Closed Vents on tour riders helmets

Got to love good old homeostasis

Apparently not having sweat evaporate from your head doesn't impair cooling much. Body core temperature won't change, thanks to homeostasis. And they do have vents at the back of the helmet.

Isolated statements such as "saving 3 watts" are meaningless. It depends how fast you're going. If you're stationary, it doesn't save anything! It will save a lot more power in a 70 kph sprint compared to a steady 40 kph cruise, since power required to overcome air resistance increases at the square of speed. (Wish I could cruise at 40 kph.) So I think that means if "saving 3 watts" was at 40 kph, then it would save roughly 9 watts at 70 kph. If, however, the "3 watts" saving was at 30 kph, it would save roughly 16 watts at 70 kph.

It's quite interesting to see riders starting in 'normal' vented helmets then switching to the closed ones as the stage gets towards the end and the pace picks up when the advantage would be I guess be greater. Cav did it the other day, and just seen Greipel do it. That would suggest to me that they're not as good for all day riding as the manufacturers would have us believe.

i think it'll depend on conditions. if it's not a hot day and you're a pro rider sitting in the peloton then you're not in any danger of overheating. Giro claim that their new Air Attack lid draws air in under the front and over the head of the rider, creating a cooling airflow without lots of vents. the Kask ones look to be just the vented design with a solid cover closing off the holes.

come the mountains i'd expect riders to switch back to vented lids. i guess we'll see