Volume 46, Issue 8 - September 2011


Answers Needed Stat
Can Glazing Help Essential Facilities Do A Better
Job of Protecting Occupants from Tornadoes?

by Megan Headley

“The whole hospital shook and vibrated as we heard glass shattering, light bulbs popping, walls collapsing, people screaming, the ceiling caving in above us and water pipes breaking, showering water down on everything,” recalls Dr. Kevin Kikta.

Kikta was one of two emergency room doctors on duty at St. John’s Regional Medical Center in Joplin, Mo., on May 22, 2011. The EF5 tornado that touched down at 5:41 p.m. that Sunday would cut a path of destruction 3/4 of a mile wide and nearly 7 miles long within the city limits, according to reports issued later by the National Weather Service (NWS). But to Kikta, it was “like a bomb went off.”

“That’s the only way that I can describe what we saw next,” he says. “Patients were coming into the emergency department (ED) in droves. It was absolute, utter chaos. They were limping, bleeding, crying, terrified, with debris and glass sticking out of them, just thankful to be alive. The floor was covered with about 3 inches of water; there was no power, not even backup generators, rendering it completely dark and eerie in the ED.”

In the weeks to follow—as the bodies were recovered, the debris of nearly 8,000 structures impacted by the tornado shoveled aside and the work of rebuilding tentatively began—images of the windowless hospital sitting in silent testimony to the destruction could be found illustrating countless news reports across the country. It was as stark an illustration of destruction as the imagery of shattered glass strewn across survivors’ stories.

The question now being asked by the engineers in Missouri who are combing the remains of the city’s infrastructure, as well as by residents who are contemplating rebuilding, is: what could have been done differently?

Essential Facilities
Essential facilities are defined by the International Building Code as: “Buildings and other structures that are intended to remain operational in the event of extreme environmental loading from flood, wind, snow or earthquakes.” As Patrick Condon, PhD, LEED AP BD+C, owner of West Tampa Glass in Tampa, Fla., explains, these facilities include hospitals, fire/rescue garages, earthquake and storm shelters, power stations, ancillary support structures, aviation control towers, water storage and defense structures.

For storm shelters, one might envision a windowless room as the safest possible space, although in some cases that, too, is changing. “Previous community shelter design had little glazing, whether they were hurricane shelters or tornado shelters,” Condon says. “But shelters are designed for short-term protection of a few hours” (see July 2011 USGlass, page 30). Not so for some other essential facilities, hospitals being the notable exception.

Gantt Miller, chief executive officer of Winco Window in St. Louis, recalls a recent conversation with a hospital administrator by way of example. The administrator commented that in a typical hospital, “‘you know, [if] we have a tornado that comes through, we have a choice: people that are on critical care and are hooked up to different monitors and oxygen and IVs, etc, do we take them off that and move them to a secure location and chance that they’re going to die from that? Or do we leave them there and hope that the tornado doesn’t hit directly?’”

There doesn’t need to be a choice in today’s construction. “There are some hospitals now looking at taking certain sections of their building and basically hardening them so that they don’t have to be faced with relocating people,” Miller says.

There doesn’t need to be a choice when it comes to construction materials available. But cost? That’s another question.

“The question I’ve got is, a hospital’s going to be private or public and, whichever case it is, are they going to be able to afford to put in something that’s basically just shy of bullet-resistant glazing in every window?” asks Scott Norville, Ph.D., P.E., a professor in the department of civil engineering at Texas Tech University in Lubbock, Texas.

An Industry Precedent
In recent years, a new market for tornado-resistant glazing has sprung up. For some, this recent spate of extraordinary tornadoes brings to mind a storm from nearly 20 years ago that likewise led to the rise of a new glass industry.

The locals in Florida still cite Andrew, casually bringing him into conversation as if he were a former neighbor rather than the most destructive United States hurricane of record. After Hurricane Andrew blasted his way across South Florida on August 24, 1992, with a peak gust of 164 mph—causing 23 deaths in the United States and $26.5 billion in damage—building codes strengthened significantly along the East and Gulf Coasts. The glass industry developed new product lines and technologies in response to tightened codes, and then went beyond that to secure buildings for high winds (see July 2009 USGlass, page 40) and once-in-a-lifetime storm events.

“There are a number of test methods that exist and many were developed for hurricane products,” says Ken Brenden, technical services manager for the American Architectural Manufacturers Association (AAMA). “Tornadoes are on the same, if not higher, level than what is expected during a hurricane—but tornadoes are much more extreme wind-wise.”

The Next Evolution in Product
Norville explains that the wind speeds reached by tornadoes tend to be higher than those reached by hurricanes, and the debris fields tend to be different.

“The difference between tornado glazing and hurricane glazing is that you can pretty well hold hurricane glazing in place with a standard frame and with tornado glazing you need to notch that up a bit [with] a much thicker glass. It’s going to be thick laminated glass,” he says.

Miller offers a droll comparison between the two types of impact glazing: “Well, it’s like the difference between boys and men,” he says.

