A double unit comprises of two panes of glass. These two panes of glass are held apart by a spacer bar. There is an air gap between each pane which is sealed around the perimeter. Glass is a good conductor of heat, so, just a single glazed pane window will not insulate your property very well.
Air is a poor conductor of heat and therefore has superior insulating properties. The air gap between the glass reduces the heat conductor and helps keep more heat inside during the winter and outside during the summer. There are various thicknesses of units depending on what rebate you have in the frame.View other items in: DGU's