Its closed-cell structure stops water vapor, and the foil-covered face acts as a radiant barrier. Not recommended for exterior, below-grade applications. Not flammable, but it must be protected with wallboard.
Good for: Cathedral ceilings, walls for finished basements
R-value per inch: 7-8
Vapor barrier needed: No
Cost: 40¢ per sq. ft. for a ¾-in.-thick panel