Is it smart to leave a window open when tha ac is on?

Question

My roommate always leave's her window open when the ac is on about 70 and I told her the cold air escapes through the window is this true? Thanks!

Jeremy Herrring

Answer 1

yea of course the cold air is just going to go out that window

Answer 2

Yes that is correct. Cool air contracts and hot air expands. So, an open window will cause the hot air to enter a cooler room where there will be more room for the expanded air to move. With tha A/C on, it will cool the warmer air and the cycle continues thus never cooling to its max capacity and never automatically shutting down the a/c since it can never cool the whole planet to the set temperature. This is a huge electricity hog. So, to save money on the electric bill, properly cool your home, and not try to cool the planet, Close the window.

Answer 3

It would be OK to leave one open a small amount so that air will circulate, but if you leave it all the way open you are defeating the purpose.

Answer 4

yes you will be getting heat gain through an open window.

Answer 5

Yes, you should leave all windows closed.  If you leave them open your ac may just continue to run...it's like you're trying to cool down the outside too while heat is coming in.

Answer 6

It sure is true, it is no different than having a window open at 40 below......you are allowing the inside air to be replaced by the outside. Unless she has an abundance of money to Waste, she needs to close the window. However, 70 degrees is much too low to set your AC, you can "live" quite comfortably with the AC set at 76 or 78, every 2 degrees will save up to 10% on your Bill. You will also find it to be healthier. Definitely open up your windows on evenings when the temp dips down into the high 70's (turn the AC off) homes are virtually draft free and that means no fresh air can get it. I also got in the habit of turning my AC to 84  when I was not at home, it will only take 15 or 20 minutes to lower the temp and you have again saved money cooling a place when no one is home to need it.

Answer 7

Not a very smart thing to do. I would never tolerate a roommate that did something like that.

Answer 8

YES and NO. So now you know.

Cold air is heavier then warm air.

When you start the air conditioning, the cold air "falls to the floor" because it is heavier than warm air and pushes the warm air upwards.

If a window is open or there is another opening then the warmer air is pushed outside. This works until the colder air layer reaches the lowest point of the open window and then the colder air is also going out of the window. Thus YES open your window a Little bit also in your car when you start your air-co and then close it. Otherwise when  everything is closed the cold air has to cool the warmer air. You use an air conditioning to control the climate in your direct environment. I advise always to use an additional  fan to force  the colder air to move around your body. When the air is moving [a breeze] it gives you a nicer feeling with a higher temperature and you use less energy. [you make use of the chilling factor]

Make sense to you?