Fire-rated glass is processed to limit the spread of flame and smoke, and its performance is assessed by its fire resistance rating. Below are five glass types commonly used in fire-rated windows.
1. Grouted composite fire-rated glass
Two glass panes with a transparent fire-resistant liquid filling between them. Typical applications include commercial partitions and timber fire-rated doors and windows. Under fire exposure, the filling absorbs heat, foams and expands, and turns opaque. This blocks heat conduction and thermal radiation from the fire side to the protected side, helping to keep escape and rescue routes free of high temperatures and to delay ignition of combustible materials on the protected side. It also offers acoustic and thermal insulation.
2. High-strength monolithic fire-rated glass
Float glass treated by physical and chemical processes, intended for curtain wall, facade and window applications. The manufacturer states it can withstand 1000 °C flame exposure for 60 to 120 minutes without shattering, helping to contain flame and smoke and providing time for evacuation and firefighting.
3. Nano-silica composite fire-rated glass
Glass combined with a nano-silica fire-resistant interlayer — a hard, inorganic, transparent crystalline material. According to the manufacturer, each unit passes through more than 20 processing steps over 200-plus hours of production. It is positioned as a high-transparency, weather-stable product for fire-rated curtain walls, exterior fire windows and fire-resistant windows, available in both insulation (EI) and integrity (E) classes, and is stated not to discolour or delaminate.
4. Insulating fire-rated glass
Multiple panes separated by spacer frames around the perimeter to form sealed cavities, with one or more panes being monolithic fire-rated glass. The hollow spacer contains desiccant and is bonded to the glass with an inner sealant; the outer sealant fills and seals the perimeter. The sealed cavity provides thermal and acoustic insulation, and the spacer geometry — including 45-degree, 2 mm chamfered outer corners — supports durable sealing. The design is intended to resist condensation, contamination and sealant deformation over long-term use.
5. Borosilicate fire-rated glass
A fully tempered, non-insulating monolithic fire-rated glass made from borosilicate float glass rather than standard soda-lime glass, offering high temperature resistance and chemical stability. The manufacturer states that products in various thicknesses achieve fire resistance ratings of over 2 hours and have been tested by international testing organisations.