Performance of different insulating materials

We often get asked by customers if we have an easy way to compare our different insulating materials in one place. Up until now we didn’t… But now we do!

This table shows you the different thicknesses available for each product, plus whether it comes in slabs or rolls, its coverage per pack, the cost per metre squared, and its thermal conductivity.

We hope this makes it easier to pick the best insulation product for you!

Product Thickness Slabs/rolls Coverage (m2 per pack) Cost per m2 Thermal conductivity
Thermafleece CosyWool 50mm Rolls 14.43 £4.16 0.039W/mK
75mm Rolls 9.44 £6.36 0.039W/mK
100mm Rolls 7.22 £8.31 0.039W/mK
150mm Rolls 4.77 £12.58 0.039W/mK
Thermafleece UltraWool 50mm Slabs 14.04 £8.55 0.035W/mK
70mm Slabs 9.83 £12.21 0.035W/mK
90mm Slabs 8.42 £14.25 0.035W/mK
Thermafleece NatraHemp 50mm Slabs 21.31 £6.31 0.039W/mK
70mm Slabs 15.98 £8.41 0.039W/mK
100mm Slabs 10.66 £12.61 0.039W/mK
Thermafleece Original 50mm Slabs 19.66 £6.35 0.038W/mK
75mm Slabs 12.64 £9.87 0.038W/mK
100mm Slabs 9.83 £12.69 0.038W/mK
Comfort 100mm Rolls 4.56 £12.87 0.042W/mK
150mm Rolls 3.42 £17.16 0.042W/mK
Optimal 50mm Rolls 10.26 £7.50 0.0385W/mK
75mm Rolls 6.84 £11.25 0.0385W/mK
Premium 100mm Rolls 4.56 £19.51 0.0359W/mK
150mm Rolls 3.42 £27.77 0.0359W/mK

Introducing Thermafleece insulation

A cost-effective alternative to our 100% pure sheep wool insulation is Thermafleece insulation. Thermafleece offers a great range of insulation rolls and slabs based on natural materials. If you want to steer clear of fibreglass or chemical-based insulation materials, but don’t have the budget for pure sheep wool, Thermafleece is a great choice.

All Thermafleece’s products are suitable for DIY, as well as being great value for money and helping to prevent damp. They are a more eco-friendly solution than fully manmade insulation materials, and there are no itchy fibres given off when you move them around.

Thermafleece products


CosyWool – available in rolls- is a great product for those who want a sheep-wool rich insulation. It is 75% sheep wool, combined with a small amount of polyester to help bind the fibres and make it easier to handle. It can be used in the loft, under floorboards or on walls to help keep your home warm.

As well as having great thermal insulation qualities, it also helps to regulate humidity in the home and reduce the risk of damp and condensation. The effectiveness of most insulation materials is affected in humid conditions, but CosyWool works just as well when it absorbs water vapour.

See its product page for more information.


Thermafleece’s Original insulation comes in slabs, which are easy to fit securely between your joists and rafters. Comprised of 85% sheep wool, it’s the nearest thing to pure sheep wool insulation at a fraction of the price! A great medium-density insulation, it’s highly durable and effective in reducing heat transfer, keeping your home at a comfortable temperature. It’s also highly breathable.

See its product page for more information.


UltraWool – sold in slabs – contains 75% sheep wool and is an easy to fit, efficient insulation choice. It’s sustainably made and its thermal performance is unrivalled compared to other materials of its thickness and price. If you want a sustainably-made insulation that will insulate effectively in small amounts, UltraWool is the product to go for.

See its product page for more information.


NatraHemp is a bit different in that it is not made with sheep wool, but – you guessed it – hemp. The slabs are made from a fast-growing, low-impact crop that produces fine fibre ideal for insulation. It’s a natural, sustainable option, and hemp helps the environment by absorbing carbon dioxide from the air as it grows. As well as being the ethical choice, it also insulates brilliantly and is also breathable. This means its performance is not damaged if it gets damp.

See its product page for more information.

Should I use slabs or rolls to insulate my home?

This is a question we get asked a lot, and there’s no easy answer! Insulating your home can be a great way to keep warm and cut your bills, but with such a huge range of materials on the market, knowing which to choose can be really difficult. The final choice as to whether to use insulation slabs or rolls is yours, although it mainly depends on the application – are you using it in the loft, walls or floors? Another thing you’ll need to take into account is your budget, and (if you’re doing it yourself) your DIY skills.

