Quote Originally Posted by lunchboxGTI View Post
No. You can have a little to a lot of moisture in and out of the car and it won't fog. As soon as you change the temp in side relative to outside with out removing the moisture it will fog as it trys to reach a equilibrium (Second law of thermodynamics: Heat cannot spontaneously flow from a colder location to a hotter location) you can use heat to remove the moisture but it will take longer or you need a lot of heat quick. Recycling the air with heat as the op is trying to do will work but it takes minutes compared to seconds with the air con.
Which is why I said "but both play a role in fogging up windows."

Recycling the air will just continue to increase the humidity of the car and worsen the problem (in theory) because of the moisture we breathe out and sweat etc. building up in the cabin.