Product development
Hurricane-resistant windows are typically made with laminated glass, and can be fixed or operating windows. Tornado-resistant windows are typically fixed windows that incorporate a thick polycarbonate impact layer either through the use of glass-clad polycarbonate infill or as a separate impact barrier built into a secondary panel. They differ from hurricane-resistant windows via the specifications used for their testing. Hurricane-resistant windows use wind charts from American Society of Civil Engineers/Structural Engineering Institute (ASCE/SEI) 7, Minimum Design Loads for Buildings and Other Structures, while tornado-resistant windows use wind charts from the aforementioned FEMA P-361 (both charts are in ICC 500).
The development of tornado-resistant glazing has benefitted from the research and development that went into hurricane products, despite the contrasts in the two high-wind events’ power and duration. (See “The Difference Between Tornadoes and Hurricanes.”) Hurricane-resistant windows typically undergo a structural test at 150 percent of design load while tornado-resistant windows, due to the very short duration of a tornado event, undergo a structural test at 120 percent of design load per ICC 500. (ICC 500 and AAMA 512 only specify a 120 percent structural load to be consistent with each other, but hurricane windows, given their prevalence in the marketplace, typically get tested to 150 percent structural load to remain consistent with other window certification requirements.)
Tornado impact products are also different from hurricane glazing. A hurricane test for windborne debris involves firing a 4-kg (9-lb) 2×4 missile traveling at 55 km/h (34 mph) or, per ASTM E1996, Standard Specification for Performance of Exterior Windows, Curtain Walls, Doors, and Impact Protective Systems Impacted by Windborne Debris in Hurricanes, at 86 km/h (55 mph). In a tornado test, a 6.8-kg (15-lb) 2×4 missile is fired at up to 160 km/h (100 mph). Tornado-resistant glazing can also offer other enhanced performance attributes such as blast/ballistic resistance, acoustics, and thermal/solar control.
Seeking government grants
In some cases, federal money may help partially fund projects. According to Intertek’s Jeff Robinson, there are two main types of FEMA grant programs for tornado resistance:
- Hazard Mitigation Grant Program (HMGP); and
- Pre-disaster Mitigation (PDM ) Grants.
The pool of money and eligible communities for HMGP funding are specific to a given “Declared Disaster.” In general, once the gross non-insured cost of a disaster is calculated, and if the U.S. president has included language “reducing the cost of future disasters” in the disaster declaration, a percentage of the uninsured costs are automatically allocated for HMGP projects. When a disaster strikes and HMGP funds are going to be made available, there will be a specific 90- to 180-day window in which a Notice of Funding Availability (NOFA) is open. A project must be submitted during an open NOFA to be eligible for funding. Applicants can be either public or qualifying public non-profit organization.
PDM grants generally run in annual cycles, are not based on having been affected by a specific disaster, and are nationally competitive. The funding for this pool of money is generally set by Congress and has been reduced over the past decade.
Architectural or client teams may call their State Emergency Management Office and ask whether there are any NOFAs open or upcoming, or any additional grant programs that could help fund their mitigation project or initiative. FEMA provides the money to the state, which in turn, processes grant applications and also allocates the money for the actual projects.
Looking forward
As coastal architects and builders can attest, developing new products for hurricane resistance was a long and often contentious process. However, Florida is now widely admired for its protective building codes and has been a model for many states and even other countries. In other words, while tornado resistant glazing may not be at the top of everyone’s short list, it is comforting to know products, processes, and codes are now in place.
| THE TORNADO AT MERCY HOSPITAL |
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Mercy Hospital Joplin made headlines for the massive destruction after a devastating EF-5 tornado destroyed the entire structure in 2011. The hospital again made headlines when it was rebuilt to the toughest standards its design team could create. Patient safety was top priority, with the ability to operate normally during and after a storm. To evaluate the best path forward, the team studied the destruction of the original building. Almost every window was blown out, except for one area in the hospital. The windows in the Behavioral Sections area of the hospital were made from laminated glass and remained intact. Realizing that these high-performance windows could help, the team studied lessons learned from hurricane zone window performance. Since tornadoes have much higher wind speeds and traveling speeds than hurricanes, different criteria were developed and tested. Today, the new Mercy Hospital Joplin has windows that can resist up to 402-km/h (250-mph) winds in patient-critical areas and 225-km/h (140-mph) winds where patients can be temporarily moved |
Gantt Miller is the chair of Winco Window Company. He led the American Architectural Manufacturers Association (AAMA) task force to create a new voluntary specification, AAMA 512-11, Voluntary Specifications for Tornado Hazard Mitigating Fenestration Products. Miller has been a part of 50 different committees and task groups during the decade that he has been active in AAMA and has served as a co-chair on five of these committees. He is the former chair of the AAMA board of directors, and continues to serve in numerous other groups and roles involved in guiding the day-to-day operations of AAMA. Miller can be reached at ganttmiller@wincowindow.com.
Good to read! Tornado resistant proof things are very much necessary in our home so that a home does not get damaged in hurricane prone season. A Homeowner must take care of the things that their home remains safe during hurricane season. One should protect their home by installing storm damage windows and doors and also cover their roof from getting damage. Securing life and home property from a tornado is very much important. Damage that turned after the tornado is most difficult to handle. Everyone who lives in tornado prone areas must register for a home insurance policy as the home insurance policy can cover tornado/hurricane damage. A Home insurance claim adjuster(http://allclaimsusa.com/home-insurance-claim-adjuster) settle down the claim with the insurance company after the hurricane damage.