Sheep live in some of world's harshest environments. Dall sheep, for example, love cold climates, including the frigid temperatures of the Arctic. They live on alpine ridges and steep rocky slopes, and are able to adapt to these extreme conditions because of their wool. In recent years, scientists have taken the insulating properties of sheep's wool and applied them to home construction. A 24-inch roll of R-13 wool insulation costs around $60.
When wool fibers are compressed, they form millions of tiny air pockets. These pockets trap air, which keeps the animals -- and homes -- warm in the winter and cool in the summer [source: SheepWool Insulation]. Plus, wool is very breathable, which means it can absorb moisture from the air without affecting its capacity to retain heat [source: SheepWool Insulation]. Specifically, the outer layer of wool fiber is resistant to water. However, the fiber's inner layer loves water and can absorb about one-third of its weight in moisture without ever feeling damp. And when wool becomes moist, it generates heat, which in turn prevents condensation. The R-value of wool falls between R-3 and R-4 per inch of thickness [source: Coloradoenergy.org]
What does this all mean? If you insulate your home with wool, you don't need to adjust your heating or cooling systems as often as you would with other materials and that saves money. Wool insulation keeps buildings cool in the day and warm at night, and it's more fire resistant than other types of insulation [source: SheepWool Insulation].