Windsor, Colorado -- It was only a coincidence that the Windsor, Colo., tornado struck the same day - May 22, 2008 - that ground was broken on a local custom home builder's entry in the local Parade of Homes. In their fourth year of building a parade home to benefit children's charities, builder Doug Collins and his team had decided months earlier to use insulated concrete forms. That, in conjunction with many other hazard mitigation measures, will result in a structure that should stand up well in future tornadoes and other disasters.
The hazard mitigation techniques used in the construction of the house are the sorts of activities encouraged by the Federal Emergency Management Agency. Hazard mitigation techniques help to create safer communities by reducing the loss of life and property, enable individuals to recover more rapidly from disasters, and reduce the financial impact of disasters on the nation.
When Collins heard about the insulated concrete forms in the early 2000s, he and Glenn Heeney, project manager for the 2008 parade home, attended a certification class where they learned to install this hazard mitigation-friendly building system. Located in Windsor, the parade home is their fifth using the technology.
The outside walls are made of concrete that is poured into forms made of interlocking panels of Styrofoam-like material. Steel rebar runs inside the forms horizontally and vertically. The walls are braced with metal supports during the pouring and drying, which take place one row at a time.
"Essentially what we end up with is an all-concrete home. All of the structural elements are steel and concrete," Collins said. But, other than their thicker walls, homes built using insulated concrete forms appear the same as those that are conventionally built. The structural part of the parade home's walls is 11.25 inches thick, compared to 3.5 inches in a conventional home.
Tests conducted by the Texas Tech University have shown that structures built of insulated concrete forms can generally withstand winds up to 250 miles per hour. Winds from the EF-3 Windsor tornado were reported to have reached about 150 miles per hour.
Due to more expensive labor and materials, the cost of building with insulated concrete forms is generally 8 percent to 10 percent higher than the cost of conventional building. This increase can be offset over time by savings in energy bills, as the performance rating can be as high as R-50. Also, Collins said, "Some insurance companies give a discount because these structures are considered fireproof."
In addition to using insulated concrete forms, the home also incorporates other features that reduce the risk of damage in future disasters. These include:
- Drain tiles - A drainage system surrounds the house below grade to collect any excess water that may come from overland flooding, ground water or even a broken sprinkler system. The water empties through a pipe into a "sump pit" in the home's interior. A submergible pump can be used with a hose to redirect the water outside and away from the house.
- Backflow valve - A flap in a main drainage pipe allows water to flow away from the house and prevents flow toward the house.
- Hurricane clips - These large metal brackets secure the connection between the top of the home's walls and the trusses in the roof. Clips can also be used for connections among other components.
- Secure sheathing - Glue and nails are used to attach the roof sheathing to the decking, which is nailed to the trusses, making the structure very wind resistant.
- "Continuous load path" - Because of the insulated concrete forms, the hurricane clips and the secure sheathing, all components of the house are securely connected from the foundation through the walls to the roof, making it less likely that wind can find a vulnerabl...