I know you want motorized to account for the times you need more air.
I live in Virginia, near the ocean, the low temps here don't get much below freezing in winter but the highs in summer get to 99*F @ 99% humidity. Heat index around 120*F.
My daughters grill is 100% closed. I used foam pipe insulation and crammed it between the horizontals. White car + blue foam = odd look. You might want to color match.
My point, (ah good you think, finally a caboose to his train of thought)
She never had an overheating problem last summer and she drives like a maniac.
Two speeds;
Haul@$$ &
!STOP!
Maybe you don't need the motor?
Just my .02,
Schultz