Insulating a roof-Warm roof?

[ssray]

A. Can I fill the space in between the rafters in the loft with celotex type foam sheeting?
B. Or would it have to be fixed to the inside of the rafters allowing for air flow?

If B would i need to put a membrain behind the celotex?

This would then have vaporlock plasterboard on it.

Am i going in the right direction?thanks
Ray

 

[noseall]

Am i going in the right direction?thanks
Ray

Er, no.

A 'warm roof' describes a scenario whereby the insulation sits wholly above the rafters.

There is also a precedent that allows more insulation to sit between the rafters, where achieving adequate thickness above is not possible. In this case you fit the added insulation tight against the underside of that above the rafters and seal all gaps and joints.

Any other insulation scenario is deemed a 'cold deck' and will need ventilation and vapour barrier.

 

[r896neo]

Is this on a pitched roof? Do you have underfelt or a breathable membrane under your tiles? Check out the kingspan or other major insulation manufacturers website fro some initial advise.

 

[ssray]

Its a pitched roof, built in 1930`s but has been retiled about 5-6yrs ago and has a membrain under the tiles.

So should i fill the space in between the rafters with celotex? or put another membrain onto the rafters and attach the celotex to that?
Ray

 

[r896neo]

is it a detached house? was it counter battened? i.e were laths run up along the rafters before the slating laths were fixed perpendicular?

You need to leave a ventilation gap either using counter battens as above or by leaving the void between the rafters partially clear for air flow.

check this out and then come back if you need specific help.

http://www.insulation.kingspan.com/uk/pdf/k7.pdf

 

[geraint]

why are you insulating between the rafters...if to make a room in the loft, quick case ... make sure there is 50mm gap betwen the celotex and the felt... so say 50mm cellotex... use a tri iso layer on top of that...

dont even attempt to put a screw through it.... best to staple it to the rafters... then counter batten... again... dont even attempt to screw through the iso... then board..... you should use a foil backed board.. and hey presto.....

 

[ssray]

Thanks very much, plan now in place.
ray