Hi lads. I’m about to box in these steel but want some advice if poss about trying to prevent cold air transfer from the cavity wall down through the plasterboard below the steel. The cavity wall above the steel runs up to the loft and let’s a lot of cold in. I can’t afdord to do cavity wall insulation at the moment but hope to in the future. Could I pack some kingspan in there or fill it with foam? Any issues with damp or similar? Cheers.