Impact Resistant Glazing - 11/22/2004 - Home Condo Doors Windows

Impact Resistant Glazing

Impact-resistant glazing is available in two forms: laminated glass and shatter-resistant films.

Laminated glass consists of two or more panes of any type of clear glass bonded together with a plastic interlayer, usually polyvinyl butyral (PVB), which tends to hold the glass together upon impact. Depending on the application, the plastic interlayer ranges in thickness from .015" to .090" and can be ordered in various colored tints. Laminated glass is widely used in automobile windshields and commercial construction, and is now available for residential windows. Laminated glass, or impact-resistant windows can reduce the risk of window failure and personal injury during tornadoes, hurricanes, and explosions, and deter burglars from gaining entry into a home.

A less expensive alternative to laminated glass, especially for retrofit operations, is shatter-resistant film. These specially designed films are placed with an adhesive over the interior side of existing window glass, and are designed to hold the shards of broken glass to the film after an impact occurrence.

Impact-resistant windows contain laminated glass similar to that used in automobiles. When struck with flying debris, the glass cracks or shatters, but the laminate holds the window pane together, and glass fragments will tend to adhere to the plastic interlayer. This prevents the penetration of the building envelope and the consequential structural and water damage or loss due to burglary.

Several impact-resistant windows have passed Southern Florida's "large missile impact" test, resisting a 2 x 4 stud fired at the window at 80 miles per hour.

	When struck with flying debris, the glass cracks or shatters, but the laminate holds the window pane together, and glass fragments will tend to adhere to the plastic interlayer.
	This prevents the penetration of the building envelope and the consequential structural and water damage or loss due to burglary

According to an independent study commissioned by the North American Laminated Glass Information Center, laminated glass windows can add from one to two thousand dollars to the price of the average new home.

Not Applicable

Impact-resistant glazing or other window impact protection methods are required in the building codes of some areas prone to hurricanes and tornadoes. They have gained acceptance in the building codes in portions of Florida and Texas. Laminated glass should comply with local building codes, applicable ASTM standards, Consumer Product Safety Standards and SGCC/ANSI Z97.1 - 1984 (Rev. 1994).

Not Applicable

Laminated glass windows are commonly installed in a similar manner as standard windows. Instructions and details, however, differ between manufacturers. Due to the increased weight of laminated glass, stronger balancer springs may be needed. If insulated glass is specified, the air space between the two panes may be occupied by the plastic interlayer, and thermal performance may be diminished. In order to keep an air space and the plastic interlayer, window sashes will be wider than normal, and require wider sashes and frames to accommodate the thicker glass and sash. Careful consideration should be given to the design and strength of the window frame assembly, and the fastening methods that attach the sashes to the frame and the frame to the building.

Installation of shatter-resistant window film is typically performed by a manufacturer trained installer. A special adhesive is applied to the window glass and then the film is pressure applied by hand.

Varies with manufacturer.

Unlike other methods for severe weather preparation such as shutters and plywood, impact resistant windows are permanently in place and do not need to be moved to prepare for an impending weather event. Impact resistant windows can protect occupants from accidentally falling through windows or from being injured by airborne objects. The windows have no effect on the appearance of the home.

According to manufacturers, laminated glass does a better job absorbing outdoor noise and blocking ultraviolet rays that can fade carpet and furniture. Since about 99% of the ultra violet rays are blocked, there is some potential energy efficiency enhancement by decreasing the solar gain and reducing cooling loads.