Insulation for an above the garage room.

5 Jan 2004
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United Kingdom
My 4th bedroom is above our garage. It is seperate to the house in relation to the loft.The ceiling follows the line of the pitched roof. The room is always colder than the rest of the house. I think this is due to no insulation in the pitched roof rafters which form the ceiling.
I have some 100mm Celotex insulation and also some rolls of 100mm insulation. I am looking to insulate both the garage ceiling/bedroom floor and the bedroom ceiling following the pitched roof.
Which way round shall I place the two types of insulation? Does it really matter?? I am trying to find the U value of each product but I am thinking of putting the Celotex in the garage ceiling and the 100mm roll in the pitched roof.

Any ideas????
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Celotex 100 mm = U 0.25
Fibre wool .. .. = U 0.40

Probably easier other way round. Fibre will lay flat on the ceiling and you can put in more/pull around to cover any spaces.

Cut to right size Celotex will hold itself between rafters and allow you time to get your pb/whatever in position whereas the fibre would need some way of securing.

I'll leave it to someone else to talk about air-gaps above the Celotex as I'm a bit hazy on that.

What depth are your rafters though ?
I am presuming my rafters are at least 100mm. Need to pull some pb down and have a look. A nice little xmas project...

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