Architectural Glass Types: Annealed vs. Tempered Glass

Over the years the glass market has went through many technologies, some beneficial, some not, and some that are not necessary.

Types of Architectural Glass

Annealed, Laminated, Heat Soaked, Heat-Strengthened, and Tempered Glass

Architectural glass plays a crucial role in modern construction, offering a blend of functionality, aesthetics, and safety. As building designs evolve to incorporate more glass elements, understanding the different types of architectural glass is essential. These materials are tailored to meet varying requirements for strength, safety, energy efficiency, and design, allowing architects and builders to create structures that are not only visually striking but also highly durable and safe. Whether it's for expansive facades, energy-efficient windows, or safety glazing, the right type of glass can make a significant difference in a building's performance and appearance.

Annealed vs. Tempered Glass: A Detailed Comparison

Annealed glass is a soft glass that is heated up and then slowly cooled, and it typically breaks into long shards that can cause significant injury.

Tempered glass is a toughened glass that has been heated to a very high temperature and then rapidly brought back to room temperature. Tempered glass is four times stronger than annealed glass, and breaks into tiny pieces that look like rock salt. Typical applications include entrance doors and sliding glass doors.

Both annealed and tempered glass have unique characteristics that make them suitable for different applications:

• Strength: Tempered glass is up to four times stronger than annealed glass due to its specialized manufacturing process.
• Safety: Tempered glass shatters into small, rounded pieces, reducing injury risk, while annealed glass breaks into large, sharp shards.
• Applications: Annealed glass is commonly used in non-safety-critical applications like picture frames and single-pane windows, while tempered glass is preferred for safety applications like vehicle windows, shower doors, and architectural features where breakage resistance is important.

Other Popular Types of Architectural Glass

Laminated glass is two or more lites of glass bonded together under heat and pressure with a polyvinyl butyral (PVB) inner layer. Typical applications include impact, blast, security, and sound control windows. Laminated glass not only provides additional strength but also ensures that even if the glass breaks, the inner PVB layer holds the broken pieces together, preventing glass from scattering. This is crucial in applications like hurricane-resistant windows and security glass.

Heat soaked glass undergoes a second round of heating the glass in hopes of eliminating the nickel contaminates that sometimes occur in glass production. If nickel sulfide inclusions get trapped inside the glass, they could lead to spontaneous glass breakage later. Nickel sulfide inclusions are very rare in domestic produced float glass due to our strict quality standards in the United States. However, there have been recent problems with the glass coming from other countries that resulted in spontaneous glass breakage, so always vet your glass manufacturer. Most likely, if float glass produced inside the United States, there is not a need for heat soaking. Typical applications are overhead glazing and glass railing. Though heat soaking is not always necessary, it provides an extra layer of safety by reducing the chance of spontaneous breakage caused by nickel sulfide inclusions. This is particularly important for overhead glazing and glass railing installations, where spontaneous breakage could cause significant safety hazards.

Heat-strengthened glass is heated to a very high temperature and then rapidly brought back to room temperature. Heat strengthed glass is two times stronger than annealed glass and will crack into big pieces similar to annealed glass. Typical applications include spandrel glass applications. Heat-strengthened glass strikes a balance between strength and safety. It's not as strong as tempered glass, but it is twice as strong as annealed glass. Although it will crack into larger shards, the reduced likelihood of breakage makes it suitable for architectural spandrels and other applications where strength is required without the full safety of tempered glass.

What type of glass you choose is overall project dependent, if your project is blast or hurricane than laminated glass is crucial to protect the interior of the building. Many acoustically rated projects use laminated glass packages to achieve sound requirements but are not always necessary. For more questions on what type of glass to use for your project, please fill out our RFQ form.

Tints vs Low E coatings

When it comes to tints, the real question is, why do you want a tint? Is it for aesthetic reasons? Is it for performance? Once you determine the why behind tint you can start considering if you need it. Overall we have found that tinting glass for aesthetic reasons could make the building age faster than if you use clear glass. Choosing a timeless look over trendy tints will look better years after. Using tints to achieve better performance is ok. Still, there are better technologies on the market currently that will deliver the same if not better performance without the aging look tints can sometimes give building appearances. Something to remember is tinted glass almost always requires heat-treatment to reduce potential stress and breakage due to its heat-absorbing properties.

A better option than using tinted glass would be a Low E glass. Low emissivity glass is a transparent coating applied to a glass surface that reduces the amount of direct solar energy from entering the building. Low E coating reflects solar energy away from the glazing, often without requiring heat-treatment, and generally lower visible light reflection.

Below is a visual example of how tinted glass and Low E technology compare.

Gray tinted glass(left) vs Clear glass with Low E 366(right)

You can see that the building on the right looks fresher and more appealing with Low E clear glass.

There is a lot more we could go into when it comes to choosing what glass is precisely right for your project that we cannot begin to discover without project-specific information. Head over to our Rep Locator or fill out our RFQ form with questions.