There are many choices when it comes to home insulation. Walk down the isle at your local builders merchant and you’ll find mineral wool, rigid foam boards, multifoil reflectives, and hiding away at the back (usually priced considerably higher) sheep wool insulation. Marketing hype has it natural wonder material that outperforms all the others and cares for our planet too. The price tag says you’re paying through the nose to make yourself feel better.
I’ve been doing some proper research on this subject as I’m faced with making this decision myself. I need to add insulation to my flat and due to it being rented, I can’t touch the walls or loft space. However I can improve on what’s already there so it’s down to the attic for me. It’s not about bettering synthetic materials for moral reasons, it’s about does sheep wool actually perform well enough to justify the additional cost and are the eco credentials actually true or just clever marketing speak.
It would appear that the answer is neither as positive as sheep wool enthusiasts would like you to believe, or as negative as cynics will tell you. Sheep wool insulation can offer similar performance to man made alternatives for most applications, but it does have some benefits that make it perform better in specific circumstances. It’s not a miracle material though so don’t fork out the extra if you don’t need to.
## What is the Science that Makes Sheep Wool So Good?
When insulating your home you want to prevent heat escaping, the simple science lesson you learnt at school about heat transfer applies here. There are multiple methods heat can transfer; conduction, convection and radiation. The wool insulation you’ll buy from the builders merchant utilises lots of tiny air pockets within wool fibres to trap still air. Stopped air is key to insulation materials as heat cannot conduct through it. Sheep wool insulation differs from other types because of its ability to deal with moisture and regulate humidity.
| Property | Sheep Wool | Importance |
|---|---|---|
| Thermal Conductivity | 0.035-0.040 W per metre kelvin (British Board of Agrément) | The fundamental building block of all insulation materials. Lower is better |
| Water Absorption | Up to 30% of its weight in moisture (Wool Insulation Manufacturers Association) without loss of thermal performance | Ability to absorb water, preventing retardant of performance unlike most synthetic materials |
| Lifespan | 50+ Years (Industry Today) | Sheep wool insulation can maintain its performance for longer periods of time when installed correctly. |
| Elasticity | Naturally able to regain it’s shape, meaning it won’t Compact over time (Durawool Industries) | The insulation won’t degrade or compact over time meaning it will always perform to the same level when installed correctly. |
Air stillness is only part of the battle. Standard synthetic insulation performance can degrade over time when exposed to moisture, especially higher humidity. UK weather; rain, snow and condensation creates moisture we have to deal with inside our homes on a regular basis. Wool insulation’s ability to absorb and release water vapour means its thermal performance isn’t affected by moisture in the same way.
Sheep wool insulation will perform better over time because of this ability. Plus wool fibres are naturally elastic and spring back to their original shape. Other forms of insulation compact over time, with wool insulation you install it once and it’s done.
Another pro is wool insulation helps regulate humidity. Increased humidity levels inside the home can have negative effects on comfort levels. Humidity control can have a huge impact on how comfortable you feel within your home.
So what does this mean in reality? Combined these properties should help maintain a better interior environment within your home. Expect to see reduced swings in humidity levels which should make your home feel more comfortable to live in.
I covered thermal conductivity earlier but to reiterate, sheep wool insulation has roughly the same insulation value as mineral wool and slightly better than standard glasswool. It won’t wow you with its performance when compared to synthetic materials, but it certainly doesn’t fall behind either.
## How Does it Perform? Real World Situations and Application
Just like any insulation material sheep wool works best in certain situations. All insulation will perform differently depending on how and where it’s installed. Let’s take a closer look at some of these scenarios.
First off loft insulation. Sheep wool insulation has pretty much the same performance characteristics as synthetic materials when used in loft applications. You’re not likely to run into moisture issues in loft spaces and the airspace remains relatively stable, dry conditions play to wool fibres advantages.
