Achieving 24/7 Protection with Fire-Resistant Glazing

Devin Bowman, General Manager, Technical Glass Products

Towards the end of the 19th century, the building and insurance industries were at a crossroads—electricity had just begun brightening factories, stores and other commercial buildings, but it also presented fire hazards. The installation of wires and hookups was largely unstandardized. Likewise, protective systems, like sprinklers, were unregulated. This combination created uncertainty around building performance and occupant protection.

For this reason, several professionals came together to form what would later be known as the National Fire Protection Association (NFPA). To this day, this association helps develop national model fire and life safety codes. Although building professionals have several means to achieve the standards in these (and other) model codes, they can readily achieve code-driven standards without compromising on design by specifying fire-rated glass. This is particularly true when it comes to fire-resistant glazing.

Contributing to open interiors, access to daylight and more, fire-resistant glazing allows for eye-catching interiors and exteriors that help keep occupants safe with passive protection. But how does fire-resistant glazing work? Where is it required? And why is passive protection important to fire and life safety?

How does fire-resistant glazing work?

To fully understand the answer to this question, it’s important to first distinguish between two classifications of fire-rated glazing: fire-protective and fire-resistive. Fire-protective ratings measure a glazing system’s ability to defend against the spread of flames and smoke for a designated time period. Fire-resistant glazing goes a step beyond by also defending against radiant and conductive heat transfer. These classifications not only have bearing as to where a glazing system can be installed but the total area of glazing that is allowable by code. Knowing this difference is vital to ensuring a code-compliant design.

While fire-protective glazing is made from materials like glass ceramics, fire-resistant glazing is commonly made from glass with transparent intumescent interlayers. When such glazing is exposed to temperatures that are hot enough to shatter the outer layers of glass, this material will expand and crystalize into an opaque, heat-absorbing barrier. This ability allows it to guard paths of egress, ensuring safe passage for up to 180 minutes.

Where is fire-resistant glazing required?

Technically, fire-resistant glazing is not required within the built environment, but it does provide several benefits when compared to opaque, fire-rated materials. As a transparent alternative to fire-rated gypsum or concrete, this type of glass can help designers meet code requirements without having to sacrifice design goals, such as providing open sightlines and access to daylight.

As with all code requirements, it is important to note certain locations may adopt more stringent requirements than what is listed in the latest editions of the various national model codes. For this reason, it is recommended that designers consult with a local Authority Having Jurisdiction (AHJ) to clarify the exact requirements for a specific project. Doing so will not only help ensure a design is code-compliant, but it will also allow adequate time for firms to work with manufacturers and cities to solve any potential challenges to achieving a safe and beautiful building. It could also clarify if an application needs fire-resistant or fire-protective glazing.

In general, fire-resistant materials are required for structural elements (including floors and load-bearing walls), along paths of egress and as fire and heat transfer barriers for compartmentalization. Fire-resistant glazing can be used as floors, non-load-bearing walls and as barriers for compartmentalization. It can also be used as windows within load-bearing walls. Fire-resistant glazing can help designers create code-compliant buildings that are open, visually connected and filled with light.

Why is passive protection important for fire and life safety? 

Ensuring code compliance without compromising design intent is not the only benefit fire-resistant glazing provides. Fire-resistant glazing works as passive protection, meaning it requires no activation—it is ready to protect 24 hours a day, seven days a week. As such, it can act as a complementary system to prevent tragedy in case an active system fails.

Designing redundancies in protective systems and reducing the dangers of system failure are key considerations for creating safer structures. The NFPA estimates that automatic extinguishing systems (AES) either failed to operate or operated ineffectively during 12 percent of fires large enough to trigger them. While this number may seem low, given there are, on average, approximately 499,000 structural fires per year, which may amount to over 4,158 failures annually. Having a system that is always on guard can ensure backup protection should a failure occur, which significantly improves occupant safety.

As design professionals continue to address building safety, it is important that shielding occupants from fire continues to be a top priority. Fire-resistant glazing can be a path to safer and more occupant-centric designs by providing an additional layer of protection against fire that does not run counter to aesthetic goals.