Originally Posted by
woodcraft
Sweating doesn't cause cooling, it's the evaporation- turning from liquid to gas- that does it.
If the sweat runs onto a loose-fitting jersey, & evaporates there, it cools the jersey, but not as much the skin.
By keeping the evaporation right at the skin, the base layer produces more cooling with less sweat.
But there isn't going to be much evaporation happening on a base layer if it's protected by another layer. If the other layer is a tight jersey how does the extra wicking layer help?
The one potential benefit I see is that the base layer might capture sweat that might otherwise drip away rather than evaporating. Still think one tight jersey would be cooler.