What are the best best layers for warmth?
Base layers are designed to sit next to the skin and wick moisture away from your body by absorbing moisture from the surface of your skin and allowing it to evaporate. By wicking sweat away from the body and drying quickly, a base layer keeps your body dry and therefore warm.
Thicker base layers also work to trap an insulating layer of warm air around the skin. Base layer + mid layer layering system Two thin layers can be warmer yet lighter than one thick layer, because the air trapped between layers serves as thermal insulation.
For cold weather base layers we recommended Denali Crew Base layer shirt + base layer pant We used our heaviest-weight base layer fabric EXPEDITIONweight to make the Denali Crew and it's our warmest long-sleeved base layer shirt yet.
More info can be found on our "Do base layers keep you warm" page