Loft insulation

I think these days it's mainly used to insulate round flue liners, having the obvious advantage that you just pour it down from the roof.

I use it a lot in the garden. Great soil improver

The last surveyor we had used a laptop and his program had drop-down options. If what you had was not on the drop-down then tough he could not enter it and did not feel inclined to add his own notes. In my case I had a combination of 100mm of Rockwell and 100mm of Celotex plus boards. All he could do was enter the physical thickness so it went in as 200mm of 'insulation' which assumed, in the calcs, to be as efficient as fibreglass and not the approximate effectiveness of

Mike

snipped-for-privacy@btinternet.com posted

When I put this forward in my building plans the local authority building control people wouldn't accept it, on the grounds that different layers of materials with different insulation properties would cause condensation.

I guess if there was wool under celotex and no vapour barrier, you could get condensation on the underside of the celotex, and if wool gets wet it loses its insulation properties, but this would then be no worse than just the celotex. My BCO was OK with rockwool above celotex in a roof. In a loft with just wool, moisture can percolate through the wool and into the air above. Simon.

Yes, if you do this, the wool must be on the cold side, and the celotex on the warm side. Otherwise, you will eventually get condensation at the boundary. The more serious problem is that this will make any timber go rotten.