December 28, 2020
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:
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.
Plan and prepare
While the details around multifunctional protection should be attended to during the design stage, there are numerous areas where installers hold responsibility for the security glazing product’s future performance. Proper glazing installation begins with appropriate upfront preparation. Before the glass product arrives onsite, it is critical to properly measure the openings. Window openings that are not square or plumb cannot be appropriately secured, so proper installation begins with appropriate measuring and an inspection of the openings.
This is also an excellent time to become familiar with the project’s shop drawings and installation instructions. The shop drawings will include specific details for the project, while the general installation instructions will provide some insight into how to handle most common conditions.
Once products begin to arrive on the jobsite, it is important to check the packing list thoroughly to ensure all the right parts have been received. The supplier should also include in the packing list every part’s specific placement. During this step, installers must inspect the material for damage. Superficial chips smaller than 4 mm (158 mils) are acceptable, but glass with wider or deep chips with V-profiles should not be installed. Damage to a product this critical could cause problems down the line. If signs of damage are noted, it is important to call the manufacturer immediately. The manufacturer will be able to inspect the glass to ensure its protective layers have not been compromised in any way and the product is still suitable for installation.
Protect parts onsite
If damage during shipment is cause for concern, then it is clear damage must also be prevented once the product arrives onsite. Proper care must be taken to prevent any damage to either the glass or the frame. This includes keeping materials away from water, mud, or cement/plaster spray, not stacking glazing units horizontally, and protecting the glazing after installation during the course of all future construction activities.
Installation instructions may also advise cleaning the glass prior to glazing. To prevent damage to coatings applied on the exterior surface, it is important to follow the manufacturer’s recommendations for cleaning. Generally, one would avoid the use of bristle brushes or other abrasive cleaning materials, and instead opt for a soft cloth or sponge.
Fire-rated and other security glazing products must be handled carefully due to their weight. Security glazing may be made up of multiple, thick glass lites. The glass alone may weigh approximately five to six times more than a standard tempered glass unit. As a result, these products are likely to require specialized equipment for handling. This may include a boom lift or power lift suction cups.
A level installation
Proper preparation lays the groundwork for installation in line with industry standards including ASTM F1233-08 (2019), Standard Test Method for Security Glazing Materials and Systems, and ASTM E2395, Standard Specification for Voluntary Security Performance of Window and Door Assemblies with Glazing Impact, and the National Fire Protection Association (NFPA) 80, Standard for Fire Doors and Other Protective Openings.
For doors and windows, openings must be plumb, true, and level. Installers must ensure any framing is also installed plumb and level. If not level, doors may bind up or fail to open and close or latch properly.
If field adjustments are necessary or hardware is removed for installation, it is important to ensure it is re-installed and adjusted properly. For example, factory-installed glazing beads in windows are often removed during installation. Since these small trim pieces are sized for individual applications, it is important to replace them precisely as they were removed. If an incorrect bead is installed, it could lead to small openings, thereby compromising the frame’s integrity.
For security film products, appropriate application and installation is critical. These thick polyester or polymeric films are useless unless they completely cover the entire piece of glass/glass ceramic, including the edge that is covered by the glazing stop or glazing bead. Without this critical step, the film might detach or the opening could be compromised in the event of an impact.
There are two typical methods of proper film installation. Wet glaze installation replaces the rubber gaskets in the window frame between the face of glass and the glazing stop with a silicone sealant that fills the gap between the frame and glass. This method allows some flexibility in installation across different frame types. A mechanical attachment system involves applying a metal plate or cable over the window film and screwing this secondary frame into the window frame and the wall. It is a particularly strong option as it anchors the security film to the building’s frame. However, attachment systems will not work with every type of framing system.
Security film adhesives are specifically designed to have the strength required to disburse the potentially intense energy of a blast or attack and transfer that load across the window opening. Swapping out this more expensive product for standard silicone caulking that may be more readily at hand on a jobsite will weaken the resulting system. Additionally, some contractors fail to use enough adhesive, neglecting to overlap both the film and frame. This is not the time to scrimp on materials, as this also negates the film’s protective abilities.
Think whole system
Fire-rated and security glazing units also require careful attention to the supplies used to install the product. For example, a fire-rated glass ceramic must be installed using fire-rated setting blocks and ceramic glazing tape or closed-cell polyvinyl chloride (PVC) tape (per their fire-rated listing). A bead of silicone sealant may be used for cosmetic purposes, but the foundation of the installation must be fire-rated.
However, glazing units face another potential installation risk: non-adherence to important code requirements. Sometimes, fire-rated glazing units are required to be installed as a rated assembly, meaning within an approved frame and wall opening. Other times, a fire-rated window will have different requirements than the surrounding wall. Understanding code requirements are critical to maximizing fire protection, investment, and resources.
Stoneman Douglas High School in Parkland, Fl., is a tragic example of the need to look at the protection provided by a full wall system. Police reports note the shooter in the 2018 attack had attempted to shoot through a third-floor window to target students leaving the school. However, that particular window had been strengthened with hurricane glazing in accordance with local codes, and withstood initial attacks. On the other hand, the 150 x 760-mm (6 x 30-in.) glass inset within the classroom doors was a standard, unreinforced product. While the shooter could not breach the door, he was able to fire through the glass to unlock doors and enter classrooms.
It is understandable clients working with tight budgets may only want to strengthen key areas of a project. While this is an effective first step, it depends upon critically thinking about how best to layer protection and from where a threat would approach. Installation is the final opportunity to consider the products going into a project and how they all work together to protect building occupants.
Handle with care
As fire-rated and other security glazing products become applicable for increasing numbers of applications, more contractors find themselves dealing with these heavy, and somewhat delicate, products. To ensure the project gets the level of protection specified, it is critical to follow the manufacturer’s installation instructions to the letter. No matter how many windows or glass systems a contract has installed, fire-rated and other security glazing should always be treated with care. A security glazing product is only as good as its installation and the surrounding system keeping it intact.
Stephanie Miller leads marketing and communications for Vetrotech Saint-Gobain in North America. Miller can be reached at email@example.com.
Source URL: https://www.constructioncanada.net/fire-rated-and-high-security-glazing-demand-a-secure-installation/
Copyright ©2021 Construction Canada unless otherwise noted.