My husbandy might be the only man who runs the furnace and the a/c at the same time.
It is hot outside so he keeps his central a/c running, like a normal person, however, unlike a normal person, he also keeps lots of exotic creatures and so he has two rooms in his home that have a furnace in them.
These oil furnaces kick on and off all afternoon long to keep his several parakeets, reptiles, amphibians, and invertebrates comfortable. The thought of residing with all of these creatures in the home someday does not bother myself and others nearly as much as the thought of residing with that electric bill does, then james keeps the vents closed off in those rooms and he had cardboard taped over the vents in order to keep much of the air conditioned air out. However, I can still suppose cool air getting in when I go into the rooms. I can also suppose heated air escaping under the door and into the main home from the heated room. I think that it would save a lot of money if there was a way to completely close off the vents leading into the creature’s rooms when James runs the a/c! Being able to seal off the doors would also be helpful. Then there is the matter of safety when it comes to the space oil furnaces in those rooms. I never trust a space heater. What if an Heating and Air Conditioning plan could be programed to put out cool air into certain rooms and heated air into other programed rooms? That would solve just about everything.