Loft insulation

Cold loft

Installing insulation between the joists will create what is known as a cold loft. This means you lay the insulation on the floor of the loft, preventing heat getting into the loft space. If you just use your loft for storage, and you don’t have a room in the roof, there’s little point paying to heat it. In this case, it’s quite an easy DIY job to just roll insulation out and then trim off any excess. If you’re using roll insulation, and you’re planning to keep stuff on top of it, you will need to put boards on top, without squashing the insulation, as this will affect its performance! Slabs are more expensive but mean you can store things straight on top. So it really depends what you use your attic for.

Warm loft

If you go for a warm loft instead, this means insulating the rafters. Although again it is a personal choice, it may be easier to use insulation slabs rather than rolls. This is just because of gravity really. It’s probably going to be easier to install semi-rigid slabs above head height than it is to try to attach insulation from a roll, and then having to put netting underneath it to keep it in place. Slabs are pretty easy because they can be cut to size and fit snugly side by side.

Wall insulation

If your property has solid walls, cavity wall insulation is not an option, and you may not have the budget for external wall insulation. Insulation can be installed on internal walls, but there are quite a few things to take into account: how much space are you willing to lose, and how much work do you want to put in? You will also need to think about whether you need a damp proof membrane, or a stud wall.

Slabs can be glued directly to the wall, and provide a flat surface to plaster over. Some slabs already incorporate a vapour barrier too, so can be a straightforward and structurally wise choice. Although rolls of wool can also be effective if installed properly, wool will encroach more on your room space, and installation will be more complicated.

Floor insulation

What kind of insulation you can use for floors depends on what kind of floor you have. If you have floorboards, you can lay wool or semi-rigid boards under the floorboards between the joists. If you’re insulating a solid floor, you can obviously only lay insulation over the top of it. You will have to use fully rigid slabs for this, because fibres in any other kind insulation will compress when you walk over it – and most people don’t want a squashy floor! You can then put chipboard over the top to finish the job. You will lose some of the height of your room doing this, and it’s also recommended to carry the measure out across a whole floor, or you’ll end up with different floor levels in each room.

If you need more information on choosing the best type of insulation for your project, just give us a call and we’ll be happy to help!


5 Reasons to get your sheep wool insulation from Sheepwool4Homes

 100% British

 Our wool only comes from British sheep. Most of our insulation products are 100% pure wool too.


Sheep wool insulation is the natural, ethical, environmental choice.

Specially treated wool

Our insulation is treated with non-toxic pesticide to make it resistant to vermin and insects.

Great customer service

We’re only a phone call away if you have any questions. expert advice from qualified energy assessors

Free shipping

Our orders are shipped free of charge.

Why 100% sheep wool is best

Our 100% sheep wool insulation is totally natural. Other options, although cheaper, can be less effective because plastic binders are melted into the wool. This means it loses some of the qualities which make it such a great choice in the first place.

If you’ve chosen sheep wool insulation because it is eco-friendly, this may be disappointing news. Some companies boast that their insulation is made from ‘95% natural fibres’. We can do better than that!

Our sheep wool insulation combats indoor air pollution

We think it’s a shame to waste a natural product by mixing it with a load of chemicals. One of the reasons 100% sheep wool insulation is so great is that it helps to purify the air in your home, keeping you and your family healthy. It helps to soak up nasty toxins and cancer-causing VOCs such as formaldehyde (which is released by everyday household products and even the fabric of your home).  This works because of the unique shape of its fibres. Chemical binders in some products mean that it loses some of its ability to filter air through these fibres.

Our sheep wool insulation regulates moisture

Another disadvantage of sheep wool insulation containing chemicals is that it loses some of its ability to regulate humidity in the home. The change in its makeup means it becomes less breathable, and less able to absorb and dissipate moisture.

Our 100% pure sheep wool product is hygroscopic, meaning it can soak up 33% of its own weight in water before its insulating properties are reduced. This helps prevent condensation settling in your loft, potentially causing damp and structural issues.

Our sheep wool insulation is easy to mould

Clearly, sheep wool is a very soft material, which means that it can be shaped and cut easily to fit into any space. When mixed with plastics, it becomes harder to cut. Our 100% sheep wool insulation is also fully recyclable, unlike products containing chemicals. 

Our sheep wool insulation is the true eco choice

Unfortunately, untreated sheep wool can become a haven for moths and insects. It needs to be treated to prevent this. There is another option instead of insecticides such as borax, though. Our 100% pure sheep wool insulation is treated without chemicals so we don’t waste a natural product by spoiling it at the last minute. We use plasma ionic treatment to alter the texture of the sheep wool, rendering it inedible to insects.

