Surviving the storm in style

In August 1992, Hurricane Andrew wrought devastation throughout far southern Florida, causing 65 deaths and $26.5 billion of damage. Andrew was the most-destructive U.S. hurricane on record until Hurricane Katrina hit two years ago. The deadly storm prompted legislators and building officials to toughen hurricane building codes, starting in Miami-Dade County and spreading through the rest of the state.

Faced with the most stringent hurricane building codes in the country, architects using lots of glass on their buildings looked to manufacturers to come up with tougher products to stand up to the codes. For the most part, design didn’t suffer.

“We haven’t had too many problems,” says Sergio Bakas, senior vice president of Arquitectonica in Miami, about designing innovative and interesting glass designs on projects in the region. “At this point, most of the manufacturers have a variety of products that meet the code. We often look to providing impact glass rather than shutters.”
Impact laminated glass and reinforced metal framing systems made glass façades possible for architects in the region, Bakas says.

However, segments of the market calling for zero sightlines weren’t being served by the current hurricane-resistant glazing innovations, says Angelo Rivera, vice president of Faour Glass Technologies in Tampa, Fla. “Before the change in building codes, architects and designers had great flexibility in the use of glass to provide clear unobstructed views and bring the outside in. Since the code changes, these previously clear views have required bulky metal systems to support laminated or tempered glass,” he says.

Sol Fleischman, chairman and CEO of FleischmanGarcia in Tampa, says the codes created roadblocks for glass wall applications that previously used butt-glazed systems, forcing architects and owners to make concessions.

“We found that we could not do the butt-glazed systems that we’d done for years because of the new Florida Building Codes, especially in coastal areas—the high-end custom projects with walls of glass from floor to ceiling, now had views blocked with framing,” Fleischman says.

Called on by Fleischman and other architects to eliminate the problem, Faour Glass Technologies started work three and a half years ago to develop an impact-resistant butt-glazing system.

Company employees set out to develop the system with the following objectives:

• Eliminate vertical and horizontal metal mullions
• Utilize high-tech hardware to fasten the glass panels
• Develop a system with flexibility in design and clear sight lines.

Faour Glass met their objectives and applied for a patent on the technology in July.

In the test lab
Butt glazing by definition eliminates structural supporting mullions along the edges, using structural silicone instead. Traditional systems fail the required impact and cycle pressure hurricane code tests, Rivera says.

“Typical butt-glazed systems cannot survive hurricane impact tests due to minimal surface areas for silicone attachment and lack of support at the joint, which causes them to detach during cycle or impact tests,” Rivera says. 

To develop a system that could pass the tests and meet the code, Faour Glass officials needed thick, strong glass to stand up to large missile impact and flexibility to sustain wind pressures.

Faour Glass worked closely with hardware supplier Custom Hardware Manufacturing Inc. of Keokuk, Iowa; hurricane glass manufacturer Dlubak Corp. of Blairsville, Pa.; and adhesive and sealant company Dow Corning Corp. of Midland, Mich., to make a system that would solve both impact and flexibility problems.

The hardware proved the biggest challenge. “We knew we wanted to incorporate a spider type fitting system,” says John Faour, president. “We concentrated on the failure mode surrounding the hole and finally determined the best approach would be to eliminate the hole completely.”

Faour Glass officials worked closely with CHMI to develop a fitting that could be essentially glued to the interior side of the glass.

“Our involvement started in October [2006] when I sat down with John Faour at glasstec,” says Andrew Chatfield, vice president for CHMI, referring to the show in Dusseldorf, Germany. “They needed a fitting with a slight change in the way it grabs hold of the glass.

“Instead of having a flat face bonded to the glass, we developed a fitting with concentric circles on the face that increases the area of contact, making a stronger bond,” Chatfield says.

Traditional fittings that require holes drilled in the glass diminish glass strength and provide much less flexibility, he says. The bonding system, in addition to Dow 795 silicone sealant, allows movement of the lites, enabling it to pass the cycle tests.

The adhesive provides more than enough strength for the system, Chatfield says. “The bond is stronger than the glass itself. You will pull the face of the glass off before the bond would break,” he says.

For the glass lite, team members experimented with various interlayer configurations through computer modeling and physical testing, says Chris Cotton, vice president of engineering for Dlubak Corp. “Dlubak Corp. supplied a glass-clad polycarbonate to Faour’s Glass for the … butt-glazing system,” Cotton says. “Glass-clad polycarbonate was the product of choice because it tends to be more rigid than some of the current laminates available. Due to its rigidity, it will typically withstand high loads during the testing and is also a great security product for high-end applications.”

The system has additional glass layers, making it about twice as thick as traditional butt-glazed systems.

After years of development and testing, team members developed the right combination and quality of components that passed both impact and cycle tests, Faour says. “Although the glass broke during tests, the combination of the glass attachment system, glass makeup and silicone maintained the glass system in place to successfully pass the tests,” he says.

In the real world
The system is an important innovation in impact-resistant glazing—Rivera says it is the first butt-glazed system to have passed the Miami-Dade hurricane tests. Architects say the high cost of the system makes it applicable for only specific projects.

“By nature, it’s expensive, as it requires glass of exceptional thickness,” Rivera says. “You have to get the right client with a taste for contemporary style that is going to pay the premium for these glass walls.”

Bakas says a system such as this lends itself to small, but important, accents in a building. “Architects are limited in quantity and only afford using these kinds of things as features in lobbies and accent areas,” he says.

Faour Glass has already been targeting those high-end applications, Rivera says. “This system will be targeted toward projects requiring high-impact views, such as showcases in a high-end auto dealership, mega homes in coastal areas or penthouse views—applications where the view is a key component,” he says.

So far, the impact system has been specified for a BMW dealership and a 20,000-square-foot coastal home.

Fleischman says he met with Faour representatives and is looking for projects where he can use the system. “We’re very excited about Faour’s new tested butt-glazed system,” he says. “We’ve been at them for years to develop something like this and certainly plan on using it in the future. Architects and clients will benefit.”