Maybe I'm just a dumb hick from the sticks, but how can it be possible that a wicking base layer makes you cooler? One designed to transport moisture out for more rapid evaporation will do better than one that doesn't (poly vs cotton, for example). But no way can a layer of any fabric have a negative insulating effect, one that will insulate less than no layer would. It will hold a layer of heat between itself and you, there's really no getting around that.