FAQ – Frequently Asked Questions
about fire-rated glass & framing

FAQ's

1. What is the difference between fire-protective and fire-resistive glazing systems?

“Fire-protective” means the glazing defends against the spread of flames and smoke. Such materials include traditional wired glass, glass ceramics and specially tempered glass. Fire-protective glazing typically is suitable where building codes allow “opening protective” assemblies. While such glazing is available with fire ratings ranging from 20 to 180 minutes, it is subject to area and size limitations under the applicable building code and/or authority having jurisdiction.

“Fire-resistive” glass provides the same defense against flames and smoke as fire-protective glazing, and adds further protection by blocking the transfer of radiant and conductive heat. Fire-resistive glass products generally are multi-laminates incorporating several layers of glass with fire-resistive interlayers. They are typically suitable where building codes require an assembly designated “fire resistant” to enclose a space. Examples include wall applications requiring a 60-minute or greater fire rating that must meet temperature-rise criteria, such as stairwells, exit access corridors, or other fire barriers dividing interior construction. In these instances, the IBC requires the temperature rise on the non-fire side of the glass not to exceed 250 degrees Fahrenheit above the ambient temperature at the end of the fire test (generally 60 or 120 minutes). Such glass must also pass the hose stream test.

2. What are my primary options in fire-rated glass?

The glass product most often associated with fire rating is polished wired glass. It has provided fire protection for more than 100 years. In North America, wired glass is typically rated for 45 minutes in lite sizes up to 9 square feet (1,296 square inches). Wired glass with a fire rating greater than 45 minutes is restricted to 100-square inch lites in doors with temperature-rise criteria. The biggest advantage of wired glass is its low cost. However, because wired glass has low impact resistance, since 2006 the International Building Code (IBC) has prohibited its use in hazardous locations in all facility types. See www.iccsafe.org for information on the IBC.

A second type of fire-rated glazing is glass ceramic. Once installed, this wireless product looks similar to ordinary window glass, which provides great design flexibility. Glass ceramic, such as the FireLite® family, provide fire ratings from 20 minutes to 3 hours, and come in sizes up to 24 square feet per lite. Like wired glass, glass ceramics are able to withstand the thermal shock of water from sprinklers or fire hoses. Where impact safety is required, they are available with up to Category II (CPSC 16CFR 1201) impact-safety ratings. This is the highest standard impact-safety rating available, indicating that the glass can safely withstand an impact similar to that of a full-grown, fast moving adult.

Glass ceramic is also available in insulated glass units (IGUs). The IGUs are made of two layers of glass with an air space in between. They can incorporate many types of float glass, including clear, tinted, Low-E and mirrored glass. Depending on which components are used, they can provide fire protection and comply with energy codes. IGUs are sometimes used for interior applications where sound reduction is desired.

Another category of fire-rated glass is fire-rated glass wall panels. These units are special, multi-layer assemblies that block the transfer of radiant and conductive heat. They are tested to the same fire-resistance standards as solid walls, and are not restricted to 25 percent of the wall, as may be the case with fire-protective glazing. This flexibility makes products like Pilkington Pyrostop® suitable for use in floor-to-ceiling and wall-to-wall designs, or in full lite glass doors. These large expanses of glass have obtained fire ratings up to 2 hours. They are typically used where architects desire (or building codes require) the blockage of heat transfer through the glass. Designers can thus provide clear, fire-rated glass walls that allow visibility, light and security. Like glass ceramic, fire-rated glass wall panels are available with up to Category II (CPSC 16CFR 1201) impact-safety ratings.

A final category of fire-rated glazing is specially tempered glass. Products such as Fireglass®20 only carry 20-minute ratings. It is important to note such products cannot withstand thermal shock, and are therefore unable to pass the ‘hose stream test’ required for ratings greater than 20 minutes. As a result, applications for these products are generally limited to use in 20-minute fire doors.

3. Why is the "fire hose stream" (thermal shock) test important?

The fire hose stream test shows how hot glass and surrounding frame assemblies will react when hit by water from a fire hose or sprinkler. Most glass is unable to withstand the thermal shock of fire and water. If nearby sprinklers activate during a fire, the heated glass may shatter and vacate the frame, thus allowing the spread of flames and smoke.

NFPA 257 states, "The hose stream test provides a method for evaluating the integrity of constructions and assemblies and for eliminating inadequate materials or constructions. The cooling, impact, and erosion effects of the hose stream provide tests of the integrity of the specimen being evaluated.” The hose stream test is required in the United States for glass with fire ratings greater than 20 minutes. In Canada, all fire-rated glass must pass the test.

4. Why is fire-rated glazing required to have a permanent label?

Because fire-rated glazing is available with a wide variety of performance characteristics, specifying an appropriate one for a given application is critical for life and property safety. To help ensure the proper use of glass for various fire-rated applications, a multi-faceted product labeling system was implemented in the 2006 IBC and further simplified in the 2012 IBC [see Table 716.3 (Marking fire-rated glazing assemblies)].

