Do I need fresh air

[J_string]

I am finishing the interior of the s13 and my plan was originaly to reuse the stock fan and make a duct to the windshield with a little control in the glove box . But the stock fan weight a ton ( not really ) so i thought about using and aftermarket fan which leads me to the question:
Do I really have to get fresh air or can i just push it form the inside of the car ( which would be alot easier to make ) Is it gonna be enough to remove all the fog in the window in raining day's in summer ( don't care about winter the car is stored )

Thanks

JF

[citizen]

well interior air usually has more humidity then outside so it won't be as effective at clearing the windows, don't know if it will make much of a difference though.

[AKADriver]

In my Mazda, turning the knob to defrost automatically opens the vents to the outside.

[J_string]

yeah I think it's doing the same thing in my corolla but will it work enough without fresh air....