You already know fiberglass insulation. It's the pink scratchy stuff inside almost every American home. But do you know what it's doing to your family's health? After 20 years of renovation work, I've pulled fiberglass out of thousands of homes — and what I've seen inside those walls changed everything about how I build.
This is the complete, honest comparison between hemp insulation and fiberglass. No fluff, no greenwashing. Just what every homeowner needs to know before their next insulation decision.
What Is Hemp Insulation?
Hemp insulation is made from the inner fibers of industrial hemp plants — the same plant that has been used in construction for thousands of years across Europe and Asia. It comes in batts and rolls just like fiberglass, fits standard 2×4 and 2×6 stud cavities, and can be installed by any contractor. Since the 2018 Farm Bill legalized industrial hemp nationwide, American-made hemp insulation products have been rapidly expanding.
At Mr Hemp House, our flagship insulation system is GaiaCrete® — our proprietary bio-based building material that combines hemp hurd with a lime binder for walls, and hemp fiber batts for standard stud cavity insulation. Both are 100% bio-based, American-made, and veteran-owned.
R-Value: How They Compare
Hemp insulation carries an R-value of approximately 3.5 to 3.7 per inch — comparable to standard fiberglass batts which run between 2.9 and 3.8 per inch. Here is where it gets interesting: hemp batts can be compressed into a smaller cavity without losing R-value. A 5.5-inch hemp batt compressed into a 3.5-inch stud cavity still delivers R-19.25. Fiberglass loses R-value when compressed because the air that provides its insulating capacity gets squeezed out.
Hemp also has a U-value of 0.039 — nearly the equivalent of 8 inches of fiberglass in a standard wall assembly.
Health and Safety: The Honest Truth About Fiberglass
This is where the conversation changes completely.
Fiberglass insulation is made from literal strands of glass blown so thin they are measured in microns. During installation, removal, or disturbance, these microscopic glass fibers become airborne. Inhaling them irritates the respiratory tract, causes coughing and throat irritation, and with prolonged exposure, increases the risk of asthma and bronchitis. Installation requires masks, gloves, goggles, and full protective clothing.
Hemp insulation contains no VOCs, no chemical binders, and no glass fibers. You can install it bare-handed. It does not off-gas. It does not cause skin irritation. For families with children, elderly members, or anyone with respiratory conditions, the difference is not a matter of preference — it is a matter of health.
After 20 years of seeing families suffer from homes filled with toxic building materials, this is exactly why I wrote The Poisoned Home and founded Mr Hemp House. The materials inside your walls are affecting your family's health right now, whether you know it or not.
Moisture Management: Where Fiberglass Fails
Fiberglass behaves like a cotton ball when it gets wet — it absorbs moisture and holds it there. That trapped moisture becomes the perfect breeding ground for mold. This is why so many American homes have mold problems hidden inside the walls, and why the CDC estimates 72 million American homes have mold issues.
Hemp insulation is hygroscopic — it absorbs and releases moisture naturally, just like wood. When a wall cavity gets wet from condensation or a minor leak, hemp dries out and returns to full performance. It never traps moisture. It never creates mold conditions. When combined with a GaiaCrete® or lime plaster wall system, the breathable wall assembly actually regulates indoor humidity automatically — no vapor barriers required.
Fire Resistance
Fiberglass itself does not burn, but the binders and facings used in many fiberglass products do — and when spray foam or fiberglass facings burn, they release toxic fumes including cyanide compounds.
Hemp insulation is naturally fire-resistant. The dense plant fiber chars on the surface and self-extinguishes rather than spreading flame. When combined with our GaiaCrete® lime-based wall system, fire ratings extend to several hours with zero toxic fume release.
Environmental Impact
Fiberglass production is energy-intensive and the product does not biodegrade. At the end of its life, it goes to the landfill.
Hemp insulation sequesters more carbon during plant growth than is released during manufacturing — making it carbon negative. At end of life it can be composted or recycled. A 2025 study from Georgia Tech published in the Journal of Cleaner Production confirmed that hemp insulation can directly replace fiberglass in residential and commercial buildings while significantly reducing a structure's carbon footprint.
Cost Comparison
Hemp insulation costs more upfront — typically $1.40 to $3.10 per square foot versus $0.30 to $1.50 for standard fiberglass. However, when you factor in improved durability, zero mold remediation costs, no vapor barrier requirement, and the long-term health costs avoided, the lifetime value calculation shifts significantly. As American hemp production scales, prices are projected to drop considerably over the next five years.
The Bottom Line
If you are building a new home or planning a renovation and you want the healthiest, most durable, most sustainable insulation available — bio-based hemp insulation wins in every category that matters for your family's health and your home's longevity.
Fiberglass is cheaper today. But it costs you in ways that don't show up on the invoice.
Schedule a Healthy Home Assessment with Mr Hemp House to evaluate your current insulation and get a personalized plan for upgrading to bio-based materials.