Wool beats fiberglass as home insulator

A handful of companies are turning sheep's wool -- washed, carded, and sprayed with borax to deter pests and mold -- into precut batts of home insulation.

According to GreenSpec, which identifies green building products in Britain, sheep's wool insulation has a long list of eco-attributes: It's recyclable, a renewable resource, nonhazardous to install, biodegradable in landfills, and its manufacture uses little energy.

It's also a good insulator. The U.S. Energy Department rates its R-value at 3.5 -- about 10 percent higher than fiberglass. Wool can absorb up to 40 percent of its weight in moisture without becoming wet, drawing moisture away from wood framing in walls and helping to prevent condensation. It's also naturally flame-retardant.

The main drawback of wool insulation is that it costs about three times more than fiberglass.

Kimberly Hagen, vice president of the Vermont Sheep and Goat Association, says one of the biggest obstacles to making wool insulation in the United States is the lack of infrastructure.

"When the price of wool bottomed out in 2000, most of the machinery in the United States for processing wool was snapped up by the Chinese and Europeans," she said. "I'm not sure what's left."