hand holding a piece of mushroom insulation
Photo: Ben Stechschulte
Greensulate eo-friendly, fire-retardant insulation made from mushrooms
Newspaper and denim used to be the coolest-sounding insulation options. But now Eben Bayer, son of a Vermont maple syrup farmer, and his college classmate Gavin McIntyre have created insulation from oyster mushrooms—a petrified slurry of water, hydrogen peroxide, mushroom spores, perlite (that flaky volcanic glass you see in potting soil), and starch. Bayer first came up with the idea while trying to win a sustainable-housing contest in his sophomore year at Rensselaer Polytechnic Institute in Troy, New York. He'd hunted for mushrooms as a kid on the family farm, knew their root systems (where you find the rapidly multiplying spores), and thought the way they grow might be harnessed to bond materials together. McIntyre encouraged the experiments and raised samples under his bed. Since graduation, the 20-somethings have patented the 2-inch-thick panels they call Greensulate and forecast manufacturing costs of $1 per square foot. (They studied marketing, too.) Unlike insulation made of newspaper or denim, Greensulate is naturally fire-retardant and doesn’t need to be chemically treated. If their classroom projections hold, the insulation, which for now has a low R-value of 2.9, could be cheaper than options made from newspaper and fiberglass. A debut is expected in 2008. For more information, visit Ecovative Design

Why Mushrooms?

The colonizing and parasitic nature of mushroom spores easily transforms Greensulate's raw materials into a foamlike insulation. When Bayer and McIntyre add water to the mix, the spores of Pleurotus ostreatus, the botanical name for the North American oyster mushroom, attach themselves to individual bits of perlite, begin feeding on the starch, and grow until they bind all the particles together. The hydrogen peroxide helps stop the process just before recognizable mushroom caps appear. In preparation for a commercial debut, the inventors are also experimenting with coffee grounds and corncobs (starch stand-ins) as a growth medium. Additional possibilities include certain mushroom species that resist insects—a plus in the walls of any home.

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