Invisible Forces

As Buildings Become Increasingly Secure, Will Glass Still Have a Role in Future Designs?

By Ellen Rogers

Buildings today are designed increasingly with an eye toward threat protection—both natural and man-made. From hurricanes and tornadoes to terrorist attacks and school shootings, architects are searching for options to design safe and secure structures that are attractive and still employ the use of glazing to provide bright, natural light.

According to Paul Beers, owner of CGI Consultants in West Palm Beach, Fla., over the past ten to 15 years there have been significant increases in designs for bomb blast and hurricane protection.

“Glass products can meet any type of threat, so there is no need to return to a bunker mentality. Those products are now available and are well tested,” he says, adding that insurance companies have also been influential in retrofits.

“Many owners now replace their windows just to meet insurance requirements, which have been a huge driver in the marketplace.”

While the products themselves may not have seen drastic change over the past decade-plus, some design practices and the way glazing is being used have evolved. There’s also been a growing level of awareness and understanding that’s shaping where and how these products are used.

Increasing Awareness

After events such as the bombing of the Beirut barracks in 1983 and the Alfred P. Murrah Federal Building in Oklahoma City in 1995, the glass and glazing industry saw significant inter-est in the development and awareness surrounding bomb-blast protection. Carrie Davis, a project engineer, practice leader and principal with Protection Engineering Consultants based in Austin, Texas, says she’s seen a shift recently in the type of products being requested.

“What’s been on the rise have been concerns, project requirements and products to mitigate armed aggressor scenarios, along with natural disasters,” she says. “Severe storms are increasing both in frequency and severity and the damage they’re doing to the built environment is quite substantial.”

Ray Crawford, president of Crawford-Tracey, a contract glazier based in Deerfield Beach, Fla., agrees.

“Being based in South Florida, the foundation of our business is built upon providing high-performance glazing systems that are specifically designed to withstand impact force winds and offer the highest rating in water resistance,” says Crawford. “The Florida Building Code [FBC] has had stringent codes in place in regards to fenestration and the building envelope due to extreme weather ever since the aftermath of Hurricane Andrew back in the early 1990s.”

He continues, “We’re seeing more inquiries and interest in impact-resistant glazing filtering up into the coastal Northeast and Louisiana and Texas in response to the past year’s hurricane activity, and more fl ood barrier products are being specified to prepare for storm surge and flash flooding.”

Crawford adds that both bullet- and blast-resistant glazing remain most prominent in federal and high-security government buildings. “However, I don’t doubt we will see some activity for bullet-resistant glazing in the after-math of this recent school shooting.” (See related article on page 48.)

Preparing to Protect

When it comes to deterrence against armed aggressors, delaying entry time is critical. This is a focus making its way into more and more projects.

“I think what we’ve seen shift is more of an emphasis on the lobby and entryway façade design for armed aggressors,” says Davis. “The government wants a more secure entry space with security close to the front entry door. The lobby is a highly trafficked space and is easily accessible to the public, so that’s been a big concern because it’s an area they can control.”

For example, Davis says they’re seeing lobby spaces designed and constructed with entry vestibules, where the outer entrance acts as the sacrificial opening and the interior door system is hardened. This can increase the facility’s level of protection, particularly com-pared to other products, such as a single sliding or revolving door.

She says in years past, there wasn’t as much focus on the door panel itself as part of the criteria, as these were designed in a similar fashion to the surrounding façade. Now, she says, the entire door system is being designed for blast loads.

“You can reduce the number of windows, but you always need a door,” says Davis.

Traditionally, when an architect or owner wanted to incorporate glazing into the project’s design, extensive testing was required, which adds to the overall cost. That’s changing.

“Now, with all the data we’ve been gathering, we have validated tools that are simple to use and that work with traditional façade systems, such as Single-Degree-of-Freedom Blast Effects Design Spreadsheets for Windows (SBEDS-W), a program controlled and distributed by the U.S. Army Corps of Engineers Protective Design Center,” says Davis. “But once you step away from that, we need more advanced tools that are capable of capturing the structural performance of architecturally complex glazed façade systems, but also remain relatively user-friendly, quick and cost-effective to perform.”

Eric L. Sammarco, principal and senior engineer with Protection Engineering Consultants, adds that increasing architectural demands are changing the way they analyze the façade.

“Many state-of-the-practice window analysis tools simply aren’t valid for today’s complex glazed façade designs,” he says. “We need to leverage the accessibility and power of today’s computational resources to re-define glazed façade analysis and value engineering for extreme loading scenarios.”

