I have a large north facing bay with 4 single glazed sash windows - as you would expect its not the warmest room in the house. It has a nice wooden panelled surround/architrave, and I can feel draughts coming through at some of joins and overall the panels are cold to the touch. Also condensation is worst on this window. Obviously I can fill the gaps, but is there also any worth in insulating the cavity between what essentially is the outside sand stone and the wood?
