New IBC code means rethinking fire-rated glass.
For decades, wired glass has been the most common fire-rated glass product specified in schools across the United States. It’s no wonder: it provides economical and reliable fire protection. And for a long time, wired glass was the only product available that could do the job.
But there is a down side: Despite its tough appearance, wired glass can’t tolerate much impact. And when it breaks, the wires create nasty snags that can inflict serious injury.
When fire codes were first being drafted, there were no alternatives to wired glass. So when high traffic areas called for a fire rating, wired glass was granted an exemption from meeting impact safety requirements. The consensus was that the risks posed by fire were greater than the risks posed by breakage.
But fire safety without impact safety isn’t enough when you have a corridor filled with students jostling each other on their way to class. In such settings, wired glass can be a disaster waiting to happen.
Realizing this, the International Code Council decided to lift the long-standing impact exemption for wired glass. Now, all fire-rated glass in K-12 schools and athletic facilities, when used in hazardous locations (doors, sidelites, etc.) must meet the higher impact requirements.
This is a monumental shift, having far-reaching implications. SchoolFacilities.com recently talked about the change with Jerry Razwick, president of Technical Glass Products and an industry expert on fire-rated glazing.
Q. What distinguishes fire-rated glass from ordinary glass?
A. 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 is on duty 24 hours a day. 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.
Q. What testing does fire-rated glass have to pass?
A. Glass and framing are installed vertically in the test furnace of an independent test laboratory, such as Underwriters Laboratories (UL). The fire is ignited and temperatures are measured on the surface of the glass. Ratings are given based on the length of time the glass remains intact, from 20 minutes to 3 hours.
Ordinary window glass can withstand temperatures of approximately 250 F. However, a “real world” fire (and the fire test) produce temperatures of nearly 1,000 F at only 5 minutes. Glass able to withstand an hour in the test is subjected to nearly 1,700 F.
At the conclusion of the fire test, to achieve a rating greater than 20 minutes, the glass is subjected to the impact pressure and thermal shock of water from a two-man fire hose. This tests the ability of the glass and framing system to stay in place if structural damage takes place. It also proves the glass will stay in its protective position, to block passage of flames and the deadly smoke, if subjected to the cooling effect of water from sprinklers or fire extinguishers.
Q. What is the impact safety test for glass?
A. A 34” x 76” piece of glass is mounted in a vertical frame. A punching “speed” bag is filled with 100 pounds of lead shot (similar to BB’s found in shotgun shells). This very heavy bag is hung from a cable and swung, in pendulum fashion, from various heights to impact the glass. The velocity of the bag, at high impact levels (CPSC 16 CFR 1201 (Cat. II) corresponds to the impact of a full grown adult. running into the glass. This level of impact resistance is typical for standard tempered or laminated glass. By contrast, wired glass and products meeting only (Cat. I) of the CPSC standard could only withstand the running impact of a small child. To qualify for an impact safety rating, glass must either not break, or break in a safe manner.
Q. Are there different levels of impact safety for glazing materials?
A. Yes. This issue is extremely important in schools and relates to the impact safety test and the level from which the impact bag is dropped. The various impact ratings are very revealing. Let’s start with the most common level of impact safety and work our way to lower levels.
48-inch drop
This represents 400 foot-pounds of impact, and is called Category II by the Federal CPSC (Consumer Products Safety Commission). It is the highest level of required impact safety. This represents the impact of a full-grown adult running into the glass with insignificant or no injury. With few exceptions, all tempered or laminated safety glass in use today falls into this category. More importantly (important ?), there are numerous products available today that meet this impact rating and also offer high levels of fire protection.
18-inch drop
This represents 150 foot-pounds of impact, and is called Category I by the CPSC. Glass that can only meet this test is limited to a maximum size of 9 square feet per lite (or less). This roughly represents the expected impact from an 85 lb. child running into the glass. As stated above, nearly all tempered or laminated glass has far exceeded this impact level for many years, so Cat. I products are a bit of a “holdover” from earlier times. As you can see, there is a significant difference between the two categories. Category II products will withstand the impact of an adult, while Category II products may allow injury to many school age kids. If you see fire-rated glazing that only has a Category I impact listing, consider the consequences of using this substantially lower impact product.
12-inch drop
This represents only 100 ft./lb. of impact and was created as an exception for wired glass. It indicates the glass may only withstand the impact of a very young child.
Q. When using glass in fire-rated locations, is impact safety glass always required?
A. No. Building codes clearly define where impact safety glass is required. Common applications for high impact glass are doors, sidelites, glass located near the floor, and other “hazardous locations”, as clearly defined by building codes. In those areas, any fire-rated product would also need to be impact safety rated.
