I used to work in HVAC. I remember we had a small cold room that was struggling to maintain temperature, as in, design was supposed to be 0°F but it couldn't get below 36°F. There was a large hole in the box that was undoubtedly the cause of the problem, so I asked the installer how they accounted for that. "Oh, I doubled the infiltration value." When I tried calculating the actual losses it was way, way higher than the infiltration value. Like, the room needed someting like 3-4 times its total refrigeration capacity to reach target with a giant fucking hole in the box.

No idea who thought putting a giant hole in the box was a good idea.