Of course one of the most important items in a theatre HVAC system is the thermostat placed in a highly visible location that ushers can adjust. It shouldn't be connected to anything other than maybe to DC power to make it light up, but it's amazing how patrons often feel better simply because they saw someone go adjust the thermostat after they mentioned that they were too hot or too cold.
I stumbled across one of these in an older building It was just one of those programmable household ones, tacked onto the wall with 1 screw, powered by a 9V battery. Stuck out like a sore thumb, though, since all the other thermostats were a different model and about 20 years older. I'm still sure it worked like a charm!