I have an old house with, from the inside, a gypsum board followed by an old type of fiber-like/insulation board. Then comes the plank wall and finally the facade with boards and battens. Today, the facade is nailed directly onto the external plank wall. I was thinking of adding insulation from the outside by removing the facade and insulating externally. Do I need to remove the board on the inside and redo everything there first, or can it stay and I can do regular external insulation? Peo
