Introduction
Sheep’s wool is becoming a popular insulation material in the construction industry. This natural fibre is grown by sheep and is called the fleece of sheep. It covers most of their body helping them accommodate well to differing weather conditions. This keeps them warm in winter and cool in summer.
Although primarily known for its use in textiles, sheep’s wool has been utilised by ancient civilisations to insulate their dwellings in the past and is now a key option in modern building practices. It is a versatile and sustainable option that can help to lower the carbon footprint of buildings while maintaining excellent performance.
In this post we will be looking at its historic use, applications, advantages, and challenges to give you a broader view of this natural material. So, continue reading to discover more about sheep’s wool as insulation.
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Historical Use of Sheep’s Wool
Sheep’s wool has been an integral part of human history for thousands of years. Its earliest known use dates back to ancient Mesopotamia around 6,000 BC, where domesticated sheep were bred for their fleece. From there, wool production spread across Europe, Asia, and North Africa, with the expansion of trade routes. These helped facilitate the exchange of sheep breeds and wool processing techniques.
Sheep were introduced to the British Isles around 4,000 BC during the Neolithic period. By the Bronze Age, around 1,900 BC, spinning and weaving technologies had developed in Britain, allowing wool to be spun into cloth. By the time of the Roman invasion in 55 BC, Britain had a thriving wool industry, which the Romans enhanced by introducing new sheep breeds. Later Viking influences helped further diversify the British flocks.
In medieval England, the wool trade was an integral part of the economy. Guilds were established as early as the 12th century to regulate wool production and trade. Exports to Flanders and Italy brought in significant amounts of wealth, bringing prosperity to many English towns and monasteries. By the 16th century, however, England’s dominance in fine wool production declined as Spain’s Merino sheep gained popularity.
With the Industrial Revolution in the 18th century, the focus of sheep breeding shifted from wool production to meat production to meet the demands of growing urban populations. While wool quality declined, innovations like the spinning jenny, power loom and established wool mills helped to revitalise the wool textile industry by making wool fabrics more affordable and widely available. However, in the 20th century, synthetic fibres eventually overshadowed wool as a primary textile material.
Architecturally, felted, or woven wool was used for hangings, coverings, and underlays to indirectly insulate traditional rural structures from medieval times. It may have been packed into the walls of stone cottages or layered beneath thatched roofs. Agricultural buildings such as shepherds’ huts and livestock shelters may also have made use of wool for warmth and moisture control. In some cases, wool could have been used to seal joints in wooden beams, improving waterproofing and draft resistance.
Industrialisation also brought about the mass production and widespread use of materials like steel, glass, and concrete which were favoured for their scalability and efficiency. As a result, natural building materials like sheep’s wool became less commonly used.
Today, however, as sustainability has become an important consideration in our world, there is a renewed interest in natural materials such as sheep’s wool.
Processing Sheep’s Wool
Sheep’s wool comes in a wide range of colours, textures, and lengths. Globally, there are about 1,000 breeds of sheep. The UK alone is home to approximately 60 breeds, including Wensleydale, Suffolk, Herdwick and Swaledale. These native breeds produce diverse fleece qualities and support a range of industries from textiles to construction.
The process begins by shearing the sheep to obtain its fleece. This is typically carried out once a year in late spring. Each sheep produces about 3-5 kg of raw wool, which is then sorted based on colour, fibre thickness, and length. Sorting ensures the wool is suited to its intended purpose, whether for fine fabrics or dense insulation materials.
The sorted wool is compressed into bales and transported to scouring plants. Here, the raw wool may be blended together with other types of wool to meet specific technical requirements. After this, the blends are cleaned in a series of warm water baths – a process called scouring. This removes impurities such as dirt, lanolin, and vegetation and leaves pure wool fibres. Once cleaned, the wool is dried and prepared for its next stage depending on its final use.
For textiles, the sheep’s wool is carded to align the fibres, spun into yarn, and dyed or woven into fabrics for clothing, carpets, or upholstery. For construction, the wool is similarly carded or combed, but it is then layered multiple times to reach the required thickness. These layers are then mechanically bonded to create rolls or batts of insulation, ready to be packaged for use.
Some manufacturers offer 100% natural wool options, which are biodegradable. However, other manufacturers produce products in compositions such as – 75% sheep wool with polyester. This may be done to enhance performance in terms of fire resistance and insect control. However, these additives can reduce the material’s compostability.
