What Is Mycelium Insulation?

Mycelium insulation is a composite material made by growing plant spores–usually mushroom–through waste organic material such as rice hulls, wood chips, or straw. Multiple studies, research, and development are ongoing but products are already being marketed in the US and Europe.

What Is Mycelium Insulation?

What Is Mycelium?

Mycelium is defined as: “the vegetative part of a fungus, consisting of a network of fine white filaments (hyphae)”. The threads grow into the soil, rotting tree trunks, leaves, etc. to provide nutrients to the mushroom or other types of fungus.

One cubic inch of soil can contain over 8 miles of mycelium. It holds 30,000 times its size and acts as a natural adhesive binding particles together. Mycelium is extremely tenacious–making it difficult to break apart bonded products like insulation.

How Mycelium Insulation Is Made

Mycelium spores are introduced into organic waste products such as sawdust, straw, soybean hulls, etc. in a controlled environment. Within 5 to 10 days the mycelium grows throughout the organic material–forming a foam-like rigid board. The boards are strong and rigid. Also fire, mold, and water resistant.

The resulting material is compressed and sterilized to stop growth–then cut to size. The boards or blocks remain inert unless they become soaked–allowing the growth process to resume. Mycelium insulation must be protected from weather and cannot be in contact with the ground.

Mycelium Insulation Uses

Mycelium insulation has many potential uses. Research and development are constantly improving the product. Mycelium may soon replace foam insulation on walls, in door cores, and be used in paneling, flooring, and furniture. Products available today include:

  • Rigid Insulation Boards. Used on walls and roofs. Still awaiting approvals and code upgrades in many locations.
  • Structural Insulated Panels. Mycelium is sandwiched between OSB panels to form SIPs. The mycelium acts as an adhesive–eliminating chemical glue.


The production of mycelium insulation makes use of growing agents instead of blowing agents like many traditional foam insulation products. Mycelium insulation has many benefits.

  • Green. Eco-friendly insulation. Uses all natural and renewable inputs during production. Low environmental impact. Low carbon footprint.
  • R-value. Approximately R-3.0.
  • Fire Resistant.
  • Moisture Resistant. Cannot be soaked.
  • Mold Resistant.
  • Non-toxic. No toxic chemicals used during the manufacturing process. No off-gassing of formaldehyde or volatile organic chemicals (VOC).
  • Biodegradable. Waste created during construction is compostable. The entire product composts at the end of life.
  • Sound. Claims to reduce 75% of noise under 1500 kHz.


  • Availability. Very few manufacturers. Distribution system is almost non-existent. Can be ordered from the manufacturers.
  • R-value. R-1.8 to R-4.0 per inch. Approximate average of R-3.0 per inch. (Living plant structure R-values are difficult to control.) For comparison, extruded polystyrene rigid board insulation is R-5.0 per inch.
  • Cost. Approximately $0.66 per board foot. (A board foot is 12” x 12” x 1” thick.) For comparison, extruded polystyrene costs approximately $0.42 per board foot. XPS is readily available.
  • Water. Mycelium cannot get soaked. It will start growing again.

DIY Mycelium Insulation

Factory-produced mycelium insulation can be difficult to find. There are few mass producers in the market–yet. Some inventive homeowners/builders are “growing” homemade mycelium insulation onsite. 

Additional Uses Of Mycelium

Mycelium blocks are also molded into furniture and used as packaging material. In addition to insulation panels, one English company (Grown Bio) offers “Grow It Yourself” mycelium growing kits c/w with molds for products such as planter pots, drink holders, bricks, and many more.

Mycelium insulation may become one of the preferred insulations in the near future. It is a very eco-friendly insulation with a decent R-value. Fire resistant. Water resistant. Biodegradable. Non-toxic. More improvements and standardization are sure to come with increased research and development.