Installation is straightforward and no different from mineral wool insulation. Yes it’s itchy but less so than mineral wool and when armed with protective equipment no different. The benefits of moisture management aren’t going to come into play up a loft spaces unless you have chronic condensation issues. If so simply installing insulation could help but ensure you have adequate ventilation or the problem will likely persist.
Wall cavities are similar story here. Standard UK cavity walls are just fine for sheep wool insulation. You won’t be able to use the material as external wall insulation but interior wall cavities are fine, as long as they stay dry of course. Sheep wool insulation has been tested to meet fire standards so long as it’s treated correctly during the manufacturing process (British Standards Institution).
Floor insulation offers similar benefits, when used between joists of suspended floors. There’s unlikely to be any issues with moisture from above but you may get some from underneath. In older properties where you can’t guarantee a perfect vapour barrier wool insulation can handle the odd moisture without losing performance.
Finally where wool really shines is retrofit applications. If you can’t achieve perfect installation conditions synthetic materials lose their advantage. Weeping walls with moisture ingress, loft spaces where you can’t fully stop air flow; these are all situations where wool insulation can outperform alternative materials just by being a little more forgiving when things aren’t perfect.
Professional vs DIY installation? Pretty much every scenario I covered is suitable for DIY installation. No special tools required beyond what you’d use for mineral wool. Remember installation affects performance so take care to do the job right. Wool insulation doesn’t require any special handling techniques but you should still wear proper protective equipment.
## Is Sheep Wool Insulation Actually More Expensive?
If you’ve made it this far you’ll know that sheep wool insulation has a lot to offer. But does all this come at a cost? Unfortunately when comparing materials Sheep wool insulation comes with a nice price premium. Exact prices will vary by supplier but roughly you can expect to pay 30-50% more than similar amounts of mineral wool insulation. Twice as much as basic glasswool too.
Does it justify the cost? That depends on who you ask and what you’re comparing it too. Compared to basic glasswool insulation yes it’s expensive. Compared to other higher performance alternatives the price is comparable.
Whilst the material itself is more expensive when compared to mineral wool. Do you get better performance overall? No. Will it likely outlast most products giving better performance over the lifetime of your house? Probably.
When doing your cost comparison look at total cost over the insulation lifetime. Also look beyond just thermal performance. If you purchase enough wool insulation to meet building regulations do you notice a difference? Probably not. Are there benefits to wool insulation that provide real benefits to your home that other products don’t?
## What About the Environment?…
Sheep wool insulation has been promoted as better for the environment. Lower embodied carbon when compared to foaming and better for sheep farms who struggle to sell raw wool. Is it actually better for the environment or strong green credentials just being used as marketing hype?
Sheep wool has significantly lower embodied carbon when compared to PIR (ICE Database University of Bath) insulation foams. Easy enough to believe when you consider wool insulation is literally sheep turning grass (and other food) into fantastic insulation material using solar power. There’s still manufacturing processes of washing the wool and treating it with fire retardant chemicals, but it’s far less work than converting petroleum into foam products.
Producing over 60 million kg of raw wool per year(British Wool), the UK is able to source insulation material grown literally on our doorstep. Yes we have to process it, but the vast majority of that wool has little commercial value so we have to drive anywhere to source it. Using UK wool helps the environment by reducing transport emissions and supports an industry that would struggle to sell the raw material.
It’s biodegradable and can be composted at end of life. Sure there are fire retardant chemicals in the insulation but it will still likely end up composted instead of lining a landfill. Synthetic insulation will likely remain in that landfill for decades. Sure wool insulation lasts a long time so end of life may be a long time coming but every little helps right?