In areas where human contact is not a concern (transoms, some windows) an impact rating would not be required. For those areas, there are fire-rated products that are not impact rated which are generally less expensive than glazing that offers 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 in some cases and use an impact safety rated product even when codes don’t demand it.
Q. If, due to the IBC, schools are no longer using wired glass, what products are available?
A. There are two primary categories of alternatives to wired glass that can be labeled as “Thin” and “Thick” Glass.
Thin
These wireless products are similar in thickness to wired glass. They fit in standard fire-rated frames. Depending on the product, they are available in large sizes and have fire ratings from 20 to 90 minutes (up to 3 hours in small door lites). Products are available with high impact safety (Cat II) or without impact ratings. School maintenance personnel or local glazing contractors can cut some of these products with standard tools -- so availability is nearly immediate. (JP: What do we say about “thin” products that only meet Cat I? CGI’s product, etc.) Idea: “these high impact products are preferable to some thin products that can only meet the lower (Cat I) impact standards. Let’s not forget we are here working with youth that seem to have unbridled energy.
Thick
These special glass products are commonly called glass walls because they allow virtually unlimited expanses of glass. Tested to the same standards as solid barrier walls, glass walls block heat in addition to flames and smoke. Corridors that contain more than 25% of glass openings should definitely consider these products that, during a fire, block heat transfer through the glass, and allow safe passage. They may not fit in standard window and door frames – although some, with lower fire ratings may. Glass walls require special cutting equipment, so shipments usually come from the glass manufacturer/fabricator. A lead time of a few weeks is not unusual, so use as a replacement glass is not always practical. These products typically have a Cat II impact rating.
Q. What special considerations should be taken into account when choosing fire-rated glazing for schools?
A. Schools are unique in the construction industry, because they raise several issues that typically do not arise with other occupancies.
High activity
Educational facilities are subject to a great deal more activity than a typical office building. The constant movement of students throughout the day means that impact safety must be a high priority.
Abuse
School hallways and common areas are likely to be defaced, either intentionally or unintentionally. The fire-rated glazing chosen should be durable.
Maintenance
For building and life safety (not to mention legal) considerations, damaged products must be replaced or repaired in short order.
Longevity
Schools are expected to operate for many, many years. Since school construction and maintenance budgets are tight, it is extremely important that building products stand up over time.
Q. Why not just apply a safety film to wired glass?
A. As we mentioned before, schools are more prone to abuse than other types of facilities. Even the toughest films can be marred, lacerated or peeled by a determined vandal.
When the film is damaged, it not only is unsightly -- it potentially can impair the performance ability of the product and render the impact ratings invalid.
It isn’t that we are against the use of film -- we even sell a fire-rated product that has a film applied for impact safety. We simply do not recommend its use in high traffic areas such as schools.
Q. What specific products do you recommend for schools?
A. In non-impact rated areas, we typically recommend transparent glass ceramic (FireLite, manufactured by Nippon Electric Glass Company, Ltd., is the most common brand). At only 3/16” thick, it easily fits into new or existing fire-rated frames. It can be cut with normal glass cutting tools, which means it can be delivered quickly from school maintenance personnel or local glazing contractors. And since it is a ceramic, it has a surface even more durable than regular glass.
For high traffic, “hazardous” locations, we recommend laminated ceramic (FireLite Plus). It meets the CPSC 16 CFR 1201 (Cat. II) impact requirements. The high impact laminating materials are sandwiched between two lites of ceramic, so both exposed surfaces are durable. Like FireLite, FireLite Plus can be cut in the field for quick delivery.
Q. When should I use the “thick” glass that is a barrier to heat transfer?
A. These products are typically used where large expanses of glass are required, i.e., where glazed areas exceed 25% of the wall area. Their ability to block heat transfer can prove invaluable when protecting exit corridors is important. And the benefit of blocking heat is increasingly being considered, even when heat blockage is not required. However, due to the need for special cutting equipment, delivery can take a few weeks. This extended lead time is an important consideration if glass requires immediate replacement. Further, with a typical thickness of at least 3/4”, frames and glazing “stops” may require modification.
Having said that, there are many times when such a product is the best choice. In those instances, we recommend Pilkington Pyrostop. It is available in a broad range of make-ups for interior and exterior use, with ratings from 45-minutes up to 2 hours.
Q. Is this change positive or negative for schools?
A. Positive, in the long run. As with most changes, it may seem like more work at first. But ultimately, schools will be safer places. That’s really the bottom line.
For more information on fire-rated glazing issues and products, visit
www.fireglass.com.
For reference:IBC
2003 Revision
2406.1.1 CPSC 16 CFR 1201. Except as provided in Sections 2406.1.2 through 2406.1.5, all glazing shall pass the test requirements of CPSC 16 CFR 1201, listed in Chapter 35.