Insulation on external wall

Hi, Insulating buildings with no cavity wall should be done externally, and if not possible there are certain things you should bear in mind when doing it internally as follows: The solid 9 or 12 inch walls are built from porous bricks. This allows for a healthy vapour diffusion. By just adding a layer of insulated plasterboard internally, you'd disrupt that by causing severe thermal bridge and as a result incur mould growth, deterioration of floor joists, built up of water in the brickwork which will blow the facade as water freeze and algae on the outside. You must take the old plaster off, use timber battens or metal furring system on the walls and then install plasterboard over. This way you can also add vapour barriers as well. Still risky but far better than just adding plasterboard on top of the old plaster. In my opinion, you are far better off cost wise, and get a much warmer house if you insulate all ceiling spaces, as heat usually rises up and that's how you get most of heat loss. Hope this helps Good luck James

As long as the exterior wall is repointed in lime mortar, and the interior wall is also you can dot & dab with drywall adhesive and use insulated plasterboard. I would recommend using insulated lime render & lime plaster but sometimes this is not practical if you want to save on available space. I've used the dot & dab method for years with insulated plasterboard and have never experienced any foeing, mould or facade problems. The walls must be solid with no voids or perished joints though.