Wool in the wall: a sweater for your home
Insulation is typically one of the least ecofriendly materials that go into a house. Fiberglass is irritating to the skin, can be harmful to breathe, and uses large quantities of energy in its manufacture. Polystyrene foam, another common choice, has more than twice the embodied energy of fiberglass. But with increased demand for sustainable building practices, various types of natural insulation are appearing on the global housing scene. These include cotton, hemp, and sheep鈥檚 wool.
A handful of companies turn sheep鈥檚 fleeces 鈥� washed, carded, and sprayed with borax to deter pests and mold 鈥� into precut batts that home-owners such as Kathleen Sauer of Northfield, Vt., say is 鈥渁 real pleasure to install.鈥�
According to GreenSpec, which identifies green building products in Britain, sheep鈥檚 wool insulation has a long list of eco-attributes: It鈥檚 recyclable, a renewable resource, nonhazardous to install, biodegradable in landfills, and its manufacture uses little energy.
It鈥檚 also a good insulator. The US Department of Energy rates its R-value at 3.5 鈥� about 10 percent higher than fiberglass. Proponents of the product also point out that 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鈥檚 also naturally flame-retardant.
The use of sheep鈥檚 wool insulation began in Europe more than a decade ago. Andrew Evans of Black Mountain Insulation in Denbighshire, Wales, saw the number of visitors to his booth at the Ecobuild event in London increase four times this year over last. 鈥淚t鈥檚 the only insulation product people want to touch,鈥� he said. 鈥淭hey stroke it like a dog.鈥�
The main drawback of wool insulation is that it costs about three times more than fiberglass. Also, it must be protected from water leakage, which could leach out its pest-repelling borate.
Wool insulation meshes well with the growing interest in natural products, Mr. Evans notes. 鈥淕iven the choice, I think people will choose natural every day.鈥�
In Canada, Stan Potter, a shepherd-turned-businessman, has been selling his version of the product since he saw a woman selling wool rope for insulating the spaces between logs in log homes. He started making and selling wool roping and then expanded to wool batts for insulating frame houses.
As one of his customers, Ms. Sauer used the batts in a small home she and her husband renovated. She says the material 鈥渇orms very well into odd crevices. It gives you peace of mind if you鈥檙e a green thinker.鈥�
Kimberly Hagen, vice-president of the Vermont Sheep and Goat Association, has researched the possibility of creating a new regional market for wool through the manufacture of natural wool insulation.
One of the biggest obstacles to making wool insulation in the US, she says, is the lack of infrastructure. 鈥淲hen the price of wool bottomed out in 2000, most of the machinery in the US for processing wool was snapped up by the Chinese and Europeans. I鈥檓 not sure what鈥檚 left.鈥�
Ms. Hagen visited France two years ago to trace the budding industry there.
鈥淭hey鈥檝e been making wool insulation for 15 years,鈥� she says, 鈥渁nd they鈥檙e going gangbusters now.鈥� She also saw the difficulties they faced, such as the need to treat the wastewater at wool-washing facilities. So far Hagen doesn鈥檛 see a clear solution for growing the industry on home turf. But, she notes, 鈥淸the industry] started out really small in France.鈥�
If sheep鈥檚 wool insulation grows on the global market, more people may find themselves stroking their insulation like a dog 鈥� or sheep.
