Hempcrete (Hemp Concrete)
Concrete from hemp — builds, breathes, absorbs CO₂
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Hempcrete is a biocomposite of industrial hemp shiv (Cannabis sativa, non-narcotic) + lime binder. Lightweight: 6–8× lighter than concrete. Insulation: R-value 2.0–3.5 per inch. Vapor-permeable: 'breathes' (regulates humidity). Carbon-negative: absorbs CO₂ (hemp during growth + lime during carbonation). For furniture and interiors: wall panels, acoustics, decorative blocks, countertops (with reinforcement), art objects.
TECHNICAL PASSPORT
Reception Space experiments with hempcrete on 0.5% of projects: acoustic panels (porosity = NRC 0.60–0.75), decorative wall blocks (texture: natural, 'alive'), furniture inserts (eco-statement). 2026 trend: hempcrete prefab panels — fast installation. Leaders: IsoHemp (Belgium), Just BioFiber (Canada), UK Hempcrete (UK).
Varieties & Types
Monolithic (Cast-in-Place)
$$$Formwork casting — classic
Hemp shiv + lime + water → cast in formwork on frame (wood/steel). Drying: 4–8 weeks. On frame: non-structural (frame bears load). Thickness: 8–16". For: walls, partitions.
Blocks (IsoHemp)
$$$$Prefab blocks — fast installation
Factory blocks: 24"×12"×6" (like AAC). Installation: laid with lime mortar. 3× faster than cast. For: walls, partitions, cladding. IsoHemp (Belgium): leader.
Panels (Compressed)
$$$Thin panels — for finishing
Hemp shiv + lime → compressed → thin panels (¾–2"). For: acoustics, wall decor, interior insulation. Installation: on frame/adhesive. Lighter than blocks.
Plaster (Hemp Plaster)
$$Lime-hemp plaster
Fine hemp shiv + lime + sand → plaster (⅜–1¼"). For: finish coat (textured, breathable). Over hempcrete or brick. Hand-applied.
Advantages
- ✓Carbon-negative — absorbs 175–280 lb CO₂/yd³. Only building material with negative carbon footprint
- ✓Insulation — R-value 2.0–3.5: 12" wall = R-24 (no additional insulation needed). Warm winter, cool summer
- ✓Breathing — μ = 5–8: regulates humidity 40–60% (no mold, no condensation). Healthy indoor climate
- ✓Fire resistance — self-extinguishing: 2 hours fire. Won't burn, won't melt. Safe
- ✓Acoustics — NRC 0.60–0.75: sound absorption. For: office partitions, bedrooms
- ✓Durability — lime: hardens over time (100+ years). Like Roman buildings. Gains strength
Limitations
- ⚠Strength — 72–290 PSI: non-structural (frame mandatory: wood/steel). Can't replace concrete for foundation
- ⚠Drying — cast: 4–8 weeks drying (wet installation). Blocks: dry (faster). Winter: difficult
- ⚠Price — from $36/sq ft (vs AAC: from $18/sq ft). 2× more expensive (but: no insulation needed → savings)
- ⚠Availability — hemp shiv: limited supply in many regions. Import: Belgium, France, Canada
- ⚠Moisture — direct water contact: not recommended (absorbs). Foundation: waterproofing mandatory
- ⚠Skill — builders: little experience (rare material). Mistakes: wrong proportions → weak result
Applications
Walls — cast/blocks: thermal + acoustic + breathing. For: private homes, co-working, eco-hotels.
Partitions — blocks/panels: sound insulation + humidity regulation. For: offices, studios.
Acoustic panels — NRC 0.60–0.75. Natural texture. For: restaurants, lobbies, co-working.
Insulation — panels (2") interior: R-7. For: renovation of old buildings (breathable assembly).
Decor — blocks/panels: natural texture (shiv visible). Eco-statement. For: lobbies, showrooms.
Plaster — hemp plaster: finish coat. Textured, breathable. For: eco-interiors, spa.
Pricing & Economics
Pricing Factors
- ·Method — cast: base. Blocks: ×1.3. Panels: ×0.5 (thinner). Plaster: ×0.3
- ·Thickness — 6": base. 8": ×1.3. 12": ×1.8. 16": ×2.5
- ·Source — local hemp: base. IsoHemp (import): ×1.5. Just BioFiber: ×1.8
- ·Finish — natural: base. Plaster: +30%. Lime wash: +15%
- ·Volume — 100 sq ft: base. 500+: –15%. 2000+: –25%
Care & Longevity
Daily Care
Dry cloth. Lime surface: don't wash with water (absorbs). Stains: soft brush.
What to Avoid
Water (absorption). Impacts (brittle: 72–290 PSI). Cement plaster over it (blocks breathing).
