Fork the ply foam stuff as it's highly flammable after only a few years, what's that company??? Oh yea Cool and Cozy or something like that, it's a paper product with a fire retardant in it (kills any bugs that come in contact but is safe for humans) and the whole thing is sprayed on. Doesn't do the water proofing but does a lot better on keeping the heat out and will last years longer. Your roofer should be doing a proper job to begin with so you shouldn't have leaks.