"Growable Homes Made With Mushrooms Greensulate
Tracy Staedter, Discovery News
May 11, 2007 — Insulation made with mushroom spores could eventually replace the familiar pink synthetic foam used by many homeowners to pad their attics and walls.
Although excellent insulators, traditional polystyrene and polyurethane foam blends require petroleum, are expensive to produce, and are not biodegradable.
The patented Greensulate formula is an organic, fire-retardant board made of water, flour, minerals and mushroom spores. It not only hinders heat flow but could also be modified to produce sustainable, "growable" homes.
"You could grow it up in a matter of weeks," said Eben Bayer, a student of mechanical engineering and product design innovation at Rensselaer Polytechnic Institute in Troy, N.Y. Bayer and classmate Gavin McIntyre developed the product together and are launching a company in the next few weeks.
The insulation starts with a slurry of water, biodegradable mineral particles called Pearlite (those white beads in potting soil), hydrogen peroxide and starch. (Waste polystyrene could be substituted for the Pearlite, said Bayer, offering an alternative solution for a product that often ends up in landfills.)
The mixture is poured into a panel-shaped mold and injected with living mushroom cells. As the cells grow, they digest the starch as food and begin sprouting thousands of cellular strands called mycelium. In nature, these strands act as roots, providing nutrients and structural support.
After a week or two, a three to six-inch panel of insulation is fully grown, consisting of the insulating particles of Pearlite suspended in a tightly meshed network of mycelium.
According to Bayer, the organic composite board has an insulating value similar to fiberglass, some foams, or loose-fill cellulose.
He also thinks the Greensulate could be competitively priced. The total cost for synthetic insulation runs from between $1 and $2 per square foot. The mushroom-based panels would sell for around $1.50 per square foot.
A competitive price point is just one of many challenges Greensulate is up against, said Mitchell Joachim, executive director of New York City-based Terreform, a nonprofit design collaborative that integrates ecological principles with urban environments.
"'Greener' is usually low on the list. It has to outperform what is out there, be lighter, denser, have a better R-value, and be cheaper," he said.
In addition to insulation, Bayer thinks the product could be used to build inexpensive homes in developing countries or where temporary housing is needed, such as in disaster areas.
He envisions a dome-shaped structure made of two inflatable membranes with a space in between. The mushroom mixture could be pumped into the space, cured, and left to produce a nicely insulated, fire-proof structure."