In other words: “With hurricane [glazing] most of the testing—and there are different levels of testing—are done by propelling a 2-by-4 that’s 8-foot long at around 34 mph at a window. The window has to resist that or only tear a certain amount. When you go to a tornado window, all of a sudden instead of going at 30-some mph you’re going at more than 100 mph and you’re using a 12-foot 2-by-4 that weighs 15 pounds. Your kinetic energy is a whole lot higher. And in the tornado tests, you basically have to have that 2-by-4 bounce off the windows, so the people inside the critical facilities can continue to do their jobs,” Miller says.

According to information from Hurricane Test Laboratory LLC headquartered in Riviera Beach, Fla., performance testing for tornadoes can include impact, static, cyclic and water penetration evaluations. At the conclusion of testing, products are rated for tornado-prone areas up to a certain wind speed or level of protection. These ratings give building and emergency officials the ability to measure and publish the quality of shelters and other emergency buildings, especially in tornado prone areas.

Some say that polycarbonate products need to be a part of the product formula to stand up to these tests.

According to Dr. David O. Prevatt, PE (Massachusetts), an assistant professor in the Department of Civil and Coastal Engineering for the University of Florida, “What we are finding in tornado shelters is they have to go to polycarbonate-type glazing instead of glass to work at wind speeds we are talking about [for tornadoes].”

“That is the perception,” Condon says, but adds his own observations. “First, it is difficult to glaze polycarbonate because the structural silicone required for anchoring polycarbonate during extreme wind loads and impacts will not hold the polycarbonate to the framing. Second, polycarbonate and film products tend to scratch easily. Third, the benefits of polycarbonates can be duplicated, as well as their shortcoming avoided, by using laminated glass.”

Supplying New Demand
Products are beginning to show up on the market with this tornado rating, and a price tag to match their increased sophistication. But the question is still asked: why include windows at all?

Norville harkens back to a tornado in Ft. Worth in 2000 that destroyed 3,200 lites in what was then the Bank One Building (see April 2000 USGlass, page 16). “They ended up razing the building even though it was structurally fine because it was going to be so expensive to replace the curtainwall,” Norville says.

He continues, “One thing I observed from that building is that if you were in … an inside hallway, the damage was relatively light. And so I start to wonder if in major works and things like this—maybe you ought to start thinking about not putting things you can’t live without, or people you don’t want to get injured, or whatever the case may be, in outside rooms that are going to be subjected to this.”

In some structures, maybe that’s a reasonable solution. However, architects will cite the overarching importance of having natural light in facilities such as hospitals.

“Designers will balance the low risk of a catastrophic storm against the therapeutic impact of vision glass,” Condon says. He offers a forecast: “My opinion is that glass usage will not be minimized but superior impact glass will evolve and be adopted.”

In fact, Condon’s company has introduced what he believes to be the first curtainwall to pass all testing requirements for ICC 500-08, ICC/NSSA Standard for the Design and Construction of Storm Shelters, at a laboratory with International Accreditation Service certification.

“West Tampa Glass tested a product to comply with the ICC 500, both the hurricane as well as the tornado shelter requirements. At this time, these shelter products are the basis of design for two projects but have not been installed, except in the laboratory testing,” he says.

AAMA recently developed a standard, AAMA 512-11, Voluntary Specifications for Tornado Hazard Mitigating Fenestration Products, to structure this emerging market.

“We’ve been working on this AAMA standard for a few years as our members determined this was a gap in the market,” Brenden says. “If manufacturers will test to these [tornado glazing] standards it is up to them on how they market these products. I would expect that, at least initially, you will see commercial companies adding this to their offering.”

That seems to be the case today.

“Due to the increase in tornado testing requirements in project specifications, Kawneer is exploring tornado testing standards for products,” says Tanya Dolby, product engineer at Kawneer Co. Inc. “In light of recent tornado events, we believe this will be a growing requirement in future building projects.”

In the case of an event such as in Joplin, or Tuscaloosa, Ala., back in April (see chart Below), with the price tag of rebuilding growing and the body count still in vivid memory, the cost of these products seems a weakened argument.

Miller recently put this into perspective for the CEO of a large hospital chain.

“We were chatting and he was telling me that his hospital rooms, in a full-service hospital, would cost him anywhere from $700,000 to $1 million per bed, or per room,” Miller says. “My response to him was ‘if you’re spending that much for the room—or the bed, as you refer to it—why wouldn’t you spend an extra $1,000 or $1,500 on the window in that room, and then be able to say that it meets the multi-threat or hurricane or tornado level? He just laughed and said ‘I need to put you in touch with my head of construction.’ So it’s all relative. There’s no question it’s more expensive—but what are you going to get for it?”

For now, that seems incentive enough. But what happens when a few years pass and the inevitable complacency returns?

“If the building code would include metrics for a ‘tornado-resistant’ building, I believe it would encourage essential facilities such as hospitals to focus their designs,” Condon suggests. “This happened with the LEED categories where premium dollars are spent to save energy and the environment. A similar program should exist to encourage premium dollars to invest in hurricane- and tornado-resistant building categories that save lives.”

