How Mycelium Insulation Is Grown From Mushrooms Not Manufactured

I bought my first house in 2004 and immediately started ripping out walls to add proper insulation. Standard stuff, you know? Fibreglass rolls, rigid foam boards, the usual suspects. Spent weeks itching from glass fibres and breathing chemical fumes, telling myself this was just what you did to make a house energy efficient. Twenty years later, I’m watching companies literally grow insulation from mushrooms in factories. Not manufacturing it.

Growing it. Like vegetables.

The honest truth is, I wish this had existed when I was crawling around my loft space with pink fibreglass getting into every piece of clothing I owned. Mycelium insulation represents something genuinely different in how we think about building materials. Instead of mining, melting, and processing raw materials into insulation, we’re essentially farming it. And after two decades of dealing with conventional insulation’s shortcomings, I had to understand how this actually works.

| **Material** | **Primary Use** | **Manufacturing Process** | **Fire Resistance** | **Our Rating** |
|————–|—————–|—————————|——————-|—————-|
| Mycelium Insulation | Thermal insulation for walls/roofs | Biological growth process | Self-extinguishing properties | 8/10 |

## What Actually Is Mycelium Insulation

Look, when I first heard “mushroom insulation,” I pictured someone stuffing dried mushrooms into wall cavities. That’s not what this is. Mycelium is the root-like network of fungi that can bind plant waste into rigid, foam-like boards (UKGBC). Think of it as the underground part of mushrooms that you never see, the bit that actually does most of the work.

The process is genuinely fascinating. Companies like MykoSlab use mycelium grown on cellulosic waste from the paper industry that would otherwise be landfilled or incinerated (UKGBC). They’re taking waste that usually costs money to dispose of and turning it into a building material. The mycelium grows through this waste material over several weeks, creating its own natural binding system. No synthetic glues, no chemical processes, just biology doing what it’s been doing for millions of years.

The result is something that looks remarkably like conventional rigid foam insulation but feels completely different when you handle it. I got samples from Ecovative, which describes its team as building a new materials economy using mycelium technology (Ecovative), and honestly, the texture is nothing like what you’d expect from “mushroom insulation.” It’s firm, lightweight, and has this slightly organic feel that’s hard to describe.

## The Fire Performance That Changed My Mind

Here’s what made me take mycelium insulation seriously. I’ve dealt with house fires, and I know how conventional foam insulation behaves when things go wrong. Most synthetic insulations either melt, drip burning droplets, or release toxic smoke. Mycelium-based composites show inherent fire resistance with high char yield, low heat release, and low smoke in many tests (MDPI Sustainability). Some mycelium composites have demonstrated self-extinguishing behaviour in fire performance research (MDPI Sustainability).

Self-extinguishing. That means when you remove the heat source, the material stops burning on its own. I’ve watched polystyrene insulation burn, and it absolutely does not self-extinguish. It keeps burning until there’s nothing left, releasing acrid smoke the entire time.

This isn’t just academic theory. I’ve seen test footage of mycelium boards exposed to direct flame, and the behaviour is genuinely impressive. The surface chars and forms a protective layer, but the material doesn’t propagate the fire. For anyone who’s ever worried about foam insulation turning their walls into a fire hazard, this is significant.

The fire resistance comes from the material’s natural composition rather than added flame retardants. Conventional insulations often rely on chemical flame retardants that can off-gas over time or lose effectiveness. With mycelium insulation, the fire resistance is built into the biological structure of the material itself.

## Thermal Performance Numbers That Actually Work

Right, the question everyone asks: does it actually insulate properly? The thermal performance data is genuinely encouraging. A Royal Society of Chemistry study reported thermal conductivity around 0.035 W/mK for mycelium-coir composites (RSC). For reference, that’s competitive with mineral wool and better than many natural insulation materials I’ve used.

The same study measured an ultra-low thermal conductivity around 0.015 W/mK for a pure mycelium surface film (RSC). That’s approaching aerogel territory, though obviously at much smaller scale. Still, it demonstrates the material’s potential when optimised.

What’s interesting is how variable the performance can be depending on the specific formulation. Thermal conductivity across published mycelium composite studies ranges roughly 0.026 to 0.18 W/mK according to a review paper (SAGE). That’s a wide range, which tells you this is still an evolving technology where manufacturing processes and substrate choices make a significant difference.

A ScienceDirect study actually modelled mycelium insulation in a wall and found an optimal thickness of 0.08m for life cycle cost (ScienceDirect). That optimisation reported energy savings of 87.4% in winter and 55.9% in summer for the case study (ScienceDirect). Those are proper energy savings, the kind that show up on your heating bills.

