insulating a loft with kingspan/celotex

Feb 09, 2017 25 Replies

Beware interstitial condensation if you use continous taped celotex or bubble wrap.. A relative stuffed rockwool willy nilly into the eaves of his link detached house and the condensation got trapped around the truss ends (Along the valley on top of the party wall) in an unventilated space and did thousands of pounds of damage requiring major timber replacement and strengthening.

Myth..Celotex is closed cell, so will not allow the passage of water vapour molecules.

Thanks, the derating goes up much faster than I would have thought. Though I promise I would have looked it up if I was actually doing anything like that.

In practice I think it is going to get much less hot in an open vertical conduit than direct insulation though I don't suppose this helps evade the regs. If it is really a nuisance complying with cable size, could you put it in a bigger pipe?

Across the cells. But will between them

On 10-Feb-17 10:44 AM, harry wrote: ...

I found it effective to cut very slightly oversize and press firmly into place. It compresses enough to close up any gaps. I also taped over all joins with 6" wide aluminium tape.

I found the stuff be only slightly compressible and brittle. If you try to force it in, the edges spall away.

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