House of Straw Resistant to Tornadoes?
Contrary to what the Three Little Pigs learned about the stability of straw houses, they may be highly resistant to strong winds and even tornadoes.
The Big Bad Wolf huffed, puffed and blew down a pig-built straw house, but the windy wolf might have met his match in a modern straw bale house. With some design specializations, a straw bale house might even be able to survive a tornado, like the one that recently killed 24 people in Oklahoma.
Straw bale construction uses plaster-coated bales anchored to a solid foundation and sturdy roof. The technique continues to grow in popularity as more builders seek environmentally-responsible, energy efficient, cost-effective architectural techniques. As straw structures become more common, more research focuses on their ability to survive disasters.
"Straw bale construction continues to prove itself across a wide range of climates and geographies," said Colin MacDougall, civil engineering associate professor at Queen's College in Ontario, Canada. MacDougall's recent research has focused on the reaction of straw bales to physical stresses.
"It has been shown that properly designed, straw bale construction can resist wind, earthquake, fire, and insects at least as well, in some cases better, than conventional construction materials and techniques," said MacDougall. "Our knowledge and understanding of how it works and how to best design with it, is certainly not complete, but grows every year."
Architect Joseph Bilello's experiments using the "tornado cannon" at Texas Tech University suggested that straw bales could be used to make tornado-resistant homes. The tornado cannon shoots 2x4's at up to 100 mph at structures to test their resilience to projectiles flung by a tornado. At that speed wood beats rock. The blazing-fast boards shoot though brick walls and straw bales alike.
However, by shifting the way the straw bales were aligned, Bilello, now dean of the College of Architecture and Planning at Ball State, found that the 100 mph boards bounced off the bales. Normally, straw bales are laid lengthwise to form walls. When the bales are laid with their smaller ends facing out, they became tornado shields. Bilello explained to Discovery News that this has to do with the pattern formed by the straw when it is baled.
"Unless builders don't mind having three-foot-think walls, if people want to use straw bales to make tornado resistant structures, they will have to change the way balers bundle the straw," said Bilello.
For now, there haven't been many real world tests of Bilello's observations.
When a tornado touched down near his southwest Missouri straw bale home, George Parsons slept soundly. Parsons is an environmental specialist for Joplin Regional Stockyard.
"I feel safer in a straw bale house than in a stick house, as I call your typical wooden house," Parsons told Discovery News.
Despite Parsons' comfort during a close call with a tornado, the true test will come when a straw bale structure survives a direct hit from a tornado.
"Straw bale buildings do not have a good track record in tornadoes, because there is no track record," said Michael Rakowski, design engineer with Kiewit Engineering and co-author with MacDougall on straw bale studies.
This lack of experiential evidence may make schools and home owners leery of straw bale structures as tornado shelters.
"The public probably does not see these as a viable shelter as there is no past experience," said Rakowski. "They may work but require further research."
Workers build a straw bale house.
On May 20, 2013, a two-mile wide EF5 tornado touched down in the Oklahoma City suburbs, killing 24 people.
Here, workers repair tornado-damaged power lines on May 23, 2013 in Moore, Oklahoma.
Children play in a tornado-destroyed neighborhood in Moore, Oklahoma, the United States, May 22, 2013.
Lawrence family clean up a tornado-destroyed preschool in Moore, Oklahoma, the United States, May 22, 2013.
This aerial view shows the destruction of the Plaza Towers Elementary School (L) and neighboring streets. Parents and teachers in the school huddled in hallways over the children facing the walls as the tornado destroyed everything around them. Several children died.
Rescue workers continue to search through rubble of Plaza Towers Elementary School on May 21, 2013 in Moore, Oklahoma.
An aerial view of Briarwood Elementary school destroyed after a powerful tornado ripped through the area on May 21, 2013 in Moore, Oklahoma. Despite the damage, the school reported no fatalities.
Macie Thompson looks over tornado damage at Briarwood Elementary School on May 21, 2013 in Moore, Oklahoma.
Shown is the storm shelter that Gary and Ferrell Mitchusson used to ride out a massive tornado on May 21, 2013 in Moore, Ok. Their home was completely destroyed in the massive tornado.
Rescuers search for lost animals in Moore, Oklahoma, the United States, May 20, 2013.
Tornado damage in Moore, Oklahoma, near Oklahoma City.
A destroyed medical office is seen after a tornado struck Moore, Oklahoma, near Oklahoma City, May 20, 2013.
Destroyed buildings and overturned cars are seen after a huge tornado struck Moore, Oklahoma, near Oklahoma City, May 20, 2013.
Damage is seen primarily on one side of a movie theater after a tornado struck Moore, Oklahoma, near Oklahoma City, May 20, 2013.
People rescue a kitten from the tornado wreckage in Shawnee, Oklahoma, the United States, May 20, 2013.
Rescuers search for lost animals in Shawnee, Oklahoma, the United States, May 20, 2013.
Overturned cars are seen after a huge tornado struck Moore, Oklahoma, near Oklahoma City, May 20, 2013.
Flipped vehicles are piled up outside the heavily damaged Moore Medical Center in Moore, Oklahoma.
People walk through a damaged area near the Moore Warren Theater after a powerful tornado ripped through the area.
Yellow caution tape marks off the area surrounding the heavily damaged Moore Medical Center.
Nathan Ulepich searches outside the back of his house destroyed by the tornado.
Yvonne Barragar, Joe Marshall and Barbara Garcia sit in front of Barragar's destroyed house after a powerful tornado ripped through the area.
St. Louis Cardinals players bow their heads during a moment of silence for the Oklahoma tornado victims before a baseball game against the San Diego Padres at Petco Park in San Diego, Calif. Similar scenes could be found at sporting events up and down the country.
A vehicle lies upside down in the road in Moore, Oklahoma.
Dana Ulepich looks at the debris from her house.
Dana Ulepich searches inside a room left standing at the back of her destroyed house.
Piles of debris and mangled trees remain after a powerful tornado ripped through the area on May 20, 2013 in Moore, Oklahoma.