Tempered glass and laminated glass are two of the most common types of safety glass. If you’re in the process of building or upgrading your home you may have already been asked to choose some safety glass for some of your windows and doors.

This article will review the differences between tempered glass and laminated glass and provide info around the following glass topics:

• What is laminated glass?
• What is tempered glass?
• Does tempered glass break? 
• Can tempered glass be repaired? 
• What glass should be tempered in your home?

^{Example of broken glass types. Image from Pioneer Glass.}

Safety Glass, why do you need it?

Building codes did not address safety glass concerns until the 1960s. Around this time hospitals were seeing thousands of patients each year for glass related incidents. Some of these injuries occurred in falls against glass shower door enclosures and glass patio doors. 

With injuries and lawsuits on the rise, the National Safety Commission organized a task force to reduce the number of glass-related injuries and deaths.

According to the National Glass Association, there are now 4 criteria that require safety glass:

1. The glazing (glass) is less than 18 inches above the floor
2. The top of the glass is less than 36 inches above the floor
3. The size of the glass exceeds 9 square feet
4. The glass is within 36 inches of where people walk

Any doors made of glass — sliding, French, or shower doors — are all always made of tempered glass.
^{**Consult your local building guides to confirm these parameters.}

Laminated Glass  

What is laminated glass?

Laminated glass is made of two pieces of regular or tempered glass sandwiched around a layer of clear plastic film (PVB). The set of glass is treated through a process intended to expel air pockets and then it is heated for an initial round of melting. After this, the glass is heated under pressure to create a finished bound product. Laminated glass can be made stronger by adding layers making the end product thicker.

The plastic layer of the film does give the glass a stretchable quality but don’t imagine the glass stretching like a rubber band. The laminated glass has just enough give and stick in it to hold the glass in place if it were to break.

What does laminated glass do?

When laminated glass was originally invented it was designed for use in car windshields to reduce the number of injuries in car accidents. If the glass is dealt with a high-intensity impact, one side of the glass can shatter without causing the other side to shatter. Even if the glass does break on either side the pieces will stay together resulting in a spider-web pattern.

Some additional benefits of laminated glass are that it reduces transmission of high-frequency sound (soundproofing) and it blocks 97% of ultraviolet radiation. One major benefit is that laminated glass with minor impact damage can be repaired with a special clear adhesive resin.

Where is laminated glass used?

In addition to being found in vehicles, laminated glass is also commonly used for the windows of tall buildings, skylights, balconies, and frameless glass railings. At Brennan, homeowners that live near an airport or golf course often request laminated glass. 

Tempered Glass

What is tempered glass?

Tempered glass is a piece of annealed (ordinary) glass that gets its safety properties from a heating and cooling procedure called “tempering”. The process involves heating the glass and cooling it immediately. Quickly cooling the incredibly hot glass causes the outside of the glass to harden quicker than the center. This process leaves the center in tension making the glass significantly stronger and more durable than ordinary glass.

Tempered glass differs from laminated glass in that it is a single piece of glass. Remember, laminated glass is two pieces of glass sandwiched around a piece of plastic film.

^{Compressive and tensile stresses in the tempered glass. Photo from Węgier Glass.}

What does tempered glass do?

Tempered glass, also known as toughened glass, is stronger than ordinary glass but can shatter. Similar to laminated glass, when the tempered glass suffers an impact it can break into a web-like interlocking pattern and remain within its frame. This is not always the case as the broken pieces only hold onto adjoining pieces and can fall out of their frame.

What makes tempered glass a safety glass is that it is significantly more durable than ordinary glass and it is designed to break into less harmful pebble-like pieces instead of sharp and jagged shards. 

Unlike laminated glass, tempered glass cannot be repaired. Laminated glass can be repaired in cases of minor damage but damage to any part of a tempered glass will eventually result in the glass shattering. The glass shatters because the balanced stresses in the glass are disturbed by the high-stress impact. 

Where is tempered glass used?

Like laminated glass, tempered glass is intended for use in areas where the glass can pose a risk to friends and family. If you're looking to know where tempered glass is required, by code, in your home please review this document from Anemostat Doors

Also, like laminated glass tempered glass is found in vehicles. While laminated glass is used in the windshield, tempered glass is required for use in car rear windows and passenger seat windows. Tempered glass is also found in skylights, refrigerator shelves, oven doors, storm doors, shower doors, and bathroom areas. 

Tempered or Laminated: How to choose the right glass for your job?

Keep in mind that both tempered glass and laminated glass qualify as safety glass and that laminated glass is more expensive than tempered glass. Although laminated glass is stronger than tempered glass, tempered glass is more often used in household windows and doors. Due to its expensive price, laminated glass is used sparingly in residential construction. 

Tempered glass offers strength and breakage-resistance but laminated glass provides UV-resistance, extra security, and soundproofing. Both types of glass are easy to clean and maintain as long as they are installed properly.

After learning about the benefits of safety glass it can seem like a good idea to use it in all applications, especially when considering them for your home, but opting for all safety glass can be very costly. Regular glass is perfectly adequate for most applications. In fact, the vast majority of window glass is not required to be tempered, but all door glass is tempered. If you have any questions regarding the use of safety glass in your home windows or doors, please reach out to us with any questions.