I am calling this Life Support: Monitor and Control. Why you ask? This is a complete system that can control heating or cooling without changing settings. run the fan automatically for air quality and also handle a dehumidifier as well as detection for smoke, fire and carbon monoxide.
To show what's going on I will have the following connected to the Arduino:
Other sensors could be attached to the system as well ie. I fire detection could close the vents and turn off the AC, Radon detector, water level (sump pump), and many, many others.
Included items are:
ach | air changes per hour: Air flow in volume units per hour divided by the volume of the space.