I use the Visorgogs down to about 18f-20f. Once they reach their threshold they start to fog. I've tried using dishsoap, spit. To prevent fogging. It worked OK at first but the problem still persisted. So I switched to Uvex flex seal goggles from http://www.labsafety.com/uvex-Flex-S...gles_24537158/ last year. The coldest I rode in was 6f. And with my mouth and nose covered with my balaclava I had no fogging issues. To me, I guess the key is to have a goggle with a tight seal around the face to prevent warm air from rising up into the goggle. This model worked over my eyeglasses, my periphal(?) vision was somewhat limited. But I was still able to use my helmet mounted mirror. So with that problem solved I'm looking forward to season number four of riding in the coldest temps that I've ever ridden in. In '09' I rode in -14 and I had to strip off the Visorgogs because they had frost build-up on both sides. My eyes didn't freeze but I was worried they would. Thank goodness those temps didn't last long. But I feel the Uvex flex seal googles would've handled those temps. Maybe we'll find out this year.

One problem with the Visorgogs are the UV ray damage they suffer after a few years. The first pair I had lasted two seasons. The third year I tried them and the lens were too clouded-up from UV damage. Thank goodness they're cheap. I bought two pair last year that should last awhile. The Uvex's, I only used a few times last year. So the jury is still out on whether they go thru the same thing.