“Fire-protection” vs. “fire-resistive.” How should a building code official understand these often confused terms when considering fire-rated glass? Even though both terms describe fire rating categories, there’s a world of difference between the two in terms of public safety and the growing use of transparent materials in wall assemblies and doors.
For example, the results of a side-by-side, time-to-failure test of fire-protective glazing and fire-resistive glazing conducted in September 2005 at the IFT&S laboratory in Berne, Switzerland and supervised by International Fire Consultants, Ltd sharply contrast the differences between the two:
Within 20 minutes of furnace exposure
Within 27 minutes of furnace exposure
Within 45 minutes of furnace exposure
This time-to-failure test presents the hazards of radiant heat transmission as well as the stopping power of fire-resistive glass.
A subsequent third-party test conducted in March 2006 at the Intertek Testing Services center subjected three types of fire protective glazing products wired glass, ceramic glass, and heat-reflective specialty tempered glass to the same ASTM E-119 test. Mannequins were placed on the non-fire side to see the effect of radiant heat on clothing and other combustible items.
Within 10 minutes
At 12 minutes
At 16 minutes
To view the short video of the mannequin test, click here.
To measure radiant heat flux on a glass ceramic panel a common fire-protective glazing material another third-party test was conducted in April 2016 at the Intertek Testing Services Center. The ceramic panel was tested in accordance with UL 9 voluntary heat flux testing procedures. A radiometer was positioned one meter from the center of the test panel to monitor radiant heat flux. Results:
Within 5 minutes
Within 10 minutes
Within 30 minutes
The 2012 AND 2015 International Building Code severely limits fire protection products like glass ceramic in doors and wall assemblies. The rapid, uncontrolled transmission of deadly radiant heat makes them a concern to public safety, as shown by the combusting mannequin and the rising surface temperatures in the tests. To see how IBC limits glass ceramic size, look here.
Fire-resistive glazing blocks fire and smoke passage (just as fire-protected glazing does) while it minimizes lethal radiant heat transmission, in accordance with ASTM E-119. That’s a critical distinction in today’s build environment, where architects place a growing emphasis on natural light and outside exposure through expansive glass walls and doorways.
The challenge for code officials is to understand the 60/90/120/180 minute claims of some fire-rated glass manufacturers are heavily qualified by code, with material size strictly limited. For example, 60/90/180 minute doors cannot exceed 100 square inches of ceramic glazing just a 10-inch by 10-inch transparent portal. Designers seeking a more open, transparent aesthetic must look beyond ceramic glass.
Now that architects are doing more and more with glass design, pressure is growing to specify more fire-resistive glass.
Robert Davidson, a former fire marshal, knows from firsthand experience about the power of radiant heat. Davidson recalls from his firefighting days that, “If a building was on fire and close to another building, we used to create a curtain wall of water between the buildings, thinking that would somehow stop the fire from spreading. It didn’t. The building next door would catch fire anyway because the radiant heat would pass right through the water.”
Davidson also cautions the remarkable ability of ceramic to transfer radiant heat should not be underestimated. He points to ceramic stovetops as an example. “Ceramic is used on stovetops because of its rapid heat transfer. Is that how we want our buildings to behave during a fire? Fire-resistive glass can save lives without compromising an architect’s design vision.”
For code officials wishing to investigate the matter in greater detail, a number of resources are available. For a copy of the 2016 Intertek test results, click here. To review videos of time-to-failure tests and other materials about fire-rated glass, click here and visit Resources.
The views and opinions expressed in this article are those of the sponsor and do not necessarily reflect those of the International Code Council, or Hanley Wood.
i See Tables 716.5 (Opening Fire Protection Assemblies, Ratings and Markings) and 716.6 (Fire Window Assembly Fire Protection Ratings) in the 2012 and 2015 IBC.
ii See Tables 716.5 (Opening Fire Protection Assemblies, Ratings and Markings) and 716.6 (Fire Window Assembly Fire Protection Ratings) in the 2012 and 2015 IBC.