What is Tempered Glass?

tempered glass windows film alternatives

When it comes to building safety and security, glass windows and doors are a top concern. Since regular, annealed glass shatters so easily, it is a prime target for intruders and can be a source of danger in extreme weather circumstances when the glass may shatter, leaving sharp edges that can harm those nearby.

Fortunately, there are solutions to fortify glass windows and doors and improve overall safety and security. One of the solutions often offered is tempered glass. While tempered glass is useful in some scenarios, it isn’t the best solution in others. Here, we’ll explain what is tempered glass, what is tempered glass used for, and the best alternatives to tempered glass.

What is Tempered Glass?

When regular, annealed glass breaks, it shatters into sharp, dangerous glass shards and leaves behind ragged edges in the window frame. The broken pieces are collectively referred to as spall. In extreme weather or bomb blasts, these sharp pieces often fly through the air and injure those nearby. Spall is one of the leading causes of injuries related to bomb blasts.

To mitigate these injuries, scientists came up with a way to strengthen regular glass in the manufacturing process through intense heating, called tempering, to prevent spall.

The glass is heated to extreme temperatures and then rapidly cooled via blasts of air which causes the outside layers of the glass to solidify before the inside layers do. As the inside layers cool, they pull at the outer layers, creating tension and changing the properties of the glass.

Instead of shattering into dangerous pieces, when tempered glass is struck, it shatters into small, dull cubes which is much safer for those nearby.

What is tempered glass used for?

While tempered glass is very useful in many situations, it’s not the best solution when trying to increase security. Instead, you’re likely to find tempered glass used in other ways. It’s frequently used in mobile phones, phone screen protectors, kitchen appliances, and vehicle windows. In residential and commercial settings, here are the recommended uses of tempered glass:


Tempered glass, or some form of safety glass, is recommended in commercial settings and under certain circumstances in residential settings, depending on the size of the window and its proximity to walking surfaces.


Any swinging, sliding, or bifold door should use tempered glass, regardless of size.

Wet Areas

Glass in wet areas like shower doors in bathrooms and doors and windows around swimming pools and saunas should be made of tempered glass due to the increased risk of falls.

Near Stairs

Building codes require that glass near or adjacent to stairs and glass used for stair rails should use some form of safety glass, like tempered glass. Steps with glass surfaces should also be made using some form of safety glass.

Disadvantages of Tempered Glass

Now that you know some of the better uses of tempered glass, here are some of the disadvantages so you can better understand if tempered glass windows and doors are right for you:

Intruders Easily Gain Access

As we stated above, tempered glass is not the best solution to increase security in areas prone to smash and grab attempts. Although it is much stronger than conventional glass, when tempered glass does break it will completely shatter. This leaves you even more vulnerable to forced entry since criminals are so easily able to gain access by damaging just one piece of glass.

Expensive to Install

Tempered glass can’t be adjusted once it has undergone the tempering process, which means each piece of glass has to be custom manufactured. This makes it much more expensive to install than some other options, like security window films.


Impurities in tempered glass can cause it to spontaneously explode, creating dangerous openings and raining glass on anyone nearby.

Costly Replacements

Since any small injury to the window causes the entire window to break apart, it can be costly to maintain tempered glass windows since the entire window has to be replaced after any sort of impact or serious damage.

Tempered Glass Window Alternatives

Fortunately, there are solutions available that can both increase security and prevent dangerous shattered glass: security window films and polycarbonate security shields.

Tempered Glass vs Film

While tempered glass would require the replacement of the entire window, security films, sometimes known as safety films, are an option for those that are looking for a faster and more affordable solution. They are made out of multiple layers of ultra-thin plastics and adhesives which, when installed properly over the existing window, hold the glass together upon impact. This simultaneously slows criminals to prevent theft and also keeps those inside safe and protected from dangerous flying debris.

Tempered Glass vs Polycarbonate

Much like security films, polycarbonate security shields like DefenseLite are a retrofit solution which means they are applied over your existing windows. However, polycarbonate shields create a ventilated buffer zone to protect the original glass which saves you the hassle of a full replacement when damaged. Our engineered ventilation system protects windows from condensation, eliminating the need for costly maintenance.

These smash-proof polycarbonate panels deflect energy away, slowing criminals down and causing them to flee the scene. Since the original glass is left unharmed, there are no costly replacements with polycarbonate panels. This is a permanent solution, so the glass is always protected, keeping people nearby protected from dangerous glass debris in extreme weather or bomb blasts. They also provide additional benefits like noise reduction, UV protection, and temperature regulation. Installed by certified and trained professionals, DefenseLite retrofit panels are covered under warranty.

Improve Safety & Security with DefenseLite

Hopefully, you’ve found some answers to your questions about tempered glass and how it should be used. If you’re looking for a way to increase both safety and security in your residential or commercial building, contact us at DefenseLite for more information about our custom engineered polycarbonate panels.

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