What is window glazing?

Window glazing refers to the glass pane or glass assembly that is installed within a window sash or frame. It can take several forms depending on the performance requirements of the window: a single pane of glass in older or low-cost applications; a double-pane insulated glass unit (IGU) consisting of two panes of glass separated by a spacer bar and sealed with an air or gas fill in the cavity between them; or a triple-pane unit with three glass layers for maximum thermal performance in cold climates. The space between panes in an IGU is typically filled with argon or krypton gas, which has lower thermal conductivity than air, improving the insulating performance of the unit. The term window glazing also historically referred to the glazing compound or putty used to seal a single pane of glass into a wooden sash frame — a soft, linseed-oil-based material that hardened over time and had to be periodically replaced when it cracked and fell out. Modern windows use rubber gaskets, foam glazing tape, or structural silicone in place of putty, but the term ‘glazing’ still applies to the glass unit and the act of installing it. Low-emissivity (low-e) coatings on modern window glazing are thin metallic films applied to one or more glass surfaces to reflect infrared radiation and improve thermal efficiency without significantly reducing visible light.