Low-Emittance (Low E) is a term used for a surface that radiates, or emits, low levels of radiant energy. Emittance refers to the ability of a materials surface to emit radiant energy. Low-E building materials include window glass manufactured with metal-oxide coatings as well as housewrap material reflective insulation’s and other forms of radiant barriers. In a window, low-e means better insulating value and possible cost savings on energy expenses. Centennial Glass Depot is your source for low-e glass products.