I am remodelling a 1950s home in Hamilton Ontario And I am pretty sold on closed cell spray foam in the old 2×4 walls with plank sheeting. It will give me the insulation I want and a good vapour barrier. If I want to put exterior insulation on, can I use rigid foam or will that prevent drying to the outside and trap moisture between the spray foam and the rigid insulation?  I have considered rock wool but it is  an added cost that I would like to avoid if possible. I will be putting using a ventilated rain screen on the outside.