Ceiling fan misinformation?
lance_p
| Posted in General Questions on
I just read this Government of Ontario page on ceiling fan usage to save money on air conditioning: https://saveonenergy.ca/For-Your-Home/Advice-and-Tips/Seasonal-ceiling-fan-direction Other than creating airflow and using the “wind chill” effect to help keep you cool, I’m wondering if ANY of the other claims on that page make sense? I’m thinking from the point of view of an average residence with 8-9’ ceilings.
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It sounds backwards. Ceiling fans help in the winter by pushing warm air that accumulates near the ceiling back down to keep things from stratifying. This helps to even out the air temperature throughout the room, so don’t have a cold area hear the floor while the ceiling is warm.
In the winter, stratification generally helps you. Heat naturally rises, leaving the lower part of a room cooler. In buildings with very high ceilings (box stores, warehouses, etc), this effect is very noticeable. If you’ve ever worked in one of these places, you’ll notice that on hot days it is uncomfortably hot near the ceiling while it can still be fairly comfortable near the floor. In a typical residential structure with ~8 foot ceilings, I doubt you’d see much noticeable comfort from air stratification like this.
Ceiling fans do create a nice, gentle breeze in a room. This breeze does make you feel cooler since your body is a natural evaporative cooler. You do want your ceiling fan to blow air downwards in this case, which is the normal configuration. Aside from this breeze effect, I think they’re overstating the benefits of a ceiling fan in this document.
Bill
> In the winter, stratification generally helps you.
I expect that you meant to write "In the summer".
> breeze does make you feel cooler
Agreed (because of evaporation and convection). If you spend substantial time in one place (eg, bed or office), then a fan (of some type) can pay for itself by allowing a higher summer thermostat setting (at the same comfort level). During some weather, this will cause the AC to not run at all (providing a large but short term "up to" savings). It definitely works - with a fan on, I have to raise the AC thermostat to be comfortable.
>I expect that you meant to write "In the summer".
Yes I did. Thanks for catching that. In the winter, hot air at the ceiling is basically wasted if it leaves the floor cool. Fans help with stratification in the winter, but in the summer it’s the breeze that helps. Either way, the savings are going to be pretty small in a typical house.
Bill
Lance,
There is absolutely no evidence to support these ridiculous claims:
"While it may not replace your air conditioning entirely, a ceiling fan will complement your air conditioning unit and help you save up to 40 per cent on air conditioning costs in your home."
"Using a ceiling fan in the winter may seem counterintuitive, but it could save you as much as 15 per cent on your heating bills."
For accurate information, check out this GBA article: "Using Ceiling Fans To Keep Cool Without AC."
Bill, I once recommended to my friend's dad to install fans along the peak of the cathedral ceiling in his 20' tall 33 x 66 shop. He used a big wood stove to heat the place and it took a LONG time to take the chill out of the air in the dead of winter. With the fans in place he could circulate all that warm air down to the floor and as a result could heat the place in about 1/3 of the time and maintain a comfortable temperature with about 1/4 of the wood.
In that application (super high ceiling, stagnant air, wood stove) the fans worked wonders.
Martin, I remember reading your article a long time ago. Agreed, most of that article seems like nothing more than an excuse for the Gov't to appear to be helping people. Nothing in there seemed to make sense, thanks for confirming.
Lance,
You claim that adding a ceiling fan reduced heating energy use by 75%?
I think that's impossible.
Martin, the cross section of that shop is 16’ high walls 33’ apart with open scissor trusses about 20’ high from floor to center, and probably 23’ floor to peak. That building is near Uxbridge, ON, just North of Toronto. It's a steel post and beam building with poorly installed fiberglass batts and the posts and trusses are all thermal bridges exposed on the interior. Very poorly insulated.
The shop is unheated unless in use. When it was -15C outside after a -20C overnight low, prior to installing the fans one had to build a raging fire and then wait. In order to be “comfortable” while working on a car, the air temperature at head level had to be very warm because the air near the concrete slab was still freezing. Your feet were always cold, and before he installed a hoist, working on a creeper close to the floor under a cold car meant having a sweater and gloves on, even though you’d be “comfortable” in a T-shirt standing up. In that temporary “heat-to-use” scenario, the floor never actually got warm yet the air at head height was surely above 80F. Who knows how hot it was at the ceiling peak.
With the ceiling fans installed, the same raging fire was built but by the time it died down the shop was comfortable. At that point only enough wood was required to barely keep the fire going. After a short while the floor actually warmed up, as did the cars sitting on it.
If the shop was kept heated I doubt the impact the fans on wood consumption would have been nearly as high since the building would eventually soak and reach a more even temperature. However, in this case where it was heated only for an afternoon, or at most a day at a time, the impact of having the fans was enormous.
