On May 4, 2007, a funnel cloud creating wind speeds exceeding 200 mph ripped through the town of Greensburg, Kan. The category EF-5 tornado cut a path 1.7 miles wide through the 2-mile-wide downtown area, according to Daniel Wallach, executive director of the Greensburg GreenTown nonprofit organization. The town's concrete silo grain elevator survived intact, but little else did. Eleven people died and almost everyone else was homeless. Before the tornado, the population of Greensburg was approximately 1400, now the population is between 800 to 1000.
Greensburg is one among several Midwestern towns devastated by tornadoes over the past couple of years. Jim Offner, business editor for the Waterloo Cedar Falls Courier, reports that on Sunday, May 25, an EF-5 tornado also completely destroyed a third of Parkersburg, Iowa—a town of 3000 people, killing nine. Many small towns in this area have been hit in recent months, he says.
John Parsons, president of Mid America Pipe Fabricating and Supply, Scammon, Kan., says that his area didn't have any tornadoes in the 90s but over the past couple of years several have passed by, destroying property just a couple miles away, causing him to begin building concrete homes for his employees and himself.
Tornado strength
It's one thing to build a home that can resist hurricane wind forces; it's quite another to build a house that resists tornado force winds exceeding 200 mph. Wood-frame construction can resist hurricane force winds if the construction follows guidelines established by states such as Florida, where building code mandates that new homes withstand 146-mph wind forces. But concrete currently is the only material that can hold up to severe tornados. However, there are decisions to make with concrete: designing and engineering for human safety and deciding how much to minimize the possibility of damage to the structure.
Safety and sustainability
If you are willing to build a concrete bunker, it's possible to provide ultimate safety for your family, as well as build an indestructible structure. But few are willing to do that so safety and sustainability become separate issues. People make decisions about what parts of their home to save and what parts to sacrifice.
Chuck Vance, manager of the Fortified…for safer living program of the Institute for Business & Home Safety (IBHS), Tampa, Fla., says that the greatest damage and risk to life results from flying debris from both hurricanes and tornados. “Air cannon” demonstrations show how easily 2x4 wood studs propel through standard wood-built and brick-veneer walls at hurricane wind speeds—not to mention windows and doors. “Providing safety for people can only happen by including a ‘safe room' in a home construction,” says Vance. In practical terms that means building a room with concrete walls and ceilings, no windows, and a door area that can't be breached by flying debris.
The issue of sustainability is more complicated. Here, the focus is on saving buildings to avoid replacement and using additional resources. Owners and designers make choices about what can be saved and what can be replaced after a tornado. For example, pitched roofs, doors, windows, and garage doors often are regarded as sacrificial items in a strong tornado. But an owner might decide to build a box-frame structure with a structural concrete flat roof to avoid losing a roof to a tornado of any size.
Most tornados are smaller than EF-5s and there are many precautions that can be taken during construction to increase a home's resistance to wind events. IBHS studies the nature of building failures under seismic, fire, and wind events in order to find ways to strengthen structures. From these investigations, recommended solutions are included in IBHS's Fortified…for safer living program. It requires continuous load path connections from the top roof rafter to house footings. Other items include specifications for roofing materials, windows, and doors. Owners and builders must apply for the Fortified designation before construction begins so that plans are reviewed and third-party verifiers can check that standards are met throughout the construction process.
Home insurance issues
Carl Schneider, owner of Schneider Insurance, Mobile, Ala., is an independent insurance agent. He also lives in a concrete home. “I am on a mission—a passionate one,” he says. “In the past, insurance companies didn't provide an incentive for people to build resistant homes because they didn't recognize differences in construction type. Risk tended to be assigned more by a homeowner's credit rating and prior claims than by a home's resistance to fire, flood, wind, termites, or mold.” This means people aren't rewarded for building safer and more sustainable homes. However, several major insurance companies are beginning to recognize the values and benefits of concrete home construction and are offering substantial reduced costs for insurance premiums. People then are more influenced to build concrete homes when they know they can save money (and peace of mind) on monthly energy and insurance bills.
Rebuilding in tornado-devastated areas
Picking up the pieces after a destructive storm is never easy. Here are three stories of starting over.
Farrell Allison. When the tornado passed through Greensburg, Farrell Allison and his wife lost their 100-year-old home. Unlike some people in town, they still had their jobs so they decided to rebuild. Allison says he's always hated paying utility bills and has done his best to save energy. They once saw an ICF home and chose this construction method as the best concrete system to use. Their new 2000-square-foot home features 1100 square feet of porches and a basement. It will include high-efficiency geothermal heat, energy-efficient windows, and a high-efficiency energy recovery system. “I'm not in this just for myself,” he says. “This house is for future generations who will live in it too.”
Wallach says that several other ICF buildings are going up in Greensburg, including an incubator building owned by the city, The Greensburg State Bank, a Methodist church, and several homes.
John Parsons. As the president of Mid America Pipe Fabricating and Supply, he has seen numerous tornados pass close by and he has grown concerned about his workers. He decided to build a total of 22 concrete homes using the removable form method. Building two at a time, the three-bedroom, two-bath houses are sold at cost to his employees when completed. Each structure features a concrete exterior and key inside walls, and a deck (ceiling), all cast together to create a box-frame concrete shell. The utility room also serves as a safe room. Parsons adds that when the weather becomes threatening, several people take cover in the homes under construction. He intends to build himself a concrete home.
Jerry Spude. He is the president of ICF manufacturer TF Systems, Green Bay, Wisc., and recently was moved to help out in Parkersburg after the tornado. With the help of local distributor Gypsum Supply, TF supplier ACH Foam Technologies, and other local companies, they donated the materials needed to complete an entire home's shell for someone unable to rebuild. A volunteer fireman was chosen. The first step involved hiring a company to clear enough debris away to start the construction. The two-level, 1600-square-foot house features a lower level lacking windows with a structural steel floor system anchored into the concrete walls. The roof is also steel truss construction. Spude says the superstructure of the house is now complete and his company is exploring ways to help others in devastated areas.
Rebuilding isn't easy, but reconstructing with materials and designs to withstand high wind damage can prevent future reconstruction projects from occurring, as well as lend some peace of mind to the inhabitants of the home.
