In article ,
sm_jamieson writes:
On Saturday, December 7, 2013 5:46:49 PM UTC, Big Les Wade wrote:
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.

--
Andrew Gabriel
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