AGG - 2006 - March/April

Volume 20 • Issue 2 • March/April 2006

Fire Away
A guide to the types of fire-rated glazing available today

By Jerry Razwick

Omni Park, San Diego, Calif., is an example of how fire-rated glazing can offer obscured vision to preserve privacy while still allowing light to pass through. Hornberger + Worstell Inc. was the architect for the project.

For the past two decades, fire-rated glazing has been leading a quiet revolution in the glass industry. Once, options were nonexistent. If you wanted glass in a fire-rated opening, it had to be wired glass. The size of the opening was severely restricted. The framing choices consisted of hollow metal steel and not much else.

Today, a dizzying array of choices is available with a wide range of performance levels. It is a tremendous boon for design, opening up possibilities. However, the rapid pace of change has made it challenging for architects and specifiers to stay informed about all the current fire-rated products and their capabilities.

However, keeping up to speed can be more manageable if you follow the simple acronym C.P.R. as you set about selecting fire-rated glass and framing.

C - Category

While the number of products available continues to grow exponentially, the basic types of fire-rated glass can still be broken down into a handful of categories.

Polished wired glass, the workhorse of the industry, 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), with a 90-minute rating restricted to 100 square inches for use in fire doors. The biggest advantage of wired glass may be its low cost. However, it offers little protection against impact and can represent a significant safety threat when broken. As a result, the latest version of the International Building Code (IBC 2004) has eliminated the use of traditional wired glass in doors, sidelites and other “hazardous” locations in all types of construction.

Wired glass manufacturers have developed two solutions to the impact issue. Newer generations of wired glass are now available in a laminated form or with a special fire-rated surface applied film. Both offer improved impact resistance, meeting the Consumer Product Safety Commission regulation CPSC 16 CFR 1201 (Category I or II, depending on the product).

When using any product with a surface-applied film, special consideration should be given to the exposure the film could have to vandalism, as damage to the film could nullify the product’s performance ratings.

Due to its inherent ability to withstand heat, glass ceramic is used for everything from cooktops to car engines and fire-rated glazing.

Once installed in an opening, glass ceramic looks similar to ordinary window glass—clear and wireless. Glass ceramic products provide fire ratings from 20 minutes to 3 hours, and in sizes ranging up to 24 square feet per lite. Like wired glass, the glass ceramics are able to withstand the thermal shock of water thrown by sprinklers or fire hose. Yet because they contain no wires, they don’t create the “institutional” look and feel common to wired glass.

Where impact safety is required, glass ceramic is available that offers at least four times the impact resistance of wired glass, thus meeting CPSC 16 CFR1201, Category II. Glass ceramic can also have beveled edges and be sandblasted for artistic effect.

When installed in insulating glass units, glass ceramic offers even greater design flexibility. The IG units can incorporate many types of float glass—clear, tinted, low-E, mirrored, etc. Depending on which components are used, they provide not only fire protection but compliance with energy codes as well. The IG units are sometimes used for interior applications where sound reduction is desired.

Glass Fire Walls

In areas such as stairwells and computer rooms, heat from a fire is often as much of a concern as flames and smoke. Ordinary fire-rated glazing isn’t intended to be a barrier to heat. But glass fire walls are. They often look like bullet-resistant glass from the edge, with multiple sheets of glass that sandwich intumescent interlayers. The thicker composition of glass fire walls allows them to pass the same testing as a fire-rated masonry wall.

Glass fire walls can be installed from wall to wall and floor to ceiling. These large expanses of glass have obtained fire ratings up to 2 hours. They block so much heat that when a fire is raging on one side of the glass, someone can touch the opposite surface without any discomfort. This allows architects to provide clear, fire-rated glass “walls” that provide visibility, light, and security. Like wired glass and glass ceramics, the glass fire walls withstand thermal shock. In addition, they meet high levels of impact safety as well.

For 20-minute door applications, there are specially-tempered products that offer a degree of fire protection at a nominal cost. However, these products are extremely limited in their applications. Specially tempered glass does not pass the critical fire hose stream test, meaning it cannot withstand the thermal shock of water thrown from sprinklers or fire hose.

Once you’ve identified which category of glazing is best suited to the application, you can then narrow the search and begin comparing products and suppliers within that category.

P—Performance Requirements

Because all types of fire-rated glazing are not the same, they don’t all give the same levels of performance. This is true not only in terms of fire protection, but in other characteristics as well. That makes it important that all performance requirements of a particular location be carefully reviewed before specifying a product solely because of its fire rating.

Typically, glass needs to perform a variety of functions. Fire codes may be a consideration, but usually there are a number of other needs that can come into play. As mentioned earlier, impact safety is often one such need, particularly in locations that see high volumes of foot traffic.

Fortunately, with so many options on the market today, fire-rated glazing materials are available that can “multi-task,” offering many different capabilities. For the first time in history, a single piece of glass can perform a wide range of functions.

For example, in today’s security-conscious environment, many buildings have a need for bullet-resistant glass in locations that are normally fire-rated. Yet most bullet-resistant glass contains highly flammable plastic. New glass fire walls provide a solution, offering bullet-resistance rating as well as fire and impact safety ratings.

Other times, a project may require fire-rated glazing that meets energy codes. There may be aesthetic or privacy needs for sandblasted glass. Settings may require sound reduction, one way mirrors or tinted glass. All these options are now available in fire-rated configurations.

In other words, there is no need to compromise other design requirements to achieve the necessary fire safety. Clarify your “wish list,” and there is almost certainly a glazing option out there that can give you what you want.

R—Restrictions

In addition to knowing what products can do, it is important to know what they cannot do. This is not always easy. A thorough reading of the product listing can often shed light on the matter. If it appears a product has not passed or requires special approval by the authority having jurisdiction, take note.

Now, armed with CPR (the categories of glass, performance requirements and restrictions on the different choices), you will be able to take full advantage of the incredible innovations in fire-rated glazing available today.

Jerry Razwick is president of Technical Glass Products, Kirkland, Wash.