Where is Tempered Window (Glass) Necessary, and What Does it Do?

Where is Tempered Window (Glass) Necessary, and What Does it Do?

August 30, 2017
Martin Whitmore, President of US Window & Door
Aluminum Windows

Tempered glass is that which has been treated to make it up to five times stronger than conventional glass. The treatment involves rapid heating of the glass followed by quick cooling, which makes the glass stronger and changes the way it breaks. What does tempered window (glass) do? When it shatters, it turns into small square pieces that are less likely to pose a safety risk. Here, readers can learn what it is and where is tempered window (glass) necessary.

Following Residential Building Codes

As mentioned above, when conventional glass breaks, it usually forms dangerous shards. When the glass is heated and rapidly cooled, it becomes tempered or safety glass. In most places, residential building codes answer the question of where is tempered window (glass) necessary.

Tempered Glass in Doors

According to the International Residential Code, you must temper all glass and panels in swinging, sliding, operable, fixed, and bifold doors, regardless of the panel’s size. Additionally, it is required to temper any glass located within 24″ of a door if the bottom edge is less than five feet above the floor. While the code applies to every home in the US, some states’ laws have stricter requirements on where is tempered window (glass) necessary

Using Tempered Glass in Windows

Why is tempered window (glass) necessary:

-The window measures more than nine square feet

-It has a bottom edge that’s under 18″ from the floor

-It has a top edge that’s more than three feet above the floor

-There’s a walkway within three feet

Unless your window meets all these criteria, it’s not a situation where is tempered window (glass) necessary.

Using Tempered Glass in Windows

Milgard Tempered Windows

It is necessary to temper all glass next to stairs, landings, and ramps if it is within three feet of a walkway and the glass’ exposed surface is less than five feet above that walkway. This is when is it a good idea to use tempered window (glass).

Tempered Glass in Wet Areas

The greater risk of slip and fall injuries in wet areas means that bathrooms, saunas, and hot tubs are places where is tempered window (glass) necessary. You must temper all glass if its bottom edge is less than five feet above a walking or standing surface such as a shower floor. Where a hot tub is outdoors, all glass must be tempered if the bottom edge is less than five feet above the walkway and five feet away from the water’s edge, according to the International Residential Code.

Do Older Homes Have (or Need) Tempered Glass?

In older or renovated homes, there may be glass in windows and doors that would be unsafe by today’s stricter standards. Because non-tempered windows are a definite safety concern, renovating an older home is another situation where is tempered window (glass) necessary.

The Dangers of Non-Tempered Glass

If a door or window with non-tempered glass breaks, the sharp pieces of glass are likely to fly around or fall off. These large shards of glass can be dangerous to adults, kids, and even pets. On the other hand, if tempered glass breaks, it breaks into small square pieces much like a car windshield would. Therefore, if a piece of glass is more likely to be broken or hit, it’s in a place where is tempered window (glass) necessary.

Is it Necessary to Worry About a Tempered Glass Broken Window

Toughening a piece of glass provides several advantages, but making it unbreakable is another matter entirely. While tempered glass is stronger than conventional annealed glass, and it’s safer to handle if it breaks, it still poses risks in certain situations.

Can Tempered Glass be Cut to Size?

During the tempering process, the glass is subject to high heat and fast cooling. Once you temper the pane, it can’t be modified, or it may break. While it’s impossible to cut a piece of tempered glass to the correct size, it can be cut before it is tempered. When a homeowner or customer is in a situation where is tempered window (glass) necessary, they should get the glass sized before it is tempered.

Wood Doors - Single Wood In-Swing Door

Tempered vs. Annealed Glass

Both tempered and annealed glass are modern and wildly available, and they’ve been successfully used in a variety of applications. When determining where is tempered window (glass) necessary, customers should keep a few things in mind. Below are the basics of tempered and annealed glass.

Tempered Glass Provides Greater Durability

A significant difference between annealed and tempered glass is the level of durability provided. As shown here, tempered glass is much stronger than annealed glass; it will hold up to additional wear and tear, and it’s usually harder and thicker. That means there’s less worry about breakage if a window or door panel has tempered glass.

Cost of Tempered Glass

Another big difference between tempered and annealed glass is the cost. Tempered glass requires a more significant upfront investment, which makes annealed glass a common choice among budget-conscious customers. Most of the least expensive windows on the market are made of annealed glass, as tempered glass takes longer and costs more to manufacture. However, when you consider the long-term costs, tempered glass is cheaper in many cases.


Another area where these glass types differ is safety. When annealed glass breaks, it creates jagged, sharp shards that fly everywhere and pose a severe risk of injury. As mentioned here, tempered glass breaks into round, small pieces. Therefore, when safety is a primary concern, it’s an area where is tempered window (glass) necessary.


When choosing between annealed and tempered glass, the customer should consider how and where it will be used. If the glass is going in a lightly-trafficked area where it will remain untouched, a piece of annealed glass may be sufficient. However, if the glass is going in a highly-trafficked area, tempered glass is the best, safest, and most cost-effective choice.