they do have vents on them. Not sure if they are closable, but with my Bern Watts Carbon the vents arent closable and i have never felt I would want to close them.
I dunno about you guys but sometimes I ride in -25 degree (C) weather, and other times I'm in +5... So far I really like the ability to adjust the vents. Even in one day if I go from groomer bombing to playing in trees I've got to open the vents to let out some heat.