On 08/04/2012 12:57, AL_n wrote:
stuart wrote in news:XRdgr.32840
:


Try Rockwool. Ridiculously cheap at B&Q. You may need to prevent the
insulation becoming compressed by the soil.

Thanks; your suggestion gave me another idea: polyurethane foam, as used in
Celotex wall board, etc. I seem to recall that it absorbs water like a
sponge, but doesn't compress significantly.

Al

I think you'll find Celotex is closed cell foam which absorbs no
moisture at all :-)
Loft insulation is basically the same stuff as the Rockwool plugs used
in hydroponics. I've used it as a base in hanging baskets but, unless
very well concealed, the tits will take it away for nest building