had about 15cm of it.
Situation now - the loft has been cleared of all insualtion and the plasterboard ceilings below have been taken out.
I want to re-insualte with rigid celotex or kingspan boards primarily because I want to use the loft for storage and I don't want the nasty mineral wool.
My roof 'joists' are 10cm.
I contacted Celotex and the advised I get a vapour barrier, then use 9cm of celotex between the joists (the reason seems to be because they vary in size) and then put a further 6cm of celotext on top of the 9cm between the joists.
My questions are aroudn the sue of a vapour barrier.
1 - is there any particular type to use (vapour barrier)?
2 - I presume you just tack it to the underside of the loft (i.e basically where the plasterboard goes and you just plasterboard over the vapour barrier?
Obviously where I want to use the loft as storage what I don't want is when I walk upstairs it doesn;t push the celotex down and break the ceiling plasterboard so I need to ensure that the first layer of celotex stays within the 10cm joist which is why it makes sense to use 9cm - that could then cause a 1cm airgap between the 2 layers of insualtion - will this be a problem?
Celotex also said I can store/walk stuff directly ontp the top level of celotex - is that OK or is it safer to put chipboard on top to spread the weight?
Finally, I have a breathable membrane - I wonder if I shoudl add additional veintilation like soffit vents or ventilation tiles to be sure the roo is ventilation enough.
A simple issue seems to have become a complex one
Situation before - loft was insulated with mineral fibre type stuff. Probably had about 15cm of it.
Situation now - the loft has been cleared of all insualtion and the plasterboard ceilings below have been taken out.
I want to re-insualte with rigid celotex or kingspan boards primarily because I want to use the loft for storage and I don't want the nasty mineral wool.
My roof 'joists' are 10cm.
I contacted Celotex and the advised I get a vapour barrier, then use 9cm of celotex between the joists (the reason seems to be because they vary in size) and then put a further 6cm of celotext on top of the 9cm between the joists.
My questions are aroudn the sue of a vapour barrier.
1 - is there any particular type to use (vapour barrier)?
2 - I presume you just tack it to the underside of the loft (i.e basically where the plasterboard goes and you just plasterboard over the vapour barrier?
Obviously where I want to use the loft as storage what I don't want is when I walk upstairs it doesn;t push the celotex down and break the ceiling plasterboard so I need to ensure that the first layer of celotex stays within the 10cm joist which is why it makes sense to use 9cm - that could then cause a 1cm airgap between the 2 layers of insualtion - will this be a problem?
Celotex also said I can store/walk stuff directly ontp the top level of celotex - is that OK or is it safer to put chipboard on top to spread the weight?
Finally, I have a breathable membrane - I wonder if I shoudl add additional veintilation like soffit vents or ventilation tiles to be sure the roo is ventilation enough.
my understanding is that the silver foil on the underside of the celotex between the celotex and the plasterboard ceiling can cause condensation.
I havent got round to doign this yet but I was thinking of just using mineral wool stuff and putting soemsort of breathable roofing membrane over it to keep the nastiness away and using bits fo timber to increase the floor before board it out.
I havent got round to doign this yet but I was thinking of just using mineral wool stuff and putting soemsort of breathable roofing membrane over it to keep the nastiness away and using bits fo timber to increase the floor before board it out.
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