Originally Posted by
Iride01
I'd think a base layer will just keep more sweat in which in turns means that you are holding more heat next to your body. For anything over 70ºF I'm only wearing one layer.
Even if the sweat isn't evaporating at a fast rate, just the fact it can drip off of you means it's carrying heat away from you.
I'm not taking a position on base layer or no, but you've got the physics wrong. The cooling effect comes from the heat of evaporation - the energy required to transform liquid water to vapor - resulting in a net decrease in heat (well, really, enthalpy) on your skin. Just dripping off has no effect on your skin temperature.