Using AC with the windows open - will the house cool off quicker? The other night, a few of my friends and I got into a cool (although some would argue it was heated) argument about the efficiency of cooling a house with air conditioning.  I wanted to leave the windows open for 20 minutes or so, but they told me I was wasting energy.
My argument: As cold air enters the room, it will fall and create a small draft that will blow the hotter air outside.
It is hotter inside the house than outside.
Does science back my argument?  Does leaving the windows open temporarily when air conditioning a house or a car cause for faster cooling?
 A: It depnds on the inside and outside temperature.
If the outside temperature is higher than the inside  one, keeping windows open will be waste of energy, trying to cool the ouside too.
If the outside temperature is lower than the inside, a fan is enough to help cold air come in. The airconditioning itself will only work as a fan so it makes no difference in the energy spent, except the fan energy which accelerates the natural convection.
A: Turns out, you're a giga-savant whos brain works better than a trained physicist, who could tell you exactly how air conditioning is supposed to work but has never experimented with one empirically. See, air, much like water, flows in the direction of least resistance. Guess what happens to air when you pump it into a sealed room? Hot air, cold air: it doesn't matter... If you said something along the line of "it begins to push against itself until it finds an easier place to go," then you've got some mind! Just try it for yourself. shade your room with blinds, crack the window, maybe crack the doors open in other rooms. Make sure the other rooms have closed windows (remember, we're directing air at this point), and let the AC blast... Booya! Your friends were just getting on your case because their parents got on theirs, not because closing your window cools a room faster. Should you have all the windows open while running the AC? Heck no. Think of the ratio! how much air does your AC blast anyway? So, then, guess what you do when your room is finally nice and cold, and likely one of, if not the coolest room in the house? Yep. Close the window. It should take about 20 minutes! 
