Under the wool underwear, I like a pair of silk long johns such as a skier would wear. This adds a layer of warmth with no noticeable weight increase, which is helpful, because I have not found a fully effective non-synthetic top layer. Fortunately, winter in the South is not generally excessively cold or windy so my down vest gives a fair amount of wind breaking protection. Not being a wool purist, I usually just reach for my camo Army field jacket. However, I do remember seeing a German sweater with a wind breaker lining in a military surplus ad some time ago, possibly Sportsman's Guide, but I don't recall if it had any customer rating.