Window Security Film Doesn’t Stop Bullets

Once again, we’re hearing a lot about security film for windows. Schools are especially interested in these films, which are often advertised as a viable DIY bullet-proofing solution for facilities with tight budgets. However, while window security film can be part of a comprehensive plan to harden your building security, it does not provide meaningful ballistic protection.

In the past, we have not found any security film products that verifiably performed as described. (In contrast, UL-rated bullet-resistant components and systems are always tested under rigorous and reproducible conditions by an established NRTL.)

But times change. So we contacted Brad Campbell, an industry expert who draws on over two decades of experience with all sorts of window films.

We asked Brad: “Have security films improved so much in the last five years that they can now offer some level of meaningful bullet resistance?”

Brad’s answer was simple and complete: “No.



Recent Advances in Window Security Film

Brad is quick to point out that there have been great strides in window security film over the last few years. He has seen glass companies constructing viable security solutions using layers of extremely thick security film, interleaved with layers of hefty heat-treated and annealed glass, then bonded with a specialized film-mounting solution. The result: remarkably rugged glass that reportedly stops some pistol calibers under some conditions.

“It’s quite impressive,” Brad says, “but the whole thing just seems like a really expensive, difficult way you can do much more easily by using other solutions,” such as commercially available UL-rated glass-clad polycarbonate.

“If they’re getting the results,” Brad continues, “and the customer wants to go through it, and it’s actually working to what their specification is claiming, that’s great.  At least people are getting protected. But to me, it’s kind of a long way around the bend to get to the same result.”

But companies specializing in security films aren’t enthusiastic about these new solutions. The major problem: confusion. Security companies and contractors are finding themselves flooded with calls about these cheap, easy aftermarket “bulletproof” films for standard windows.

“Guys are misinterpreting the data,” Brad says, “misinterpreting the whole concept. As a result, more people are erroneously claiming that a standard security film applied to a standard window will stop bullets.”

Window Security Films Are Misunderstood And Misrepresented

Without a doubt, some of the journalists, contractors, consultants, and companies promoting “bulletproof” films simply misunderstand the products. They see videos online, or read a report without fully understanding the testing conditions, and jump to a conclusion.

“That said,” Brad adds, “there’s certainly nefarious actors here.”

As an example, Brad pointed to a prominent security film manufacturer who specifies that their films can increase a window’s bullet resistance to a UL Level 2 or 3.  (That would stop clusters of three shots from a .357 or .44 Magnum pistol.)  The problem? They fail to clearly indicate that they tested their films on half-inch thick annealed or heat strengthened glass. Such glass is roughly four times thicker than standard residential glazing. Even skyscraper windows, which most building codes demand, must be very strong and are still just two quarter-inch panes separated by a roughly half-inch air gap. Such a configuration is nowhere near as strong as a single solid half-inch pane.

“That’s nefarious,” Brad says. “That’s really profiteering.  It’s an evil thing to do.” Worse yet, it runs the risk of fueling a backlash against security films which, when used properly and for the right application, are a fantastically cost-effective way to increase security, especially when blasts or forced-entry are a concern.

Eight Levels bullet resistance

The Role of Window Security Films in Ballistic Security

According to Brad, there are “two ways to look at a gun-wielding attacker and window film. One is that we’re actually going to try to stop his ability to shoot through the window.”

That’s not going to happen.

But the second scenario is an absolutely legitimate use of security films. “We’ll delay [the shooter’s] ability to get in the building.” Brad continues. “Even if it’s only a few seconds, that can be the difference” between an emergency and a tragedy. “Window films are a really good, cost-effective solution there — if they’re properly applied, and if they’re properly attached to the frame.”

Those two ifs are important: Window films are reliable only when properly applied and anchored.

A “security film” window treatment has two components. There’s the film itself, which is usually a multi-layer cross-laminated plastic film applied with a water-based solution. Then there’s the structural silicone sealant (a sort of heavy black caulk, like Dow Corning 995). The film absorbs the force, while the structural sealant anchors the film to the building. By securely anchoring the film, the force can dissipate into the structure, rather than blasting the window out of its frame.

The Proper Application of Window Security Films

Brad explains: “When the film is properly attached at the frame [on the interior of the glass], it creates a net effect, like a trampoline. You can get a Level 2 GSA performance condition for blast because the film is stretching and pulling against the frame. It even buckles the [aluminum or steel window] mullions, but remains intact with minimal spall.”  (“Spall” are dangerous chunks and flakes knocked off the window; in this case, flying shards of glass that might injure occupants.)

GSArefers to the GSA/ISC Blast Resistance Criteria.  This is the forced-entry and blast-rating standard used by the US government for federal facilities. The criteria specify the exact dimensions of a dummy room used to test the blast-stopping characteristics of a window when it’s confronted with the sort of peak pressures and impulses generated by bombs in the range of a suitcase bomb to a van loaded with explosives.  A “Level 2” window will weather such a blast without breaching.

According to the GSA/ISC glass hazard rating scheme, with a “Performance Condition 2” window: Glazing cracks but is retained by the frame. Dusting or very small fragments [of spall] near sill or on floor acceptable.

You can get that enormous boost in forced-entry and blast security with an aftermarket film on your existing windows and the entire installation process takes no more than a weekend.

But it still won’t stop a bullet.

As Brad reminds us, “stopping a bullet is a completely different story.”

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