Fire-rated glass products are growing in popularity as more product options become available and as codes continue to require these products in certain applications. To dispel some of the confusion surrounding these products, Safti First vice president of sales Tim Nass explained the differences between fire-protective and fire-resistive products and how they should be used in a webinar sponsored by Safti First and hosted by Architectural Record.
Nass began the discussion by explaining that North America is the only market that uses 120-minute rated products. In the global market the focus is predominately on 60-minute ratings.
There are two performance categories for the market segment: fire-protective and fire-resistive. Fire-protective products are generally referred to as openings, i.e. a window or door, whereas fire-resistive systems are referred to as walls regardless of configuration. The general rule of thumb, according to Nass, is that fire-resistive systems are tested to 45 minutes or less while fire-resistive products are tested to 60 minutes or higher.
“There is no such thing as a two-hour window. It’s a two-hour transparent wall regardless of configuration,” explained Nass.
Fire-protective systems are tested to NFPA 257/252 and control the visual elements of a fire which are smoke and flames. Fire-resistive products are tested in accordance with ASTM E119/NFPA 251 and even UL 263. These products control smoke and flames as well as stop the transfer of radiant heat or energy generated from a fire. Fire-resistive glass products do not have size limitations because of this ability.
All fire-rated glass products are required to do an endurance test to see how long the glass remains in the opening. At the conclusion of the test it will receive a corresponding duration rating. Next is the hose-stream test. This is done with a fire hose 20 feet away from the glass at a pressure of 30 psi. The test evenly distributes water across the surface of the glass and frame. There is allowable breakage of 30% at the perimeter of the glass and 5% at the center of glass. However, the glass is not allowed to leave the opening.
“The purpose of this is to test the structural integrity of the assembly,” said Nass, adding that the hose-stream test is not meant to duplicate a fire fight or thermal shock. Fires are fought at a much closer range in excess of 30 psi, meaning that the glass will likely be damaged.
Nass emphasized the importance of checking to make sure that a product meets the requirements of a specific project. The International Building Code outlines the requirements.
He said that it’s possible to see a 20-minute door used with a one-hour partition or barrier. This glass is not subjected to the hose-stream test; however, sidelites and transoms need to meet the hose-stream test requirements at 45 minutes. Nass explained that 45-minute assemblies are less common and typically used for exterior applications. The door and sidelites are held to the same standard in this application, meaning they must meet 45-minute ratings and the hose-stream test requirements. Sixty-minute door assemblies are used for exits. The glass must be limited to 100 square inches. If the glass is to exceed that amount then it must be fire-resistive glass. The sidelites and transoms must meet the wall standard in these applications. Nass emphasized that glass must be fire-resistive if it is to exceed 100 square inches whether or not the building is sprinklered. Fire-protective glass is allowed in a 90-minute door but it is limited to 100 square inches. Sidelights and transoms must meet the wall standard of 120 minutes for two-hour wall applications.
In hazardous locations, the glass must meet the impact standards for either CPSC 16 CFR 1201 Cat. I or CPSC 16 CFR 1201 Cat. II. Cat I applies to glazing openings of less than 1,296 square inches and subjected to 150 foot pounds of force. Cat. II applies to more than 1,296 square inches and must survive an impact of 400 foot pounds of force.
Fire-protective products are limited to 25% of the wall area. If glass is to exceed 25% it will be required to meet the wall standard.