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01-20-2011, 03:00 PM   #1
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Ceiling Fans: Useful Or Myth

Yes I know. "What a strange and useless topic" is what some of you might think. But with the collective pool of thinkers on the forum I just wanted to stretch my reputation and ponder a bit.
What can be said about running a ceiling fan during the cold months to circulate warmer air from the ceiling back down in an effort to reduce furnace running time and energy bills? Or is it nonsense and the energy used by the fans only adds to energy consumptions with very little difference made?
Fans cool people; not rooms. Fans generally make the skin feel cooler by pushing the air but if a ceiling fan is set at a low or medium speed, pushing the warmer air back down, will this help keep the room warmer and thereby shorten the time your furnace runs? Has this all been approached by Mythbusters before?
Let's have some arguments.

01-20-2011, 03:15 PM   #2
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There are many variables. What kind of furnace, how many floors, etc. We found that heating the basement or lowest level warms the floor which then radiates heat to the upper level. Also run a fan above a light to push the heat down in one room in winter and out the window in summer. Never calculated the relative costs. Something similar to viewing a photo, whatever one likes works.
01-20-2011, 03:33 PM   #3
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I have no scientific proof, but from anecdotes I can tell you it seems to make a big difference.

At my country house we have a high ceiling with a few fans in the main room, and in winter just going up a stepladder to dust the fans (when they are off) you can tell there is a serious accumulation of heat up there. We run the fans on the lowest settings and when you stand below them you feel the draft of warmer air.

We have a similar situation at work (a fire station) in the apparatus garage. In winter if we don't run the ceiling fans, it gets real cold in there. After the fans have run 10-15 minutes the air has mixed and the garage is warmer.

Of course this is anecdotal, your mileage may vary =D

Pat
01-20-2011, 04:09 PM   #4
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Can they save you money? That depends on you.

For me, I moved form an apartment with forced air central heating and AC to an old house with ceiling fans, radiators, and window ACs. Geographically I moved less than two miles, and outside weather was essentially the same both places.

Ceiling fans and open windows let me not turn on the AC until a few days into June. At the old place, I definitely would have had to turn it on either last week of April or first week of May. Probably about $400 worth of cooling for that year I didn't have to pay for.

01-20-2011, 08:29 PM   #5
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QuoteOriginally posted by Nowhere Matt Quote
Yes I know. "What a strange and useless topic" is what some of you might think. But with the collective pool of thinkers on the forum I just wanted to stretch my reputation and ponder a bit.
What can be said about running a ceiling fan during the cold months to circulate warmer air from the ceiling back down in an effort to reduce furnace running time and energy bills? Or is it nonsense and the energy used by the fans only adds to energy consumptions with very little difference made?
Fans cool people; not rooms. Fans generally make the skin feel cooler by pushing the air but if a ceiling fan is set at a low or medium speed, pushing the warmer air back down, will this help keep the room warmer and thereby shorten the time your furnace runs? Has this all been approached by Mythbusters before?
Let's have some arguments.
I used a regular oscillating fan aimed upward to circulate the warm gas-heater air, much like circulating the chemicals in a developing tank. Now, I'm trying a space heater. But, I'm in So California so any heater has not much use, really.
01-21-2011, 07:33 AM   #6
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Under normal circumstances, heat rises, so a ceiling fan will help force that heat back down (no matter which direction it's running). The problem is, air moving over our skin creates a chill as it draws heat from the surface of our bodies. The conclusion is during winter months, a ceiling fan will help level out the temps in a confined space, thus saving some money, but will be uncomfortable for most people. In the summer, the opposite would be true: ceiling fans will still level out temps by forcing warmer air down, which would cause additional a/c costs, but will promote cooling on the surface of our bodies making us more comfortable.
01-21-2011, 07:38 AM   #7
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I think it would help as long as you are also wearing long sleeves and pants so the breeze doesn't cause moisture from your skin to evaporate.

luckily I don't have any way to test this as the high here yesterday was 60 degrees

01-21-2011, 08:19 AM   #8
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I'm willing to bet there is always a non-zero fan setting that is optimum even when there's a sweaty person in the room (ie., when the wind chill factor is important. Certainly when wind chill is not important, the fan will homogenize the distribution of heat energy in the room and 100% of the energy used by the fan will go into heating the room implying that the fan always helps.

