Flying glass can be deadly: window film can strengthen glass to withstand everything from accidental impact to explosions.

Today's typical windows and fixed glass are designed to insulate against heat loss, block excessive solar energy, reduce air infiltration, control fading damage from ultraviolet radiation, and reduce noise transmission. Unfortunately, such otherwise sophisticated fenestration systems are not capable of effectively resisting the often powerful and devastating force of windblown debris, earthquakes, explosions, and even terrorist attacks.

Subjected to stress, existing glass often breaks into lethal shards that may be ejected from window frames, endangering facility occupants. If your facility contains unprotected window glass at or near floor level, glass observation rooms, glass doors, or other glass installations, both residents and staff are at risk of glass-related injuries and possible death.

Most injury from glass occurs when people accidentally walk into a glass door or window, resulting in trauma to the knee and upper leg from falling glass. The next most likely area of injury is to the head, neck, and shoulders. These injuries can lead to severe damage to tendons and loss of limb or limb function. Pieces of broken glass can be as deadly and dangerous as a knife.

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Hurricane-force winds can hurl an object through a window, causing glass shards to strike occupants. An explosion creates a shock wave that may atomize glass particles, which can be inhaled by building occupants and result in death. Some explosions are so powerful they can break glass in buildings blocks away, causing property damage that would not have occurred had the glass remained in its frame.

Window Glass Safety Options

Tempered glass is stronger than conventional glass and is commonly required in glass doors, shower doors, and glass and windows near the floor of a structure. If it shatters, the glass breaks in small pieces and is not as likely to cause injury. However, if broken by excessive force, tempered glass will fly into the room and endanger residents and staff. Conventional and tempered glass can be replaced with expensive laminated glass, two or more pieces of glass bonded by a polyvinyl butyral plastic interlayer. Compared with conventional and tempered glass, laminated glass provides increased resistance to glass breakage.

While laminated glass may be the logical choice in newly constructed facilities, security window film is a cost-effective alternative in existing facilities restricted by limited budgets. Security window film is made up of either optically clear, tinted, or reflective layers of polyester film applied to the interior surface of existing glass. Unfortunately, the benefits and relatively low cost of security film are not widely known.

Security window film can improve the ability of existing glass to mitigate the impact of accidental breakage. Its primary function is to hold glass intact if broken, preventing shards from becoming lethal projectiles or dangerous weapons. Because the film stretches without tearing, it can absorb a significant degree of the force of accidental or intentional glass breakage. The impact, when great enough to break the glass, is not enough to shear the film, and the broken glass is held intact by the film. Not only are there no injuries, but there is no damage to the building. If the force of impact breaks the glass and shears the film, the glass collapses attached to the security film with minimal damage and injuries.

Security film can be applied to single-pane and many types of insulating glass. Applied security window film is available with and without heat-blocking solar control capabilities.

Laminated Glass Versus Security Window Film

The performance of laminated glass and security window film depends on the relationship of each to the existing window frames. In the case of laminated glass, the window frame must support the weight and thickness of the glass for the total window system to resist impact. Installing laminated glass in existing window frames that are not designed to support this weight may cause the glass to separate from the frame when the former is stressed. Similarly, the ability of security window film to resist force may increase if the film is not only applied to the glass, but also attached to the frame. Many window film manufacturers market attachment mechanisms to secure film to the window frame.

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Independent tests verify that many security window films provide equivalent or, in some cases, superior ability to withstand stress compared with laminated glass. Also, laminated glass is not as energy efficient as some security films, resulting in a trade-off between energy conservation and safety/security performance.

Cost of Laminated Glass Versus Security Window Film

Installed laminated glass costs approximately $20 a square foot. The cost of conventional security window film is approximately $5 to $6 a square foot, although the most energy-efficient security films cost from $10 to $13 a square foot installed. A system to physically attach the film to the window frames would cost approximately $6 to $16 a square foot.

The optimum security window film not only provides increased protection from accidental and intentional force, it may also reduce a building's energy consumption. The cost of disruptions to staff and residents in removing and replacing existing glass compared with simply applying security window film to existing glass should be considered, as well.

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Marty Watts is President and CEO of V-Kool, Inc., Houston, Texas, a sales and marketing distribution company that offers security and spectrally selective applied films for architectural, automotive, and specialized vehicular applications. For more information, phone [phone] or visit www.v-kool-usa.com. To send your comments to the author and editors, e-mail [e-mail].