Definitions for "Low-emissivity"
Coatings applied to glass which allow transmission of light through glass but reflect thermal energy. Emissivity varies from 0 to 1; the lower the emissivity, the lower the resultant U-value. Low-E coatings help keep heat in when it's cold outside, and help keep it out when it's hot.
A coating or film applied between panes of glass in high-efficiency glazing; abbreviated "low-E."
A coating consisting of a very thin layer of metallic oxide or silver which is applied to the third surface of an insulating glass unit to block radiant heat transfer and ultra-violet rays.