An insulating glass unit (IGU) consists of two or more glass panes bonded and sealed around their perimeter. A spacer separates the panes, dry gas fills the cavity, and desiccant within the spacer system helps keep the enclosed space dry. This sealed construction improves the environmental performance of building glazing while allowing the glass make-up to be tailored to the project.
Glass and cavity options
IGUs can be fabricated from clear float, patterned, heat-absorbing, solar-reflective, wired or tempered glass. Coated glass can be incorporated when solar control or a particular appearance is required. The cavity may also use an inert gas, while decorative bars or coloured cavity treatments can be added where the design calls for them.
Building performance
By separating the interior and exterior panes, an IGU limits heat transfer, reduces cold-surface radiation and helps control condensation. It can also reduce noise compared with single glazing. High-performance coated configurations achieve a shading coefficient of 0.22–0.49 and a U-value of 1.4–2.8 W/m²K; actual performance depends on the complete glass and spacer build-up.
For the same glass thickness, an IGU can provide approximately 1.5 times the wind-pressure resistance of a single pane. Structural design still depends on pane type, thickness, unit dimensions, supports and project loads.
Applications
IGUs are used where heating or air conditioning, acoustic control, condensation resistance or solar control matters. Typical building applications include residential developments, hotels, offices, schools, hospitals, shops, exhibition spaces and libraries. They can also serve temperature-controlled rooms and other spaces that need stable indoor conditions. The appropriate optical, thermal and acoustic properties should be selected as part of the overall facade or window design.