Hello Everyone, I'm trying to find out how much additional BTU from mini ac split units I will need for the radiant heat of the sun hitting the shipping container so I can properly cool the inside. The average temperature of the environment is 84 degrees F and humidity is 84% as well. I was hoping to use a heat gun and recording the temperature inside the container without any ac turned on and finding out the additional btu I would need. Any help would be appreciated, thanks

You won't be able to tell anything from the ceiling & wall temperatures if there isn't any AC running, but you might be able to infer something if you measure the difference between the average indoor temp and the ceiling/wall temps when it's being actively cooled.

The solar spectrum reflectivity and infra-red emissivity of the exterior finish can make a substantial difference in the cooling loads too.