A bulletproof glass entry system consists of ballistic windows, framing, and bullet-resistant doors. Other integrations include access control and some affordance for communication. When they’re ballistic, these systems can be very different from their non-rated counterparts. If you’re an architect working on a ballistic entryway, it’s important to understand the constraints and pitfalls that might affect your project.
Understand Ballistic Materials Characteristics Before Designing a Bulletproof Glass Entry System
It’s important to consider the ways in which ballistic materials differ from standard construction materials when designing a bulletproof glass entry system. Failing to do so might necessitate a re-design or cause the design to change significantly during engineering.
1. Weight and Thickness of Ballistic Materials
Ballistic materials are typically thicker and heavier than conventional building materials. That difference can vary significantly based on which ballistic glass you are using. Weight and thickness affect most design elements, because they require appropriate framing and structural support.
For example, a Level 1, laminated polycarbonate or glass-clad polycarbonate (GCP) window is roughly ¾” thick. A Level 1 insulated ballistic glass window is 1 ¼” thick. In monolithic acrylic, a Level 1 window is 1 ½ ” thick.
Although the GCP and polycarbonate windows are the same thickness, the GCP window weighs 50 percent more than the polycarbonate. The insulated glass and acrylic are even heavier at nearly nine pounds per square foot.
Most entryway systems will be at least Level 3. Level 3 bulletproof glazing is always a laminated material. It measures between 1” and 1 ¼” thick, and weighs between eight and 11 pounds per square foot. A Level 3 exterior glass door will be roughly five times heavier than a standard glass door. So, your framing and door hardware must be able to withstand the extra weight.
2. Design Elements Drive Costs Up
Many finishes (like edge polishing) on ballistic materials must be completed by hand, and can be done much more efficiently at specific stages in the project. For example, adding edge-polishing to a five-station teller line system late in the game can double the total cost of the system, due to the additional labor. While you can’t always control your clients’ design choices, it’s helpful to know how those choices impact the rest of the project.
3. Limited Available Dimensions
Most bullet-resistant glass is made of laminated layers of glass, polycarbonate, and interlayers fused in an autoclave. Because of the limitations on the sizes of autoclaves, laminated bullet-resistant glazing is typically not available in widths greater than six feet. Many architects assume bullet-resistant glazing is available in the same dimensions as tempered glass without realizing there are size constraints.
4. Glazing Warpage and Variance
Any laminated glass product is going to warp as it cools; ASTM standards allow for this. However, warping can be much greater in ballistic glass than most architects are accustomed to.
For example, ¼” tempered glass is essentially flat over a length of eight feet. By comparison, for Level 3 or 4 “no-spall” GCP ASTM standards permit up to ½” of warpage over eight feet. Even low-spall GCP (which tends to cool flatter), can still be warped by nearly ¼” over eight feet.
Once ballistic glass is fully framed, warping is rarely a problem. TSS’s framing systems have a gasket and wedge system designed to accommodate any variance. But designs that butt seams together might not be practical or look good, depending on the dimensions of the ballistic glass and how this element fits into the overall design and structure. If you’re not sure whether your design will work or if warpage will interfere, it’s best to consult with an expert.
Common Problems to Avoid When Designing a Bulletproof Glass Entry System
Given the weight, thickness, variance, and available dimensions of ballistic materials, there are a few common design practices that consistently require redesign when applied to a bulletproof entry system.
Choosing the Wrong Style of Speak Hole
Architects might design an oversized hole-and-backer system for a reception area. The goal is to allow visitors and staff to have a clear view of each other’s faces. But that large, hard, thick backer plate will muffle voices. (This effect is very pronounced with ballistic glazing, due to its unique composition).
TSS has specially designed solutions, like arch windows and baffle systems, that show the full face while making it easier to communicate through the barrier.
Eliminating Vertical Lines
In a standard entryway system, architects often eliminate vertical lines. This could be through a “floating glass” design, or by reducing glazing overlaps in a baffle window system.
However, altering the overlap in a baffle system either muffles communication or creates a shooting lane. Instead, we recommend using ¼” tempered glass, which weighs around three pounds per square foot, to achieve the floating glass effect.
Oversized Doors and Sliders
TSS experts often see oversized ballistic doors and sliding windows that would work fine with non-ballistic materials, but are too large to be functional in a ballistic barrier system. Again, this results from a failure to factor in the weight and thickness of ballistic materials—especially those at higher UL levels.
For example, Level 7 GCP weighs more than 23 pounds per square foot. TSS has seen beautifully designed, oversized horizontal sliding windows at this level of protection. But, the glazing alone would weigh nearly 300 pounds; the window would be inoperable and likely impossible to install using standard window hardware.
Similarly, a standard-size Level 8 bullet-resistant glass door weighs about 600 pounds and is four inches thick. TSS can make and install these doors, but they require special closers, hinges, and hardware to operate safely.
TSS Supports Architects Working on Bulletproof Entryway Projects
“When architects have a project, if it’s something they haven’t done before, just call us. Even if it’s only a half hour conversation, that gives us an opportunity to understand what you’re trying to achieve, and where the challenges may lie: What’s the traffic flow like at this entryway? What’s the functionality your client needs? How can we design all that in with an aesthetically pleasing system?” “Ultimately,” Jim Richards, CEO and founder of TSS says, “ if we can help make that architect successful, that’s what we want to do. That’s what we’re concerned about: making sure that it’s a successful project. That’s always our biggest area of concern.”
Contact our ballistic security experts to learn more about designing your ideal bulletproof entry system, or request a quote if you are ready to begin. Our team of experts look forward to speaking with you.