Simple Green: Turn Off the Fan

Here's a current debate in our house:

If a fan is on in a room and there’s no one around to feel it, does it cool the air?

We know keeping cool with fans (instead of air conditioners) is a green way to beat the heat. But whether or not to keep a fan on when no one is around is a common question…

The reason fans are great for cooling is because blowing air across the skin increases evaporation, which creates a cooling effect on the body. So… if nobody’s there to feel the air blown from the fan, than no body is getting cooler.

However, a window fan can help bring in outside fresh cool air, a floor mounted fan can push up low cooler air and ceiling fans can help circulate stale air. But again, this is only useful if the room is occupied, or will be occupied shortly after the fan is turned on.

So to end the debate: keeping cool by a fan is merely a sensation, as a fan does not literally cool the ambient temperature of a space. Only air conditioners can do that. Turning on fans to stay cool is easy, but don't forget to turn them off to save electricity.

(Image by Flickr member kmtucker licensed for use under Creative Commons)

wow, makes sense! i have been lazy about turning off fans all around the house (somehow it seemed justified since i have hardly turned on the AC this year) but this is a good reminder to get on it!

posted by vyzl on July 7th 2009 at 6:57pm
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is this the first kōan of re-nest?

posted by witchbaby on July 8th 2009 at 8:43am
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I often leave a window fan on when following a night-time cooling strategy for my apartment. The windows stay closed during the day, preventing warmer outside air from entering and slowing the temperature rise indoors. At night, if the outside temperature drops below the indoor temperature, the window fans are used to draw the cooler air in and get the temperature down again.

posted by Michelle of Montreal on July 8th 2009 at 11:23am
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I have found that if I don't have the fan on the shaded side of my apartment pulling cool air in while I am away at work the ambient temperature of my apartment is 5-10 degrees warmer when I come home, even if I have all the shades closed. It may not be as energy efficient, but the issue of comfort is more important to me when the summer sun starts beating down on my top-floor apartment.

posted by Domestic Intellectual on July 10th 2009 at 11:35am
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