Wood Fire-Rated Doors Combine Safety and Aesthetics

Advances in fire-retardant technology offer alternatives to traditional steel fire doors
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Frames

There is a saying in the industry that a door is only as good as its frame-and the good news is that fire-rated doors no longer have to be installed in steel frames. Many manufacturers offer complete fire door and frame packages, representing several advantages to architects. Such all-in-one door and frame systems dispense with the need for applying unattractive surface intumescent around the door, additional framing preparation, and/or extra packing between the frame and the stud-which in turn reduce cost for supplies and labor. "Architects may not realize the importance of a complete listed assembly," adds Solomon, "and the best way to go is usually to purchase the entire fire-rated assembly from a reputable manufacturer who delivers certified products."

Glass

Until recently, fire doors that contained glass were virtually slabs of steel with small sections of polished wired glass. Still the most frequently used type of glazing material, wired glass has been around for more than 100 years and is known to be effective in a fire. Intense heat causes ordinary glass to splinter or blow apart, whereas the wire mesh keeps the glass intact. As a result, wire glass has been the performance benchmark in the industry for nearly a century and was, in fact, one of the only materials that could stand up to fire testing. The downside is that wire glass has hazardous breakage patterns, and can leave dangerous jagged edges. While recognizing the potential danger of broken wire glass, building codes acknowledged its superior performance in the event of a fire, hence its specification in many fire rated doors.

In response to a safer, more attractive, glazing material, manufacturers developed a new round of products to challenge the supremacy of wired glass. The new glass is largely a function of advances in glass ceramic, a material well known to withstand heat. Displaying a low coefficient of expansion when heated, ceramic is used in diverse "hot" applications including car engines. In fact, some new product options are actually transparent ceramic that looks like window glass but has the superior heat-resistant qualities of ceramic.

Regular flat glass will not perform under extreme temperatures; it breaks at around 250°F, allowing the spread of fire and smoke. To be fire-rated, glass is placed in a test furnace in temperatures of more than 1,600 ºF. The better the glass is able to withstand the heat, the higher its rating. To achieve levels above a 20-minute rating, glass is also subject to the hose test. Only the glass that is able to withstand the drastic changes in temperature from an intense blaze to a deluge of cool water can be fire rated. The purpose is to simulate a real situation during a fire where water from a sprinkler system douses and determine whether the glass will function as a barrier or fail, enabling smoke and fire to spread. Fire-rated glass that has passed these rigorous tests should remain intact and restrict the expansion of flames and smoke.

Typically, wired glass carries a fire rating of 45 minutes. So well do transparent glass ceramic products withstand heat, they can achieve a three-hour fire rating. Glass ceramics also have safer breakage patterns and can withstand four times the impact of traditional wire glass, satisfying Consumer Product Safety Commission (CPSC) 16CFR1201 (Category II), the highest impact safety standard for window glass. CPSC is charged with protecting the public from unreasonable risks of serious injury or death from more than 15,000 types of consumer products under the agency's jurisdiction.

 

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Originally published in Architectural Record.
Originally published in October 2006

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