Low-Emissivity Glass
Low-Emissivity (Low-E) glass is specially treated with a microscopically thin, transparent coating. The coating reflects heat back into the building, thereby reducing the heat loss through the window. It also reduces the heat transfer from the warm (inner) pane of glass to the cooler (outer) pane, thus further lowering the amount of heat that escapes from the window. These properties thus reduce the demand for energy in order to heat the building.
In addition, the coating allows large amounts of free solar energy to enter the building, thereby heating it passively. Low-E insulating glazing can therefore be a net contributor of energy in buildings.
Other innovations such as triple glazing products can offer additional improvements in the window's insulating properties while the use of low-iron glass can increase light transmittance and free solar-heat gain. These technologies offer additional benefits in terms of energy efficiency.