A Complete Guide to Sheep’s Wool Insulation – Advantages & Disadvantages

A guide to sheep wool insulation

Whether you want to save the world or just save money on your heating bills, it’s evident that having proper insulation installed in our homes is critical. The question is, which form of insulation material is the best, and what are the advantages of using one type over another?

Natural insulation includes sheep’s wool, flex, and hemp, as well as items made with a high proportion of recycled materials such as cotton, paper pulp, or wood pulp. In recent years, the building industry has relied heavily on oil-based insulation materials which are clearly not as environmentally friendly.

In terms of heat resistance, plastic materials such as polystyrene insulation boards polyurethane and phenolic foam, outperform natural insulation. In practice, this means that natural materials frequently necessitate a thicker layer of insulation to perform the same function in a building. That said, sheep’s wool has many additional advantages over just thermal resistance which make it still a useful insulation option for the more eco-conscious householder.

What is Sheep’s Wool Insulation?

what is Sheep's wool insulation
Image: Sheep’s wool

Regardless of the weather, the wool on a sheep’s back has made them hardy animals with the ability to survive outdoors. Wool fibres produce millions of small air pockets due to their crimped shape, trapping air and slowing heat transfer. This is why wool is a natural insulator, and possesses the ability to keep properties warm in the winter and cool in the summer.

Wool insulation is manufactured from sheep wool fibres that are mechanically or chemically bound together to develop insulating rolls and batts. Sheep’s wool insulation can be trimmed to size and used much like other types of insulation. Some manufacturers provide 100% sheep’s wool insulation, while other manufacturers provide wool-rich insulation (75% wool, 25% recycled polyester).

Let’s have a look at some of the advantages and disadvantages of Sheep’s Wool Insulation.

Advantages of Sheep’s Wool Insulation

Natural, Renewable, and Sustainable

Sheep’s wool is one of the most sustainable insulating materials. Sheep are shorn at least once every year (sometimes twice), and the wool grows back naturally. Wool is a plentiful raw resource that is continuously renewable and produced domestically in the United Kingdom. It lasts for decades and can be composted at the end of its life. There are no plastic fibres in this insulation, as opposed to oil-based insulation.

Plastic pollution’s negative consequences on our planet are becoming more widely recognised. While the amount of recovered plastic insulation is increasing, the vast majority is still discarded, but thankfully this is not an issue with a plastic-free insulator like sheep’s wool.

Low Carbon Production

Production of insulating material still comes with an environmental cost in terms of taking into account the gases emitted by fossil fuels either extracting the raw material and manufacturing it. For example, to make plastic insulation, for example, you need oil, chemicals, and a lot of energy. Meanwhile, rock wool requires heat to manufacture and spin it to produce fibres.

Where sheep’s wool has the advantage is it only requires a small percentage of the energy required to produce than manufactured synthetic insulating materials. This means the gases produced during the manufacturing process will be more than negated by the amount conserved by the sheep’s wool insulation.

High Moisture Performance

Wool, according to manufacturers, is one of the few permeable insulating materials, naturally absorbing and releasing moisture.

While the outside layer of wool is hydrophobic (resistant to water), the cortex or interior layer is hydrophilic (water-loving). The cortex may absorb water without causing the wool to become moist. This helps to keep the surrounding timbers dry and prevents mould growth when used as an insulating material within the home.

Wool, unlike many other textiles, can absorb 30% of its weight in moisture before it affects its thermal qualities. This makes it ideal for use as an insulator in humid climates such as the UK.

Aids Temperature Control

When the fibres from wool absorb moisture, they release it as heat back into the atmosphere, increasing the temperature of the surrounding area. Wool’s natural tendency to absorb moisture in humid situations and release it when dry, according to manufacturers, can assist maintain stable temperatures within a building, delivering more comfort.

