Today, dozens of glazing materials are used in fire-rated applications, a tremendous boon to design. But when each product has unique characteristics, sifting through the alternatives and selecting the best material can be a daunting task. 

The key to a good choice does not start with the products, but with the project at hand. By thoroughly evaluating an individual application, you can quickly narrow your search and feel confident about your selection. The simple acronym F.I.R.E. can serve as a quick checklist to help evaluate a project’s needs.

F-Fire rating
It is critical to determine the fire rating required in the specific setting where it will be installed. 

For glazing, fire ratings are given in increments ranging from 20 minutes to 3 hours. These ratings indicate how long the glass can be expected to withstand the intense heat of a fire. Independent laboratories install the glass in a special furnace and subject it to fires that burn at temperatures in excess of 1600 degrees Fahrenheit. In comparison, ordinary window glass shatters at roughly 250 degrees Fahrenheit.

Test standards require that for a product to earn a fire rating of 45 minutes or greater in the United States, it must pass a hose stream test in addition to a furnace test. In Canada, all fire ratings require the hose stream test. 

A second important consideration regarding fire ratings pertains to the rest of the system. For a rating to be valid, the framing and any sealant or caulking must carry a matching rating. A 45-minute glass product must be installed with other components that have an equal or higher rating.

I-Impact Safety
Once the fire rating has been determined, it is important to consider other factors such as impact safety. 

Products offer a range of different levels of protection. Wired glass meets ANSI Z97.1, which is 100 ft/lb of impact. That is roughly equivalent to a small child running into the glass. Other glazing materials satisfy CPSC 16 CFR 1201 (Category I). This standard is 150 ft/lb of impact, simulating an adolescent hitting the glass. The highest standard for glazing is CPSC 16 CFR 1201 (Category II). At 400 ft/lb of impact, this indicates the glazing can withstand the impact of a running adult.

For many years, there was no glazing material on the market that could provide both fire and impact protection. Fortunately, today there are ample choices that offer both types of safety. However, as with fire ratings, no two products are identical. Carefully determine what level of impact safety is needed, then seek out the product that can offer what the application requires.

R-Resistance to heat transfer
Heat transfer is sometimes confusing. Some people may assume that a fire rating indicates a material can block heat, but that is not the case. Fire ratings are concerned with stopping the spread of flames and the deadly smoke. The materials may well provide a barrier to the progress of the fire while allowing heat to pass through.

This is normally not a concern. Most areas requiring fire-rated glazing are not intended to keep a location from overheating. For example, a corridor is a means of egress and not intended to house people during a fire for long periods. On the other hand, a stairwell could potentially become a place where people are trapped for longer periods of time as they wait to evacuate the premises. Computer data rooms are also extremely heat sensitive, as are hospital wings where patients may be immobilized and unable to exit quickly.

When heat transfer is an issue, a location will have clearly-defined additional requirements. In those settings, the glazing must actually be tested to the same standards as a wall (referred to as ASTM E119). Fire can be raging on one side of the glass, and the other side will remain cool enough to touch. These products are generally thicker and heavier than standard fire-rated glazing, and they can be used in much larger dimensions since they are considered walls rather than windows.

E-Extra performance capabilities
Finally, some projects may have special additional needs. Will the glass be used in an exterior wall and need to meet energy codes? Are acoustics a concern? Is there a need to provide security or bullet resistance in addition to fire and impact safety?

Fire-rated products are available that can meet nearly every conceivable need. Ceramics can be insulated with virtually any type of glazing, giving unlimited possibilities. Glass firewalls can offer bullet resistance. Products can even be etched, sandblasted and beveled for the perfect finishing touch.

Undoubtedly, the number of available products and their features will continue to expand, creating even more flexibility.

Jerry Razwick, founder and president of Technical Glass Products (TGP), a distributor of specialty glass and framing as well as architectural products, has been a glass factory agent in foreign and domestic markets for over 25 years and is an active member of AIA and CSI.

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