In message , The Natural
Philosopher writes

Ply membrane is a typo. damp proof membrane - usually polythene.
Heh, I was scratching my head over the ply membrane! But do you
really
need the DPM anyway if you have a clear air gap between the studwork
and the wall? (And the insulation is foil-backed?)
David

No, but belt and braces, and you have to fix the studs to
something..typically what you want is surface finish, then vapour
barrier (the aluminium tape, and the celotex facing) then studs and
celotex matrix for insulation. At this point you get cold and
condensation make take place in the gap..so you want to try and both
keep the studs clear of damp wall, and also allow perhaps moisture to
permeate outwards through the wall - or provide ventilation (airbrick etc)

Umm.. I've been consorting with architects and they seem to have latched
on to *insulating the inside* in a big way.

OK for plain walls (so long as you have floor standing shelves) but I'm
trying to repair and insulate some Victorian barns which have a mix of
9" dwarf walls topped with 4" studwork and exterior feather edge
boarding. To retain any visual interest in the construction I need to
insulate on the outside.

They have suggested insulating the brickwork internally and putting
insulation between the timbers. Is condensation likely to be an issue?

I have to rebuild the wall anyway and would find cavity work easier than
9" solid.

Any pointers to how others have approached this problem?

regards
--
Tim Lamb