I am not a fan of polypropylene compression layers unless I’m going to be sitting still in very cold weather. I find that they get sweaty and clammy pretty quickly. If I’m active, my go-to base layer is silk, which breathes and resists absorbing odors, but also regulates temperature, keeping you alternately cool and warm. Next, I opt for a lightweight polyprop layer, preferably with a half zipper to regulate my body temperature. Then I add a loose-fitting layer of either merino wool or a scent-controlling synthetic. And lastly, I’ll add a heavy fleece if the air is especially cold, the wind is biting, or I will be sitting. It’s a cinch to remove or add layers as conditions require.