After using different types of thermal underwear for the last 25 years of a life in the outdoors, my conclusion is that the choice is a very personal one. Either you like wool. Or high tech yarns. A few observations though:
- I have noticed that thermal underwear which are marketed by brands who primarily focus on extreme sports, like competitive skiing, are not made for users who are outdoors a long time. This type of underwear are far too cold and should only be used for short time competition. Definitely not for Expedition. These brands tend to dominate the market today. So, look out!
- Good quality thermal underwear has to do with they machinery they´re produced by. Some outdoor brands are produced in a way that needed changes and developments are hard to do. An important question is, do they have there own factory and machinery to produce their own brand? Important!
- So, regarding my personal opinion, wool or high tech yarns? I think wool does itch on and off.
Thermal underwear are for me with the most important items of gear. This layer is the most important aspect of your choice of how to dress on your Expedition or adventure. Or day out in the woods. This applies whether we are talking Arctic or tropical adventures. For example, at this precise moment, together with Termo, I am trying to figure out the best thermal underwear to use on desert travel. Thermal underwear is at least as important on such an Expedition as in the Arctic. And as regards to which thermal underwear to use, the following has to be taken into account:
- It has to be thermal underwear with unique channels of construction to both insulate and help regulate body temperature
- Light weight
- Highest quality yarns
- Anti-bacterial treatment that is not wash away
- Active fit
- Flat-lock seams to minimize chaffing
- Fast wicking
Please do come with your own personal opinions in this interesting subject!