How Do You Best Design for a Tornado?

Photo Art by Chuck Carlton

With the 1 year anniversary of Greensburg, Kansas being leveled by a EF5 tornado and the recent string of deaths and destruction due to tornadoes, I though I would ask the question "How do you best design for a tornado"? Better yet, how do you rebuild a community in the best sustainable way to survive a tornado and not have to rebuild, thus saving materials and energy.

In the Midwest plains, one of the main reasons that tornadoes form and continue a path of destruction, is the lack of natural features dispersing the wind forces. One idea that was raised in a recent Discovery channel program "Blown Away : Greensburg, Kansas" was to plant a forest ring of trees around the town. This was shown in models to mitigate the overall power of the tornado and as long as the correct trees and spacing are used this seems to be a good plan, however, how long until the groves of trees are tornado-protecting size?

To rebuild the homes that are more tornado resistant, what design techniques and materials should be employed? Let's start from the bottom; the foundation is an important aspect of many homes and unfortunately the trailer homes and others that rest on blocks or a concrete slab are the most at risk of destruction. In the Midwest, many new homes don't have basements anymore and storm cellars are becoming rare. So why not build a strong foundation that will act as an secure anchoring system for the house and give it's inhabitant's safe shelter? The reasons I found were flooding due to high water table, stresses and stains due to freezing in the winter, and a solid bedrock under site surface. Fair enough, if these factors are the case, then one must think about building a strong lower level that attaches firmly to the ground slab.

The latest material I am beginning to see in pre-fab construction and in the rebuilding efforts of the city of Greensburg is ECO-Block. ECO-Block is simpler and easier to install than wood-frame methods — and, even other ICF systems. It's faster, taking less time with fewer people. And it’s more sustainable, because ECO-Block buildings are vastly more energy-efficient. Stronger. Quieter. Resistant to fire, moisture, mold and the elements. Debris driven by high winds presents the greatest hazard to homeowners and their property during tornadoes and hurricanes. Recent laboratory testing at Texas Tech University (see video below) compared the impact resistance of residential concrete wall construction to conventionally framed walls. Only concrete wall systems, such as ICFs and concrete masonry, successfully demonstrated the strength and mass to resist the impact of wind-driven debris. The wood-frame walls failed to stop the penetration of airborne hazards. These insulated concrete forms can be filled with recycled fly-ash concrete to make the wall even "greener". Another advantage to ICFs is that they can be cut into radius rounded walls for greater aerodynamics if wanted.


After the walls are up, impact-resistant window systems, when properly installed, have a much better chance of surviving a major windstorm. Alternatively, impact-resistant shutters that close over window openings prevent flying debris from breaking windowpanes. Strengthen door frames, hinges, latches, and dead-bolt locks should be strong enough to resist high wind pressures. Double doors such as French doors need special attention because of the stress on the center latch. Door frames must be securely anchored to house frames. Another idea is to reduce the design of adornments on the exterior that could become damaging projectiles.

Hip roofs without gables and with minimal eaves have proven to be the best roof design to combat high winds in hurricane and tornadic areas especially if the slope of the roof from horizontal is 35 degrees or greater (to reduce/eliminate the airfoil effect of extreme high winds that blow over the roof). Also, steep angled roofs seem to handle winds better than a standard gabled roof. Most importantly, the roof must be securely tied into the wall structure with metal roof tie fastener systems and the soffit and eave area should have reinforced connections. A home has to be well-connected in order to distribute the forces caused by wind pressure, which reduces the chance it will come apart or collapse.

Last year a post was started on the Alternative Building Architecture Usenet Group as a result of the Greensburg disaster. They suggest an aerodynamic cylindrical structure, maybe the Monolithic Dome?
If you can't build your entire house to be tornado resistant you can always just build a tornado safe room or shelter.

Some other good links:
The Institute for Business & Home Safety - Disaster Safety - Tornado

I'd love some feedback on this topic if you have further information to add, please comment below.

Architecture for Humanity Burma/Myanmar Rebuilding Appeal

Architecture for Humanity is raising funds to support reconstruction efforts in Burma/Myanmar. Their work will focus on rebuilding sustainable clinics, schools, community centers and other critical infrastructure as well as housing. Please help them rebuild communities and lives. Support sustainable reconstruction. Make a donation today. I've also added a Architecture for Humanity donation link to the right sidebar. If you'd like to donate to Unicef or Direct Relief International you can do so by clicking on this link.

Greensburg - One Year Later

Photo by Greg Henshall
On May 4, 2007, Greensburg, Kansas was leveled by an EF5 tornado, one of the strongest in American history. In that storm, 11 people lost their lives as the tornado tore through the town of about 1500. Within days of the disaster, the people of Greensburg decided not only to rebuild their town, but to rebuild it "green". Today marks the 1 year anniversary of this event.

Treehugger has several different perspectives from the townspeople of Greensburg with interviews from the Mayor, a Resident, the Principle and a Student from Greensburg, KS High School. Green ArchiTEXT picks up on an Architectural Record article stating that the master planning for the town is aiming to be LEED Certified Platinum.

There are also many current and upcoming Web and TV shows devoted to the town and it's plan to become "green". Including "The Good Fight" on the Sundance Channel.com, which you can watch now on their website. The Discovery Channel had a show called "Blown Away : Greensburg, Kansas" which you can view in the video segment below. Also, be on the lookout for the Discovery Channel's Planet Green network, starting on June 4th, who will host a 13 part documentary series called "Greensburg" which "follows the rebirth of a rural town in Middle America into a model for the future. With more than 1,500 people displaced by the tornado and waiting to return to their homes, Greensburg documents the story of a community coming together and facing the enormous task of greening a small city. From climate impact to architecture, building and design, to the personal stories of those affected by the disaster, Greensburg is an inspiring look into the human spirit."

Several relief organizations such as the Greensburg Future Fund and the Greensburg GreenTown are out there to collect money for the rebuilding, so go out and support them in this noble cause if you can.

Floating Houses and Mass Cultural Like-Mindedness

Over the last week I've been thinking about New Orleans and Katrina, the Weather Channel had an overview of what happened and it got me thinking about an idea for a house that rests on a raised hollow solid foundation but can detach with a floating floor level that could rise with rushing floods. This seems like a sensible approach to areas that are prone to general rising sea rate, river delta flooding, hurricanes, and tsunamis. In a brief overview of some of my frequented sites I find several posts that show this idea in varying degrees, all within this last week, interesting coincidence, I find it interesting how anniversaries of events can focus peoples efforts and thoughts toward future solutions. I'll add to the collective with my overview of these floating structures and how they could pose a solution to these disaster-prone areas. Next step is to make them affordable and sustainable.

Inhabitat DuraVermeer and Waterstudio
Inhabitat Katrina Anniversary
BLDGBLOG Single Hauz
Archidose Floating in Illinois
Treehugger Steel Floating Tower
Seattle Times LSU professor suggests back in April