On a college campus in upstate New York, seniors are growing mushrooms beneath their beds. Sure, you say. What else is new? But it’s not what you think—they’re experimenting with eco-friendly insulation. 

Eben Bayer and Gavin McIntyre, both students at Rensselaer Polytechnic Institute in Troy, New York, have developed insulation made with organic material. It can be grown on site, requires no heat, very little energy, and it blocks air flow just as well as commercial insulation does. As long as it’s not exposed to light, the insulation serves as an environmentally friendly alternative to the conventional kind that is made with fiberglass and other materials produced with fossil fuels.

“I just happened to notice that some of the substrate that was insulating the particles was really similar to some of the substrate used in commercial mushroom production,” says Bayer. “That kind of got me thinking, ‘Wouldn’t it be neat to grow your own insulation?’” 

Bayer, who was raised on a farm in Vermont and grew gourmet mushrooms with his father, proposed the idea in his Inventor’s Studio class about two years ago while working on a sustainable housing assignment. Urged by his professor, Burt Swersey, to develop the idea further, Bayer took on a partner and got to work. The result was a product that is both cheap and environmentally friendly. 

“Some people say that if you want green things you have to compromise. Nonsense!” says Swersey. “The vision of growing your own insulation has so much going for it.”

According to the Department of Energy, heating and cooling account for 50 to 70 percent of overall energy costs in the average American home. If a house is well insulated, it will consume less energy and costs will go down. 

Most conventional insulations are made of polystyrene or polyurethane foams, which contain a certain percentage of post-consumer, recycled products, says Andre Desjarais, the group leader of the Building Envelopes Program at Oak Ridge National Laboratories, part of the Department of Energy.

“The amount of energy consumption saved makes these materials very cost effective from an environmental perspective,” he says. 

Although Desjarais has never heard of organic insulation, he says he’s aware that the green movement is gaining momentum.

“From now on we’ll all be looking at that aspect of [the industry],” he says.

Bayer and McIntyre grow their insulation by combining perlite (a material used in potting soil), vermiculite (a mineral), water, starch, hydrogen peroxide, and mushroom cells. They pour the mixture into six-inch by six-inch molds and slide them under their beds. Over the course of one to two weeks, the mushroom cells digest the starch, and form mycelium, tiny unicellular fibers that are analogous to the roots on a tree. When the fibers touch, they form rigid insulation. 

Because the mushroom cells are added to the mixture while they are in an early stage of development, they do not have the characteristics of spores. 

“When people speak about allergies related to mold and fungus, what they’re talking about is the spores that the fruiting bodies produce,” says Bayer. “As long as it stays dark, it won’t fruit.” 

In just about a week, Bayer and McIntyre will both graduate with dual degrees in mechanical engineering and product design and innovation. Then they will officially start their company, Greensulate. Bayer expects that it will take about a year to finish the research and development needed before he starts commercial production of his organic insulation.

He and McIntyre are also hoping that the technology can be used to build temporary housing that can be bulldozed when it’s no longer needed (the insulation is, of course, 100 percent biodegradable). 

“We’re constantly developing new ideas, but for right now this is our primary focus,” says McIntyre.

Well, almost their primary focus—before anything else, they have to finish their exams.

Story by Susan Cosier. This article originally appeared in "Plenty" in May 2007.

Copyright Environ Press 2007

Organic insulation
College seniors are developing building material that's better for the planet.