I want to insulate in between the roof joist. Is it ok to use 2" rigid foam, I heard that this will do the trick. We don't use the cottage in the winter, we have no ceiling it's an open concept and so it gets hot during the day and I thought this would help.
Answer:
It will, and at the same time it will cook the shingles so be careful what you do here. There has to be at least an inch of air space between the insulation and roof sheathing and there has to be opportunity for air to expel at the very highest point - a baffled ridge vent going from gable to gable.