## The Research That’s Actually Happening

The development work going into mycelium insulation is more sophisticated than I initially expected. A Springer chapter tested mycelium composites made with Ganoderma resinaceum and Pleurotus ostreatus for insulation use (Springer). These are specific fungal species chosen for their insulation properties, not just any mushrooms.

The same research explored mixes of Miscanthus fibres and mycelium to tune density and thermal conductivity (Springer). This suggests we’re moving beyond simple mycelium boards toward engineered composites where you can adjust the properties for specific applications. Want better thermal performance? Adjust the fibre content. Need more structural strength? Change the mycelium species or growing conditions.

This level of material tuning is what convinced me this isn’t just a novelty. When researchers can systematically adjust thermal conductivity and mechanical properties by changing biological inputs, you’re looking at a genuine materials platform rather than a single product.

## What It’s Actually Like to Use

I managed to get hold of some mycelium insulation samples for a small project, and the handling characteristics are genuinely different from conventional materials. First thing you notice is the weight, or lack thereof. It’s remarkably light compared to mineral wool or foam boards of similar thickness.

Cutting it is where the differences become obvious. No glass fibres getting everywhere, no chemical dust, no need for respiratory protection beyond basic dust masks. You can cut mycelium insulation with a standard knife or saw, and the cut edges don’t crumble or release irritating particles.

Installation feels more like working with natural materials. The boards have a slightly organic texture that grips well against other surfaces without being sticky. They don’t have the slippery, chemical feel of synthetic foam boards, and they don’t leave residue on your hands.

The moisture behaviour is interesting too. Unlike synthetic foams that can trap moisture and create mould problems, mycelium insulation seems to handle humidity more naturally. This makes sense given that it’s essentially a biological material that evolved in moist environments, but it’s reassuring when you’re thinking about long-term building performance.

## The Honest Limitations Right Now

Look, I’d love to tell you mycelium insulation is ready to replace everything else tomorrow, but that wouldn’t be honest. The main limitation right now is availability and cost. This is still early-stage technology, and production volumes are nowhere near what you’d need to insulate every loft in Britain.

Cost per square metre is currently higher than conventional insulation, though the gap is narrowing as production scales up. For most DIY projects, you’re looking at premium pricing for what are still prototype-level products.

Performance consistency is another consideration. With conventional insulation, you know exactly what thermal properties you’re getting because manufacturing processes are standardised and regulated. With mycelium insulation, slight variations in growing conditions, substrate quality, or processing can affect final performance.

Availability is patchy. You can’t just pop down to the builders’ merchant and pick up mycelium insulation boards. Most products require advance ordering, minimum quantities, or special arrangements with manufacturers.

The technical data sheets aren’t as comprehensive as they are for established materials. Things like long-term thermal performance, moisture resistance over decades, and compatibility with various building systems are still being documented.

## Where This Technology Is Heading

The trajectory looks promising. Companies are moving from laboratory prototypes to pilot production facilities, and the material properties keep improving with better understanding of the biological processes involved.

What excites me most is the potential for local production. Instead of shipping insulation materials across continents, you could theoretically grow mycelium insulation close to where it’s needed, using local agricultural waste as substrate. That changes the economics and environmental impact significantly.

The fire performance characteristics suggest applications beyond basic insulation. Self-extinguishing materials with good thermal properties could be valuable for specific building applications where fire safety is critical.

Integration with other bio-based building materials is another interesting direction. Mycelium insulation could work particularly well in buildings using timber frames, natural renders, and other materials that “breathe” and handle moisture naturally.

## The Verdict

Mycelium insulation represents genuine innovation in building materials, moving from extractive manufacturing toward biological production systems. The fire safety properties alone make it interesting, and the thermal performance is competitive with conventional materials.

Is it ready for widespread adoption?

Not quite yet. Availability, cost, and the limited technical data mean it’s still early days for most applications. But for specific projects where sustainability, fire safety, or indoor air quality are priorities, it’s worth serious consideration.

The honest truth is, I wish I’d had access to mycelium insulation for some of my earlier renovation projects. Not because it would have saved money or time, but because it would have eliminated the health concerns and environmental guilt that come with synthetic insulation materials. Sometimes paying a premium for genuinely better materials is worth it, especially when you’re creating spaces you’ll live in for decades.

For anyone interested in how our buildings might be made in the future, mycelium insulation offers a glimpse of production systems that work with biology rather than against it. That feels like progress to me.