The crucial difference between fire-protective and fire-resistive glass is the latter also serves as a barrier to radiant and conductive heat. Throughout North America, fire-rated glass providing this extra safeguard is tested to stringent Canadian and U.S. standards, including CAN/ULC-S101, Fire Endurance Tests of Building Construction and Materials—the fire-resistance test standard for walls.
While fire-resistive-rated glass technologies vary by manufacturer, a common method for achieving this level of performance is to sandwich an intumescent material—which foams during a fire—between multiple layers of glass. This internal reaction allows the glass to remain below 121 C (250 F) for the duration of its fire rating. By keeping the glass relatively cool on the non-fire side of the wall, it is possible to protect students and faculty (as well as valuables) from high heat as they exit a building.
Fire-resistive glass’s internal reaction also allows it to defend against radiant heat transfer. This unseen form of heat is carried through electromagnetic waves, and can pass through building materials to ignite surrounding structures. By serving as a barrier to the invisible threat of radiant heat transfer, fire-resistive-rated glass can help prevent rapid fire buildup, which can give students and faculty extra time to exit the premises and firefighters time to arrive and extinguish the fire.
Fire-resistive-rated glass can carry fire ratings up to 120 minutes, pass the fire and hose stream tests, and block significant amounts of heat. It is suitable where building codes require an assembly designated fire-resistive to enclose a space. This includes wall and door applications that require a 60-minute or greater fire rating and must meet temperature-rise criteria. Given this type of glass meets such requirements, it is not restricted to 25 per cent of the wall area. This provides design teams with great flexibility when working to create light-filled and inviting spaces that also meet strict fire- and life-safety criteria.
Do the specified glass and framing both meet or exceed required code minimums?
To work effectively, fire-rated glass must be installed into an appropriately rated frame for the required protection level. One might consider an application where building codes mandate use of 60-minute or greater fire-resistive-rated materials meeting CAN/ULC-S101. In this instance, specifying 45-minute fire-protective-rated glass in a 60-minute fire-resistive-rated framing system is a mismatch for the required protection level of the assembly. It can also place students and faculty at risk if the fire-rated glazing fails before the frame, allowing flames and smoke to spread throughout the school prematurely.
To avoid this mistake, it is important to verify the fire-rated glass, framing, seal, and other components have the same or greater ratings than the required code minimums for the opening. It is also essential to confirm the fire-rated glass and frame provide the same type of protection (i.e. fire protection or fire resistance). To ensure fire-rated materials have consistent ratings and provide the appropriate level of defense against fire, one should check the product label. If questions still remain, it is best to confirm with the manufacturer or supplier.
When specifying fire-resistive-rated glazing systems, such as curtain walls or fire-rated glass floor assemblies, it is necessary to go a step further. One should verify with the manufacturer or supplier that the performance requirements of the glass and frame system match, and that they have been tested and listed to work together as an assembly. To simplify this process while still meeting the high performance requirements of modern buildings, some manufacturers offer complete systems from a single source. In these systems, all components are designed and tested in the same assembly, eliminating concerns about inconsistent fire ratings.