With our sheep wool insulation, you can make sure you’re getting a truly effective and eco-friendly product!

What’s the lifespan of insulation?

The lifespan of different insulating materials varies widely, and most of them require a bit of looking after! If you want insulation that you can just install and then forget about, 100% pure sheep wool is the perfect choice. You won’t be worrying about conditions in your loft, unlike with other insulating materials.

Fibreglass, foam board, rock wool and spray foam insulation are all estimated to last a minimum of 1oo years, but this is really dependent on how well it’s looked after.

Sheep wool is not affected by damp

The types of insulation just mentioned need to be kept dry in order to perform. Once they get wet their insulating properties are compromised and water can get trapped between boards and walls, encouraging damp and mould. Even if you manage to dry out the insulation, it may have settled into a different shape, leaving spaces unevenly filled. However, our sheep wool insulation actively regulates moisture, so it is not affected by damp. It is able to absorb about 30% of its weight in water without losing any thermal insulation performance.The core of the sheep wool fibre is hygroscopic, meaning it absorbs water vapour – perfect for loft spaces, where condensation is common.

Another edge sheep wool insulation has over fibreglass is that it is less affected by compression. Squashing fibreglass wool also reduces its thermal resistance value. Avoiding putting anything on top of the insulation is easier said than done in your attic, which is probably where you store all those boxes you moved in with 5 years ago and haven’t got around to opening…

Our sheep wool insulation doesn’t degrade and is treated against moths and insects. Untreated sheep wool can be a haven for moths and before you know it, 200mm of insulation can become a lot less! Unlike borax,  which is commonly used to treat sheep wool insulation, our treatment is 100% natural and also permanent.

Sheep wool insulation can be reused

While most insulating materials are billed as lasting ‘as long as your house’, sheep wool insulation can outlive any of these because if you move house, you can take it with you! This makes the cost worthwhile even if you think you may not stay put where you are forever. Solid insulation boards are easy to damage if knocked, but sheep wool is easy to relocate, within or outside of your home.

All this, plus unrivalled thermal performance, no chemicals and air filtering qualities. And of course it’s sustainable too!

  • Comfort Sheep Wool Insulation 100mm

  • Optimal Sheep Wool Insulation 50mm

  • Premium Sheep Wool Insulation 100mm



And we are live…..!

We are thrilled to announce the new version of our website is finally live. It has been a very busy few weeks, and our thanks must go to the development teams at the GreenAge who helped put all this into place.

We are very excited by the new design and we hope you like it too. The plan was to make a website more accessible to all, easier to navigate and ultimately easier to find the products you are looking for.

As part of the move we have also moved to SagePay to handle all of our online payments – the payments are taken on their secure payments so transactions are safer than ever!

We would love to get your thoughts- anything missing? Anything you’re not sure about? Please feel free to comment below!

Can I use my own sheep wool for insulation?

We get a few queries a month from people who have access to their own sheep wool supply – the question they tend to ask is whether they can use their own sheep wool for insulation in their home?

The answer in theory is yes – after all, we sell 100% pure sheep wool insulation with no additives. The issue however is that untreated wool becomes a breeding ground for moths, who unfortunately find the stuff rather tasty!

Once moths are present, it is almost impossible to get rid of them. Even if the insulation material is removed, they can move on to clothes, carpet and so forth. The eradication of the moths can cost £1000s and unfortunately most insurance companies will not cover it.

Treatment of sheep wool prior to install is absolutely imperative to prevent this happening; so yes, while you could install your own locally sourced sheep wool, we really wouldn’t recommend it.

Prior to installing sheep wool insulation, it should be scoured. This cleans the sheep wool and removes the lanolin – which is the oil found on the sheep wool fibres. The next step is to treat the sheep wool to prevent moths eating it.

How is sheep wool insulation treated?

There are broadly two ranges of sheep wool treatment – the first kills the moths when they start eating the wool. The common chemicals used to treat the sheep wool include Borax and Thorax IW. They are both insecticides that kill the moths if they start eating the wool.

The second, and the treatment that we now use, actually alters the wool fibres and means that moths simply don’t feed on the wool. The treatment we use is called plasma ionic treatment – basically we alter the surface of the sheep wool which makes it inedible for the moths. This treatment is revolutionary in the sheep wool industry because the sheep wool after treatment is 100% safe. It even carries the prestigious nature plus certificate.

>>> See the Natureplus Certificate <<<

So yes – you could use your own sheep wool to insulate your home, but we would recommend getting ours instead. It is still 100% natural and sustainable, but just means your home won’t be overrun with moths!

