Originally Posted by
Ken Wind
Wool also keeps you warm even when it's wet though. I've never had a synthetic fabric do that.
I suspect you don't have any experience with polar fleece. Wool keeps you warmer than cotton when wet, it does not keep you warm by any stretch of the imagination.
Equating the performance of all synthetics is like equating the performance of all natural fabrics - it makes no sense.
Wool is for fashion - if you need to stay warm in extreme conditions, polyester fleece as the insulation layer is the answer. OTOH, biking in the cold is normally not "extreme" conditions compared with other activities like winter camping, hunting, ice climbing, etc. You won't find many of those guys messing with wool, except on their feet.