Tornado-Resistant House for Missouri
In May of 2011, Joplin, Missouri was hit by a catastrophic EF-5 tornado. Killing 158 people and destroying nearly 7,000 homes, it was the deadliest American tornado in over 60 years, and it is thought to be the most expensive tornado in history.
Designing for a tornado-prone region is a unique challenge, but one that is nonetheless important to the many residents who find themselves facing these circumstances. Fortunately, it is not impossible.
Joplin House takes its shape from the archetypal street-front profile often seen in older parts of the city. Two large covered porches constructed of wood sit at the front and rear of the house, serving as the “outdoor rooms” familiar to the district, while also shading the front and rear from direct sunlight. Inside, the generously lit open living space occupies the southern side of the building, while the private spaces lie along the northern side.
The structure consists of a simple frame, easily constructed using conventional construction methods or, if finances allow, structural-insulated panels (SIPS), which could expedite the construction process as well as being significantly thermally efficient.
The exterior is clad in corrugated Galvalume, which is very long-lasting, reflects heat, and is resistant to damage from hail. Adjustable perforated metal shutters, mounted on tracks, address security and privacy while blocking sun in the summer to keep the interior cool. In the winter (or when desired) they are adjustable and can be lowered to allow daylight and solar heat gain. Similar perforated panels may be attached seasonally onto the clerestory at the top of the house; the southern roof contains small lengthwise ridges for safety while this installation occurs.
While much of the construction outlined above would address some aspects of tornado-aware design, it is the safe-room at the core of the house that provides the strongest response. Designed to FEMA standards, the room rests on its own foundation and is unconnected to the surrounding structure. The reinforced concrete masonry unit ((CMU) wall construction is largely projectile-resistant and contains a tornado-safe door and no windows. Nonetheless it serves a double purpose as a washroom for the home. Similarly, the concrete that keeps the occupants safe in an emergency also acts as thermal mass, storing solar heat for long winter nights. As it cannot contact the structure, a nook exists above the room, for storage or as a child’s loft play area. The safe-room need not be an oppressive element within the design; the very features that render it safe have a role to play in day-to-day life, as well.