Does Insulation work in the summer?

Did you know insulation is not just for Christmas?

Most people assume that sheep wool insulation is installed only to help keep houses warm during the cold winter months and there are a few media reports of insu­la­tion caus­ing over­heat­ing.

I’ve written this blog to let the public know that this is not the case. If the writ­ers of those arti­cles had a clue how insu­la­tion worked they might see how absurd their claims are! Of course, in the winter, insulation holds heat, prevents warmth from escaping generally  makes your home feel comfortable, but it can also make a difference to your home in the summer.

Insulation works during the summer!

When someone mentions ‘wool’, what is the first thing that comes into your head? Probably something relating to winter or cold. Most people see wool as a way to stay warm. Come the warmer days of the year, wool is thrown far back in the wardrobe!


‘It might be hard to imagine; a fabric that can both keep you warm and cool you down. It does sound too good to be true. However, when you think about it, who are the world’s premiere users of wool? Sheep of course. These animals need their wool to protect them from the elements – no matter the season. So maybe it is not so hard to believe the magic of wool when you consider the range of temperatures a sheep in New Zealand or Australia has to endure.’ – Daniel Naslum, Using Wool for Cool.

So how does insulation actually work?

Insulation works by slowing the movement of heat between two spaces – it doesn’t ‘keep cold out’ which is what people often assume!

During the winter, homes tend to be heated so the inside of the house is nice and warm while the outside environment tends to be very cold. In an uninsulated house, the rate at which equilibrium is met – i.e. the temperatures either side of the wall becoming equal – is relatively quick. The result of this movement of heat is that the internal temperature of the house cools down.

In reality, the heat that travels out of the house is constantly replenished by the heating system, so the home never gets cold. You just have big energy bills!

In an insulated house, the insulation slows the rate at which heat moves across the wall / roof / floor. Therefore, the rate at which the house gets cooler during the winter months slows down – this means less heat is required, resulting in lower energy bills.

Once you understand how insulation, it becomes clear how it can also help during the summer.

Our 100% pure sheep wool insulation works by stopping your home from overheating. Personally, when I’m home on a hot summer’s day I like to feel cosy and snug, not hot and stuffy. I hate having to open all the windows around the house which then brings draughts, slamming doors and hot air… Annoying!

100% sheep wool insulation – a natural way to keep cool in summer!

During the summer, wool insulation will reduce the amount of heat coming in through the walls and help keep cool air inside your home. In the summer the sun tends to beat down on the house causing the walls to heat up. These heated walls often tend to radiate heat into the home, even well after sunset. When you insulate, the heat entering the home is dramatically reduced. For example, if it is 30 degrees outside your house, the inside will not ever get close to that temperature. Instead it should stay at a comfortable 20 degrees or so.


Sheep’s wool is today’s most practical insulator because it is very energy efficient compared to other insulation materials. Sheep wool insulation acts as a barrier between the cold damp weather outdoors and the warm dry environment inside your home. Because wool is breathable, it grips moisture to keep your house warm during winter, and releases moisture in summer to keep your house cool.


U-values and sheep wool insulation

What is a U-value?

U-value is a measure of how much heat is lost through a certain thickness of a building element, through conduction, convection and radiation. The lower the U-value is, the better the material is as a heat insulator. Current building regulations stipulate that a roof should have a U-value of 0.16w/m2K.

Sheep wool insulation can be an effective way of meeting these regulations – and it has lots of other benefits too. At Sheepwool4homes we have a range of sheep wool insulation; Comfort, Optimal and Premium. The higher the quality, the lower the thickness you will need to achieve a good U-value.

How do I work out how much insulation I will need to hit the right U-value?

Using the thermal conductivity of the product, you can work out either the thickness you require or the U-value you will achieve. Simply divide the thermal conductivity by the thickness to work out the U-value, or divide it by the U-value you want to reach to work out the thickness required. Follow the links to the products for details of thermal conductivity.

The calculations for our Comfort sheep wool insulation, for instance, are as follows:

Thermal conductivity 0.042 / required U-value 0.16 = thickness 0.263 (263mm). Therefore, two lengths of the 150mm thick insulation would give you just over the U-value required.


0.0385 / 0.16 = 0.240 (240mm) so you will need five lengths of the 50mm thick insulation.


0.0359 / 0.16 = 0.224 (224mm). Therefore, two lengths of the 150mm thick insulation would give you just over the U-value required.


If you need any help with these calculations, or any more information on the products, just get in touch!


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