In the KnowJuly 30th, 2020 | Category: Architects' Guide to Glass and Metal
Understand What You Need to Defend Against”
The term “security glazing” can be misunderstood in the architecture and design community, but with building security at the top of many peoples’ minds in recent years, awareness of what it means is imperative. This edition of “In the Know” addresses some of the misconceptions and key points regarding this type of glass application.
Safety is Not Security
Safety glazing and security glazing some-times may be used interchangeably, but they shouldn’t be.
According to Hernán Gil, vice president of sales at Global Security Glazing, safety glazing primarily refers to risk management of injury and/or loss from natural causes, such as hurricanes, tornadoes or unintended human impact. Requirements for safety glazing are code-driven.
Security glazing, however, is a very different animal. Security refers to risk management of injury or loss from the intended actions of an individual or group—in other words, man-made occurrences. Examples of these include forced entry, ballistics and bomb blast. Requirements for security glazing are typically voluntary.
Since security glazing is not mandated by building codes, security requirements are deter-mined by the building owner, specifier or the authority with jurisdiction over decisions related to the building. The latter may include the government, which often has its own self-imposed requirements for security.
What’s in Security Glazing?
Security glazing can come in a variety of forms and is dependent of the level of threat the application is protecting against. These forms include various thicknesses, layers and material types.
Tempered and heat-strengthened glass is often used in security glazing, typically in multiple layers that are sandwiched together with a plastic interlayer. Glass is sometimes used in combination with polycarbonate, a clear plastic that adds additional strength and security.
Applications and Testing
Three key security glazing applications are forced entry, ballistics and blast. Gil says designing for forced entry typically “eliminate(s) or minimize(s) the ability to gain illegal forced entry into a property.” He says that detention, or “containment,” also falls under this category since it requires similar performance criteria. “Detention is keeping them in, and forced entry is keeping them out,” says Gil. “But both are within the same type of security glazing.”
There are various test methods for this type of glazing, including those under the ASTM standards. Gil says glass-clad polycarbonates, laminated glass, laminated polycarbonates and applied films are examples of forced-entry glazing product types. He notes, though, that while glass is a critical component to security glazing, the entire system—including framing—must be designed to meet the various performance standards.
Ballistics attacks include those from handguns, shotguns or rifles. Gil says glazing for ballistics “is designed foremost to prevent penetration of the impacting projectile, and then to eliminate or minimize excessive spall.” Underwriters Laboratory (UL) has a rating on the books for “Bullet Resistant Materials.”
Products that fall under ballistic glazing often include multi-layer laminated glass, glass-clad polycarbonate, laminated polycarbonate and acrylic. Gil notes that glass-clad polycarbonate constructions “are thinner and lighter than ‘all-glass’ equivalents for a specific bullet-resistance level,” but that “exposed polycarbonate is more susceptible to scratching and chemical attack.”
Finally, blast-resistant glazing is designed to maintain the integrity of the building envelope following an explosion to reduce interior dam-age. This type of system may include a combination of laminated glass and plastic glazing bonded with a high-performance polymer interlayer.
Testing for blast mitigation can be conducted on the entire glazed fenestration system by using ASTM and U.S. General Services Administration standards. The American Architectural Manufacturers Association (AAMA) and the Department of Defense also have standards related to blast-resistant laminate design.
Gaining an Understanding
Gil says it is critical to fully understand the particular security glazing application and how it is being considered for a project. “Understand what you need to defend against,” he says.
He notes that no single product does everything, and that installation and maintenance of security glazing is critical. Finally, it’s important to work with professional and reputable companies to ensure products are being tested properly and to the correct standard.
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