D.G.U (Double Glazing Unit) - Insulatedglazing.Insulating glass (IG), more commonly known as double glazing (or double-pane, and increasingly triple glazing/pane), consists of two or three glass window panes separated by a vacuum or gas filled space to reduce heat transfer across a part of the building envelope. It serves the purpose of keeping buildings interior cool in the summer, and warm in the winter by reducing heat gain or loss, depending on the region's climate and chosen IGU configuration.