Loft insulation

28 Mar 2016
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United Kingdom
I am planning to insulate my loft ceiling (floor, not rafters). This is just for storage and not habitation.

I want to use Celotex insulating board, rather than Rockwool.

If I insulate between the joists and then a layer on top of them (to achieve the required U-value), can I then place chipboard directly on top of the Celotex, or does it need supporting?

Do I also need to leave a ventilation space between the plasterboard and celotex in the joists to avoid interstitial condensation (as with insulating rafters?).

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Thanks. Will celotex hold weight if laid directly across the joists, or do I need to support it with chipboard underneath (and then more chipboard on top)?
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Should be fine, just make sure it really is supposed by the joists and not resting on the ceiling itself

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