Periodic Maintenance
Lime wash: every 5 years (refreshes surface). Inspect: cracks (fill with mortar).
Professional Care
Crack repair: hemp shiv + lime → fill = from $12. Plaster: refresh from $9/sq ft.
Expert Reviews
Average Rating · 5 expert reviews
«Hempcrete: 5 homes in 3 years (Moscow region, Kaluga). Cast-in-place: hemp shiv (Penza) + lime (Tula). 12" wall: R-22 (warm without insulation!). Drying: 6 weeks (summer). Indoor climate: clients say 'breathing feels easy.' Issue: builders don't know material (trained myself: 3 days). Price: ×1.3 vs AAC + insulation (but: long-term cheaper).»
«Hempcrete panels (2"): 8 offices. NRC 0.65: good absorption. Texture: natural (shiv visible — eco-look). Install: on frame (1 day / 500 sq ft). ESG report: carbon-negative material. Minus: fragile (during transport: 5% breakage). For eco-offices: perfect.»
«IsoHemp: 1,000+ homes in 10 years (EU). Blocks: factory quality (dry, calibrated). Laying: like AAC (1 day / 300 sq ft). R-value: 12" wall = R-24. Mold: 0 (pH 12+). CO₂: 1,600 sq ft home = –33,000 lb CO₂ (carbon-negative). Warranty: 20 years. Future of construction.»
«Hempcrete for LEED projects: 3 projects (office, eco-hotel, co-working). Carbon-negative: LEED MR + EA credit. Acoustics: NRC 0.65 (partitions). Humidity: 45–55% (no humidifier). Story: 'walls absorb CO₂' — PR gold. Minus: availability (import ×1.5). But: local hemp emerging (2026+).»
«Hemp plaster: 30+ projects. Texture: velvety (fine shiv + lime). Application: like regular plaster (trowel). Thickness: ⅝–1". Result: warm, breathable wall (vs gypsum: cold). For spa/eco-hotels: clients love it. Price: ×1.5 vs gypsum (but: no vapor barrier → savings).»
Frequently Asked Questions
No — industrial hemp (Cannabis sativa L.): THC < 0.2% (non-narcotic). Used: shiv (woody core of stem: byproduct after fiber extraction). Legal: in EU, Canada, USA, most countries. For: building materials, textiles, paper. Absolutely safe and legal.
Strength: hempcrete 72–290 PSI vs concrete 4,350+ PSI (hempcrete: non-structural). Weight: hempcrete 6–8× lighter. Thermal: hempcrete R-3.5/inch (concrete: R-0.1 = cold). CO₂: hempcrete absorbs (concrete: emits 8×). For: hempcrete = insulation + infill. Concrete = structure. Combination: frame (concrete/wood) + hempcrete (walls).
Globally: 30+ countries cultivate industrial hemp. Major producers: China, France, Canada, Russia. USA: 2018 Farm Bill legalized. Growth: 100 days seed-to-harvest. Yield: 8–10 tons shiv/ha. CO₂: 1 ha absorbs 15 tons CO₂. The plant that could save construction.
Limited: 1) Acoustic panels (NRC 0.60–0.75): yes. 2) Decorative blocks (shelving, partitions): yes (with frame). 3) Countertops: no (weak, porous). 4) Inserts (eco-statement): yes. 5) Art objects: yes. For furniture: hempcrete = decorative-acoustic material. Not structural.
Cast: 4–8 weeks (depends on thickness, ventilation, temperature). At 68°F: 4 weeks. Winter (<41°F): not recommended. Blocks (IsoHemp): factory-dried → installation = 1 day. Panels: dry → adhesive/frame = 1 day. For speed: blocks/panels (cast: summer only).
No mold — lime binder: pH 12+ (alkaline environment = fungicidal). Mold: won't grow on lime. + Vapor permeability (μ = 5–8): moisture exits. Condensation: none. For: bathrooms (if no direct water contact), bedrooms (healthy indoor climate). Antimicrobial: by nature.
1) Hemp during growth: absorbs CO₂ (1 ha = 15 tons CO₂). 2) Lime: during carbonation (years after application) absorbs CO₂ (Ca(OH)₂ + CO₂ → CaCO₃). 3) Total: 1 yd³ hempcrete = –175–280 lb CO₂. Comparison: 1 yd³ concrete = +525 lb CO₂. Difference: –800 lb CO₂/yd³. Only carbon-negative building material.
Yes — 5,000+ homes worldwide (France, UK, Canada, Australia). Frame: wood/steel (hempcrete: infill). R-value: 12" wall = R-24 (no additional insulation). Lifespan: 100+ years (lime hardens). Cost: ×1.5 vs conventional (but: no insulation, no vapor barrier → operational savings). Trend: 2026+ — mainstream construction.
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