Windows Security, Safety Glass

Typical insulated glass units (IGU) used in most residential applications comprise of 3 mm or 4 mm thick annealed glass panes; thicker panes of glass may be required for very large windows. Glazing at entrance doors, or where additional strength is required, should be heat-strength glass.

Other types of glass include the following:

Tempered Glass

Specially heat-treated to resist shattering. On impact, it shatters completely ”into thousands of small, blunt pieces” even if the initial damage is slight. Like laminated and wired glass, it is used in schools, public buildings and patio doors to prevent injury if accidentally broken. It is more expensive than normal glass and cannot be cut once tempered. Although generally more break-resistant than plate glass, tempered glass has disadvantages where security is a consideration. Because it shatters into many small, blunt fragments, it does not make the distinctive sound of breaking glass; therefore, it doesn't attract attention, and poses little physical danger to burglars.

Laminated Glass

Consists of a layer of tough, clear plastic sandwiched between two sheets of glass. The plastic holds the glass together when the pane is shattered. An example of laminated glass is the front windshield of a car.

Wired Glass

A mesh of thin wires is embedded in the glass to hold it together when broken. Suitable for use in skylights, sidelights, garage windows, basement windows and large windows in public areas.

Acrylic Plastic

A transparent, shatter-resistant material that offers a high-security alternative to glass. It can be cut with ordinary hand tools, making installation easy. Its surface hardness, however, is less than that of glass, making it easily scratched. Polishing compounds are available that will restore some of the original clarity.

Polycarbonate Plastic

The toughest glazing material you can buy. It will resist repeated blows from a sledgehammer. Two to three times as expensive as glass and, like acrylics, easily scratched. Although coated scratch-resistant varieties of acrylic and polycarbonate plastics are now available, both materials will become increasingly opaque after several years of use as a result of weathering and abrasion.

Polyester Safety Film

Existing glass can also be covered with this product to reduce the likelihood of breaking; also prevents shattering if breakage does occur.

Note: Be sure the plastic you choose is designed for exterior use. Plastics expand and contract more than glass and require different clearances and special flexible putty. Unless the sheet of plastic is mounted firmly in a sturdy frame and sash, you will be wasting your money. Consult the manufacturer or distributor before installing these