Okay. . .wool is the key. What about long underwear?

[KSdan]

Thanks for all the info guys. . . I am keeping an eye on this. . .

[ArcticArcher]

I use 100% silk next to the skin, then merino wool over that.  I only use the silk when it's really cold.  And most of my outer gear is wool also.  Dressing in layers are the key to keeping warm.  

I'm amped and ready for late season moose hunt during Thanksgiving, usually -20 or colder, the combo works great.

Nick

[swp]

SmartWool, Icebreakers, you can also find some decent wool at Sierra Trading Post plus the above on sale from time to time.

[northener]

Duofold  Heavyweights  Merino wool for me.

[woodchucker]

What long underwear???