It's probably going to vary a lot from season to season - even a shaded garage will build up heat in the summer and get cold in the winter, unless it's well-insulated and/or connected to your house's heating/cooling system. What may work in the winter might be totally inadequate in the summer months, so you might want to take that into consideration.
I'd probably go a little overkill with the fan and dial it back with a speed controller. That way you can always increase the fan speed if you need more ventilation. And insulated ducting, bungee cords (or other vibration reducing tricks), and a box for the fan will all help with the noise too.
Ur exactly right. I will not grow nov till april. Not worryin bout puttin a heater in garage