We are renovating and extending our home. The house has stone quoins on all corners and pebbledash in-between.
This is a conservation area and we have planning permission for external insulation boards of 40mm and 10mm render between the quoins on the walls, instead of pebbledash.
However, this will not provide enough insulation. I had previously thought of adding Kingspan stuck to plasterboard on every wall but have realised that this is not actually possible as it would involve moving a staircase and destroying wood panelling in two rooms.
So, is it better to just externally insulate and cavity fill the existing empty cavity (late 1930s house, likely a 50mm cavity) or should I scrap cavity fill and internally insulate all possible rooms leaving a couple of rooms cold?