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As seen in the December 2009 edition of Doors & Hardware.

Fire Away! Ceramics and Other Advanced Fire-Rated Glazing Materials Solve a Variety of Design Needs

By Jeff Razwick

In the 1967 film The Graduate, an older family friend advises college-age Benjamin Braddock (Dustin Hoffman) about a hot career field: "I just want to say one word to you – just one word. Plastics." If the film had been made decades later, the advice may have been "ceramics." Industrial and commercial applications now rely on various classes of ceramics for uses from mirrors in astronomical telescopes to computer semiconductors.

In buildings, design professionals specify ceramics for multiple applications, especially where the material’s ability to withstand thermal shock is critical. A case in point is fire-rated ceramic glass. Advanced manufacturing techniques create transparent sheets of ceramic that are strong, able to withstand the high heat of structural fires, and not shatter when cool water from fire sprinklers or fire hoses strikes them. These clear and wireless materials have become a product of choice where glazing is necessary or desired and where protection from flames and smoke is required.

Fire-rated ceramic glass comes in a number of product make-ups that allow it to be used for specialized windows, doors and sidelites. In addition to fire-ratings, certain ceramic glazing products also offer impact safety resistance, and can be combined with other glass in insulated glass units (IGUs) for energy efficiency.

While ceramics can be used in many fire-rated glazing applications, in certain instances, other advanced glazing materials such as transparent wall panels may be more appropriate. Following are technical and performance criteria to consider when specifying ceramics and transparent wall panels.

Fire-Ratings and Areas of Use

Glass fire ratings for window and door assemblies are determined based on national test standards, which incorporate two key testing requirements: a fire test and a hose stream test. For the fire portion of the test, an independent lab constructs a wall assembly with window frames or doors holding the subject glass. The assembly is heated in a large furnace following a standard temperature-time curve per National Fire Protection Association (NFPA) test standards. The window or door assembly must remain in the wall for the duration of the test and have no flaming on the unexposed surface of the assembly and no openings.

The second portion of the test occurs immediately after the fire test and involves subjecting the glass and framing assembly to the impact, erosion, and cooling effects of water sprayed from a standard fire hose. To successfully pass the test, the glass and framing must remain intact. The hose stream test is required for fire ratings of 45 minutes or longer in the United States and for all fire ratings in Canada. The hose stream test provides a method for evaluating the integrity of materials and constructions, and eliminates inadequate materials.

Ceramics

Basic ceramic glass offers fire ratings of 20 minutes to 90 minutes and is suitable in non-impact applications, such as transoms and borrowed lites. For fire ratings up to 180 minutes and instances where impact safety is required, such as doors and sidelites, a laminated or filmed ceramic product may be appropriate. This was the case for glass in the subway station doors at the Seattle-Tacoma International Airport. For aesthetics and to allow visibility into and out of the arriving trains while providing a barrier to fire, the project architects selected a laminated fire-rated ceramic glass – FireLite Plus®.

Transparent Wall Panels

In many instances, a fire-rated ceramic glass product is available to meet the specific performance criteria required by codes or design needs. In applications where a barrier to heat is needed, however, ceramics should not be used. While ceramic glass is able to withstand high temperatures without breaking, it is not effective at blocking heat transfer.

For exit corridors or areas such as stairwells where people could be trapped for long periods of time, where heat-sensitive equipment must be protected, or where large expanses of glass are desired, transparent wall panels such as Pilkington Pyrostop® may be considered. Such units are tested and classified as walls, carry fire ratings up to 120 minutes, pass the fire and hose stream tests, block significant amounts of heat, and offer impact safety ratings.

Dimensions

Fire-rated ceramic glass is available in large sizes, allowing fire safety in areas where visibility and capturing of natural light is desired. The material is available in sheets up to 48 by 96 inches and is typically thin – as low as 3/16 inches depending on the product make-up.

For floor-to-ceiling designs or other extensive, uninterrupted areas of fire-rated glazing, transparent wall panels and door units are an option. (See “Art Institute of Chicago Modern Wing Relies on Heat-Barrier Fire-Rated Glass and Frames”)

Clarity and Surface Quality

A key benefit to architects and designers of using fire-rated ceramic glass and transparent wall panels is that the materials are clear and wireless, making them a good choice for designs where the glazing should not call attention to itself.

An important consideration when specifying fire-rated ceramic glass is the surface finish. Manufacturers produce ceramic glass by drawing it out between rollers, which leaves a slight surface distortion. In many cases this is not a concern, but in instances where even higher clarity is desired, polished ceramics are available. Products that are polished on both surfaces provide a finish that is very nearly distortion free and have high transmission of visible light and low reflection. Some manufacturers also offer ceramics with a patterned surface for translucency, suited for applications requiring a degree of privacy.

In the case of transparent wall panels, the clarity is nearly the same as ordinary float glass. The panels, as well as ceramic glass, can be lightly sandblasted or etched on one side without affecting the fire rating.

Product Make-up Options

Fire-rated ceramic glass offers great design flexibility, with a range of make-ups that can provide many different performance characteristics. These include high impact safety ratings, energy efficiency, and sound reduction. Enhanced performance is achieved with either lamination or with a surface-applied fire-rated film. Laminated products are typically thicker than standard ceramics, with a profile of approximately 5/16 inches compared to 3/16 inches for non-laminated products.

Laminated and filmed ceramic glass products can meet the highest standard of impact safety for glass, CPSC 16CFR1201 Category II. Such materials are designed to safely withstand an impact similar to that of a fast moving, full-grown adult.

Ceramic glass and transparent wall panels can both be incorporated into insulated glass units (IGU) in conjunction with many types of tempered or annealed float glass for a range of design needs. These can include tinted, low-E, mirrored, reflective and art glass.

Whether included as part of an IGU or not, the specification of fire-rated glazing should also take into account the fire rating of the framing materials. To ensure adequate fire safety, the framing should carry a fire rating equivalent to the glazing. A range of fire-rated frames is now available, including narrow profile metal frames, as well as fire-rated hardwood frames.

Conclusion

Fire-rated glazing materials technology enables design professionals to meet a wide range of life and property safety needs, while not sacrificing other design requirements such as aesthetics, security and energy performance. Ceramics are available in configurations to meet a variety of needs, and can be combined with other glazing products for even more options. Beyond ceramics, transparent wall panels are also available for the most demanding fire-resistive applications. For assistance in specifying a product for a given need, consult a fire-rated glazing manufacturer or supplier.

Jeff Razwick is the vice president of business development for Technical Glass Products (TGP), a supplier of specialty architectural glazing products and fire-rated glass and framing systems. He writes frequently about the design and specification of glazing systems for institutional and commercial buildings. Jeff Razwick is the vice president of business development for Technical Glass Products (TGP), a supplier of specialty architectural glazing products and fire-rated glass and framing systems. He writes frequently about the design and specification of glazing systems for institutional and commercial buildings. www.fireglass.com, (800) 426-0279.

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