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Sheep's Wool Insulation

Naturally fire-resistant, moisture-buffering animal fiber — biodegradable at end of life.

Sheep's Wool Insulation — a natural material we specify on every Earth Bound Homes project

Toxicity Screening — All Clear

This material screens clear across all seven independent toxicology authorities we use on every project.

LBC Red List

Not Listed

Prop 65

Not Listed

IARC

Not Listed

NTP RoC

Not Listed

GSPI

Not Listed

REACH SVHC

Not Listed

TSCA

Not Listed

Material Type

Animal-Fiber Thermal Insulation

Material Description

Sheep's wool insulation is exactly what it sounds like — wool fibers, cleaned, lightly carded, and batted into mats or loose-fill. The keratin protein in wool is naturally hygroscopic: it can absorb and release up to 35% of its weight in moisture without losing R-value, which makes it remarkable at buffering humidity swings inside a wall cavity. Wool is also naturally flame-resistant — it self-extinguishes rather than burning, because keratin has a high nitrogen content and a high autoignition temperature. Manufacturers typically treat wool with borate for insect resistance; borate is itself low-toxicity to mammals and the levels used pose negligible health risk. End-of-life: compostable.

Composition & Origin

Sheep's wool fiber — keratin protein backbone, naturally crimped, hygroscopic, with a thermal conductivity ≈ 0.038 W/m·K

Health Profile — All Endpoints Clear

Severity scored 0–10 against the same 10 hazard endpoints we use for the chemical families on the avoid list. Every score is 1–2 — essentially no signal across every endpoint.

Cancer

1/10

Endocrine

1/10

Reproductive

1/10

Developmental

1/10

Neurological

1/10

Respiratory

2/10

Cardiovascular

1/10

Liver/Kidney

1/10

Skin

1/10

Immune

2/10

Common Forms & Brands

Havelock Wool batts and loose-fill
Black Mountain Insulation NatuWool
Oregon Shepherd loose-fill wool
Common framing: 100% wool batts, wool/borate batts, dense-pack loose-fill

Why We Use It

No off-gassing — wool is the cured product, not a reactive chemistry
Naturally flame-resistant — self-extinguishes, no added flame retardants required
Moisture-buffering — absorbs and releases water vapor without losing R-value
Biodegradable at end of life — compostable rather than landfill-bound
Carbon-storing — sequesters atmospheric carbon in the keratin protein

Where It Performs Best

Wall cavity insulation (batts) in stud and rafter bays
Loose-fill attic insulation (dense-pack capable)
Acoustic insulation in interior partitions
Sound-deadening between floors

Building Applications for Sheep's Wool Insulation

Listed alphabetically. Where in a home this material earns its keep.

Attic Loose-Fill
Cathedral Ceiling Cavity
Floor Joist Bays
Interior Sound Partitions
Rim Joist Air Seal Backing
Wall Cavity Batts

Specifying a project? Drop the manufacturer's SDS into our SDS Toxic Chemical Screener to verify any specific product you're considering screens clear on all seven databases.