The exhale escapes through the balaclava rather than up to the shades. No fog.
For less than two pairs of new winter socks, you can have the best head comfort you have ever had. Trust me. I own two Pace P3 Thermal Polypro Balaclavas(I still get to wear it when it's in the wash!!!). Chin, cheeks and nose are safe down to minus10 in my book.
Nashbar has it for $14.99. You might want to also buy a couple of these to ease your shipping cost pains
Click pic to buy