Uncommon Forms of Insulation

Scientist with test tubes

Some safer specialty materials on the U.S. market are not well known. These alternatives also face the burden of having a higher price tag, being more difficult to source, or both. Here are some examples:

Cellular Glass This doesn’t sound very durable, but in fact this mixture of sand, limestone and soda ash has a high compressive rate and extreme heat resistance. It also isn’t that new—under the brand name Foamglas it’s been in production since 1937. Good for wall, roof and below ground use. Health Threat: None Known

Cork The byproduct from wine cork production is superheated and then cut into various depths. Heating activates a naturally occurring binder, and the material is inherently flame resistant. Since cork forests are renewable, this may be the greenest boardstock insulation around. Health Threat: None Known

Cementitious Foam The only non-petroleum based spray foam on the market, Air Krete mixes magnesium oxychloride cement (from seawater) with heated water, compressed air and an expanding agent. Natural qualities make it fireproof and resistant to pests, moisture and mold. The foam is only for use in wall or ceiling cavities. Health Threat: None Known


These alternative materials could be joined by soybeans and mushrooms. Soybean oil already is in use as part of the Side B polyls in SPF. This slightly reduces the use of petroleum-based ingredients in SPF, but so far does not translate into any significant health benefits.

Meanwhile, mushrooms are being used to create sustainable packaging instead of expanded polystyrene foam, or EPS. The next step is to replace EPS used for insulation. In one demonstration project, the creators took mycelium, or mushroom roots, and placed it between two walls. The mycelium then grew in place around such agricultural byproducts as seed hulls and cornhusks. The resulting insulation not only had good thermal properties, but was also fire and water resistant—and chemical free.

Any small-scale demonstration can appear promising: for the last several years mushroom insulation has been just out of reach of commercial viability. But you never know when one little breakthrough can shine a light on a whole new way to make healthier insulation.