My family has air conditioners installed in two bedrooms, each about 20 square meters. We do not have AC on the ground floor because the space is not airtight. At bedtime, I always remind my wife and children to keep the bedroom doors tightly closed to avoid losing cool air and wasting electricity.
However, I have come across differing opinions on social media. Some say rooms should be sealed, while others suggest leaving them partially open to allow ventilation. I would appreciate advice from experienced readers or experts on what is actually best.