Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I remember learning this in high school, but have forgotten it, and can't seem to find it anywhere online.

Air travels from areas of high pressure to low pressure...correct? So if I have a cold room in my house, does the air move from the warm rooms to the cold room or the other way around?

share|cite|improve this question
up vote 10 down vote accepted

Air does indeed flow from high pressure to low pressure area (see the wind arrows on a weather chart), but in the case of two rooms the much more important effect is that of warm thinner air rising towards the ceiling when the air from the two rooms gets mixed.

Thus, cold air from the cold room will be leaving the room close to the floor (if the temperature difference is large enough you can actually feel it, otherwise you can use a candle to detect the direction of air movement). At the same time, warm air from the warm room will rise and move into the cold room close to the ceiling (again, sometimes you can feel this otherwise you can detect it with a candle). Similar air movements take place between your house and the outside when you open your house's door in winter or summer.

The tendency of warm air to rise towards the ceiling is actually exploited in floor heating. This was understood and taken advantage of already by the ancient Romans, see hypocaust.

share|cite|improve this answer

Actually, cold air just sinks while hot air rises (due to density of the collection of particles)... this "flowing" is just the wind pushing particles around, so you'll sense a change in temperature... if we want to talk about heat transfer (which I believe the question is really getting at), then "cold disappears" by "hot entering"... think about it, temperature in some sense is related to the speed of the collection of particles.

share|cite|improve this answer

Cold air flows downward according to hot air because it is more dense and sinks while hot air rises.

share|cite|improve this answer

In hot room the air will be much thinner thus reducing the pressure so the air flows from cold room to hot rooms.

share|cite|improve this answer
But isn't this forgetting the temperature dependence of the pressure? At constant pressure, hot air is thinner, but this assumes the pressure is equilibrated. – Ron Maimon Dec 30 '11 at 11:32

Cold air sucks out the energy of hot air! Moisture always is attracted to cold! The air in your room will move through the house as warm air leaves the room or house through cracks at ceiling height. Cold air will always come in through other cracks! Air goes out and new has to replace it! Seal the cracks around windowes doors light switch and plug plates and check the baseboards air can come in to the House through holes in the wall from attic or basements along the path of electric wires in the wall!

share|cite|improve this answer

protected by Qmechanic Dec 22 '13 at 16:38

Thank you for your interest in this question. Because it has attracted low-quality or spam answers that had to be removed, posting an answer now requires 10 reputation on this site.

Would you like to answer one of these unanswered questions instead?

Not the answer you're looking for? Browse other questions tagged or ask your own question.