By Stephanie Miller
Since 1990, wired glass has been the sole material cited in the National Building Code (NBC) for safety glazing in fire-rated applications. This is going to change soon. The change will have major implications for designers and contractors working with fire-rated glazing materials.
There is evidence that even before NBC adopts updated requirements for safety glazing in its forthcoming editions, designers and contractors may need to make some changes today to avoid future liability.
Fire-rated glass has, for many years, been an effective barrier in preventing the passage of hot gas, flame, and smoke. Hence, NBC 3.1.9.1, Fire Stopping of Service Penetrations, was updated in 1990 to note openings “in a fire separation having a fire-resistance rating of not more than 1 hour may be protected with fixed wired glass assemblies.”
However, unless it is organically coated, wired glass falls far short as a safety glazing because it does not safely withstand human impact. The wire embedded in the glass is meant to hold the material together after it breaks in a fire, reducing the spread of flames, smoke, and hot gasses. The wire accomplishes this, but when the assembly breaks from human contact, the resulting jagged glass shards and strong wire can cause lacerations to anyone moving forcefully through the broken material. Evidence has stacked up over the years that these products cause as much, if not more, damage than they stop.
Photo © Rachel Dancks
This damage is troubling as the material has been used in schools across Canada, among other applications. Even though the Canadian Hospitals Injuries Reporting and Prevention Program does not track the number of injuries attributable to falls through wired glass in detail, Laura Rosella of the Dalla Lana School of Public Health at the University of Toronto, published research in 2015 based on U.S. injury estimates that suggest approximately 368 wired glass injuries take place each year in Canadian schools.
The problem has been widely recognized, and manufacturers and regulatory authorities have taken action. Since the 1990s, glass manufacturers have committed to developing safer safety glazing solutions that can meet the demands of fire-rated applications. In 2003, the U.S. building codes began banning the use of wired glass in hazardous locations, such as doors. In 2015, Canada began working on this.
Rewriting wired glass standards
In 2015, the Canadian Glass Association (CGA) issued an advisory recommending wired glass not be used in any location subject to human impact due to the threat of injury. Around that time, the Canadian General Standards Board (CGSB) had convened a glass committee to rewrite the country’s safety glazing standards. Thomas Zaremba, a partner with Roetzel & Andress, an expert in building codes and standards, and a member of the CGSB committee, notes the resulting standard is very much modelled on the United States’ American National Standards Institute (ANSI) Z97.1, Safety Glazing Materials Used in Buildings – Safety Performance Specifications and Methods of Test. In fact, it includes input from the then chair and members of ANSI Z97.1 committee. The intended result was comparable standards that will make it easier to source fire-rated products throughout North America.
“If a product passes the safety glazing requirements of 16 [Codes of Federal Regulations] CFR 1201, Safety Standard for Architectural Glazing Materials, or ANSI Z97.1, it will pass the new Canadian safety glazing standard as well,” Zaremba says.
In 2016, CGSB withdrew CAN/CGSB12.11-M90, Wired Safety Glass. The standard had tested wired glass’ impact resistance with three tests at 300, 450, and a maximum of 1200-mm (12, 18, and 47-in.).
drop height for an impactor providing 136 N⋅m (100 ft-lb) of impact energy. It is a test that standard 6-mm (¼-in.) polished wired glass was able to pass successfully. The following February, CGSB replaced CAN/CGSB 12.11-M90 with CAN/CGSB 12.1–2017, Safety Glazing. The updated standard now covers all forms of safety glazing, including tempered and laminated glass as well as glass products with a safety film.
With this change, as CGA points out, wired glass not organically coated and tested to the new safety glazing standard, will no longer be considered a safety glass in Canada. In fact, CGA recommends “wired glass should no longer be used in doors or other locations subject to human impact.”
The challenge, however, is standards are voluntary—and thus, unenforceable—until adopted by a code. Yet, even voluntary standards may push some degree of responsibility on architects and contractors.
