Laminated Glass: Separating Fact from Fiction
Laminated glass improves safety and sound attenuation, while strengthening windows and allowing for creative designs.
However, despite the popularity of laminated glass, there are a few misconceptions that remain.
USGlass magazine recently addressed some of these common mistaken beliefs:
Fiction: Fully Tempered Glass is the Only Safety Glass
Fact: Laminated Glass Also is Safety Glass
Many times, brochures or marketing will refer to fully tempered glass as safety glass and the only material that complies with codes. This isn’t entirely the case. USGlass interviewed Julia Schimmelpenningh, an industry technical manager for architectural products at Eastman Chemical Co. According to Schimmelpenningh, the laminated material simply needs to meet the requirements of CPSC 16 CFR 1201 or ANSI Z97.1 to be considered safety glass.
The building codes reference the performance and not the type of safety glazing except when glass fall-out is a concern. In these cases, they specifically reference laminated safety glazing (skylights, overhead, balcony, etc.),” Schimmelpenningh explains.
Fiction: Hurricane Glass is Bullet Resistant
Fact: Hurricane-Rated Glass and Bullet-Resistant Glass Are Different
Many schools already use hurricane glass that’s been tempered and/or glazed to be impact-resistant – but they assume that this protection extends to bullet resistance. However, bullet-resistant glass is significantly thicker than hurricane glass. It’s also cost-prohibitive to install bullet-resistant glass throughout an entire school. However, there are other ways to provide forced entry-resistance. Similarly, there’s a misconception that hurricane-rated glass alone is enough. Truthfully, the whole system has to be hurricane-rated to withstand storms, not just the glass.
Fiction: An IGU’s Outboard Lite Should be Laminated
Fact: This is Not Always Needed
USGlass spoke with Robert Carlson, who works in mechanical engineering at fabricator Tristar Glass in Tulsa, OK. Carlson stated that using an IGU with laminated glass provides protection and insulation for energy efficiency.
In a chemical factory where you’re worried about an explosion from the inside hurting people on the street it makes sense, but the laminated lite should be placed toward the area you’re trying to keep safe,” Carlson said. “If there’s wind or an explosion on the outside of the building then it will keep the people on the inside of the building safer if the laminated glass is the inboard lite.”
Putting the laminated glass as the outboard lite also increases the cost and challenge of fabrication.
Fiction: Exposed Edges on Laminated Glass Can’t Look Nice
Fact: Laminated Glass Can Be Made with An Attractive Edge
There’s a common concern among specifiers that exposed edges on laminated glass will be unattractive. While the edge of a monolithic lite looks smoother, there are also many ways to make laminated glass with an attractive edge. Several fabricators can make laminated glass with only a 1/16 to ¼-inch delamination of the glass, for example.
Fiction: Laminated Glass is Not Suited for Exterior Applications
Fact: Laminated Glass Can Be Used in Exterior Applications
According to Schimmelpenningh, laminated glass with PVB interlayers is well-suited for exposed and external applications. While earlier PVB interlayers were susceptible to delamination, this is no longer the case. As technology evolves, interlayers are now made with ever-evolving durability and capability.
Fiction: Increasing an Interlayer’s Thickness Improves Acoustic Testing
Fact: Using a PVB Interlayer Instead Provides Better Change
Increasing the thickness of a layer can impact sound attenuation, however, switching from a monolithic or insulating glass to a PVB interlayer provides the most significant change. And switch from regular interlayers to a sound control interlayers can make a big difference.
Fiction: A .030-Inch Interlayer Will Work with Heat-Treated Glass
Fact: A .060-Inch Interlayer is More Appropriate
Carlson explained to USGlass that he commonly sees specifications calling for a .030-inch interlayer of heat-treated laminated glass.
Due to the nature of heat treating, roller waves and distortion, you typically want to use a .060-inch thickness interlayer … It will fill any discrepancies between the profile of the two lites,” Carlson said. “People say they want .030 to reduce costs or they just pick an interlayer.”
Fiction: PVB is PVB
Fact: There are More Than Just PVB Layers
Specifiers often assume PVB is the only option for interlayers. However, there are other materials – such as ethylene vinyl acetate (EVA) or ionoplast. USGlass interviewed Ron Hull, Americas marketing manager for Kuraray America’s PVB division:
The specification might just list safety tempered or laminated glass but, for example, in glass for structural projects the specifier should be specifying a structural interlayer and not just laminated glass,” stated Hull.
This also applies for acoustic applications – Hull recommended specifiers specify an acoustic PVB instead of just PVB.
Fiction: EVA is Not a Strong Product
Fact: EVA is a Strong Product
Pete DeGorter, vice president of DeGorter Inc., told USGlass that there’s a misconception that EVA can’t receive approval for safety glass. EVA is the best option for open cap rail systems, where it’s supported by only one side.
It won’t allow the glass to fall if both lites break, but it’s not as rigid as ironplast,” per DeGorter.
EVA has a larger thermal gradient than PVB, meaning that it’s a suitable option for extremely cold or hot climates over PVB or ionoplast. This can make it a viable choice for certain projects.
Fiction: PVB Is Only for Automotive Applications
Fact: PVB Has Been Used Successfully in Architecture for Nearly 60 Years
While PVB was originally used primarily in car windshields, today it’s used in a larger variety of applications. According to Schimmelpenningh:
The products have evolved to meet the needs of the markets they serve and are no longer a one-size-fits-all product. In the architectural market, that means having the ability to act as a safety glazing, retaining glass shards for some time when broken and wet, and providing a mechanism to keep a building envelope intact, its occupants safe and comfortable, and the properties protected,” Schimmelpenningh says.
Clearing up these misconceptions about laminated glass can help specifiers choose the most effective glass, glaze and/or laminate for their project. Laminated glass is highly useful in acoustic applications for dampening noise. Have an acoustic project of your own? Contact St. Cloud Window to learn how our acoustic products complement the power of laminated windows.