Based on the little information provided the AC can't keep up. So they cut off the lower half of the building to provide better cooling to the other half
This isn't your home with open stairwells and loose venting doorjams. This is a thirteen story office building with elevators and badged access easements.
My dorm room was on the ninth floor of a nine floor building.
I assure you, heat passes through elevator shafts and floors just fine, and office buildings aren't usually built like a BSL-4 laboratory. If anything, they're typically less insulated than a regular old house.