DOUBLE GLAZING

Double glazing  assembles two or more panes of glass and controls the properties of the space between the layers.

Originally, the space was filled with air, but  filling the space with a less conductive gas such as argon or krypton improves the performance.

The layers of glass have to be  held apart at the appropriate distance by spacers. Originally aluminum spacers were used  but aluminum is an excellent conductor of heat and creates a significant thermal "short circuit" at the edge of the insulating glass unit (IGU), which reduces the benefits. Up to 80% of a window's energy loss occurs at the edge of the glass due to the aluminium spacer. Modern warm edge spacers contain a thermal break to improve insulation and silica dessicant to reduce the risk of condensation.