UKC

Fitting some windows in an old stone house and am having some condensation type insulation puzzles.

Because of water ingress ,and the age and quality (or lack of it) of the stone masonry ,I have had to form DPC trays above the windows which will guide any water out over the top of the window and then outwards.

Puzzle I whether I should insulate the area between the plasterboard and the underside of the DPC tray? 25 -30mm gap

Or , leave the area un-insulated ,and allow the well ventilated area to keep any condensation at bay.

Your thoughts would be appreciated.

In reply to andymac:

If the rest of the walls and window reveals are not insulated then you will gain little in terms of thermal performance by putting 25-30mm of foam in the gap. Also if you insulate with what is effectively a vapour barrier on the cold side and no vapour barrier on the warm side you are inviting interstitial condensation. Just make sure you have a good seal on the warm side to avoid draughts getting in.

In reply to andymac:

My house is prone to condensation on the plaster board under the lintels (house built in the 80's), how are you fixing this plasterboard? If dabbing will this cause a cold spot bridging problem?
Mark.