Do Replacement Windows Need Tempered Glass?

Characteristics

• Manufacturers use heat or chemicals to strengthen tempered panes, making them two to four times stronger than regular windowpanes. Some tempered panes are designed to shatter into small pieces with blunt edges when the glass is broken to reduce the risk of injuring people nearby. Other tempered panes crack in a linear pattern when broken, but most of the fragments remain inside the window frame to prevent injuries.

Building Codes

• Window manufacturers market tempered panes for replacement windows in bathrooms, children's rooms and sidelights that flank doors. However, building codes usually require using tempered glass for replacement windows located in bathroom showers or above bathtubs and whirlpools. A window dealer or contractor in your area would know the codes you need to follow for window installations in your home.

Wildfire Protection

• A regular pane that's exposed to high heat from a wildfire may break in three minutes or less and expose the interior of a home to windblown embers or flames, according to the Insurance Institute for Business and Home Safety. However, tempered panes are about four times more resistant to breaking when exposed to a wildfire's heat. The institute recommends replacing standard windows with double-pane windows that have tempered glass in wildfire-prone areas. Some building codes in areas where wildfires commonly occur may require that all replacement windows have tempered panes.

Labeling and Costs

• You can identify tempered panes by looking for a permanently etched label on one corner of the glass. For example, you may see "tempglass" etched on a pane, along with American National Standards Institute (ANSI) code numbers. ANSI oversees the creation and use of guidelines that apply to businesses in construction and many other business sectors. Replacement windows with tempered panes may cost at least 15 percent more than standard replacement windows, according to the Center for Fire Research at the University of California.