Where should I put a vapor barrier / vapor retarder?
I am going to add exterior insulation to an old timberframe building. The interior walls will be wood paneling attached on the outside of the beams. For the next layer, I am thinking to wrap with vapour barrier. Six to eight inches of rigid rockwool insulation would go up next, then strapping for the exterior sheath, board and batten. I have read that the optimum scenario is to have one-third of the insulation inside the vapour retarder and two-thirds outside. Would it make sense to put up one layer of insulation before wrapping with vapour barrier, and then two (or three) more layers outside? Thank you.