Since sheep’s wool is mechanically processed, it has lower embodied energy. As a natural fibre, wool absorbs carbon dioxide during its growth cycle, effectively sequestering carbon from the atmosphere. Additionally, wool products are durable and can store carbon for many years, helping to reduce the overall environmental impact of both the textile and construction industries.
Moreover, using wool from local sheep breeds supports biodiversity and reduces carbon footprints. Wool production also offers economic benefits like supporting rural farmers and providing a sustainable raw material for various industries.
Different Sheep’s Wool Products
Sheep’s wool is a versatile animal fibre with various applications ranging from clothing and home goods to industrial uses.
Here are some products made from sheep’s wool:
- Bedding
- Blankets
- Carpets
- Clothing
- Craft supplies – knitting yarn, felt sheets, felting wool
- Curtains
- Duvets
- Felted pads
- Footwear
- Insulation materials (thermal + acoustic)
- Lanolin products
- Mattresses
- Pillow stuffing
- Tapestries
- Throws
- Upholstery fabric
- Wool filters
- Wool pellets
Types of Sheep’s Wool Products in Construction
Sheep’s wool is most commonly used as an insulation material in the UK construction industry. It typically offers a thermal conductivity between 0.035 and 0.042 W/mK and is available in various thicknesses, ranging from 50mm to 200mm.
The insulation is available in several forms to suit diverse insulation needs:
- Loose fill – ideal for filling irregular spaces or cavities.
- Batts – pre-cut panels for easy installation in walls and floors.
- Rolls – continuous sheets that are versatile and simple to handle.
- Acoustic panels – designed to enhance soundproofing.
These sheep’s wool products are commonly used to insulate floors, walls, and roofs of structures. However, it is essential to avoid using them in areas prone to moisture, such as basements or masonry cavity walls. This is because prolonged exposure to damp conditions can compromise their performance. For such areas, synthetic materials are often used.
Sheep’s wool works quite well with timber frame construction. And is often paired with other natural and breathable materials like lime plaster or wood fibre boards to create healthy building envelopes. Its flexible nature allows it to fit snugly into irregular spaces, making it an excellent choice for retrofits and older buildings.
We have illustrated the step-by-step installation process for a timber stud wall using roll sheep’s wool insulation. These versions are particularly easy to handle as they can be cut or even torn to the desired size and secured with a staple gun.
Do bear in mind we have shown a simplified version of the installation process. And so, additional wall layers may be added based on the project’s requirements.
Another installation technique is the friction fit method, where slightly larger pieces of insulation are cut and pressed into place. The friction between the insulation and the timber frame keeps it secure from slumping without needing additional fasteners. The sheep’s wool insulation will naturally hold its shape, but some manufacturers may add binder fibres to prevent slumping or settling. The horizontal noggins of the timber stud wall also provide support for the bottom of the insulation. But you can always staple the insulation to the stud wall, to ensure it does not move.
Thermafleece is the leading manufacturer of sheep’s wool insulation in the UK.
Their website is a comprehensive resource for builders and homeowners, offering useful products and guidance on how to use sheep’s wool insulation.
They also offer downloadable guides with installation tips, and specific buildup details to ensure the insulation is applied correctly.
How to install Thermafleece British Wool Insulation
Here are the links to their guides on walls and roofs:
The Alliance for Sustainable Building Products (ASBP)
The Alliance for Sustainable Building Products is a UK based organisation dedicated to promoting the use of sustainable building materials and products.
They advocate the broader benefits of natural fibre insulation, emphasising that U-values are not the sole measure of thermal performance. They highlight the role of thermal diffusivity, a property influenced by thermal conductivity, density, and specific heat capacity as crucial to creating structures that are comfortable and energy efficient.
Their website is an excellent resource for those interested in sustainable materials. They provide peer-reviewed papers that explore the science behind natural fibre insulation and its benefits.
