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Schools with a view – Fire rated glass makes better educational spaces

If you walk through the recently opened Brooklin high school in Whitby, Ont., one of the first things you may notice is its open and light-filled interior. The 173,200-square foot facility includes extensive glazing throughout to provide natural light and visibility for students and staff. What you may not realize is that a significant portion of the glass used to illuminate the school also provides protection against the spread of flames and smoke. In fact, its clear form is hardly distinguishable from its non-fire-rated glass counterparts. This is a credit to recent manufacturing advances.

Over the last decades, manufacturers have developed clear, sleek and high-performing fire-rated glazing products that resemble ordinary window glass. They can meet the dual goals of code-required life safety in schools and beautiful esthetics, eliminating a common point of frustration for architects: compromising their design vision for the sake of safety.

A new way with fire-rated glazing
For years, traditional, polished, wired fire-rated glass was the most commonly specified fire-rated glass product in schools. Although it had a proven fire safety track record, its industrial appearance and size restrictions prevented design professionals from creating open, light-filled spaces conducive to student learning. It also presented challenges in areas with fire- and impact-safety requirements.

Wired glass is only capable of resisting 100 foot-pounds of impact, which is equivalent to a five-year-old running into the glass. However, because it was the only glazing material at the time that could protect against the spread of flames and smoke for a reasonable length of time (termed “fire protective”), the Canadian General Standards Board (CGSB) granted a code exemption and deemed it suitable for use in areas requiring fire- and impact-safety protection. This exemption left the door open to student injuries from glass breakage. The frequent movement of students throughout the day means that impact safety must be a high priority, even in areas with fire safety criteria. Design professionals did not have access to a glass product that could satisfy both requirements.

To combat problems with fire-protective-rated glass’ appearance and impact-safety restrictions, manufacturers set out to improve the optical quality and performance of fire-rated glazing. By the late 20th century, they were producing wireless fire-protective glass with high levels of impact safety. Products are now available that can resist approximately 400 foot-pounds of impact, which is similar to withstanding the impact of a full-grown adult. Such glass can meet CPSC 16 CFR 1201 (Category II), which is a classification similar to CAN/CGSB 12.1 (Category II).

With clear, multitasking fire-protective-rated glass products at their disposal, design professionals no longer have to trade fire protection for impact safety or appearance in educational facilities. This is evidenced in Brooklin High School. To match the esthetic of non-rated glass systems and promote daylight transfer, Aerloc Industries of Dundas, Ont., installed 3,500 square feet of high-performance fire-rated glass ceramic in doors, sidelites, transoms and interior windows. This included installations in highly visible areas, such as the school’s second-floor loft overlooking a common area. The tough, yet transparent form of the fire-rated glass ceramic provides essential life safety while resembling the look of ordinary window glass. It is also impact safety-rated to help prevent injuries from glass breakage if students run into it.

Greater design flexibility
While transparent fire-protective ceramic glazing products proved a significant improvement over their wired predecessors, the development of wireless fire-rated glass with heat-blocking capabilities (“fire resistance”) took design flexibility a step further in areas with stringent fire and life safety requirements. These products provide nearly the same level of clarity as ordinary float glass, carry fire ratings up to 120 minutes, pass the fire and hose stream tests and offer up to Category II impact safety ratings. Most notably, they pass the test standards for solid walls (CAN/ULC S101), allowing design professionals to create fire-rated glass assemblies that exceed 25 per cent of the total wall area.

When paired with fire-resistive frames, buildings teams can use fire-resistive glass to create large expanses of see-through walls in areas that would otherwise require concrete, gypsum or other opaque fire-rated materials to meet codes. This is a key design benefit for schools, as project teams can incorporate fire-rated glass wall panels throughout school corridors, where illumination and views to the outside can improve the learning environment for students. Project teams can also use fire-rated glass curtain walls to maximize daylight penetration and maintain visibility through interior spaces.

 For schools with strict design and performance criteria, a new set of fire-rated glazing systems are emerging that allow design professionals to make the most of learning environments while still providing protection from the threat of fire. Among the options are fire-rated glass floor systems. These assemblies can facilitate views and allow daylight to penetrate deep into buildings, provide a durable walking surface, and block flames, smoke and heat.

Design professionals can also select from two of the newest fire-resistive-rated glazing options on the market: silicone-glazed (SG) fire-rated curtain walls and butt-glazed, fire-rated framing systems. SG fire-rated curtain walls provide a smooth, frame-free exterior surface. They are ideal for inner city schools with lot line protection requirements in highly visible areas. Butt glazed, fire-rated systems are another design-forward option. They enable extensive fire-rated glazed walls with virtually uninterrupted views and can enhance light transmission in corridors.

Fire resistive vs. fire protective
When reading specifications for fire-rated glass, it is important to know the terms “fire resistive” and “fire protective” and what they mean. They are referring to two quite different standards of glazing.

Fire protective
Fire protective glass prevents the spread of flames and smoke for some period of time, typically anywhere from 20 to 180 minutes. These are the applications where wired glass was widely used in the past, though glass ceramics and specially tempered glass can also have this rating.

Fire resistive
Fire resistive is a higher rating of fire protection because it not only stops the spread of flames and smoke as fire protective glass does, but also blocks the transfer of radiant and conductive heat through the glass. Fire resistive glass products are usually multi-laminates incorporating several layers of glass with fire-resistive interlayers. Codes call for fire-resistive ratings when glass is performing the function of a wall, especially an interior wall for an access zone such as a stairwell or corridor. Fire protective glass must limit temperature rise on the “cold” side of the glass and also be able to withstand a hose stream test after heating.

About the author – Jeff Razwick is the president of Technical Glass Products (TGP) and is a past chair of the Glass Association of North America’s (GANA) Fire-Rated Glazing Council (FRGC).