You only have to look at a Highland sheep breed in its dense, long fleece standing in the snow to understand the special thermal capacity of wool. It seems warm to the touch, while cotton feels cool, for example.
Wool absorbs, retains and releases moisture without affecting its thermal properties. This makes it perfect for use in breathable buildings, listed and ancient structures, and anywhere where moisture is a concern. This is also why it is great to wear – it keeps feet warm but dry, even inside welly boots.
Wool is very good at soaking up reverberated sound, particularly in the range of the human voice. This is why it makes a fabulous acoustic cloud material and why it is so good inside quality speakers.
Another intriguing and useful property of wool is its ability to NOT catch fire! In its natural untreated state wool does not burn, but instead forms a self-insulating char that prevents further flame spread and extinguishes itself (wool has a very high inflammation point of 570 – 600°C due to its high nitrogen content of ~16%). Wool is self extinguishing because of its high Limiting Oxygen Index (LOI=25.2), which means to completely burn wool an oxygen content of 25.2% is necessary whereas normal air only has a 21% content.