"This happened with the LEED categories where premium dollars are
spent to save energy and the environment. A similar program should exist to encourage premium dollars to invest in hurricane- and tornado-resistant building categories that save lives."
—Patrick Condon,
West Tampa Glass

When the State Should Step In
As products evolve into this market—and with the spate of recent tornadoes having escorted 2011 into the record books as the sixth deadliest year for tornadoes in modern recordkeeping—questions might arise for mandating tornado-resistant buildings and, more specifically, glazing in the codes.

“The adequacy of building codes is often questioned after natural hazard events like this,” says Jeff Inks, vice president of codes and regulatory affairs for the Window and Door Manufacturers Association.

However, Inks cautions that the gut reaction—should we mandate stronger buildings?—isn’t the first question that should be addressed.

“When evaluating damage there are many factors that must be considered, including what code requirements the [buildings] was built to to begin with, whether those requirements were met and whether installations of components such as windows and roofs were done properly. That information is critical to determining whether the current building codes are adequate,” he says.

As it stands now, the International Building Code (IBC) does not cover tornado-resistant glazing.

“Under ASCE 7 references in the IBC there is no ‘tornado-resistant’ glazing,” Condon explains. Impact-resistant glazing in the building code is hurricane glazing if it meets ASCE 7 wind speeds for a Category 3 hurricane (see chart on below). “Wind borne debris regions are restricted to the Southeastern coastal areas, not tornado alley.”

In 2008, the International Code Council (ICC), with the support of the National Storm Shelter Association, released its consensus standard on the design and construction of storm shelters, ICC 500. The Standard for the Design and Construction of Storm Shelters describes hurricane- and tornado-resistant glazing for shelters; impact-resistant glazing that meets hurricane requirements for shelters protects against a Category 4 or Category 5 hurricane.

“Structurally, hurricane shelter glazing must meet wind loads based on the ICC 500 hurricane wind map and survive impacts from a 9-pound 2-by-4 at 40 percent of the hurricane wind speed,” Condon says by way of comparison. “Impact-resistant glazing that meets tornado shelter requirements protects against an EF4 or EF5 [tornado]. Structurally, tornado shelter glazing must meet wind loads based on the ICC 500 tornado wind map and survive impacts from a 15-pound 2-by-4, up to 100 mph.”

Today, only Alabama mandates use of that code.

The Federal Emergency Management Agency (FEMA), meanwhile, offers standards on designing safe rooms. According to information from FEMA, ICC 500 codifies much of the extreme-wind shelter recommendations of the early editions of FEMA 320, Taking Shelter From the Storm: Building a Safe Room For Your Home or Small Business, and FEMA 361, Design and Construction Guidance for Community Safe Rooms. The FEMA website states: “The ICC 500 provides minimum design and construction requirements that may be adopted by local jurisdictions for extreme-wind storm shelters, though it does not provide the same near-absolute protection of FEMA 361 and 320 (2008 editions).”

“FEMA 543 [Design Guide for Improving Critical Facility Safety from Flooding and High Winds] recommends that essential facilities such as hospitals should have no less than Missile E qualified glazing, namely, glass that can survive a 9-pound 2-by-4 traveling 55 mph,” Condon says. “This is not ‘tornado-resistant’ glazing defined by FEMA 361 or ICC 500, but tied to increased wind load requirements; it would be a reachable first step.”

Back in Joplin, engineers are still asking questions about what happened; the questions about what to do next are yet to come.

Larry Tanner traveled to Joplin as part of FEMA’s Mitigation Assessment Team (MAT). The research associate with Texas Tech’s Wind Science and Engineering Research Center saw the damage to St. John’s up close.

“That building lost so much glazing,” he says. As a cautionary afterthought, he adds, “Many of the newer hospitals being built today have lots of glass.”

Time will tell whether or not that will change, but one thing’s for certain: hospitals shouldn’t leave staff faced with the choice of whether to let their patients risk transport or risk a natural disaster.
St. John’s painfully illustrates that many of the essential facilities across the country aren’t protecting their occupants as well as they could.

“If you could have maintained 50 to 60 percent of that the glazing and protected the generators, then that hospital may not have been taken offline the way it was,” Tanner says of St. John’s, although he’s quick to elaborate, “The generator failure was not a function of glazing, but rather the wind forces.”

But Tanner also points out that limiting the glass can not be the answer—again, for the sake of its occupants.

“I believe that hospital rooms must and will always have windows. How dark and dreary one’s life would be, ill and confined in a windowless room. Patient rooms probably represent 70 percent of the glazing in a hospital. What is needed is better windows and better glazing and better protection of glazing. Double glazing, laminated glazing and perhaps films can help,” he says.

As Tanner is working on the FEMA MAT team writing about the Joplin tornado, he cannot comment specifically on the hospital at this point—those details will emerge soon enough—but he can look into the future and share how he would rebuild.

“I would rebuild beautifully, creatively and taking advantage of the envelope protection and life safety products that currently are available,” he says.

As awareness about tornado glazing grows, as research into this market continues and as the residents of this year’s disasters rebuild, more designers will learn that beauty and protection aren’t exclusive of one another, that glass can let in views of the natural world while keeping out the storm.

Megan Headley is the editor of USGlass.


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