Wool is used in several ways so I'll discuss each use case separately. I found a great reference page from MEC about how to properly layer clothing for cold weather.
Base Layer (undergarments and linings)
When dressing for activity in cold weather, an ideal base layer will conduct moisture away from the skin. Any fabric that does this is called a wicking fabric. Wool is a popular choice because it wicks away moisture and resists conducting heat away from the body even when wet. Most natural fibres other than wool (eg. cotton, hemp, rayon) perform poorly in this regard. Hemp socks in particular are considered poor for activity and cold weather.
There are no natural fibres that excel as a base layer in cold temperatures. Cotton is a poor choice in cold weather. Wool works well, but is not generally considered suitable for vegans. Polyester works well, but it is a synthetic product.
One or more insulating layers will be worn to slow the movement of heat away from the body. Because insulating layers are not normally in direct contact with skin, moisture-wicking properties are less important than their ability to resist movement of heat. It is preferable that the first insulating layer (closest to skin) should not be cotton.
Again, synthetic materials performed better than natural fibres in this area. One popular option is Thermore Ecodown which is made from recycled PET plastic fibres. Another well regarded option is Primaloft Eco. In either case, insulating materials are not likely to be in direct contact with skin so health concerns about endocrine disrupters are minimized. Of course there are still possible concerns about production, washing, and disposal.
Hemp finally makes an appearance here. The Amsterdam-based Hoodlamb company is making all-vegan clothing that uses a mix of hemp and organic cotton to create a water-resistant outer shell. Wully Outerwear doesn't say what their Vegantech shell is made of, but I'm fairly certain it's a synthetic material. Similarly Vaute Couture also uses synthetics for insulation and external shell.
No, there is no material suitable for cold, wet weather which is both natural and vegan. At this time, vegans who want to stay warm in cold weather need to choose between the following:
- Clothing made from animal by-products, especially wool from sheep or alpaca, or
- Clothing made from synthetic fibres, especially polyester and preferably recycled.