In article , Grunff
writes
fred wrote:

Gggggrn not the right answer, foil will only reflect heat where the transfer
mechanism is radiation, when in direct contact with any material, the heat
transfer mech will be conduction so it wont help at all.

I was taking that into account, which is why I said negligibl (honest!).
The foil won't be in direct contact with the plasterboard right across -
there will be a proportion of the area, maybe 10% or more, where the
foil is sitting there with a gap between it and the pb. In tose areas,
the heat transfer between the pb and the foil will be convective and
radiative.

:-P

Yeah right, was just bringing you back down to earth after my unbridled
praise in the solder thread :-).
--
fred