Weathering the Storm: Hurricane-Resistant Glazing System Trends

By Jordan Scott

Things have been fairly quiet lately when it comes to hurricane-related codes. The same can be said for glass and glazing products used in these applications, which haven’t changed drastically in recent years. What has changed, however, are the trends toward larger glass and more energy efficiency and how that combines with impact performance.

Dean Ruark, vice president of design engineering and innovation for PGT Innovations of North Venice, Fla., says that while hurricane codes and the markets that require them remain status quo, active storm systems in recent years are driving the adoption and evolution of hurricane-rated glazing products.

“There’s been a lot of awareness created from these storms about the benefits of impact-resistant, hardened envelopes,” he says.

While people recognize the need for impact protection, these products are not immune to the influence of modern trends. Ruark has noticed the increased use of larger expanses of glass and minimal, narrow sightlines.

“People want to bring the outdoors in. The places with hurricanes tend to have a beautiful climate for a good portion of the year. People there want large moving glass walls that they can shut and still have protection from the elements during a storm,” he says.

Storm of Awareness

Tim Greeson, outside sales representative for storefronts at Aldora Aluminum and Glass in Coral Springs, Fla., points out that each new size of hurricane-resistant glass has to be tested. He also says that though architects specify large glass lites, especially with low-E coatings, manufacturers often stock only certain sizes.

“If they are requesting oversized panels with a soft coat low-E we’ll sometimes add horizontals in the openings or manipulate the glass size to make it work,” he says.

The desire for energy efficiency among developers, architects and consumers is driving the use of new framing materials. Though thermally-broken aluminum systems are being specified, Ruark is also seeing polyvinyl chloride (PVC) with additives such as fiberglass to offer increased stability and a lower coefficient of thermal expansion.

“It gives us the ability to meet higher design loads and pressures with a nonmetal frame,” he says. “A lot of the industry’s attention has been on the next material with benefits beyond those of PVC that is manufacturing friendly compared to pure fiberglass.”

Hurricane Configurations

Laminated glass is the most common glass configuration for hurricane-resistant glazing systems. Ruark points out that while laminated glass has remained constant, the interlayers used are changing. Polyvinyl butyral (PVB) is the most common interlayer used in the impact industry. However, when working with larger glass or higher design pressures, Ionoplast can be preferred due to its rigidity.

“When we get above 32 square feet of glazing that’s when we go up to Ionoplast,” says Ruark, adding that there are also new interlayers such as extra stiff PVB that are being included in the mix.

Hybrid insulating glass units (IGUs) with laminated glass also are becoming more popular. Ruark credits the quest for lower U-factors for this demand. He’s even seen double laminated IGUs, though he says these are rare and used mostly to achieve high acoustical performance.

When designing laminated IGUs, the laminated lite could be either inboard or outboard. Ruark says that for most of PGT’s systems the laminated lite is inboard and the outboard, monolithic lite acts as a sacrificial or insulating lite.

“The benefits of this are two-fold. It works really well in Southern climates for energy efficiency. You want the low-E coating as close to the exterior as possible in places where it’s hot … In the event of a hurricane where the laminate lite is toward the interior, it serves to protect occupants so glass is not falling off or breaking into [a building],” he says.

Julia Schimmelpenningh, customer applications and support lab manager for Eastman Chemical Co. of Springfield, Mass., explains that the decision to orient monolithic glass on the inboard versus the outboard lite typically is driven by the window design and the location of the immovable glazing leg. However, occupant versus external safety also needs to be considered.

Monolithic Benefits

“When the monolithic is toward the outboard, the occupant tends to reap the protection, whereas when the monolithic is inboard, the chances of glass flying into the area is greater should impact occur. This has moved some systems to consider the use of double laminated IGU,” Schimmelpenningh says. “This allows for inboard and outboard protection from flying and falling debris while giving flexibility in glazing design. If a 2.29 mm (0.090 inch) interlayer was needed for large missile in a single unit laminated system, for a double laminated IGU, a split system of 0.76 mm (0.030 inch) outboard, 1.52 mm (0.060 inch) inboard may also work and offer the needed impact resistance and level of protection as well as other benefits such as sound control and solar performance.”

If the monolithic lite is the inboard lite then it should be tempered, according to Ruark.

Hurricane Center Predicts Active Season

In the past five years there have been six Category 5 hurricanes in the Atlantic Ocean. The frequency of such strong storms seems to be increasing and the National Oceanic and Atmospheric Administration (NOAA) expects an above-normal 2020 Atlantic hurricane season. The outlook predicts a 60% chance of an above-normal season, a 30% chance of a near-normal season and only a 10% chance of a below-normal season. The Atlantic hurricane season runs from June 1 through November 30.

The NOAA also predicts that there will be between 13-19 named storms (with winds of 39 mph or higher) and six to ten hurricanes (winds of 74 mph or higher), with three to six of those being major hurricanes, meaning they will be Category 3 or greater (with winds of 111 mph or higher). An average hurricane season produces 12 named storms, of which six become hurricanes, including three major hurricanes.

To view the laid-in version of this article in our digital edition, CLICK HERE.