On Sunday, Oct. 20, 10 tornadoes swept through Dallas and several of its suburbs, wiping out hundreds of homes (not to mention a Home Depot and a handful of schools). The worst of it hit along a 15.75-mile path in the northern part of the city, where an EF-3 clocked 140-mile-per-hour winds. Had those homes been built with insulated concrete forms (ICFs), they may have been able to withstand the storm.
Dallas-based builder Hoffmann Homes is putting that assertion to the test, building several homes in the city using ICFs, which he says can safeguard them from storms far greater than what just rumbled through.
“One North Texas builder says homes he builds can withstand wind from an EF-5 tornado,” said NBCDFW “From the road, you’d never know one of his homes being built in northeast Dallas is any different than a traditional wood-frame house. But, the walls are made of concrete sandwiched between two layers of foam.”
Six solid inches of concrete, to be exact, which creates a nearly impenetrable surface. “It stops a 2×4 at 100mph, it just shatters a 2×4 when it hits a wall,” Hoffmann told NBC.
Hoffmann uses this material in each of the homes he builds. “Picture a foam Lego that is hollow in the middle,” he told Voyage Dallas. “These are stacked onto re-barb to wall height and then concrete is pumped down into the center of the form system. This wall then is comprised of three layers, two outer expanded polystyrene foam layers 2 1/2″ thick with 6″ of steel reinforced concrete in the middle. These are high performance, comfortable, weather resistant, and low-maintenance homes.”
Just how strong is this material, and can it really protect a home from natural disasters? “Up to 85 percent of homes currently destroyed by tornados can be spared, according to experts at the University of Alabama,” said Insulated Concrete Forms & More. According to Andrew Graettinger, Civil Engineer at the University of Alabama, “If you are above ground and you get hit in a storm like that, (the one in Moore, Oklahoma, May 20, 2013) no matter the type of construction unless it is a concrete-reinforced structure, you are probably not going to have anything left.”
A “study published by the Portland Cement Association (PCA) found that concrete walls have more structural capacity and stiffness to withstand the in-plane shear forces of high winds than wood or steel framed walls,” said Fox Blocks. And another study, this one by Texas Tech University, found that ICF walls “resist damage from flying debris traveling over 100 mph while conventionally framed walls failed to stop the penetration of airborne hazards. Insulated concrete form walls are the best protection from windblown debris to a home and its occupants during a tornado event.”
Pictures of a home built with ICFs in Mexico went viral last year after surviving Hurricane Michael, which decimated nearly all the homes around it. “This construction method was one major factor that allowed it to survive the hurricane while the rest of the neighborhood was destroyed,” said ICF Builder.
The Attica, Kan. Homes of Randy and Linda Robbins was saved from a devastating EF-3 tornado in 2004 thanks to ICF walls. “Powerful winds leveled all the surrounding buildings, and tore the roof from the Robbins home,” said ICF Homes. “But the walls stood strong.” Another EF-3, this one with 200-mile-per-hour winds, caused mass destruction in Iowa in 1998; Monte Asbury’s home was saved—as were his kids, who rode out the storm in the basement.
The bonus to using ICF is that it is also energy-efficient. In fact, Linda Robbins noted that was initially their main motivation in using the material. “Houses built with ICF exterior walls require an estimated 32% less energy to cool and 44% less energy to heat than comparable wood-framed houses,” said Home Energy.