organic / Animal-Derived / Natural Fiber Insulation

Sheep Wool Insulation Batts

Natural sheep wool fiber insulation with thermal conductivity 0.033-0.040 W/mK, natural hygroscopic moisture regulation (up to 30% absorption without R-value loss), self-extinguishing fire properties (ignition 560-600 degC), and carbon sequestration (1.8 kg CO2 stored per kg wool).

Atlas code

ORG-ANI-INS-001

organicanimal-derivedsheep-woolnatural-insulationrenewablebiodegradablefire-resistant

At-a-glance signals

Overview

Executive summary

Sheep wool insulation is a natural, renewable fiber insulation material processed from sheep fleece. The material combines excellent thermal performance (lambda 0.033-0.040 W/mK, R-value 3.6-4.3 per inch) with natural moisture management properties — wool fibers can absorb up to 30% of their weight in moisture without losing insulation effectiveness. The keratin protein structure provides natural fire resistance with an auto-ignition temperature of 560-600 degC (twice that of wood), self-extinguishing behaviour, and low smoke/toxicity. Carbon makes up 50% of wool's weight, with 1 kg of clean wool storing 1.8 kg of CO2. Available as batts, rolls, and loose-fill for wall, ceiling, and floor applications.

Best when…

Exceptional hygroscopic moisture management — absorbs 30% weight without losing R-value
Thermal conductivity 0.033-0.040 W/mK (comparable to or better than mineral wool)
Auto-ignition temperature 560-600 degC — twice that of wood, self-extinguishing
Carbon sequestration: 1 kg wool stores 1.8 kg CO2 permanently
Non-irritant — safe to handle without protective equipment (no itching/fibres)
Naturally antimicrobial, mould-resistant, and pest-resistant (with borax treatment)
Excellent acoustic absorption — wool absorbs up to 55% of noise
50+ year service life without settling or degradation
Australian wool supports rural economies (55% of world wool production)
100% biodegradable and compostable at end of life

Top advantages

01 Exceptional hygroscopic moisture management — absorbs 30% weight without losing R-value
02 Thermal conductivity 0.033-0.040 W/mK (comparable to or better than mineral wool)
03 Auto-ignition temperature 560-600 degC — twice that of wood, self-extinguishing
04 Carbon sequestration: 1 kg wool stores 1.8 kg CO2 permanently
05 Non-irritant — safe to handle without protective equipment (no itching/fibres)

Top limitations

01 Approximately 4x cost of fiberglass insulation — significant price premium
02 Limited Australian manufacturing (Mountain Made is primary local producer)
03 40% of raw wool lost during manufacturing processing
04 Moth attraction if untreated — borax treatment essential
05 Higher embodied carbon than hemp or cotton insulation (sheep farming emissions)

Technical

Physical ·8

Density: 10-47 kg/m3 Standard thermal batts 10-26 kg/m3. High-density acoustic products up to 47 kg/m3 (Terra Lana). Wool-hemp blends 10-18 kg/m3. Density affects both thermal and acoustic performance. Source: ResearchGate thermal conductivity study; Terra Lana specifications; ISOLENA product data.
Specific gravity: 1.30-1.35 (fiber); 0.01-0.05 (batt) Wool fiber specific gravity approximately 1.30-1.35 (individual fiber). Bulk insulation batt specific gravity much lower due to air content (0.01-0.05). Source: MakeItFrom.com wool properties.
Porosity: 90-97 % Very high porosity from natural fiber crimp structure creating millions of air pockets. Open-cell structure provides both thermal insulation and moisture vapour permeability. Source: wool fiber structure literature.
Water absorption: Up to 30-33% (without losing insulation performance) % Exceptional hygroscopic property — wool absorbs up to 30-33% of its weight in moisture vapour without increasing thermal conductivity (verified under 30-60% RH at 23 degC). Wool actively regulates indoor humidity by absorbing and releasing moisture. Source: ISOLENA; ScienceDirect wool insulation study; Wikipedia wool insulation.
Hardness: N/A (soft flexible fiber) Shore Soft natural fiber — hardness not applicable. Material is flexible, compressible, and designed to friction-fit into wall/ceiling cavities. Source: product characteristic.
UV resistance: Low (not relevant — concealed application) Wool degrades under prolonged UV exposure (yellowing, fiber weakening). Typically used in concealed insulation applications where UV exposure is not a concern. Source: wool fiber degradation literature.
Chemical resistance: Good Good resistance to mild chemicals. Keratin protein stable in normal building environment. Vulnerable to strong alkalis (pH >11) which dissolve keratin. Borax treatment enhances chemical stability. Source: wool chemistry.
pH tolerance: 3-10 pH Wool keratin protein is naturally resistant to mild acids and alkalis. Borax treatment (pH ~9.3) is compatible. Vulnerable to strong alkalis which degrade keratin. Source: wool chemistry literature.

