Designers looking to make cheap, earthquake-proof homes in war-torn Afghanistan are turning to the stuff of coffee cups and packing peanuts.
As Afghanistan reels from the aftermath of war, millions of refugees have returned to the country, only to find that hundreds of thousands of homes have been destroyed. Rebuilding has begun, but some experts say it’s a mistake to simply throw up the same squat, flat-roofed mud huts that Afghanis have called home for thousands of years.
Earthquakes regularly turn those traditional structures to rubble, crushing and killing the occupants. An earthquake in December just over the border in Bam, Iran, an area with similar mud huts, killed 26,000. “It was clear they’re building death traps,” says Henry Kelly, president of the Federation of American Scientists. “We decided to try to do something about it.”
So Kelly and others issued a challenge to scientists and engineers at MIT, the Lawrence Berkeley National Laboratory and other institutions to find a better way to build houses in Afghanistan. Some of the resulting ideas might prove useful to builders in the U.S. facing rising energy and lumber costs and a shortage of skilled carpenters. The requirements were strict: The replacement house had to cost no more than a traditional adobe house; it had to be easy to construct by untrained workers using readily available material (no wood–Afghanistan is largely treeless). And it had to be light enough to minimize risk of collapse in an earthquake, yet strong enough to withstand snow loads and high winds; it had to insulate its occupants in harsh winters but cool them during boiling summers. Ideas, anyone?
Kelly’s friend, the late architect Roger Rasbach of Houston, had an answer: expanded polystyrene, related to the better-known Dow Chemical product Styrofoam. Rasbach, who died of a heart attack in July 2003, thought it was pure folly that the U.S. would spend millions to rebuild the same flawed housing. Expanded polystyrene is lightweight, cheap and strong. It can be easily molded and cut. It is 95% air by volume, and air is a great thermal barrier. That’s why you can hold scalding coffee in a foam cup without getting burned. Rasbach wanted to use foam as the building’s structural component, holding up the roof and keeping out the elements.
Rasbach had to persuade somewhat skeptical structural engineers of the virtues of foam. To do that he introduced them to H.H. (Hoot) Haddock, a 67-year-old builder in Florence, Ala. who has spent 20 years refining a polystyrene-based building system that could be constructed faster and easier than traditional “stick-built” homes, with better insulation to boot. Haddock had never gone to college, but there he was in weekly conference calls, explaining his methods to a dozen Ph.D.s and scientists.
“Turns out he had exactly what we were looking for,” says Kelly. A former construction manager on the Alaska pipeline, Haddock came up with a building panel called Thermasave, a panel with a 4- to 12-inch-thick core of expanded polystyrene sandwiched between two half-inch sheets of cement. On a construction site, the 120-pound, 4-by-8-foot panels interlock like Legos; a Thermasave house can be framed in a third of the time needed to put up a traditional stick-built house without requiring trained craftsmen. In Alaska Haddock used the panels to build an 18,000-square-foot Ford showroom and a 32,000-square-foot church. In Alabama he built his own house out of the panels. His daughter still lives in it. At trade shows Haddock parks a 3,400-pound pickup truck on a ramp made from a 24-foot-long foam panel. The panel stays straight as a nail. Even without any weight on it, a similar-size plank of wood sags about an inch and a half in the middle .
The panel’s strength owes to the “stressed skin” principle. Thin concrete outer layers act like flanges, absorbing the bulk of the building’s weight, while the foam core keeps the skin from buckling. In an earthquake a stronger, lighter building has a better chance of staying intact than a heavier one.
The building system will be used not only for houses in Afghanistan, but for several residences slated to be built in California and Texas in the next few months. Models were put through rigorous testing. Lawrence Berkeley National Laboratory subjected a simulated foam home to 8,500 hours of weather data to determine the proper thinness of the walls and the size of the windows. The group even set a mock-up on fire at a testing lab in Texas and watched the fire-resistant foam literally back away from the flames.
In the U.S., structural insulated panel systems, or SIPs, have been bouncing around the far edges of the construction industry for decades. Only 1% of new homes built in the U.S. in 2002 used foam paneling, but the application is growing 15% a year, says William Wachtler, executive director of the Structural Insulated Panel Association. In Tennessee the Oak Ridge National Laboratory uses insulated panels as part of an experimental “net-zero energy” house project. On a bright summer day solar panels on the roof may capture more energy than the house needs for cooling purposes, allowing the occupants to sell energy back to the Tennessee Valley Authority. Monotech, a small company in Houston, Tex. headed by Jeffrey Shankman, the former president of global markets at Enron, is using expanded polystyrene covered with sprayed concrete. The company has built in Nigeria, Curaçao and the U.S.; in Houston it’s putting up a museum to house several art galleries. It recently started on a modern concrete-and-glass home designed with the architect Philip Johnson.
Pulte Homes, the nation’s second-largest home builder, began experimenting with foam panels in 1998 as part of a new system to build better homes faster. SIPs have helped cut 21 days off a typical 70- to 140-day building cycle. “As energy costs go up, SIPs become more interesting. They require less labor in the field and, as labor is more difficult to get and the quality of it continues to decrease, [SIPs] become advantageous,” says James Peterson, Pulte’s chief of research.
To bring the foam concept to Afghanistan, Henry Kelly turned to Shelter for Life International, a nonprofit group that has been building homes in Central Asia since 1979. They plan to build 20 test homes this summer in Kabul with imported foam walls held in place by wire mesh and hand-plastered with cement. The next step is to raise $100,000 to build a simple fabrication plant in Kabul, where styrene beads, easily imported from Pakistan or India, could be steamed into polystyrene blocks and sliced into sheets.
The scientists figure a 226-square-foot home with 10-inch-thick walls would require $523 in foam and another $370 in concrete, in line with the $1,000 cost of a traditional mud-brick home. The bigger task is getting Afghanis to actually live in foam houses. “People are conservative, they are suspicious,” says Harry van Burik, an architect who heads Shelter for Life. “One of the challenges is to show people it will last.”
Article courtesy of Forbes.