TRADITIONALLY STRAW HAS HAD A FLIMSY reputation as a home-building material. That probably started with the children's tale about those three pigs. Then there's the story of America's first-known straw structure, a 19th-century Nebraska schoolhouse. Cows ate it.

Now come two Tucson entrepreneurs, Judy Knox, 50, and husband Matts Myhrman, 54, with the news that straw-bale construction, once used on the tree-barren American prairie, is ripe for a comeback. Stacked in bales, often bound by chicken wire—and sealed with stucco or adobe—straw is a cheap, energy-efficient resource, say the couple who, in 1990, launched their Tucson-based company, Out On Bale, to conduct workshops for would-be straw builders. So far they've overseen construction of 20 straw structures, from a sauna to a bunkhouse. "It's an annually renewable waste product," says Myhrman, that's "right for the planet."

Knox, a longtime environmental activist from New Hampshire, and Myhrman, a Maine native and former ecology teacher, became bullish on straw houses after visiting a couple in New Mexico in the 1980s. With their two-foot-thick walls, they provided "a quiet restful kind of feeling," says Knox. "It felt friendly." Walls can be raised in a day or two, and an average, 1,200-square-foot dwelling can be built for about $27,000. Quick-to-erect straw houses could, the couple say, shelter disaster victims or homeless people.

Straw, however, does have one drawback: When wet, it attracts fungi, so builders must take care to keep bales dry. And sometimes during construction "the straw bales break up, like shredded wheat," notes local architect Tom Greenwood, who recently designed a straw cabin. What then? Warns Greenwood: "Don't add milk."