Make sure you're using your HVAC system on the fresh air setting and not in recirculate. Recirculated, though it does add in some fresh air, can get saturated pretty quickly and be useless for defogging.
Also if your car ever had a leak or the carpet & padding got soaked in some way, it could take a long time for that to dry out and it would be a continued source of excess moisture.
2013 GT Premium Brembo
MGW, Blow Fish, AM Hood Struts
Tinted, Borla Touring AB, ProCal Tune
Full Shelby/Kicker Audio Upgrade