6 Things to Know About Sheep’s Wool Insulation

Say goodbye to hazardous home insulation and hello to an eco-friendly, nontoxic alternative.

Bags of Sheep Wool


From the ground up, insulation is a necessity in the home. Tucked behind walls, nestled beneath floors, and hidden above ceilings, this material helps regulate temperature, minimize sound, and conserve energy indoors. Homeowners have several different types of insulation from which to choose, and each has advantages and disadvantages.

Many old homes are rife with hazardous forms of insulation, the worst of which is asbestos. Banned in most countries since the 1980s, asbestos has been linked to mesothelioma, lung cancer, and other health problems. Other forms of outdated insulation, like vermiculite and urea formaldehyde foam, are also harmful.

If you live in an older home and plan to upgrade your insulation, be sure to test for asbestos and, if it is present, enlist professional help to remove it safely. All potential dangers to human health aside, old insulation is also less effective at insulating the home. Sheep’s wool insulation is an eco-friendly, nontoxic alternative to conventional insulations. Here are six important things to know about sheep’s wool insulation, and why it makes such a terrific insulation for the home.

1. Sheep’s wool insulation is noncarcinogenic.

Among the most popular insulation materials today are fiberglass and rockwool (also known as mineral wool). While these materials are considered safe by institutes such as the U.S. National Toxicology Program and the International Agency for Research on Cancer, they do contain synthetic, hairlike fibers that can break off and become airborne during installation. They also contain formaldehyde, which is known to release volatile organic compounds (VOCs) into the air. Both airborne fibers and formaldehyde can irritate the skin and lungs, and long-term exposure to formaldehyde may cause some types of cancer. Even spray foam insulation can be toxic. During installation and before it cures completely, the material is especially dangerous due to the high level of VOCs that off-gas into the air. Sheep’s wool insulation, however, comes from humanely sheared wool from sheep—with no hidden ingredients to be wary of.

Discarded sheep’s wool deemed too coarse to make into clothing or other fabric is often used for insulation. When sheep’s wool insulation has outlived its use inside your home, it can be recycled or composted. The fact that it’s nontoxic and eco-friendly aren’t the only reasons that this kind of insulation is worth looking into, though.

2. It has a high R-value per inch.

One of the primary benefits of sheep’s wool insulation is its stellar R-value. R-value is the measurement of an insulating material’s resistance to conductive heat flow, and the higher a material’s R-value, the more effective it is as insulation. Sheep’s wool is a thick, dense material, making it an excellent insulator. Sheep’s wool insulation offers an R-13 to R-19 value, which is equal to or greater than most of its fiberglass, cellulose, and rockwool counterparts. It’s eco-friendly and outperforms synthetic insulators, which is why sheep’s wool insulation is such a desirable product for environmentally conscious homeowners.

Close up of worker with electric screwdriver fastening drywall


3. Sheep’s wool insulation is durable.

Sheep’s wool insulation offers supreme durability due to its elasticity, and will keep a home toasty or cool for years to come. Each wool fiber acts like a coiled spring: It elongates when extended and retracts when it’s released, which is why wool is highly resistant to breakage and tearing. Sheep’s wool has a protective skin that acts as a shield against abrasion. Unlike synthetic fibers, sheep’s wool insulation is a natural, rapidly renewable material that can be reused and/or recycled because it’s so durable.

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4. It regulates humidity.

The fibers in sheep’s wool insulation have a water-repelling exterior and a water-tolerant interior. If wool becomes inundated with moisture, the follicles within the fiber can hold up to a third of its weight. The wool will still be dry to the touch but it will continue to insulate, even during periods of high humidity. Because of its semi-permeability, wool functions as a temperature regulator: it absorbs moisture from the atmosphere of greater humidity and releases it to the drier atmosphere. Essentially, sheep’s wool creates a balanced environment.

Moldy Ceiling


5. Sheep’s wool insulation resists fire and mold.

Since sheep’s wool contains moisture in each fiber, it doesn’t need the dangerous flame retardants that are added to synthetic insulation. A self-extinguishing material with a high nitrogen content of approximately 16 percent, sheep’s wool won’t support flames below temperatures of 1,040 degrees Fahrenheit. And because wool is a keratin, it resists mold growth.

6. Sheep’s wool insulation also provides good sound dampening.

With a noise reduction coefficient of 0.90 to 1.15, sheep’s wool insulation makes a supreme sound barrier for the home. The molecular makeup of sheep’s wool is helical, which reduces airborne sound, surface noise, and sound transmission. Its viscoelastic properties also help the fiber convert sound energy to heat.

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