"robert" wrote in message
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In message , "george (dicegeorge)"
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Doctor Drivel wrote:
"robert" wrote in message
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We are about to start work on renovating our kitchen.
On outside walls strip off plaster and install foam insulation against
the brick. Kingspan and Celotex do this with some refinished plaster.


Why strip the plaster?
Why not attach the kingspan to the exisitng plaster,
then put the vapour barrier on the inside of the kingspan?

Isnt plaster permeable?

Or would condensation occur there?

Is the removal of the plaster just to gain an inch of space?

Given that cavity wall insulation is in place I wonder if the installation
of the additional foam layer would produce a verifiable measurable benefit
with a payback that will compensate for the work involved.

It probably would. It all adds up. It is not going to be an upheaval to do
it at this stage, so you may as well do it. The R factor can be calculated.
Even with cavity wall insulation it will make a significant difference to
heating the room.