I had a fan in my Sinisters last year and they still fogged, that was even with rubbing with anti-fog cloth. But I have yet to find a pair of goggles that won't fog up, still searching this year, trying the Aviators.
Havn't used the fan but I bought the Klim Arctic balaclava with the nose piece. Nose piece can be kindof annoying but worth it. I usually am fogging up constantly but with the new balaclava I didnt fog/ice up once. Just a suggestion!