"I'd cut holes in it and install add high and low venting to get the heat out. You can do this and keep the mice out at the same time."
Arly, exactly my plan; I already have 4 complete "greenhouse systems" - exhaust is a 16" fan with thermostat control, will go opposite end of side wall from doors, near ceiling. Inlet is 24" louvered, actuated when exhaust fan is on, will go 2' inside door near the floor.
I have most of the parts cut out and templates made so I can plasma cut from inside - I made the templates so they can be held against the wall with a "cargo bar" from inside, they have "outriggers" ( think "4-legged spider") that'll keep the template from exiting the container along with the cutout.
The 24" inlet needs to keep out small, medium and large pests (think bugs, mice, squirrels and "2-legged"
Hexa Fox, yes - that's EXACTLY what I meant. If the sun can't get to ANY PART of the container, then the only thing that can heat it (without an actual heater inside) is ambient air... Steve