Written By: Brad Campbell | September 9, 2021
A building's windows and doors are its weakest points. They're the fastest way in during a break-in attempt, and they're usually the first thing to fail when storm debris starts flying.
Impact glass exists to mitigate those risks, but it isn't just one product. It's a category of safety and security glazing that covers a few distinct types of glass and non-glass glazing, each built differently and offering impact-resistant performance in different ways.
This comprehensive guide walks through what impact glass actually is, the three main types available, how they're tested and rated, and how to figure out which one fits your property and needs.
Impact glass is specialized glazing engineered to absorb and resist the force of impacts without shattering or allowing a breach, whether that force comes from a sledgehammer, a crowbar, a fired round, or a 2x4 traveling at hurricane wind speeds.
Standard annealed glass shatters into large, sharp shards under relatively light impact and offers almost no resistance to a determined attacker or flying debris. Impact glass is built to do the opposite: stay intact, hold its shape, and continue functioning as a barrier even after it's been struck.
While the exact composition of impact glass varies from one manufacturer to the next, there are generally three categories of impact glass: laminated security glass, polycarbonate security glazing, and glass-clad polycarbonate (GCP). Each has a different formulation, and each performs differently.
Impact glass also runs along two broad performance tracks: non-ballistic and ballistic.
Non-ballistic impact glass is built for forced entry resistance and storm damage protection. It's designed to stop a crowbar, a sledgehammer, a brick, or wind-driven debris from breaching the opening. This is the right category for most commercial storefronts and any property in a hurricane-prone zone where the primary concern is break-ins or storm exposure.
Ballistic impact glass is built for active threat protection, meaning it's rated to stop or slow actual gunfire. It's tested and graded for bullet resistance, which assigns levels based on the caliber, round count, and firearm used in testing. This is the category for properties facing a real risk of an armed intrusion or active shooter event: schools, government buildings, banks, and religious facilities are common applications.
Laminated security glass is made by bonding two or more layers of strengthened glass together with a thermoplastic interlayer material, typically PVB, in between the layers. When it's struck, the glass can crack, but the interlayer holds the broken pieces in place instead of letting them fall away or fly inward. That's what separates it from ordinary annealed glass: a crack doesn't mean a breach.
This construction makes laminated glass useful for both forced entry resistance and windborne debris protection, since a single hit generally won't let an intruder or storm debris through the opening. It's available in a range of thicknesses and interlayer types, so protection can be scaled to the application, and select laminated security glass makeups can also be rated for ballistic resistance.
Laminated glass is generally the most cost-effective entry point into real impact resistance. Its limitation is that, unlike polycarbonate-based options, it can eventually be defeated by sustained or repeated blows.
Polycarbonate security glazing contains no glass at all. Instead, it's built from one or more layers of impact-resistant plastic, primarily polycarbonate, sometimes combined with acrylics, and it's the toughest single-material option on this list.
Polycarbonate absorbs impact energy instead of transferring it into a crack. Security-grade polycarbonate panels resist repeated, high-force blows without shattering, cracking, or dislodging from their frame, which is why they're the standard choice for smash-and-grab-prone properties like luxury boutiques, pharmacies, jewelry stores, cannabis dispensaries, and storefronts in high-crime areas.
Because it's a soft plastic surface relative to glass, polycarbonate is more prone to surface scratching and yellowing over time, which is why quality panels are treated with an abrasion- and UV-resistant coating. Without that coating, a polycarbonate panel can scratch, yellow, or haze with prolonged sun exposure.
Full polycarbonate glazing can also be manufactured to ballistic-grade specifications, but for the highest ballistic ratings and long-term surface durability in high-traffic areas, glass-clad polycarbonate is typically the stronger choice.
Glass-clad polycarbonate combines a hard, laminated glass exterior (the attack side) with a polycarbonate interior (the safe side), bonded together into a single sheet. It's built to combine the best properties of both materials: the surface hardness, scratch resistance, and traditional glass appearance on the outside, with the flexibility and near-unbreakable toughness of polycarbonate absorbing the impact on the inside.
GCP is generally considered the strongest and most versatile impact glass category available. It's rated for the highest levels of forced entry and ballistic resistance, and because the polycarbonate core doesn't shatter or spall, it keeps functioning as a barrier even after the glass face has cracked.
The tradeoff is cost and weight. GCP is the most expensive category of impact glass, and it's typically heavier than full polycarbonate. It's most common in government buildings, banks, detention facilities, schools, and other high-risk sites where the highest available protection is worth the investment.
Impact glass is tested against published impact resistance standards, and the specific standard matters because different tests measure different threats.
For windborne debris resistance, one relevant standard is ASTM E1996, the specification covering exterior windows, curtain walls, doors, and impact protective systems impacted by windborne debris in hurricanes. Products certified to this standard are tested using the ASTM E1886 method, which combines large and small missile impact tests with cyclic pressure loading to simulate real storm conditions.
Miami-Dade County runs its own approval program on top of the national standard, using ASTM E1886/E1996 as a baseline and adding further requirements before issuing a Notice of Acceptance (NOA). A Miami-Dade NOA is one of the most demanding impact glazing approvals in the country, and products carrying it are generally accepted anywhere in the US.
Forced entry resistance is tested separately, under standards like ASTM F3561 and ASTM F3038, which measure how long a product resists deliberate breach attempts in an active threat or riot-type scenario, respectively.
Ballistic impact resistance is its own category, rated under UL 752, which grades products by the caliber, number of rounds, and range they're tested to withstand.
It’s important to note that every impact glass testing standard looks at different performance characteristics, so while it’s possible for a product to carry multiple impact resistance ratings, passing one test doesn’t necessarily mean it passes another. For example, a product rated for windborne debris resistance isn't automatically rated for forced entry or ballistic threats.
It’s always important to confirm exactly which standards a product has been tested to before assuming it covers a specific risk category you’re concerned about protecting your property against.
The right type of impact glass for your property depends on a few factors:
Riot Glass builds retrofittable impact-resistant security glazing systems across two product lines. The AP-Series is full polycarbonate glazing. The RG-Series is glass-clad polycarbonate, built with a laminated glass exterior over a polycarbonate core. Panels are available in both forced-entry-grade models and with ballistic ratings up to UL 752 Level 7.
Both lines can be retrofitted into or onto existing windows, doors, and storefronts without a full frame replacement (thanks to the Universal Framing System), and both are backed by third-party lab testing. You can review the underlying test data on our lab results page.
When a window fails, the broken glass is usually the smallest problem. A forced entry can mean thousands of dollars in stolen inventory or equipment, plus repair costs and downtime. A breached window during a storm exposes the interior to wind and water damage that's often far more expensive to fix than the window itself and isn't always fully covered by insurance. In a worst-case active threat scenario, the stakes are much higher.
Investing in tested, rated impact glazing before an incident happens is almost always cheaper than dealing with the aftermath of not having it.
Laminated security glass, polycarbonate security glazing, and glass-clad polycarbonate.
Glass-clad polycarbonate, since it combines a hard glass exterior with a polycarbonate core that doesn't shatter.
Not automatically. Ballistic resistance is a separate rating (UL 752), though select laminated, polycarbonate, and GCP products are tested and rated for it.
Yes, in most cases. Laminated glass and full polycarbonate panels typically retrofit onto existing frames, and GCP can too, depending on frame capacity.
Look for a Miami-Dade notification number, which confirms the product passed the county's impact and pressure testing protocol.
For more information on impact-resistant glazing from Riot Glass, contact our team today.
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