Layers, layers, layers. I think a big selling point for UA is that their stuff is very thin and light, so it is easy to layer. I have used a lot of different thermals, and a lot of times find that you lose mobility if it is too thick. Sometimes less is more. I grew up in the northwest and was a member of volunteer search and rescue, and we would find a lot of people that were cold, even though they had a lot of gear on. If you are sweating underneath, you are going to get cold, no matter what you have on. You still have to let your body breathe, to let the moisture wick away. I find that the newer materials allow that a lot easier. If you can afford them, give them a try, but start with only one pice, like a top. Don't go and drop all your money on a complete suit.
Still, it is hard to beat good old fashioned wool. Gets wet, stays warm, breathes good.
Still, it is hard to beat good old fashioned wool. Gets wet, stays warm, breathes good.