Get this. It's about five below zero this morning and clear, with a light breeze. I decided to put on my union suit long johns to make sure the cold couldn't get to me. On top of that I have regular wicking polartech and a jacket, plus gloves and bala. As it's the end of the week my energy is flagging and I had a devil of a time on the hills. I got into work and was surprised to find my bala heavier by a pound and my longjohns drenched in sweat. Now keep in mind I wasn't overheated and noticed no external sweating. It's just that the longjohns aren't wicking. They hold the moisture. It was a telling experiment. I suspect I sweat at least this much during other commutes, but never notice because it's wicked away and evaporates. That much water loss requires as much hydration as a summer ride, but I haven't been doing nearly that much. I'm going to redouble my hydration efforts and will hopefully see some increase in energy.