Mycelium Building Materials: The Future? Mycelium building materials are grown fungal composites made by feeding a fungus with agricultural waste to create panels, blocks, or infill that can replace engineered foams and some insulation products. For DIYers considering low-embodied-carbon options, this article explains what mycelium building materials are, how they perform (strength, R-value, fire behavior, durability), how they are made at both commercial and small-batch scales, current cost and code hurdles, and practical places to use them on a small project. Readers will leave with a realistic sense of when mycelium makes sense now—and where to wait for more data and certification. TL;DR: - Mycelium building materials offer low embodied carbon and comparable insulation to natural fibers (typical thermal conductivity ~0.04–0.06 W/m·K) but currently cost more per m² than mainstream insulation. - Best current uses: interior acoustic panels, non-structural infill, and temporary formwork...