Sheep wool production is far from a perfect environmental process. Lots of energy goes into producing clean wool insulation material and whilst the sheep are outside producing wool insulation doesn’t hurt they’re not exactly munching local flowers either.
| Price | Performance | Comments | |
|---|---|---|---|
| SHEEP WOOL | £8-12 per m² (100mm) | 0.035-0.040 W per mK | SComparable to Mineral Wool. Better than standard Glaswool |
| MINERAL WOOL | £3-5 per m² (100mm) | 0.032-0.040 W per mK | Similar to Sheep Wool. |
| GLASWOOL | £2-4 per m² (100mm) | 0.032-0.044 W per mK | Inferior performance when compared to Sheep and Mineral Wool |
| PIR FOAM BOARD | £6-10 per m² (25mm) | 0.018-0.025 W per mK | Fairly significantly better performance than wool batts |
…the environment still matters.
As consumer awareness of their own personal impact on the environment grows we’re starting to see demand for more natural products increase. Insulation sales on the increase by 20 percent over the last five years(AMA Research) with more people looking at natural alternatives. Just as we’ve seen with electric cars early adopters are likely happier with their decision than those who bought them years ago during the technology infancy stage.
As insulation technology improves and more manufacturing processes go clean we’ll probably find the embodied carbon of sheep wool insulation improves year on year. Same will be true for synthetic products.
When it comes down to it, sheep wool insulation has a lower impact on the environment when compared to it’s foaming alternatives. Just don’t make the decision based purely on that fact alone.
## Top Mistakes People Make When Considering Sheep Wool Insulation
Mistake #1: Believing natural means better performance
Synthetic alternatives like PIR foam boards will outperform sheep wool insulation when comparing like for like thickness. There’s far better thermal performance per millimetre with foam boards. Don’t choose sheep wool over other materials because of some misguided belief that natural means better.
Mistake #2: Treating it like a magic material
Yes it can handle moisture better than other materials but that doesn’t excuse you from drying out your home or fixing source of moisture issues. Don’t use sheep wool insulation as a way to avoid fixing underlying building issues.
Mistake #3: Expecting it to be easier to install.
Sheep wool insulation isn’t a magical material that installs itself. Whilst it may be less irritating to work with than other forms of insulation, it doesn’t mean you can slack on installation. Bad installation defeats the purpose of spending money on better insulation in the first place.
Sheep insulation performs just as good as it does because it’s installed correctly and covers all cracks and gaps. Install it properly and it’s great, stuff it in badly and you might as well use glass wool.
Mistake #4: Expect instant results
Insulation isn’t a wonder product that will immediately turn your energy bills around. Like all insulation upgrading the thermal performance of your home takes time. Some homeowners report (Energy Saving Trust) heating reductions up to 25% after insulation upgrades. But this is averaged out over poor/no insulation and best insulation values. Simply upgrading to ‘good’ insulation will still see savings, you just won’t save as much as upgrading from poor insulation to ‘great’.
Mistake #5: Only considering embodied carbon
Taking out an overnight drastic reduction in your homes carbon footprint. Operational energy from heating (or cooling) will likely account for more energy use than the embodied carbon across the insulation lifespan.
## The Bottom Line
Insulation materials should be compared based on performance, environmental impact and cost. Sheep wool insulation outperforms it’s synthetic counterparts when it comes to moisture tolerance, but falls behind when purely looking at thermal performance. Other natural alternatives will outperform sheep wool when comparing thickness to thermal performance.
Sheep wool does have genuine lower impact on the environment when compared to foam insulation materials. However if you’re looking to justify the expense based purely on helping the planet, there are probably better ways of doing that with your money.
Made from a renewable source grown on your doorstep insulation has some benefit eco-conscious homeowners are looking for. Just don’t forget to consider performance and suitability when making your final decision.
Its ability to handle moisture will last longer providing better performance over synthetic alternatives. Plus UK sheep farm have an abundance of wool that would normally go to waste, you’re helping an industry by buying sheep wool insulation.
It’s nicer to work with than other materials and suitable for DIY installation. Don’t skimp on safety and take the same precautions you would when installing alternative materials.
Prices do vary between suppliers but you’ll likely always pay more for sheep wool insulation when compared to mineral wool alternatives. Whether or not the performance, environmental benefits and ease of use justify the cost difference comes down to you and the unique circumstances of your property.<|end_of_document|>
