Perhaps one of the most talked about and attractive recent innovations, sheep’s wool insulation is of particular attraction to those of us who to the woolly West or North of the UK. But does it live up to the hype?
Sheeps wool is a renewable by-product of the farming industry. It has extremely low embodied energy is in plentiful supply and can act as a humidity regulator as it can absorb up to 40% of its own weight in water, the water being released when conditions change. It is a natural non-toxic, non-irritating material.
- Non-toxic & non-irritating.
- Low embodied energy.
- Adapts and fits well. Suitable for use in walls, floors and roofs.
- Fire resistant. Wool melts and extinguishes itself in contact with flame.
* Note: Some products contain polyester as a ‘lofting’ agent (an additive to ensure that the material maintains its structure and air trapping ability over its lifetime). This is usually a blend of recycled and ‘virgin’ polyester. The polyester is at a low enough concentration in the final product to not effect biodegradability.
Note: Early products were somewhat stigmatised due to the reputed use of chemicals in the production process and to improve structure, durability, moisture & insect protection as well as concerns over chemical residues left by sheep dipping. Rubber or polyester and borax (a compound of boron which is a mineral salt of boric acid) tend to be used for these purposes now, thus mostly doing away with such concerns. Testing has concluded that the risk from sheep dipping is negligible.
At a density of 25kg/m3 sheeps wool has a thermal conductivity or K value of 0.039 W/m.K.
(Watts per meter Kelvin ~ a lower value is a better result)
As production is still relatively small scale, cost is high relative to other materials.
A 75mm x 400mm x 1200mm roll of batts costs approximately £90 (rounded) including VAT and covers 12.96 m2 therefore approximate cost per square metre at 75mm depth is £7.
It’s has even made it into the Independant Newspapers Top 50 Great Ideas for the 21st Century …
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