SEEING ALL THE OPTIONS - Sorting out needs for fire-rated glazing
Reprinted from Buildings
You're all set: The smoke alarms have been checked, sprinkler system installed and extinguishers placed strategically throughout the building. But is the building really ready to protect from fire?
Of course, having these safeguards is necessary. But to rely exclusively on them leaves open the question of liability. What if the alarms or sprinklers don't activate properly? Worse yet, what if the sprinklers do activate, and actually cause other building elements to fail? For example, non-rated window glass that's hot from a fire will shatter if hit by water from a sprinkler. That's why detection and suppression systems are not enough. You need a third line of defense: "compartmentation," the containment of fire and smoke. That's where the importance of fire-rated glass comes in.
For years, fire-rated glass was recognized as one product: wired glass. While effective for fire and life safety, wired glass tends to project an institutional look most want to avoid. More recently, other more appealing, wireless products have emerged that provide safety through the compartmentation of fire and smoke, and offer an aesthetically pleasing look. These new options vary greatly in performance capabilities and characteristics. The challenge, then, is wading through the many options available. Not all fire-rated glass is created equal, even though the glass may look the same. The following is a brief overview of some current options.
Glass ceramics provide the best of both worlds in safety and beauty. Products such as FireLite, FireLite NT, FireLite Plus and FireLite IGU have the fire-rated glazing needed to withstand fire from 20 minutes to three hours. And when installed, glass ceramic looks similar to plain window glass.
"In meeting with architects nationwide, we've heard over and over again the desire to satisfy building and safety codes and avoid liability without compromising design," says Jerry Razwick, president of Technical Glass Products, a distributor of many fire-rated glass products in the United States. "The newer fire-rated glazing materials do just that."
Ceramic withstands the high temperatures of a fire and is unfazed by the thermal shock of water from a fire hose. It is an ideal material for fire-rated applications. When required, ceramics can be specified that also satisfy the need to provide protection from impact.
Plus, many options open up for design. Depending on the product chosen, the glass can be used in large sizes, etched, sandblasted lightly or beveled on one side without affecting the fire rating. Obscure glass can be chosen if more privacy is desired for certain parts of the building.
Glass ceramic is also available in insulated glass units (IGU). The IGUs are made of two layers of glass with an air space in between. Depending on which products are chosen, they not only can be used in fire-rated applications with ratings from 20 minutes to three hours, but meet energy codes as well. An IGU is typically one-inch thick and fits in standard hollow metal frames. Insulated glass is designed for use in exterior applications where energy codes require an insulated product, or for interior applications with special needs such as sound reduction.
Again, flexibility with design reigns because while one side of the IGU is FireLite or FireLite Plus, the other can be what the design plans call for, such as mirrored, Low-E, tinted or safety glass.
Another category of fire-rated glass that's expanding design options could be called transparent wall units. These products, such as Pyrostop, make it possible to have entire walls of glass. Transparent wall units block the transfer of heat, similar to a fire-rated masonry wall. Because of this, Pyrostop is not restricted to a limited area. If desired, Pyrostop can be installed from wall to wall and floor to ceiling, with fire ratings of up to 2 hours. Designers then can divide space without the use of solid walls that diminish visibility and light.
The new developments in this field continue to raise the standard for both design and safety. When properly specified and installed, fire-rated glazing can be a powerful ally against the devastating effects of fire.
FIRE-RATED GLASS TIPS
Before choosing which fire-rated glass to use, keep in mind these questions:
- What is the required fire rating (in minutes)?
- Is there an impact safety requirement (doors, sidelites, etc.)?
- Will sprinklers be located near the glass? (Is "thermal shock" a potential problem?)
- Is heat transfer through the glass an issue? (Does the glass need to act like a "wall"?)
- Has the product been tested and listed by an independent laboratory? (Such as UL?)
- Are you confident the fire-rated product selected will perform properly in a real fire situation?
- Will privacy concerns make an obscured glass surface desirable?
- Would you want to etch, sandblast or bevel a design on the glass surface?
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