When considering insulation beyond low-grade historical norms (fiberglass and cellulose) attention can quickly drift to wool. However, not all wool is created equal. The commentary below is an effort to discuss and highlight the differences between what we do at Havelock Wool and our real wool products versus what Rockwool does with their basalt rock and slag product.
Let’s be fair. As it relates to performance both of these products are superior to incumbents. Nevertheless, they are not equal and understanding the differences is relevant for all of us.
Both offer thermal protection and sound dampening, their impact on your health, the environment, and your home’s "breathability" is vastly different. Here is a breakdown to help you decide which is right for your project.
1. Material & Sustainability
The most fundamental difference is where these materials come from and how much energy it takes to make them.
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Havelock Wool: This is a renewable, carbon-sequestering resource. Sheep are shorn annually, and the wool grows back naturally. The manufacturing process is "low-heat," requiring a fraction of the energy compared to synthetic or mineral-based options. It is entirely biodegradable; at the end of its life, it can literally be composted.
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Rockwool: Also known as mineral wool, this is made by melting basalt rock and slag in massive furnaces at temperatures exceeding 2,900°F. This is an energy-intensive industrial process. While stone is abundant, it is not "renewable" in the same cycle as wool, and the product is not biodegradable.
2. Health & Indoor Air Quality
For many homeowners, the deciding factor is what they are putting behind their walls and breathing every day.
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Havelock Wool: It is naturally hypoallergenic and non-toxic. Remarkably, wool actually filters the air. The amino acids in wool fibers permanently bond with harmful chemicals like formaldehyde, nitrogen oxide, and sulfur dioxide, stripping them from your indoor environment.
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Rockwool: Historically, mineral wool has relied on formaldehyde-based binders to hold the fibers together. While some modern "EVO" lines are moving toward formaldehyde-free options, most standard Rockwool still contains chemical resins. Furthermore, mineral wool sheds tiny, needle-like fibers during and after installation that can irritate the skin, eyes, and lungs.
3. Moisture Management (Hygroscopic vs. Hydrophobic)
This is where the science of your house "breathing" comes into play.
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Havelock Wool is Hygroscopic: It loves moisture—but in a good way. It can absorb up to 33% of its weight in moisture vapor without feeling wet or losing its insulating R-value. It manages humidity by taking it in when it's damp and releasing it when it's dry, protecting your wooden studs from rot.
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Rockwool is Hydrophobic: It repels liquid water, which is great for flood-prone areas. However, it does not "manage" moisture vapor. It is highly permeable, meaning vapor passes through it, but it cannot actively pull moisture away from your structure like sheep's wool can.
4. Fire & Sound Performance
Both materials excel here, though for different reasons.
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Fire Resistance: Rockwool is the industrial leader of fire safety, withstanding temperatures over 2,000°F. It is often used as a "fire stop." Havelock Wool is also naturally fire-resistant; it has a high nitrogen content, meaning it will self-extinguish and char rather than melt or carry a flame.
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Sound Attenuation: Both are far superior to fiberglass. Rockwool is denser, which is excellent for blocking low-frequency thumps. Havelock Wool’s complex fiber structure is world-class at absorbing mid-to-high frequency sounds, making a room feel "quiet" rather than just "muffled."
Comparison Summary Table
|
Feature |
Havelock Wool (Sheep) |
Rockwool (Mineral) |
|
Source |
Renewable (Sheep's Wool) |
Non-renewable (Rock/Slag) |
|
Energy to Make |
Very Low |
Very High |
|
Air Quality |
Filters toxins (Formaldehyde) |
Can release fibers/particulates. May be made with formaldehyde |
|
Binders |
<10% recycled bico |
Typically uses resins/formaldehyde |
|
Moisture |
Absorbs/Releases (Hygroscopic) |
Repels liquid (Hydrophobic) |
|
Installation |
Safe to touch; no PPE needed |
Requires gloves, mask, and long sleeves |
|
End of Life |
Compostable |
Landfill |
The Verdict: Which should you buy?
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Choose Havelock Wool if: You prioritize a healthy home, want a material that manages humidity naturally, and care about a low-carbon, biodegradable footprint. It is the "gold standard" for those sensitive to chemicals.
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Choose Rockwool if: You require commercial grade fire ratings for a specific building code, or are insulating an area that may be subject to flooding.
