Fire-rated glass and framing products from Technical Glass Products (TGP)

800.426.0279

School Design

FIRE-RATED GLAZING 101

For decades, traditional wired glass has been the most common fire-rated glass product specified for schools in North America.It provides economical and reliable fire protection, and for years was the only product available that could do the job. The catch is it can’t tolerate much impact. When traditional wired glass breaks, the wires can form snags that are capable of inflicting serious injury.

So, while buildings codes typically restrict the use of low-impact safety glazing products in high traffic areas, the absence of a fire-rated glazing material with the desired impact safety performance led to an exemption. Building code officials deemed wired glass suitable for use in areas requiring fire protection and high-impact safety protection.

The good news is choosing fire safety over impact safety is no longer a tradeoff building and design professionals need to take. With the introduction of clear, wireless fire-rated glazing materials that provide superior fire and impact protection, the International Code Council (ICC) decided to lift the long-standing impact exemption for wired glass in the International Building Code (IBC). In 2003, the IBC restricted traditional polished wired glass from hazardous locations in schools, athletic facilities and daycares. As of the 2006 IBC, the restriction has extended to include hazardous locations in all types of buildings.

This change had far-reaching implications. More stringent fire and life safety standards and clear, fire-rated glazing alternatives have revolutionized the way fire-rated glazing is used in schools.

What distinguishes fire-rated glass from ordinary glass?

Like most glass, fire-rated glazing allows light and visibility for aesthetic or security reasons. But fire-rated glass does something more: It has been tested to act as a barrier to the spread of flames and smoke. In the world of fire protection, this is known as “compartmentation.”

Unlike sprinklers or other “active” protection systems, fire-rated glass does not require activation in order to protect against fire. If there is a power failure, a loss of water pressure, or a human error that interferes with the sprinklers working properly, fire-rated glass will not be affected and will continue to perform as needed. Staying in place during a fire may sound like a fairly simple task, but no ordinary glass can do it

What testing does glass have to pass to earn a fire rating?

To receive a fire rating, glass must first pass a fire test. In this test, the glass and framing are installed in a test furnace at an independent test laboratory, such as Underwriters Laboratories, Inc.® (UL). The fire is ignited and temperatures are measured on the surface of the glass. After only 5 minutes, temperatures in the furnace reach nearly 1,000° F (ordinary window glass can withstand temperatures of approximately 250° F.) After one hour, they reach nearly 1,700° F. Ratings are given based on the length of time the glass remains intact, from 20 minutes to 3 hours.

At the conclusion of the fire test, to achieve a rating greater than 20 minutes, the glass must pass a mandatory hose stream test during which testing labs spray the glass with water from a two-man fire hose. This tests the ability of the glass and framing system to stay in place if impact pressure or thermal shock cause structural damage. It also helps prove the glass will stay in its protective position to block flames and deadly smoke, if subjected to the cooling effects of water from sprinklers or fire extinguishers. According to NFPA 257, “the cooling, impact, and erosion effects of the hose stream provide important tests of the integrity of the specimen being evaluated.”

When using glass in fire-rated locations, is impact safety glass always required?

No. Building codes clearly define where impact safety glass is required, such as doors, sidelites and windows near the floor, as discussed in the following section, “Cracking the Code.” In these areas, any fire-rated glass product would also need to be impact safety-rated.

In areas where human contact is not a concern (e.g., transoms, some windows), glass with an impact rating is not required. For these applications, fire-rated glass products are available without impact safety ratings. They generally cost less than glazing that provides both fire and impact protection.

However, keep in mind that schools are high activity areas that can present abnormal situations. A window in the middle of a school wall that doesn’t technically require impact safety ratings may still fall victim to the energy of students pushing and shoving. Therefore, it may be best to err on the side of caution and use an impact safety-rated product even when codes don’t demand it.


« Previous: School Design Page Next: International Building Code »


View Full Site