Building houses out of straw: an old, economical technology

June 25, 2000|By Dail Willis | Dail Willis,SUN STAFF

Straw-bale construction has been around for centuries and was widely used in Ireland, Scotland and other parts of Europe.

It was also extensively used in the United States as settlers pushed their way to California, said Bob Armstrong, a plant geneticist who led the now-defunct Alternative Agricultural Research and Commercialization Corporation, a federally funded venture capital group that invested in alternative technologies.

"It's a very old technology that folks used when we were settling the West," Armstrong said. The oldest straw-bale house still in existence was built in Nebraska at the turn of the century - and the walls are still standing, although it is uninhabited and is in some disrepair. There are at least a dozen straw-bale houses from the same period still in use in the Midwest.

Now, straw-bale construction is enjoying a renaissance - it has been featured in Fine Homebuilding twice recently, and a straw-bale house is also featured in the current issue of Metropolitan Home.

"It's probably a growth industry," Armstrong said. "We've got a huge amount of surplus straw from wheat, there's `stover' from corn, you've got leftover stuff from every crop."

Any kind of plant produces straw, Armstrong said: it's just the stuff left after the crop is harvested. Any kind of straw can be used in straw-bale construction except rice straw, he said, explaining that rice plants have a fine layer of silica on them that is sharp, like glass, and will rip up baling machinery.

Using straw to build houses makes sense environmentally because it uses a renewable resource that might otherwise go to waste, or worse.

"Some straw gets plowed back under" in the agricultural cycle, Armstrong said. "But there's a lot left over." Until recently, he said, it was common to burn excess straw, which contributes to air pollution.

Straw-bale construction of the type that Heather Bathon and Michael Furbish are using in their Anne Arundel County house offers a number of advantages, said Sigi Koko, a Virginia-based architect who has been a consultant on the house. It's her third straw-bale house, she said.

"Straw is compacted so tightly it's not a fire hazard," she said. "It's available locally - there are not a lot of transportation costs. It's a healthy material."

For the Bathon-Furbish house, Koko said, the bales used were a standard 14 inches tall and 18 inches wide, with lengths cut to fit. The house required between 800 and 850 bales to build. At under $5 a bale, straw is a bargain.

Bamboo rods - also harvested locally - were used to secure the bales vertically. As the bales were arranged, Koko used a needle-like "hay meter" to check moisture levels in each bale.

"It has to be less than 20 percent - at 20 percent, decay can start," Koko said.

The plaster is also important in straw-bale construction. There are several options - Bathon and Furbish are using an "earth plaster" made from clay, sand, lime and water.

"It breathes," Koko said. That allows air to move gently around the straw. The house will get two layers of the earth plaster, which takes a week to set and dry completely.

With straw-bale, it's also important that the bales are put on some kind of foundation that will stop moisture. Pea gravel is sometimes used, or concrete.

The result, said Koko, is an efficient, esthetically pleasing dwelling.

"You get super energy efficiency. It's very quiet and peaceful," she said.

Straw-bale construction is used more out West, where the climate is dry, than on the East Coast - but it's beginning to gain popularity here.

Although Baltimore, Carroll and Harford County building officials say they have issued no permits for straw-bale construction, there are at least three such houses elsewhere in Maryland, said Bill Bryant, the chief building inspector in Anne Arundel County. There are two in Montgomery County and one in Western Maryland, he said. (There is also another straw-bale building in Anne Arundel County - but it was built as a storage shed, not a dwelling, so no permit was required.)

Nationally, the interest in straw-bale construction seems to be growing, too, said David Eisenberg, director of the Tucson, Ariz.-based Development Center for Appropriate Technology and co-author of "The Straw-Bale House," the book that Heather Bathon and Michael Furbish read before building their house.

Eisenberg, who did some consulting on the Bathon-Furbish house, said straw-bale construction "seems to be happening more and more." There are no hard numbers available on how many straw-bale houses there are, but Eisenberg said that his book, which costs $30 in paperback and was published in 1995, has sold 100,000 copies, suggesting a high level of interest. "For that kind of book, it's really extraordinary," he said.

Koko offers this nonscientific observation about straw-bale construction's new fame:

"When I go to Home Depot, and make small talk with the other people in line, they'll say, `What are you working on?' I'll say, `A straw-bale house,' and now they say, `Oh, I've heard of that,'" she said. "There's at least an awareness that didn't used to be there."

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