I'll speak from my own experience with it. It blocks the wind. I've experimented with layers, as the only complaint I have with it, is actually getting the sweat vapor to go someplace. It seems that if I do a wicking base layer, maybe a long sleeve merino wool jersey over it for longer spirited riding, and strip off the jacket immediately after I finish, I'm ok. For longer gravel rides at home, now that it's typically a high in the 20's at best, I use a wool/angora blend sweater over the wicking, and the vapor isn't awful, though it is there. Anything layered up heavier than that seems to result in a soaked back, etc.