I'm looking for a QUIET fan to ventilate my cabin through a vertical
wall in a loft area. It needs to move about 3-4000 cu. ft./min.
Needs to fit in 26 inch opening. I currently have gable fans that are
so noisy they can't be used. A belt driven fan would be preferable
from what I've been able to read on the net. Does anybody in this
group have any suggestions or experience that would help?

I have used those that mount horizontally in the ceiling of the first
floor and blow air into the attic. They work great, but it is my
understanding that these cannot be mounted vertically.

Thanks,
Harry