Here's a nice experimental study of the effect of a small fan on stratification: http://pages.uoregon.edu/hof/W08%20HOF/17%20FanClub%20ppr.pdf


Dave

Last edited by newarts; 01-21-2011 at 10:16 AM.
01-21-2011, 09:08 AM - 1 Like   #9
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They're not a myth. I've seen 'em.
01-21-2011, 09:15 AM   #10
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We have ceiling fans in every room in the house and I don't think I could live without them. My home (19' cathedral ceilings - never again) has a loft with 2 BR's, a bath, and my home office. Without having the ceiling fan constantly circulating in the loft's open area, I could not work up there as my wife is very cold natured and cranks the heat up when she is home. We reverse the flow of the fan in the loft depending on the season, and even on a lower speed, it does an excellent job of pushing the warm air back down. She's happy and I'm happy.
01-21-2011, 09:26 AM   #11
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In summer the fan should be blowing downward to cool people by moving air across their bodies. In winter you reverse the direction, so the fan pulls air up, aiding convection. Having a fan blowing on you in the heating season is counter-productive.

Our house is a split entry, we live on both levels. There's a fan in the entrance foyer. The air definitely stratifies in the house without the fan. I've measured a 1-2 degree C difference in my downstairs office with fan vs no fan. This is enough to make me comfortable vs uncomfortable. I would not be without it.
01-21-2011, 09:40 AM   #12
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QuoteOriginally posted by Tom S. Quote
............The conclusion is during winter months, a ceiling fan will help level out the temps in a confined space, thus saving some money, but will be uncomfortable for most people. ................
Setting the fan to blow toward the ceiling will minimize that effect. As you said, it will circulate the air either way, but there will be less felt air movement. When set to draw from the room, and blow towards the ceiling, the air tends to move across the ceiling, is deflected toward the walls, and has lost velocity by the time it gets to the lower parts of the room.
01-21-2011, 09:44 AM   #13
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QuoteOriginally posted by lithos Quote
They're not a myth. I've seen 'em.
That gets you a rep point from me.







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01-21-2011, 02:31 PM   #14
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It certainly helps in older buildings with high ceilings. In commercial buildings and warehouses, again places with high ceilings and large rooms, it makes a huge difference. Warm air rises. In the garage where I work, the thermostats are set at 65F. Standing on a ladder while repairing a reefer or marker lights across the top of a trailer, it can be 20 degrees warmer where you are working and you will be in shirt sleeves while the mechanic working on the truck engine at floor level is cold. Ceiling fans will keep the air circulating and an even temperature and will save on heating costs. It is a common complaint in 2 story homes that upstairs is hot and the downstairs is cold. Fans can help that situation also. Whether the heat savings will be worth the electricity consumed will depend on the building and the climate. The ideal set up is to have a slow speed ceiling fan set up on a thermostat switch to kick on at 10 degrees above the room thermostat, that way the fan only gets used when it will be of benefit. If you never have that kind of differential in your home, the fan won't benefit much. Hot air furnaces keep the air moving pretty good. Hot water systems benefit from fans more because it is radiant heat and also the water looses temperature as it circulates and you get hot and cold spots in the house. With a little effort, it's easy enough to figure out if a ceiling fan will benefit you. Just put a few thermometers around and monitor them. If your room is set to 68 degrees and you are regularly seeing 80 degrees at your ceiling, get a fan.
01-21-2011, 02:51 PM   #15
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We have a ceiling fan in every room and several on the screened porches. Of course, the big saving in winter comes from running the ceiling fan in the room that has the thermostat
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