Horse barn exhaust fans

[RobA]

I have a 48'x48' pole barn for horses. The 2nd floor gets 100+ degrees in the summer even with a cupola and 6 open windows. I was thinking of adding 1 or 2 thermostatically controlled exhaust fans on 1 or both ends of the barn. Any recommendations?

 

[Clay45]

How about something like this?:

Amazon.com: Air Vent Inc. 24" Whole House Fan 54301 Attic & Whole House Fans: Home Improvement

 

[Baby Grand]

I kind of like this solution:
https://en.wikipedia.org/wiki/Solar_chimney
I've seen the chimney constructed by anchoring a pipe, painted black, next to the building to be cooled.