How Security Window Films Protect Glass and Save Lives

Posted by George Tanber on August 1st, 2017

Security window films are designed to increase the shatter resistance of glass, keeping the glass in place during catastrophic events. They are similar to regular window films in that they are polyester laminates and but are often used in buildings where bomb blast mitigation may be necessary or where dangerous foul weather events are frequently occur. However, the difference is that these products are usually thicker. They are offered in thicknesses ranging from 4 to 21 mils – and use a heavier and more aggressive adhesive system.

This material is available in clear or a variety of tinted, solar energy-reflective versions to get not only the benefit of increased glass strength but to conserve energy and make the building more comfortable.

How security window film is made and installed

Security window films are the result of a sophisticated manufacturing process in which the finest raw materials and state-of-the-art technology is used for the most effective shatter-resistant window protection.

Depending on fragment retention performance and budget constraints, shatter-resistant window protection can be installed on the glass only -known as a daylight application - or physically attached to the window frame, known as attached systems.

Daylight applications

The easiest, quickest and least expensive method of window protection is daylight application. This involves placing the fragment retention window films onto the vision area of the glass only. This approach will hold glass fragments together but does little to increase the blast resistance of the glazing system. If the blast pressures exceed the strength of the glass the entire filmed piece of glass could be pushed into or sucked out of the room. The purpose of the fragment retention window film is to hold the glass shards together in one piece. Since the glass fails before the film, minimum thickness fragment retention films are usually specified.

Attached systems

There are different types of attached systems. The attachment can be on one, two or all four sides of the frame and can be achieved with either mechanical (metal) or wet glaze (structural silicone).

Mechanical systems

Mechanical systems are installed using some type of metal batten system that is secured with screws or other fasteners. Mechanical systems can be configured for various strengths in that they can be attached on one side, two sides or on all fours sides.

Wet glaze systems

Wet glaze systems are similar to mechanical attachments except a silicone adhesive (caulking) is used for the attachment instead of a metal batten. This method is also sometimes called a chemical attachment. The film is applied to the vision area of the glass or daylight opening. Then, a bead of high-strength, high-quality structural adhesive is placed around the perimeter of the window frame.

A minimum half-inch of adhesive contact the film and a half-inch of adhesive contact the window frame. It’s easier to get a quality window film installation but it’s reliant on highly skilled installers.

This system may be the only choice for certain window frame types. It also may be ideally suited to historical buildings – especially windows with multiple small panes where a mechanical attachment can’t be used or won’t fit. Heavier gauge films are generally used with this system.

Top attachment (one-sided)

Top attachment (one-sided) is the method specified and used by the FBI. To keep the glass from being ejected out of the window frame and into the room, the film is overlapped onto the head of the window frame and mechanically attached with screws using a batten system. When the other three unattached sides of the glass fail, the film holds the glass together in one piece and the glass/film unit hinges up toward the ceiling and then falls back into place, similar to a doggy door. This system is designed to allow the glass to fail, which relieves blast pressures. As a result, the film itself does not see high pressures, and a minimum thickness fragment retention film generally is specified. This system should only be used with single pane glass.

Two-sided attachments

Two-sided attachments increase blast resistance to an existing window or glazing system. The film is overlapped onto two sides of the window frame – either top and bottom or usually side-to-side. The two unattached sides will fail and the blast pressure will be vented. The attached sides are designed to hold the glass at the window opening. This system is very strong. Failure of this system is usually a result of the window frame itself giving way. Since the film receives a much higher load than either daylight or one-sided attachments, heavier gauge films are required.

Four-sided attachments

Four-sided attachments are the strongest of the mechanical attachment systems. The films are designed to withstand tremendous loads, and the full pressure of a blast event is transferred to the window framing. Most standard commercial windows or storefront systems cannot withstand this intense pressure and the window frame system will fail before the film attachment does. Four-sided attachments are often specified in day care facilities – areas where no glass particles can afford to penetrate – or as an inexpensive insurance policy against a large blast event. Since the film will experience severe pressure loads, heavier gauge films are required.

For more information on security windows films and how they can protect your building and its occupants, contact a safety and security window film installation company with considerable experience.