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Insulating roof space rafters


I'm in the middle of converting a single dwelling into two self contained flats and need advice from anyone who has previous experience of this.

All architectural drawings have been given conditional approval by Building Control, but there's one thing I'd like to push back on and that is the proposals to insulate the roof space.

The drawings are disclosing that we should insulate between rafters and fix insulated plasterboard on top of that, all of which are Kingspan products so will cost a fortune!

Given that the roof space/loft is not going to be a habitable room, nor will it ever be as the pitch of the roof is so low, is all this work necessary?



Forgot to mention that the drawings indicate we also need to lay 100mm of Rockwool Roll between floor joists and a further 170mm of Rockwool Roll at right angles to the first. I can understand this measure to prevent heat loss from the first floor flat into the unoccupied roof space, but to then insulate the rafters to prevent heat loss from roof space when this area is not going to be habitable seems difficult to justify.

2 Answers from MyBuilder Insulation Installers

Hi unfortunately it is necessary and kingspan is well known and work's if you find something with same spec but cheaper show them they can't really refuse. Kind regards. Allen Palmer


Answered 21st Feb 2016

yes all this is necessary, although the regs have changed from 270mm to 300mm in the loft, their are other types of insulated foil board available which will do exactly the same job at a lower cost than kingspan.
best bet is have a word with your local building regs officer, she what he she says.
good luck alex


Answered 22nd Feb 2016

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