"Greensulate" formula, an organic, fire-retardant board made of water, flour, oyster mushroom spores and perlite, a mineral blend found in potting soil. They're hoping the invention will soon be part of the growing market for eco-friendly products.

A 1-inch-thick sample of the perlite-mushroom composite had a 2.9 R-value, the measure of a substance's ability to resist heat flow. Commercially produced fiberglass insulation typically has an R-value between 2.7 and 3.7 per inch of thickness, according to the Oak Ridge National Laboratory in Tennessee.

With a rapidly increasing global population, a limited supply of natural resources, and rising energy prices, eco-friendly housing products are selling fast.

In the cradle-to-cradle industrial model, goods should either be fully biodegradable or reusable, limiting waste and pollution

"That's the ultimate environmental reference,"