The ASBP also hosts the Natural Fibre Insulation Group, a collective of leading manufacturers and suppliers of natural fibre insulation in the UK. This group works collaboratively to promote the advantages of these materials. They have a wealth of resources for you to explore:
Natural Fibre Insulation Group
Benefits of using Sheep’s Wool
There are a numerous advantages to using sheep’s wool as an insulating material in construction:
Thermal Insulation
Sheep’s wool provides excellent thermal insulation due to its unique composition. These natural fibres contain numerous little twists and bends that create little pockets of air that are able to trap heat and provide a warm comforting effect. This helps the wool be quite effective in colder conditions. Wool also is known to naturally regulate temperature which helps them reduce heat loss and improve energy efficiency.
Acoustic Insulation
The fibre also has sound absorbing properties that help reduce noise transmission. This is a valuable benefit in urban or multi-occupancy buildings.
Breathability
Wool is both breathable and hygroscopic, meaning it naturally absorbs and releases moisture. Its vapor open properties allow moisture to escape, preventing mold growth and maintaining a healthy indoor environment. This is particularly crucial in cold and damp climates like the UK, where effective moisture management is essential for preserving the integrity of the building and its air quality.
Sustainable
Sheep’s wool is a renewable and locally sourced material, making it an environmentally sustainable option. At the end of its life cycle, wool can be easily recycled or composted, returning valuable nutrients to the soil. It also has a low carbon footprint, making it an eco-friendly choice compared to conventional insulation materials.
Fire Resistance
Wool is naturally flame retardant, meeting safety regulations without needing chemical treatments.
Durability
When treated against pests, sheep’s wool insulation can last for decades. Wool’s durability ensures long term performance, reducing the need for frequent replacements.
Safe
Unlike synthetic materials, wool is non-toxic and does not release harmful VOCs (Volatile Organic Compounds). It can also work to filter indoor air, removing harmful pollutants like formaldehyde and promote healthier indoor air quality. Wool also does not cause skin irritation, making it safer and more pleasant to install. It is also suitable for households with young children or pets.
Challenges of using Sheep’s Wool
While sheep’s wool has numerous advantages, there are a few challenges:
Cost
One of the main drawbacks of sheep’s wool insulation is its higher cost. Due to smaller scale production compared to conventional materials, the price can be significantly higher. However, this cost can be offset by wool’s longevity and its positive environmental impact over time.
Availability
Although increasingly popular, wool insulation is still less widely available than mainstream options, which may limit its use in large-scale projects. While the UK has a significant sheep farming industry, much of the wool is used for textiles or exported, which can create competition for raw materials.
Performance Concerns
There are misconceptions regarding the durability and effectiveness of wool as an insulation material. Many builders and contractors are unfamiliar with its properties, leading to reluctance in using it for certain projects.
Environmental Impact
Fireproofing and pest proofing treatments can affect the overall sustainability of wool insulation. While wool is biodegradable, wool blends with synthetic fibres may not break down as naturally.
Pest resistance
Insect resistance is another consideration, as wool can be susceptible to pests like moths. Ensuring wool is treated with environmentally safe methods is crucial for maintaining its eco-friendly status.
Helpful Links
History of Wool (Seven Sisters Sheep Centre)
Thermafleece
How to install Thermafleece British Wool Insulation
Case Studies (Thermafleece)
The Alliance for Sustainable Building Products (ASBP)
Health and wellbeing benefits of natural fibre insulation products and systems (ASBP)
Case Studies (ASBP)
Natural Fibre Insulation (ASBP)
Books
Here are some recommendations for some sheep’s wool related further reading for you to indulge in:
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Conclusion
As the construction industry embraces sustainability, the demand for natural and renewable materials like sheep’s wool is set to grow. Its natural insulating properties, low carbon footprint, and renewable nature make it an attractive alternative to conventional materials. While challenges such as cost and availability remain, efforts to promote the use of this natural material are gaining momentum.
By embracing sheep’s wool in our building practices, we can create healthy and energy efficient structures that contribute to a more eco-friendly future.
We hope this post has helped you learn more about this natural fibre.
Thank you for reading!
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Author
Written by Valanne Fernandes, a Part 2 Architecture graduate. Valanne is a content creator with First In Architecture, spending her time researching, writing and designing inspiring new content for the website.
We tried to sell Sheep’s Wool Insulation as Black Mountain Insulation, whilst in principal it
seems like a good idea the cost per square metre is too much for most constructions.
That coupled to its relatively poor thermal performance meant that sales ended up being
small quantities used in Camper Van conversions.
Seems like a great idea to those who are just trying to be eco warriors sadly most don’t have
enough money.