Easy Installation

Sheep’s wool is both safe and simple to install. Unlike many man-made insulations, it will not irritate the skin, eyes, or lungs (unless you have a wool allergy). When working with glass wool or rock wool insulation, a full-face mask, goggles, and gloves are required.

Sheep’s wool insulation is simple to cut and shape for a precise fit. According to the manufacturers, it can be used for both sound and heat insulation throughout your home, including loft spaces, walls, roofs, ceilings and floors, as well as insulating water tanks, ducting and pipes.

Sheep Wool Insulation
Image: Insulation roll

Specific Heat Capacity

The amount of energy required to increase the temperature of a material by one degree is referred to as its specific heat capacity. Because it takes time to absorb additional heat before the temperature rises and the heat is transferred, good insulators will have a high specific heat capacity.

Sheep’s wool insulation surpasses plastic and mineral wool insulation in this respect, meaning that sheep’s wool may absorb more heat as it attempts to enter your home, which is beneficial during the hot summer months.

Flame Retardant

Wool from sheep is naturally fire-resistant. Because there is insufficient oxygen in the air to support the combustion of wool, the material just chars. In the case of a fire, it will not feed the flames and emits no hazardous fumes.

To confirm its suitability, sheep’s wool, like all insulating materials, must undergo fire testing. Euro Class C or British Standards such as BS 476 or BS 5803 are used to test products. Where necessary, inorganic mineral-based fire retardants are used.

Good Soundproofing Abilities

Another advantage of natural fibre insulation is its acoustic qualities. Noises transmitted through a building can be considerably reduced by using sheep’s wool. Wool, because of its soft fibrous nature, irregular shape and high density, provides outstanding soundproofing compared to the best mineral fibres and outperforms synthetic insulation materials.

Disadvantages of Sheep’s Wool Insulation

Reduced Thermal Efficiency

The performance of any insulating material is an important consideration. Thermal resistance (R) expresses the amount of heat lost through a certain thickness of a material in resistance per unit area (m2K/W). The greater the number, the better the performance.

According to industry experts, plastic synthetic insulation has approximately twice the heat resistance of sheep wool insulation, and has R values twice that of sheep’s wool.

Requires Chemical Treatment

Wool’s vulnerability to insects, particularly moths, is a significant drawback. To make raw wool insect-resistant, it must be treated with chemicals. Wool is treated with borax by manufacturers such as Thermafleece to reduce insect attacks.

There is another option. Manufacturer SheepWool’s ‘Ionic Protect’ plasma-ion treatment modifies the molecular structure of the wool fibre. This biocide-free technique is supposed to keep insects from eating the wool indefinitely.

More Expensive

Sheep wool insulation can be more expensive than other types of insulation. At 100mm thick, 100% wool insulation will cost around £50 per m2, inclusive of the cost of installation. Rock wool insulation, sometimes coupled with polyester, is typically less expensive. Spray foam is typically a more expensive option, costing up to £35 per metre square, inclusive of installation.

The cost of your insulation, when being installed by a specialist installer, will be determined by a number of factors aside from the type of insulating material used. This includes the amount of insulation required, whether any old insulating material needs to be removed, and the ease of accessibility of the space that needs insulating.

Insulation typeTypical average cost per sq m (inc installation)
Fibreglass wool£20-£25
Rock wool£25-£30
Spray foam£35
Sheep wool£50-60
Typical costs of insulation including installation

Sheep’s Wool Insulation Summary

Sheep’s wool is one of the most natural insulators. Not only that, it is also easy to install, breathable, sustainable, fireproof and sound-dampening. It can help you in achieving an effective temperature and humidity balance in your home. There are numerous advantages, but it is not for everyone, and may be a far too expensive option for some.

Some man-made synthetic materials may offer better thermal performance and are less expensive, but they are less environmentally friendly, so it really is down to personal choice and how “green” you are. If you don’t mind paying a bit extra for a more eco-friendly option, sheep’s wool could be the right insulating choice for you.

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