By Stephanie Miller
When it comes to fire safety and security, windows and spacious glass walkways and doors may seem like a clear entry point for disaster, and the truth is, they can be. Despite the fact that the fire-rated and security glazing industry has developed many products for new installation and renovations that can withstand fires, massive explosions, or targeted attacks, these heavyweight systems have a major weakness, too, often overlooked by contractors: improper installation.
Potential pitfalls from poor installation
To understand the role installation plays, it is important to first understand the role of fire-rated and security glazing. Specialty glazing encompasses a range of glass products designed and installed for a variety of protective and design purposes. Security glazing is designed to remain in place to resist someone or something’s entry into a building. Fire-rated products are designed and tested to withstand fire at various levels depending on the classification. These glazing products include:
fire-protective types, which stop the passage of
flames, smoke, and toxic gases for up to a maximum
of 180 minutes;
- fire-resistive ones designed to compartmentalize fire and fully block heat transfer for up to 180 minutes; and
- bullet-, blast-, and attack-resistant glass systems or window films.
However, without proper installation, these products can be rendered ineffective in the face of the threats against which they protect. This is because fire-rated and security glazing products have three essential jobs to perform. First, the glass itself must hold together in the event of a fire or attempted breach. Glass ceramics are inherently resistant to high temperatures, which allow them to hold together during a fire. In laminated glass units, an interlayer is placed between pieces of glass or glass ceramic, to hold together shards in the event of breakage caused by fire or impact. Similarly, security films are added to an exposed face of glass or glass ceramic to hold shards in place long enough to slow down an attacker. Additionally, some fire-rated products are made of glass ceramics specifically manufactured to withstand high temperatures (and thermal shocks, such as the hose stream test), for up to 180 minutes, depending on the specific application. Glass ceramics may be paired with security glazing products for added benefits.
Second, if the glass does break, it must stay within the frame. Applied film must cover the entire face of glass, not just what is exposed. Manufacturers often provide edge cover tolerances for this purpose. Otherwise, an impact or pressures caused by fire can simply push the glass out of its frame.
Third, the glass and frame must remain within the wall opening to maintain the integrity of the building envelope. That depends on installation into a similarly rated wall. This can be easily overlooked. Fire-rated glass, for example, must have the same level of fire protection as the frame, door, or wall it is being installed into. The same goes for other types of security glazing. On a recent project on which a security film was being installed around an entryway leading into a reception area, the designer had overlooked the 1 m (3 ft) of wall below the window. The security glazing product would only perform so long as the standard drywall installed around it would remain intact.