Patagonia: Ventura-based Patagonia’s thermal underwear is what you buy when you are sick of buying thermal underwear. It is pricey, but it’s made to last – my ten-year-old thermals are still going strong. It is smooth and soft, not itchy. It does not bunch under your clothes. It is warm, yet it has almost no bulk. And it is manufactured as ethically and sustainably as reasonably possible.