I found a calculator for natural ventilation : http://www.engineeringtoolbox.…ht-ventilation-d_122.html
Natural Draft Air Flow and Velocity Calculator
Inside temp : 100C Outside: 20C Height (of building) 10m
The duct is the opening in the roof ... these are a big guess:
Duct diameter 1.2m (diameter of fan) Length (height of fan) 1m
Loss coefficient 1
Gives an air flow of 17,000 CFM (VERY rough estimate) -- roughly half of what would be needed (27,000 CFM)
So we're left with radiation and convection, mostly through the roof.
So an operating fan would be required.
Also, that 27K CFM air would have to be replaced by fresh air coming in (fan or no fan). The front (office) door is presumably closed all the time, and the shipping bay doors are probably closed.
Edit: The building isn't as high I remembered : https://www.lenr-forum.com/for…ment/731-rossi-miami-jpg/ ... so the maximum height for natural draft is maybe 5m ... giving 12K CFM out of the needed 27K.