John Stumbles wrote:
On Mon, 16 Nov 2009 09:39:08 +0000, Stuart Noble wrote:

I suppose that's ok if it's wrapped in a plastic bag, but most
insulation products retain masses of water, hence their use in horticulture

I deliberately didn't wrap it in plastic because I want it to be
breathable so that any water that comes down the chimney dries out and
there's a path for water vapour and a slight flow of air to pass through
it, but without a heat-sapping chimney draught.


I might be concerned that the insulation would hold on to the moisture.
Rockwool behaves like a sponge where water's concerned