Thursday, March 8, 2007

Heat Yourself With a Fan?

MLB and I operate our ceiling fans in the winter. We run them most of the time, actually.

"What?! Is he crazy? Ceiling fans in the winter?"

Yeah, crazy like a fox. Here's why: Ceiling fans can actually save on heating costs in the winter. The temperature of the air in a heated room varies in layers; it's stratified. Because warm air is less dense than cool air, the air near the ceiling is warmer than the air near the floor. A ceiling fan can help push the warmer air that is trapped near the ceiling back down into the room, de-stratifying (or breaking apart) the layers of air. This way, the warm air is circulated where it is needed (to the middle and floor of the room, where the people are), and the heating system doesn't have to work as hard to warm the room.

"Okay, I'll just walk over here and turn it on..."

Not so fast. It's not quite that simple; it has to be running the proper direction. Have you ever noticed that there's a small toggle switch on your ceiling fan? That switch controls the fan's direction, making it spin either clockwise or counter-clockwise. But, there's a catch. That switch isn't labeled with a "forward/reverse" sticker on most ceiling fans (none of ours, for sure). You have the beauty-conscious "form before function" folks to thank for that one.

"Great. I'll just flip that little toggle switch and..."

Hold your horses. It's a bit more complex than that. The direction the fan needs to turn is dependent on the height of your ceiling.

"Now I have to measure my ceiling? I'm all about saving money, but not if I have to do math. FNN, this is getting too complicated!"

Hang in there. I promise to keep it as simple as possible and you won't need a calculator. Basically, if you have a standard height ceiling...

"Whoa, whoa, whoa. A 'standard height ceiling?' Now, I'm a contractor?"

Alright, fine. Stand up. Stick your hand up in the air. Jump. If you can touch the ceiling, or almost touch the ceiling, it's a standard height ceiling, typically eight feet. If you can't touch it, and your tallest friend probably couldn't touch it, it's greater than standard height. See? No math required.

Anyway, if you have a standard height ceiling, then you want the fan to run in the reverse direction. Specifically, the fan blades should be running with the lower edge being the leading edge into the air. Having the fan run in this direction will pull the air in the room upward, which will push the warm air near the ceiling outward and force it to mix with the rest of the air without creating turbulence that you can feel. While it seems to be common sense that running the fan in the forward direction (as you would in summer) would also push the warm air down, it also creates a breeze in the room, which gives you an undesired cooling effect, much like wind-chill. Running it reverse avoids this wind-chill effect, but still mixes the air.

However, if you have a tall ceiling (greater than eight feet or so), you want to run your fan in the forward direction. Specifically, the ceiling fan blades should be running with the upper edge of the blade being the leading edge. This pushes the warm air near the ceiling down into the room. But, because the fan is far enough from you, the breeze that is created is dissipated before you can feel it.

"Okay, I got my fan running the right direction. So, how much can I save?"

Well, according to the manufacturer of the ceiling fan I installed last year, you can save about 10% of your heating costs in the winter. That's nowhere near the 40% you can save in the summer, but still noticeable. These savings are more noticeable homes with high or vaulted ceilings.

10% in the winter...and you didn't even have to do math.

Who's crazy now?


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