Windows are a large source of heat loss in a home – but who want to live in the dark? Brighten up a home without sacrificing energy efficiency with insulated glass. Insulated glass units (IGUs) prevent heat loss through your glass doors and windows. The units consist of two panes of glass separated by an inert gas. The insulating layer provided by the gas between the windowpanes diffuses heat transfer. Most modern homes and buildings use insulated glass. The windows provide the same benefits of single-pane windows, with energy efficiency that helps homeowners save money.