Fire-rated glass has come a long way from the days of wired glass. Today’s fire-rated glazing is designed to blend seamlessly alongside non-traditional products, creating large, transparent spans that bring an uninterrupted aesthetic. That evolution, however, has also made fire-rated glazing an oft misunderstood product for both contract glaziers and architects. As architects push for more transparency and seamless design, and as building codes continue to mandate higher levels of fire performance, contract glaziers increasingly are tasked with installing complex systems with little room for error.

Fire ratings do not tell the whole story. Two rated products may share a similar label, but they can be very different. Understanding the distinctions between fire-protective and fire-resistive glazing, knowing what questions to ask early, and recognizing when a system requires increased coordination are critical skills for installers and estimators.

The belief that all fire-rated systems are the same or that all ratings are the same is a common misconception, says Ben Haigh, senior fire-rated division director with McGrory Glass in Paulsboro, New Jersey.

“You could have a 45-minute or even a two-hour rated material, but that’s often where the similarities start and end. When it comes to those higher ratings, in particular, installation matters can get complicated,” he says. “It’s about an as-tested system. That’s how it has to be installed. Every manufacturer or fabricator will provide a glass product, but in order to maintain that as-tested rating, there are specific requirements as to how you install it.”

While fire-resistive glass assemblies often are designed to look like their non-rated counterparts, they are in fact different. Tim Nass, vice president of sales with SAFTI First, based in San Francisco, says fire-rated products tested to ASTM E-119/UL 263 may look like traditional safety or tempered glass, but are actually a “wall” by code.

“Fire-resistive glass assemblies have the ability to compartmentalize smoke/flames as well as reduce radiant heat flux or energy generated by a fire,” he says. “These critical performance features require the glass and frame to be more robust than traditional storefront or pressure wall systems. That means they are heavier and, as a result, arrive at the jobsite knocked down.”

Slight adjustments to the condition or openings can significantly impact the installation of these assemblies, Nass says.

“Staying within the maximum clear views of the glass that is being provided, the size of the caulk joint could be the difference between a medium modulus silicone and a fire-resistive caulk, which could have a real financial impact on the installation of the product,” he explains.

Ron Madeley, principal engineer and business interface leader at Technical Glass Products in Snoqualmie, Washington, agrees that while many fire-rated glass solutions resemble non-rated products, fire-rated glass is a life-safety component within either a fire-protective or a fire-resistive system.

“These systems are often multi-functional, providing fire protection as well as impact safety, as required by building codes, along with threat mitigation, and even energy efficiency properties that support project goals identified by the architect and building owner,” he says. “It is crucial that fire-rated glass not be swapped between systems, unless with explicit approval from the specifier and manufacturer.”

Haigh also stresses that fire-rated glazing must be considered as a complete system. Its performance depends on a fully engineered, as-tested system in which every component plays an essential role.

“Everything has to go in as-tested in order to perform,” says Haigh. “This is a lot different than the old days of just adding a special glazing tape to wired glass. I’ve witnessed numerous tests, and it is absolutely remarkable how these systems can perform. But if you fail to install the systems properly, it can truly be catastrophic.”

Understanding the differences in “fire-resistive” and “fire-protective” products is a key detail for contract glaziers. Nass says the distinguishing feature is the ability of fire-resistive assemblies to control radiant energy transfer or heat flux.

“As a result, fire-resistive products are considered a wall by code and are required to meet the more stringent ASTM E-119/UL 263 fire-resistive wall requirement. It is important to note that the code does not distinguish between transparent and opaque. From a code perspective, they are one and the same. Any fire-resistive assembly should be referenced as a wall regardless of configuration.”

Fire-protective products are considered an opening in a wall by code.

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