The fire-rated glass marking system includes a range of information, including the product name, basic characteristics (e.g., tempered, laminated, etc.), compliance with impact safety requirements, and listing information for the applicable independent testing agency, such as Underwriters Laboratories. See our IBC Glass Label Guide to get started.

5. I recently received product information for a fire-rated glass that indicated several limitations on use. Should this be of concern?

Yes. Architects and designers should always be wary of product "listings" that carry what appear to be unusual limitations. For example, one fire-rated glazing material on the market indicates a fire rating of "60 minutes", but then goes on to say, "This product does not meet the hose stream requirements of the test standards". Further, "This product protects from fire from one direction only. The identified face MUST be installed facing the direction of expected fire attack." Such limitations should raise red flags, and prove how important it is to thoroughly read manufacturers’ literature. This clearly indicates how a laboratory "listed" product may not be exactly what you thought it might be. For more information, see this Alert.

6. Is fire-rated glass really necessary if I use sprinklers? Can't I just use tempered or heat strengthened glass with a water "deluge" system?

Some manufacturers had been submitting engineering reports to Authorities Having Jurisdiction (AHJ) in which fire-resistance ratings were obtained using fire suppression systems (i.e., deluge sprinklers to cool the glass during the fire test). However, the 2012 IBC now clarifies that fire ratings must be established based solely on a material’s own performance. According to section 703.4, “...the fire-resistance rating of a building element, component or assembly shall be established without the use of automatic sprinklers or any other fire suppression system...”

While sprinklers do much to save lives, they are no substitute for the use of passive fire-rated glazing materials. If sprinklers do not activate due to faulty manufacturing, loss of water pressure, or other reasons, fire-rated glass will perform its critical function of compartmentation—with or without water from the sprinklers.

7. Generally speaking, the "wireless" fire-rated glazing materials are more expensive than polished wired glass. How can I persuade my building owner that those products are worth the extra cost?

We generally see architects and designers using the higher price products for improved aesthetics and/or higher safety. The manufacturing processes for high performance wireless products are complicated, and frequently make use of specialty materials. While costs are coming down as production volumes increase, we suspect they will never reach the levels of wired glass. Interestingly, we often find the wireless products are in line with the architectural construction costs - they are just more expensive than traditional wired glass. In addition, the amount of fire-rated glazing used in most projects is rather small comparatively. Increasingly, we see architects and designers willing to use the newer products for aesthetics reasons, such as opening up entire glass walls that have high fire ratings. Characteristics such as higher fire ratings, larger glass sizes, increased clarity, higher impact ratings, meeting energy codes, etching and beveling, etc., also contribute to their increased use.

8. What are some of the latest developments that could enhance building designs?

New uses for fire-rated glass and frames have gone hand-in-hand with aesthetic improvements. For years, design professionals were limited to traditional hollow metal steel frames. While functional, these bulky, wrap-around frames forced many to compromise on appearance in order to provide life safety. Manufacturing advances have led to thinner, fire-rated frames that can be custom painted or powder coated to match virtually any color scheme. There are even hardwood, aluminum and stainless steel fire-rated framing options.

Manufacturing innovations have also enabled more sophisticated fire-rated glass and framing assemblies. Advanced systems include fire-rated glass floor systems and fire-rated applications that have the appearance of a structural silicone glazed systems, such as the Fireframes SG Curtainwall™ Series.

9. Can other rated frames be used with TGP fire-rated glass?

TGP offers a range of fire-rated frames that can be used in conjunction with FireLite® glass ceramic. Compatible frames include the Fireframes® Designer Series, Fireframes® Aluminum Series, Fireframes® Hardwood Series and Fireframes® Curtainwall Series. FireLite can also be used with hollow metal steel frames. However, since fire-rated framing and glass work in tandem to provide compartmentation, the frames and glass must carry the same fire rating and classification (fire protective or fire resistive) in accordance with the IBC.

10. Who is responsible if the wrong glass or framing is installed?

Potentially, multiple parties involved in the selection, specification, approval, or installation of products could be held liable. The building owner might look to the architect, who in turn could point to the code officials and the glazing contractor. Code officials will say their approval has the disclaimer that it is "subject to errors and omissions". Glaziers are the glass experts, and architects rely on them for advice. If a glazier sees a problem, he needs to alert the architect about suitable alternatives. The excuse, "I just bid what the architect specified...” may not go far in a court of law.

When it comes to life safety in a building, it is important to gather all the details to avoid making costly or dangerous mistakes. After examining the application and narrowing the option for glazing and framing materials, review an individual’s product literature in detail. Look for any special requirements, limitations or exclusions.