An insulating glass unit (IGU) consists of two or more glass panes separated by spacer bars and sealed around the edges. Units with two panes are known as double glazing; those with three panes are known as triple glazing.
The cavities between the panes contain air or a gas such as argon to improve thermal insulation. The terms double and triple glazing refer to the number of panes, not the gas fill.
The panes in the unit do not have to be identical. Depending on the project, they may include:
float glass;
Low-E glass;
solar control glass;
toughened glass;
laminated glass;
tinted glass or glass with various finishes.
More panes do not automatically make a glazing unit suitable for every window. Consider the glazing thickness supported by the frame system, the window or door dimensions, orientation and exposure to sunlight, and the required thermal, acoustic and safety performance.
The insulating glass unit is only one part of a window. Overall performance also depends on the profile, hardware, seals, dimensions and installation.
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