I once had immense difficulty with a housemate over, of all things, air conditioning.
The debate really came down to how much cool air you “lose” if you keep the windows open in one room only but also keep the door to that room closed.
The particulars of the debate centered around the fact that, in my own room, I liked to keep the windows open on warm days. My housemate, however, preferred to keep her own bedroom windows, and those in the rest of the house, sealed tighter than Fort Knox! On the hottest, most uncomfortable days of the year, she would pump up the air conditioning, but also quietly seethe at the fact that I refused to close the windows in my own bedroom. Truth be told, something really bothered me about closing my windows in summer. With the windows shut, I couldn’t hear the birds, couldn’t smell the wonderful, wafting scents of the nearby bakery, and couldn’t hear the joyful cries of the neighborhood kids playing in the street. The rest of the house, with the windows shut (and the blinds drawn!) was pleasantly cool, but also somewhat depressing. My housemate and I clashed most fiercely over the question of the space under my door. She insisted that she was losing a significant amount of cool air—and was receiving higher bills—because air was “escaping” under my door and out my open windows! We eventually resorted to consulting a trained HVAC tech in order to resolve the issue. He concluded that while some air was certainly being lost, it was likely an extremely modest amount and nothing to worry about. I felt gratified, and though my housemate seemed irritated by his conclusion, she accepted it and never raised the issue again.