Traditional log cabins and timber-framed dwellings required "extensive lengths of straight, high-quality timber," Mr. Tishler wrote in "Cordwood Building: The State of the Art." The material for a cordwood house could come from skinny, second-growth lumber, even fire-charred forests.

The professor searched for the origins of the building method in Scandinavia, Germany and Canada before concluding that the best place to find old cordwood is probably Door County, Wisconsin.

Nick Hylla, who lives in Custer, Wisconsin, said the glaciers that trudged across the Niagara Escarpment left behind a giant limestone ridge: the material for lime putty mortar. And the north woods teemed with white cedar.

Mr. Hylla, 36, is the executive director of the Midwest Renewable Energy Association, a nonprofit group that holds an annual alternative-building expo. And so he mated this old-fashioned skeleton to modern equipment: a solar space-heating system, with a 75-centimeter sand bed that stores warmth beneath the floor. The result is an energy bill of just $20 a month.

Over the years, Mr. Roy has built prolifically. Yet the home the Roys have occupied since 1981, Earthwood, is a true showpiece of the back-to-the-land building movement.

The round shape maximizes space. In place of a center pillar, they lodged a 21-metric-ton stone masonry stove. It's a massive radiator in the winter and a heat sink in the summer. They dug into a hill to shelter the bottom floor and planted a green roof to cool the second story. A stationary bike pressurizes the water system, which feeds the upstairs kitchen and bathroom.

The house is bundled in cordwood masonry walls made from salvaged cedar rail. But far more important than the insulation value of the 40-centimeter logs, Mr. Roy said, are the tons of masonry and sawdust infill. This mass buffers the temperature inside.

Mr. Roy and his younger son are building a 20-sided cordwood home in much the same style.

"Northern white cedar is a first choice," Mr. Roy said, adding that "white pine and spruce are also good choices."

He placed a glop of mortar on top of a log halfway up the wall.

Someone with an artistic eye - that would be Mrs. Roy, 63 - could insert a bottle in the wall for a skylight effect. During the pointing, or finishing, "you can put in glass beads," she said.

"Or seashells," Mr. Roy said.

"Shards of mirror," she said.

"It can get too funky," Mr. Roy said.

"Cordwood can be very forgiving," he added. "But it won't forgive stupidity."

The New York Times