I used to pal around with a Brit in Alaska... We hunted, climbed peaks, and skied everywhere. I thought I was pretty tough in those days, but when we had to sit for a few hours... he could always outlast me. He was kind enough to share his secret: silk base layers. Ounce for ounce, some of the most warmth you can get. Really surprised me. Especially in wind.
Merino wool wasn't a thing in those days, so I usually ran polypro/capilene on top of silk. Nowadays I run merino on top of silk, then whatever is outside of base.
Hope that helps!