I have a "turtle" - essentially the bottom half of a balaclava. It's a tube of fleece that fits around my neck, and to get the full warming effects, it's long enough to pull up over my nose.

Pulling the turtle over my nose places it directly underneith my sunglasses. So when I breathe, the hot air fogs up my glasses! The frames are vented to prevent fogging, but it sure isn't working!

Any suggestions other than:
a) going faster to increase the venting effect of the glasses
b) pulling the turtle down to expose my poor nose to the brutal cold.
c) not breathing so warm.

My husband, with a similar pair of glasses, had the same problem this morning with his balaclava.