I need to build some outer covers and I have some 15/32 plywood. I was thinking of using the plywood that I have and then putting a 3/4 inch piece of foam insulation on top of it. I would think that would keep them cooler in the summer, warmer in the winter, but I wasn't sure if this is a bad idea or not. I know that some folks put insulation on the inside of the top cover and leave it year round, I just figured that since I am making them from scrape I might as well sandwich the insulation between the plywood and the top sheathing. Does anyone have any opinion on this, good or bad?