Merino wool is the most efficient material for cold weather. Merino
wool is softer than regular wool, and it feels more like cotton against
the skin. Merino wool resists wind and warms better than synthetic
materials. It doesn’t absorb odors and it regulates body
temperature. It is also produced in a sustainable manner.

The jacket pictured here is the Smartwool Banff Jacket. It’s designed with a woven wool sueded fabric, and it has a heavy 100% merino wool lining. There is a women’s version
of this jacket too. Smartwool sells a whole range merino wool clothing,
including summer wear. Merino wool clothing tends to be expensive, but
you can find Smartwool on eBay and at REI Outlet.