On really really cold sub-zero temperature days, I use double paned ski goggles. Those kind of days, I usually need a full face mask too because anything exposed gets frostbite.

A windshield might work, but I noticed on really cold days, my breath freezes quickly to almost any eyewear. FOr this reason, I use the double-paned ski goggles. A simple shield might frost up and impair your vision.