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27 May 2016

The Science Behind Wool's Insulation Properties

For all our technological advancements over the last few centuries, for all the amazing developments we’ve made with insulation technology, we still use wool. Like spider silk or honey, it’s one of those miracle substances produced by animals that even our most advanced science cannot equal in some respects. What makes it such a reliable insulator, though?

If you look at coarse or fine wool fibres through a microscope, you’ll notice that they are coated with ridges, almost like the trunk of a palm tree. These ridges, or scales, are individually coated with lanolin, a kind of wax that is secreted by the sebaceous glands (located beneath the hair follicle) of woollen animals. It’s a compound of long waxy polymer chains, alcohols, acids and hydrocarbons, all of which come together to create a semi-occlusive layer, meaning that it can be breathable and absorbent, whilst also protecting what’s beneath.

When you pull further back, you find that the woolen fibres crimp together, much like the way we plat rope. This structure creates little pockets which can trap warm air and retain it. The finer the wool, the better it is at doing this, as thinner fibres are able to wind more tightly. Some new breakthroughs, particularly Clo-I insulation, actually replicate this air pocket function by combining shaped, solid and hollow man-made fibres.

The next, perhaps most important factor with wool is the way it behaves when it gets wet. Cotton and polyester are water absorbent, and lose most of their insulating capability the moment they get wet. Wool, meanwhile, can take on about a third of its weight in water and still keep you warm. This is because those lanolin-coated ridges are able to repel liquid water, but absorb vapour into the inner layer of the fibres, which actually creates its own heat source. 

Callum Davies

Callum is a film school graduate who is now making a name for himself as a journalist and content writer. His vices include flat whites and 90s hip-hop.