7 Myths about sheep's wool insulation

Are you planning to build a house, an extension onto your space or a renovation? If healthy indoor air and natural materials are important to you, you should consider sheep wool insulation.

This article is our way of helping you visualise a new concept: sheep's wool as insulation material. We clear up any concerns or prejudices and share with you the experience from our development as well as from numerous construction projects.


Sheep's wool insulation smells or stinks

If you have a sheepskin at home, you may be familiar with the typical smell of fur. Where does the smell come from?

In the case of sheepskin, the smell can be caused by tanning. The main reason for the smell emanating from the sheepskin is the lanolin, the wool fat

The smell is created because the wax in the sheep's fur is exposed to the influence of sun and weather and thus oxidises.

Factbox: Lanolin wool fat

Sheep produce the wool fat lanolin by means of their skin sebaceous glands. This fat - also called lanolin - acts as a natural protective film around the wool fibre and thus protects the sheep against cold and wetness.

So, lanolin is not a bad thing. On the contrary, the wax is even used in cosmetic products because it has many positive properties.

Are you planning to insulate your house and are now afraid that an off-putting smell will spread from room to room? We can take away this worry, as a thorough cleaning during the production process will quickly solve this problem:

  1. First, the raw wool is rinsed in a gentle washing process using curd soap.

  2. This removes wool grease and cellulosic and organic impurities from the raw wool.

  3. Afterwards, the cleaned wool is rinsed with soda to remove the soap residues.

The rinsing process removes any unpleasant odours from the wool. All that remains is a tiny amount of lanolin. We want to keep this because it ensures that the elasticity and bounce of the wool fibres are maintained. However, no odour emanates from the wool after washing. 


Sheep wool insulation moulds

Mould is a small fungus that can also settle in textile fibres as yellow or black mould stains. Moisture provides a good breeding ground for mould stains and allows the fungal spores to spread well.

When it comes to mould, sheep's wool shows one of its superpowers: it can absorb up to 33% of its own weight in moisture and release it again when dry.

The moisture management of the protein fibre works through the interaction of the outer shell and the fibre trunk:

  • The multi-layered outer shell of the sheep's wool fibre is hydrophobic, i.e., water-repellent.
  • However, this outer shell, also called the cuticle, allows water vapour to pass through.
  • The water vapour thus reaches the inside of the wool fibre, the fibre trunk.
  • In the fibre trunk, the wool fibre can absorb about 1/3 of its own weight without the wool feeling wet.

For all our insulation products, this means that the wool does not lose its insulating effect despite high moisture absorption. It absorbs the moisture when it is higher and releases it again to optimise the indoor climate.

Sheep's wool is therefore also ideal for installation in challenging building situations, because the protein fibres of sheep's wool do not provide a breeding ground for mould.

Rain on a construction site in Finland: Above sheep's wool below polypropylene insulation after the downpour
(© Alppisalvos Oy)

Caution: Added support fibres or support grids change the moisture behaviour of the sheep's wool insulation!

Be thorough when choosing a manufacturer, because unfortunately there are also black sheep in our industry. Only a sheep wool insulation manufacturer who uses 100% pure new sheep's wool, without any additions of synthetic support fibres or support grids of harmful substances, such as formaldehyde.

The behaviour of the moisture also changes with admixtures of other fibres, the product is no longer naturally degradable with synthetic admixtures and therefore landfill costs are consequential.


Make sure you have the relevant certificates, including the test numbers, in order to be protected from unpleasant surprises. 

By the way, here are our proofs →


Sheep's wool burns easily

Conventional insulation materials such as glass wool or rock wool fall into fire protection class A1 - non-combustible. The synthetic, expanded polystyrene is found in class B. We are not there yet with our environmentally friendly and healthy sheep's wool.

Nevertheless, through constant technical development, we have managed to place our ISOLENA insulation materials in fire protection class C and D and to obtain the European Technical Approval (ETA). Our sheep's wool has the following fire properties:

  • The self-ignition temperature of virgin sheep's wool is 560-600°C - about twice that of wood (270°C).
  • Sheep's wool naturally has a high nitrogen content which has a flame-retardant effect.
  • The smoke development is in the middle range (smoke development s2), there is no strong smoke development.
  • In case of ignition, the insulation melts away from any heat source without dripping (dripping behaviour d0).

Thus, sheep's wool is a suitable insulation material for a wide range of building projects and has acceptable fire behaviour in case of fire. Our many references speak for themselves.





Sheep wool insulation rots

Sheep's wool has adapted to the most adverse conditions over thousands of years and has thus developed far-reaching states of resistance.

In other words, sheep's wool "functions" permanently within all kinds of conditions. When installing sheep's wool insulation correctly, you don't have to worry about the insulation rotting, mainly because the wool fibre binds moisture.

However, one can also note that sheep's wool can be 100% recycled in an ecological cycle. Your sheep wool insulation can therefore be completely recycled without causing negative environmental impacts.

Your sheep wool insulation can be completely recycled without causing any negative environmental impact.


Mice or insects nest in sheep's wool

Mice, ants and other vermin

Mice, ants and other vermin are no threat to sheep's wool for several reasons. The wool is made of keratin and is indigestible for these animals. Unlike cellulose or plant fibres, which consist of starch fibres, sheep's wool cannot be processed by these animals' stomachs

In addition, the fibre arrangement in our insulation materials is such that there is a risk for these animals to get caught in it, so they will tend to avoid the insulation material.

Moths and carpet beetles

When it comes to moths and carpet beetles, good sheep wool insulation must have a working wool protector to withstand these critters.

We are very proud to be the only supplier to have co-developed an innovative BIOZIDE FREE wool protection. Our IONIC PROTECT® wool protection is based on a plasma process as well as being permanent and irreversible. The wool protection is tested according to EAD and CUAP


Sheep's wool insulation is out of my budget

If you make a direct price comparison between different insulation materials, sheep's wool insulation is more expensive than conventional or synthetic insulation.

However, if one considers the entire life cycle of the insulation material and any potential side effects, the price of sheep's wool insulation is put into perspective:

  1. Thanks to the outstanding quality of naturally produced sheep's wool, one’s investment would pay off after a very short time due to the excellent insulation value.
  2. With other insulation materials, high disposal costs may also be incurred during conversion and renovation work, which are often not considered in the calculation - an item that is omitted with sheep's wool insulation.
  3. He who buys cheap, buys expensive – An German saying that is unfortunately continuously relevant to house building. Time and again, builders discover our insulation material as they retrace their steps: for example, when renovation is required immediately after new construction because the formaldehyde values rocket, and costly improvements must then be made.

A higher initial investment is an investment in the future and above all in your health and that of your family. In addition, depending on the (federal) state, there are numerous subsidy programmes to help home builders.


Sheep's wool insulation shrinks

The needling and felting of our sustainable sheep's wool gives our insulation materials enough stability to be safe from shrinking, provided they are installed correctly.

Before needling, the cleaned and degreased wool fibres are shaped – we call this carding. The carded wool is then worked with felting needles, so that the fibres of the wool interlock with each other through the repeated piercing and thus a stable wool felt is created.

Our "Premium" sheep's wool insulation with continuous needling stands out in terms of stability and steadiness.



Due to the industrial mass production of cheap, synthetic materials, sheep's wool insulation is comparatively more expensive, but it scores high with many positive properties that the synthetic competition cannot match.

In addition, insulation made from sheep's wool is easy to handle and can be easily installed without safety measures such as protective goggles or dust masks!

If a fabric like sheep's wool were reinvented today, it would hit the headlines as sensational, thanks to the many positive properties of this natural product.