Insulated glass is a prefabricated unit made of two or more glass panes, which have been separated by an air gap and edge-sealed together. This is also known as double glazed unit (DGU) or insulated glass unit (IGU)
Insulated glass saves on heating and cooling, by reducing air to heat transfer. The enclosed layer of air makes the insulating capability about twice that of monolithic glass. Because of this, the load on the air conditioning is greatly reduced. The use of heat absorbing or heat reflective glass will further reduce the load on the cooling system.