yes if using Mylar you would need a flat surface to put it up on but as DP pointed out you wont have the heat issue with paint. I am using a roof coating made by Koolseal. It has 95% reflectivity and when dry has a moisture barrier to fight against mold and such which is great for me as I do Hydro. Can be purchased at home improvment stores and runs about $20 a gal but 1 gal goes a long ways.