I wear glasses. They fog up when I wear a mask in the cold. However, when I tuck the mask under the bottom of my goggles, they seal the mask to my face and my glasses do not fog up...yet. I haven't had to use the fan on the goggles (Smith turbo OG) this year (only been a few days though); they fog up a little when standing still, but clear up as soon as I get moving.Smith IO goggles have been fogging like crazy with my mask.