Vents or no vents you just need to learn to breathe a little different.
I remember when I was teaching my friend how to ride. We had the exact same halmet; color and all; I was seeing completely fine, and his shield was fogged up white (kinda funny).
Try to breathe more with your nose (but still breath with your mouth)and no large exhaling. Also; if the weather is cold or rainy try to breathe in a downward area to prevent blasting hot air onto the cold visor.
As said abouve, you can also pop open the visor one click and it can help.
Honestly this "fogging up," will become less and less the more you ride. You learn to work with it and don't even think about it.