[Exeric]

AC, I should explain a little better my rationale for down rating multiple layers of radiant barrier in air. When I installed my radiant barrier below the roof of my house it still got very warm up there. Much more warm than the standard formula you offered would indicate. Also, there was a reduced effectiveness at the point where the corners of my hip roof concentrated the heat. But the interesting thing was that you didn't feel any heat radiating directly from the radiant barrier. But if you touched it, it was hot! That's where the air transmissability of heat comes in. Even though a radiant barrier does not radiate heat it does get hot. And that heat will also heat air because air has a much bigger emmisivity than a vacuum. It is the reason that in space the side of an object facing the sun can be hundreds of degrees hotter than the side shaded from the sun. I have more knowledge on this particular subject than you. So I'm not a troll. I don't butt in on other subjects that you are much more knowledge about than me. You are just letting your ego get the better of you by calling me a troll. EDIT: I should add that insulating materials invariably have a higher emmisivity than a vacuum. So installing insulation between layers is not a solution. It's the touching of molecules to a radiant barrier that conducts (conductivity?) heat away. Of course, some molecules conduct heat better than others, but there isn't any molecules that conduct heat less than no molecules.