“During the planning process, architects always have an idea of where they want to put glass. They have to be selective,” says Davis. “On government buildings there are directives. For ex-ample, consideration is always given to reduce exterior direct lines of sight to the front of the building and what you see upon entering the front of the building. Other considerations are how accessible [the entry is] to the public and where additional security measures are needed. This all has to be done in the planning process, and is harder to do on a renovation. It’s smart when working on new buildings to be more intentional about the use of exterior and interior glass.”

She adds that standoff distance is an important design consideration.

“If it’s a new building, the more standoff (see box) you have, the easier it is to use glass. So you evaluate the site you have and work with the architect at the beginning to make [the design] as realistic as possible. There are cases in urban environments where you don’t have a large standoff distance, and you can’t control that, so there is a significant blast requirement. Those are [the applications] where we’ve seen more robust window systems or those that allow for more deflection.”

Working on an existing building, however, can pose unique challenges.

“We’ve done assessments of existing facilities and it’s harder to create more standoff, so we see more [window] retrofit,” says Davis. “They want to keep the existing windows and the openness. People want daylight and a good work environment. There have been great strides in the technology—laminated glazing products—and the profession has grown a lot, so there are many products to allow for the use of window systems for all blast loads … it’s possible, but the cost does go up.”

Huston Dawson, P.E., a principal with Thornton Tomasetti’s Weidlinger Protective Design practice, says his firm hasn’t seen any shift in where and how glazing products are used.

“Glazing products are an expression of the architect’s intent to meet the owner’s needs or the project’s function,” says Dawson. “Our job is to meet the level of protection within the architect’s vision in the most cost-efficient manner with the material available.

“If the designer has done the job correctly, you won’t notice the [protective element]; that should be an invisible shield on the building.”

He adds, “There is always a balance in the level of protection and the extent of hardening provided. Some projects might require higher levels of hardening or protection as compared to others.”

Crawford agrees and says he hasn’t seen fewer requests for glass.

“In our experience, glass remains a dominant feature. Natural light is a sustainable energy source and benefits building occupants in ways they don’t even realize. We have an extensive list of healthcare and hospital projects, most of which are essential facilities that must remain operational during and post any disaster period. Designs continue to focus on bringing in natural light and providing visibility from the inside to positively affect a patient’s mood, perception and sleep patterns—this holds true to the staff and visitors as well.”

He adds that glass remains dominant even in high regulatory and security markets, such as airport terminals.

“We recently completed our largest project yet at the Florida International Airport in Hollywood. The enormous segmented ellipse that was recently built for Terminal One is covered in our high-performance glazing system. The bottom portion of the ellipse has a frit pattern on the glass that allows light to come through, but offers no visibility from the outside for security and privacy purposes.”

He continues, “It’s not about restricting the use of glass or any de-sign element an architect or engineer chooses. It’s about refining the structure and technology that goes into the components to strengthen them and make the design work.”

Do Your Part

The glass and glazing industry has an important role to play to ensure its products remain a viable part of the building and construction industry—even with projects becoming increasingly secure. Working closely with the architect from the beginning of the project can help.

“If a glazing contractor sees some-thing [in a specification] that doesn’t make sense, they need to ask questions and push back on the architect and de-sign team to learn more,” says Davis. “Windows can be used in a lot of these applications; the technology is there and the systems are there—even with point-supported and other creative systems. Glazing contractors know the costs and where they can save money, so if they know design challenges up front, then they can assist the architect in identifying where the project can save money and still have the extra protection. That’s where a good sub-contractor can provide a lot of value.”

Davis adds that they’ve also seen an increasing number of design-assist projects, and says the approach is helpful to ensuring an adequate and efficient system is implemented correctly.

Crawford says at his company they always strategize with architects and engineers in the earliest phase of the design.

“We offer educational presentations to assist architects in under-standing what products are offered, how to incorporate them into their projects and ensure they are specified according to code requirements,” he says. “Our high-performance glazing systems are constantly evolving based on the needs of our clients. We test our products beyond industry standards, we educate design professionals and general contractors, and we keep ourselves abreast to the latest technology and offerings within the industry.”

Aside from “how much does it cost?” there are a number of other areas of information for which the industry can be a resource.

“They [architects] want an idea of feasible products that will work,” says Davis, explaining they provide information on which systems work best for certain threats.

Crawford adds, “The most prominent requests involve specifying code-compliant glazing systems; particularly assisting in selecting feasible spans and supports that will result in a structurally sound building.”

He adds, “Today’s technology and increasing advancements in glass and glazing offer solutions to keep building occupants safe, secure and happy. It’s our responsibility as glazing professionals to do our part to convey this to architects, engineers and owners.”

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

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