Also keep in mind that the wood use estimate was not scientific, that was simply my buddy’s dad’s comment after a season of use noticing how much wood he had left over. The number of days heated, the duration, temperature... lots of variables there. Maybe it’s closer to half? A third? Who knows.
Lance,
I completely agree - but isn't saveonenergy a privatized utility in Ontario? I don't think this is the Canadian government giving the advice.
Save ON Energy is definitely Ontario based, it's run by the IESO as far as I can tell:
http://www.ieso.ca/
Their marketing reads:
"The Independent Electricity System Operator (IESO) works at the heart of Ontario's power system. The IESO delivers key services across the electricity sector including: managing the power system in real-time, planning for the province's future energy needs, enabling conservation and designing a more efficient electricity marketplace to support sector evolution."
Perhaps ceiling fans are a tricky way to get us using MORE energy? LOL. Gotta keep that current flowing in the winter when nobody's using AC!
I'm pretty sure the rebate and incentive programs offered through Save ON Energy are (were) funded by the Ontario Gov't. They are now cancelled, not long after the similar Green ON program was cut by Doug Ford as soon as he took office:
https://www.cbc.ca/news/canada/toronto/greenon-program-ends-1.4713161
EDIT: Ah! I did say Gov't of Canada in my original post. I should change that to Ontario. Thanks for pointing that out!
Everything to do with Hydro One in Ontario seems to be a mess.
The heating part is clearly nonsense, and they should be embarrassed to have that pseudo info there.
I had ceiling fans in my old house. I can't say whether they did much of anything in the summer or not. When it was uncomfortably hot in the bedroom, I would sometimes run one. Did it help? Maybe. Did it produce a dramatic, cool breeze? Absolutely not. A portable fan placed closer and blowing across your body works far better. Having ceiling fans blowing in all the rooms during the day as you move about the house is certainly a waste of energy.
I would like to install a ceiling fan in the living room of our new place, which is open to the 2nd floor. My wife hates ceiling fans though, so I probably won’t end up with one.
As a kid I remember having fans that didn’t seem to do much, but I believe they were all installed close to the ceiling where they were largely ineffective at moving air. Dropping them down a bit certainly increases their efficiency, but that’s not really possible with 8’ ceilings, begging the question “why are fans being recommended to everyone by our governments and utilities?” when they likely won’t be effective for most people, even in the summer?
I think fans are being recommended for the same reasons as other misguided “green” recommendations are made: someone has a little info, but not a full understanding, so they give bad info. CFLs in many ways weren’t a good idea, but remember how hard they were pushed by many? LEDs are a much better option now that they’re available.
Ceiling fans most certainly can be beneficial, but only in certain, limited, situations as have been detailed here by myself and others. The energy savings in the summer are minimal, and I wouldn’t be surprised if the energy to run the fan cancels out a big chunk of the supposed “savings” from less air conditioning. Trying to push ceiling fans as a huge energy saver in all situations is just not accurate.
Bill
Energy Star has a spec for ceiling fan performance: https://www.energystar.gov/products/lighting_fans/ceiling_fans.
Peter
Thanks Peter!
Air, like any other solution, is best when mixed thoroughly. Fan direction and speed in a closed environment is somewhat irrelevant, as long as it is moving it will do its job.
A well air-sealed and insulated house should have very little temperature stratification. What there is typically occurs in rooms that are closed off from heat sources. I can't see how ceiling fans help with that.
Malcolm: what would you expect it to be, say in a Winter case where there is little mixing (eg, a radiant ceiling), a high ceiling and a large area of windows (sending cool air to the floor)?
In a well-built house with good ventilation, it should be in the "who cares" range.
https://www.greenbuildingadvisor.com/article/cold-floors-and-warm-ceilings
Tom: In some cases, stratification is deliberately maintained to increase energy efficiency. See "displacment ventilation" or "underfloor air distribution".
A fan's cooling effect on a person is very much related to positions and air speed.
“Underfloor air distribution” is commonly used in data centers. I work with these all the time. It’s really not “maintaining stratification”, but rather working with convection delivering cold air low and hot air returns near (or in) the ceiling. In these systems, the fan runs continuously with only the cooling part (compressor or chilled water coil) cycling to maintain a temperature setpoint. With the amount of air movement in the system, there is no chance of still-air stratification.
Bill
I work with them too - it's very much about avoiding mixing (which maintains stratification). See:
https://en.wikipedia.org/wiki/Underfloor_air_distribution#UFAD_air_distribution_and_stratification
I don't see anything wrong with the idea that ceiling fans may save significant money on AC (though of course it would depend on the climate how often they were useful -- if you badly need the dehumidifying effects of AC, for instance, obviously a fan isn't going to be nearly as good). Any time you can be comfortable with a ceiling fan rather than the AC is time spent using 50 watts rather than 3500, after all, plus being able to set the AC at a higher temp due to having a fan available. In any case I really like ceiling fans, and am kind of sorry we got rid of ours.