Originally Posted by
carpediemracing
Remember that "cooling" is limited to how much moisture the air can absorb. You can be bareheaded but if you are sweating more than the air can absorb then you'll have sweat running down your head. It's physics and no helmet will alter the air's ability to absorb moisture....
Also air velocity and flow directed on a surface will impact cooling. Expanding air will cool also, though it's not clear that a helmet could utilize that.
My coolest helmet is one where I cut out chunks of styrofoam to make bigger vents ...