It can all seem really trivial. But when you're dealing with roommates, the specific language you choose can have a big effect on your communication.
Personally, I always say "turn the AC down." I'm always thinking about the temperature, and that means that to make it cooler, you've got to turn the thermostat down.
In my group, I was in the majority. But others still argued that it depends on how you say the "AC" part. If you're asking for it to be cooler, you could say both turn the air conditioner up, or turn the air conditioning down.
What do you think, readers? Are you an "upper" or a "downer?"
Should this be another thing to have to hash out with new roommates? Has your wording ever caused a dispute? Tell us in the comments!