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This article originally appeared in the August 2011 edition of Construction Executive.

Refined by Fire — Using Fire-Rated Glass to Advance Life Safety and Aesthetics

By Jeff Razwick

Fire-rated glass not only provides fire safety, but also contributes to interior aesthetics. Unlike concrete, corrugated steel or other opaque fire-rated materials, its see-through surface creates open, luminous interiors and provides visibility for people entering and exiting spaces. This transparency can help project teams align fire and life safety plans with stylistic goals. However, it necessitates an understanding of the performance and design characteristics of fire-protective and fire-resistant glazing—the two types of fire-rated glass identified in building codes.

The Critical Distinction

Fire-protective and fire-resistant glazing most significantly differ in the forms of defense they provide. Fire-protective glazing acts as a barrier to the spread of flames and smoke. It helps compartmentalize buildings by confining a fire to its area of origin for a specified time period. Because it does not protect against radiant and conductive heat transfer, fire-protective glazing typically is suitable where building codes allow an assembly designated as “opening protective” to enclose a space.

Fire resistance is “that property of materials or their assemblies that prevents or retards the passage of excessive heat, hot gases or flames under conditions of use,” according to the Glass Association of North America. In addition to blocking the spread of flames and smoke, glazing classified as “fire-resistant” adds a second layer of defense by limiting the transfer of radiant heat to the non-fire side of a building separation. Fire-resistant materials are critical in areas where people may become trapped for prolonged time periods during a fire, including stairwells and corridors, or where the spontaneous ignition of building materials could lead to rapid fire development.

Fire-Protective Glazing

Traditional wired glass used to be one of the most common fire-protective glazing materials, but its institutional appearance and risk of injury from breakage spurred manufacturers to develop wireless alternatives.

Today, a mainstay of the fire-protective market is fire-rated ceramic glass. It is clear and strong, with a crystalline structure that holds the material together under high heat. For non-impact applications, such as transoms and borrowed lites, ceramic glass options are available with fire ratings ranging from 20 minutes to 90 minutes.

Laminated and filmed fire-rated ceramic glass options can be used in fire doors or other applications requiring safety impact-rated glass. These materials can have up to 180-minute fire ratings and Category II impact safety ratings. Fire-rated ceramic glass also can be incorporated into insulated glass units (IGUs) to comply with energy codes.

From an aesthetic standpoint, fire-rated ceramic glass resembles ordinary window glass. It features a thin profile, typically 3/16-inch thick, and can fit in standard fire-rated frames. Fire-rated ceramic glass also is available in large sizes, up to 3 feet by 8 feet per piece, allowing for greater visibility and more seamless integration with expansive curtainwall and window systems.

Some manufacturers are using new methods to further improve the overall appearance of fire-rated ceramic glass. These processes help smooth out surface distortions and reduce the slight coloring inherent in ceramic glass. Fire-protective glass with exceptional surface quality is often ideal for large glazed areas or in applications where it will be seen up close, as discoloration and surface imperfections can become more visible.

Fire-Resistant Glazing

One of today’s primary fire-resistant glazing materials is transparent wall panels. The panels incorporate multiple layers of glass with intumescent interlayers, meaning the interlayers turn to foam when exposed to heat. With this added performance, transparent wall panels can block flames, smoke and heat for up to 120 minutes. They are tested in accordance with fire-rated wall standards (ASTM E-119), pass the fire and hose streams test, defend against significant amounts of heat, and can offer up to Category II impact safety ratings and Level III bullet resistance ratings.

In appearance, transparent fire-rated wall panels provide nearly the same level of clarity as ordinary float glass, are thicker than basic fire protective options due to their intumescent interlayers, and are available in large sizes (up to 5 feet by 8 feet per lite). Because the panels satisfy fire-resistance standards, they are not restricted to 25 percent of a wall area, as may be the case with fire-protective materials. This flexibility makes them suitable for use in floor-to-ceiling designs or as large expanses of glass. For instance, project teams can incorporate them in stairwells and elevators, or use them to create safer walkways or improve illumination in school corridors.

As with fire-rated ceramic glass, transparent wall panels can be incorporated into IGUs to comply with energy requirements.

Accounting for Aesthetics

As technology advances, so do design standards. In the fire-rated glazing industry, this led to more aesthetic and multi-faceted fire-rated glazing systems.

If extra daylight is needed for designs requiring eye-catching applications, specialized offerings like fire-rated glass floors are now available. Advanced glazed floor systems are impact-resistant and fire-rated for up to two hours, and can be used as durable, non-slip walking surfaces for interior and exterior applications.

On the framing side, modern fire-rated options are sleek, slender and available in a range of materials, including aluminum, steel and hardwood. With fire ratings ranging from 20 minutes to 120 minutes, architects can incorporate them with large expanses of glass across multiple stories, or in window and door applications requiring visual symmetry with other parts of the building. Custom painting is available to match the frames to virtually any color scheme.

With proper use, today’s fire-rated glass systems can do a lot more than satisfy codes. They allow architects to push the design envelope—whether it’s installing fire-rated glass that better resembles ordinary window glass, transparent wall panels that transfer light from adjacent spaces or sleek fire-rated frames that blend in with other design components.

Jeff Razwick is vice president of business development for Technical Glass Products, Snoqualmie, Wash. For more information, call (800) 426-0279 or visit www.fireglass.com.

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