Mechanical ·5

Tensile strength: 120-180 (individual fiber) MPa Individual wool fiber tensile strength 120-180 MPa — among the strongest natural protein fibers. Excellent elongation at break (25-35%). Fiber strength not directly relevant to batt insulation performance. Source: wool fiber mechanical properties.
Compressive strength: Very low (non-load-bearing) kPa Very low — soft fibrous insulation designed for compression fit in cavities. No load-bearing capacity. Source: product characteristic.
Flexural strength: N/A (flexible fiber material) MPa Flexible fiber material — flexural strength not applicable. Material is designed to be flexible, compressible, and friction-fit into cavities. Source: product characteristic.
Impact resistance: N/A (soft compressible material) J/m Soft insulation material — impact resistance not a relevant parameter. Material compresses and recovers under impact. Source: product characteristic.
Creep resistance: Good (maintains loft and form over 50+ years) Good long-term form retention. Wool's natural crimp structure maintains loft and insulation thickness over decades. No settling or compression set in properly installed batts. 50+ year service life demonstrated. Source: wool insulation durability data.

Sustainability & Health

Embodied carbon & energy ·7

Embodied carbon: 0.8-1.5 (production) offset by 1.8 kg CO2/kg sequestration kg CO2-eq/m2 Embodied carbon 0.8-1.5 kg CO2-eq per m2 per inch of thickness (production). However, wool permanently sequesters carbon: 1 kg clean wool = 1.8 kg CO2 stored. Carbon makes up 50% of wool weight. Net carbon balance depends on manufacturing energy vs sequestration credits. Black Mountain claims carbon negative when sequestration included. Source: materialspalette.org; Ecohome embodied carbon comparison; ScienceDirect review.
Carbon footprint: 2-8 (production, before sequestration credit) kg CO2-eq/kg Complex carbon accounting. Production carbon: 2-8 kg CO2-eq/kg (includes sheep farming methane emissions). Sequestration credit: -1.8 kg CO2/kg wool. Net depends on farming practices and methane accounting methodology. Black Mountain claims carbon negative overall. Source: materialspalette.org; ScienceDirect embodied carbon review; UKRI wool insulation case study.
Embodied energy: 10-30 MJ/kg Wool insulation manufacturing uses 90% less energy than mineral wool. Light manufacturing process — washing, carding, borax treatment, batt forming. 40% wool processing waste increases energy per unit of finished product. Source: Black Mountain; materialspalette.org; ScienceDirect insulation embodied energy review.
Water footprint: 500-2000 (farming dependent) L/kg Significant water footprint from sheep farming (pasture irrigation, animal water consumption). This is the primary environmental concern for wool insulation. Estimated 500-2000 L/kg depending on farming practices and climate. Australian dryland farming has lower water footprint than irrigated systems. Source: wool lifecycle assessment literature.
Recycled content: 0-100 (product dependent, typically 75-85% wool) % Some products use recycled wool content — Mountain Made uses by-product wool from carpet manufacture. Thermafleece CosyWool contains 75% wool + 25% recycled fibers. Most products contain 15-25% recycled polyester binder for structural stability. Source: Mountain Made; Thermafleece; Pricewise Insulation.
Renewable content: 75-100 % Wool content is 100% renewable — annual sheep shearing harvest. Products containing polyester binder have 75-85% renewable content. 100% wool products (Havelock, NatuWool) achieve 100% renewable. Source: manufacturer specifications.
Circular score: 8.5 /10 Excellent circular economy potential — annually renewable, biodegradable, compostable, recyclable. Sheep farming concerns (methane, water, land use) reduce overall sustainability score slightly. Source: circular economy assessment.

