re: Attic Insulation Questions

I think you can use closed cell it's just harder to execute in practice thus the preference for open cell. With open cell your roof deck will be able to dry to the inside. With 2 inches of closed cell you have a vapor barrier and any moisture that finds its way to your sheathing will be trapped. I would also suggest you add a whole home dehumidifier if you go the fully conditioned attic route to ensure you do not have problems with high humidity in your attic. FWIW we have 8 inches of open cell at the roof line and a whole dehum and we love it. I think it really helps moderate the temperature in the house.