Here are two major suppliers of interior and exterior rigid foam insulation, with or without foil faces. This product is for interior or exterior application as insulation typically offering an R-Value of 7.20 per inch of thickness. If the rigid foam is foil faced, it will reflect heat directly like a mirror reflects light, but only if the heat touches it. If we are trying to prevent heat from escaping, we place the reflective foil on the interior of the wall. However, it makes a lousy finish, so over that would go gypsum wallboard, which can store heat if it doesn’t escape from within the wall. Well, the rigid foam just behind it will reflect it back into the room. You can get a huge savings from only one inch of foam behind the wallboard. It can boost your total wall R-Value up to 27.
May 25