Compliance & Fire

Fire performance ·6

Combustibility class: Self-extinguishing (Class A ASTM E84, with borax treatment) Self-extinguishing — wool chars and smolders but does not support sustained flame. High nitrogen content (16%) in keratin protein provides inherent flame retardancy. Borax treatment enhances fire performance. When exposed to flame, wool self-extinguishes when flame source removed. Source: ISOLENA; Green Coast; Wikipedia wool insulation.
Fire resistance level: Assembly dependent (wool contributes through self-extinguishing behaviour) minutes Fire resistance as part of wall/ceiling assembly depends on total construction. Wool insulation contributes through self-extinguishing behaviour and slow charring without flame propagation. Source: fire performance data.
Ignition temp: 560-600 degC Auto-ignition temperature 560-600 degC — approximately twice that of wood (270 degC). Among the highest ignition temperatures of any natural fiber. Source: ISOLENA; Green Coast; Building Renewable.
Flame spread index: <25 (Class A, ASTM E84) FSI Wool conforms to Class A of ASTM E84 test (best rating). Very low flame spread — will not support a flame below 593 degC (1100 degF). Borax treatment further reduces flame spread. Source: Havelock Wool; ASTM E84 testing data.
Smoke dev. index: 25-75 SDI Low smoke development from natural protein combustion. Wool does not melt or drip — chars in place. Significantly less smoke than polystyrene, polyurethane, or PVC-containing materials. Source: wool fire performance.
Heat release rate: 30-80 kW/m2 Very low heat release rate. Wool smolders and singes rather than burning with flame. Self-extinguishing when flame source removed. Source: ISOLENA; Green Coast wool fire properties.

Cost & Lifecycle

Capex & lead time ·6

Material cost (range): 15-60 (R-value dependent) AUD/m2 Approximately 4x cost of fiberglass insulation. Varies significantly with density, R-value, and source. R2.0 batts approximately $15-25/m2, R4.0 batts approximately $35-60/m2. 40% raw wool processing waste contributes to cost. Source: Pricewise Insulation; Black Mountain pricing extrapolated to AUD; general industry data.
Material cost (per unit): 12-50 (volume and R-value dependent) AUD/m2 Volume pricing for larger projects. Bulk discounts available from manufacturers. Source: industry estimates.
Lead time: 7-70 (source dependent) days Australian-manufactured products (Mountain Made): 7-14 days. International imports (Thermafleece, Black Mountain, Havelock): 6-10 weeks. Terra Lana (NZ): 2-4 weeks. Source: supplier estimates.
Lifecycle cost: 25-80 AUD/m2 Higher initial cost offset by 50+ year lifespan with zero maintenance and no replacement cycles. When annualised over building lifespan, cost premium reduces significantly. Carbon credit potential from sequestered CO2. Source: lifecycle cost analysis.
Annual maintenance: 0 AUD/m2/year Zero maintenance cost — permanent installation. Source: insulation practice.
Market availability: Moderate — specialist supply, growing availability Growing but limited Australian market. Mountain Made is primary local manufacturer (recycled carpet wool + synthetic binder). International products available through specialist sustainable building suppliers. Growing demand driven by Passive House, Green Star, and healthy building movements. Source: Build.com.au; Green Magazine; Pricewise Insulation.

Service life & durability ·3

Expected lifespan: 50+ years 50+ year service life without settling, degradation, or loss of thermal performance. Wool's natural resilience maintains loft indefinitely. Borax treatment provides permanent pest protection. Source: wool insulation industry data.
Maintenance interval: None required years Zero maintenance required once properly installed. No top-up, no retreatment, no replacement needed during building lifespan. Source: insulation practice.
Warranty period: 15-25 (lifetime available from some manufacturers) years Manufacturer warranties typically 15-25 years for correctly installed products. Some products carry lifetime warranties (Havelock Wool). Source: manufacturer specifications.

Layer D

Where it's used

Wall cavity insulation (timber and steel frame)

Roof and ceiling insulation

Floor insulation (suspended floors)

Acoustic insulation (internal walls)

Green building and Passive House construction

Renovation and retrofit projects

Commercial and residential applications

Heritage building restoration

Where it's used

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