Florida Solar Energy Center Warning!

“Placing the material directly on top of insulation is not recommended. In this type of installation, dust will accumulate on the foil surface facing the roof. In time, the dust will negate the radiant barrier effect. An exception to this is the “chip” and multi layer products on the market. Their multiple layers give them resistance to the effects of dust build up, making them suitable for floor installations. In all installations beware; problems could develop with moisture condensation”.

US DEPARTMENT OF ENERGY WARNING!

“A radiant barrier installed on top of attic floor insulation is more susceptible to dust accumulation. This undesirable installation method may also trap moisture in fiber insulation during cold weather. A radiant barrier installed on the cold side of the insulation acts as a vapor barrier in the wrong location. When warm moisture carrying house air leaks into the attic in the winter, it may condense on the underside of the barrier. Even a perforated radiant barrier can trap moisture in cold climates since the water can freeze in the small holes and seal them.”