Insulated glass is used in projects and homes when a high possibility of heat or cold loss through windows, and energy costs as well as comfort are factors to be considered. An insulated glass unit is constructed of two panes of glass are put into a metal, or vinyl frame with an air gap between them. The air gap is usually between 1/2″ to 3/4″ thick. The standard size for optimum efficiency is 5/8″ thick. Instead of air, Argon gas can be used as a filler in this space.This type of window is known in the industry as an IG Unit, or a double-glazed window, and has become the new standard in residential homes as a way to reduce energy costs.