Myth: Aluminum/Foil products will oxidize over time and lose it's reflectivity.
This new unfounded myth has recently been propagated by a few manufacturers and suppliers of metallized film insulation products in hopes of directing consumers away from the higher reflective (more beneficial) aluminum based foil insulation products.
FACT: All aluminum surfaces oxidize when exposed to the environment. This oxidation forms a CLEAR layer over the surface. The thickness of this oxidation layer will increase until such a time that the layer is too thick for the environment to be capable of supporting further oxidation of the aluminum.
With regards to an aluminum / foil insulation product, the oxidation process does NOT diminish the reflectivity / emissivity of the product because of the vast amount of aluminum in the product (i.e. the aluminum remaining under the clear layer continues to reflect radiant heat as efficiently as before oxidation).
HOWEVER, with regards to a metalized product (which is merely a liquid aluminum sprayed onto a film or similar substrate), this same oxidation process GREATLY AFFECTS the reflectivity / emissivity of the product because there is so little aluminum remaining after the oxidation process has finally stopped. Therefore, for metallized products to maintain their integrity, they MUST BE COATED with a protective coating to guard against oxidation.
Our high quality RadiantGUARD® aluminum / foil insulation products DO NOT NEED a protective coating as our product stays well within the specification requirements.