Low-e is standard clear glass which has a special coating on one surface of the glass. Low-e refers to low emissivity and this describes the capacity of a surface to radiate heat. Emissivity is measured across a scale from 0 to 1 with 1 representing the highest emissivity.
The low-e coating is spectrally selective, which means it affects some wave lengths of light but not others. Long wave infrared is the heat produced by our bodies, heaters and the furnishings in a warm room. The transmission of long wave infrared is significantly reduced by the low-e coating. It reflects the amount of energy escaping through the glass keeping the room warmer and reducing the amount of heat required to be generated by the artificial heaters. The energy from the sun is called short wave infrared; a high proportion of energy from the sun will be transmitted straight through the glass.
Low-e coatings provide various performance levels and the glass can be used in a variety of ways including single glazing, laminated glass or double glazed windows.