Theres basically two types of helmets: aero and not aero. Theres really no inbetween. The closest one could come to in the middle would be something liek a skate helmet with little in the way of vents. Its not jus tthe shape of the helmet, it the vents that really disrupt air flow. So if you are going to bother with a hot helmet, you might as well get one with a aero shape, too. Some people tape their vents closed for races.