Updated March 2026 · 10 min read
Spray foam is the most commonly installed insulation in new construction. Hempcrete is the fastest-growing alternative. We compared them across 12 practical factors so you can judge which fits your project — not which "wins."
Hempcrete (also called hemp-lime) is a category of bio-based building materials, not a single product. Mr Hemp House® works with hemp-lime and other healthier material systems and also develops its own Gaia™ Building Systems, including GaiaCrete™.
The appropriate system depends on climate, assembly design, budget, project goals, code requirements, and installation quality. Spray foam offers higher R-per-inch and lower upfront cost; hemp-lime offers vapor-open drying, moisture buffering, and thermal mass within a thicker wall.
Comparison tables show R-values and costs. Material chemistry and moisture behavior matter too:
Spray foam is produced on site from methylene diphenyl diisocyanate (MDI) and a resin blend. MDI is a recognized respiratory sensitizer, and improperly mixed or applied foam has been documented to emit for extended periods. Correct mixing, application, ventilation, and cure time are central to product performance.
Hemp-lime is hemp hurd, a lime-based binder, and water. It has no added VOCs, is vapor-permeable, and its mineral alkalinity gives it mold-resistant characteristics. Actual mold risk still depends on bulk-water management, assembly design, indoor humidity, ventilation, workmanship, exposure, and maintenance.
You spend 90% of your life indoors. The insulation surrounding you matters more than almost any other building decision. Read our full guide on spray foam dangers → Coastal homeowners weighing this decision can also see our regional playbook for hemp insulation in Virginia Beach, VA.
Upfront price is only one input. A fair comparison accounts for:
Because those variables differ on every project, Mr Hemp House® does not publish a fixed payback period or percentage saving. Work the numbers for your own project with our cost calculator, or review the material options on our natural and bio-based building materials hub.
They solve different problems. Spray foam is a high-R, air-sealing cavity fill with isocyanate-based chemistry, while hemp-lime is a vapor-permeable, moisture-buffering infill with mold-resistant characteristics from its mineral alkalinity and no added VOCs. The appropriate system depends on climate, assembly design, budget, project goals, code requirements, and installation quality.
GaiaCrete™ hemp-lime building material costs $180–$360+ per square foot installed for completed wall assemblies vs $3-7/sq ft for spray foam. Long-run cost of ownership depends on service life, maintenance, energy prices, climate, and assembly design, so Mr Hemp House® does not publish a payback period.
For planning purposes, GaiaCrete™ hemp-lime is R-2.5+ per inch, compared to spray foam at R-3.5 to R-6.5 per inch. Actual hemp-lime performance varies by formulation, density, moisture content, installation, and assembly. Beyond per-inch R-value, GaiaCrete™ adds thermal mass that stores and releases heat slowly, reducing HVAC cycling.
Discuss a hemp-lime building project with our team, or explore the material options first.
Detailed cost comparison of hemp vs spray foam
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