Myth or science? Ceiling fan in winter mode reduces heat bill

Motorapido

Every information source on earth claims that a ceiling fan in winter-mode rotation will lower heating bills. Nobody backs up these claims with data. I suspect BS.

In my amateur analysis, it would seem to me that leaving the colder air undisturbed down at floor level and allowing the air to be naturally warmer the farther toward the ceiling you travel, would be best. You live your life in the middle third of the room, from floor to ceiling. With the stat set so that your head and shoulders are comfortable at head and shoulders height, all is well. But if the fan simply churns the air around and achieves an even temperature from ceiling to floor, I would assume that you're spending more heating dollars to heat the colder air that without the fan would just naturally sit lower toward the floor.

I hereby assign Jamie and ChrisJ to opine on this matter of physics. My master's degree in 19th century English literature gives me no advantage in this particular situation, but if you ever have a question about the novels of Anthony Trollope or about Victorian pre-Raphaelite poetry, I'm your man. You gotta know your limitations.

hot_rod

hot goes to cold always. The rate of heat exchange is based on the temperature difference. With forced air the warmer the stratified air at the ceiling the greater the loss through the insulation.

That was always the "selling feature" of radiant floor heat, little to know stratifications, lowers the losses up top.

I guess the same applies for lowering your indoor temperature, less loss through the building shell, lower energy required.

Jamie Hall

Too many variables. What they do is reduce stratification in the space. Now -- is that necessary or even desirable? Well... In some applications overhead fans are unquestionably useful. High bay work areas and big barns are some examples (big barns particularly) -- but those fans are huge (ten to 20 foot or more diameter) and the ceiling (often the underside of the roof) is a long way up -- and is a major heat loss.

In a residence... I'll have to contemplate this. I think the key variables will turn out to be the type of emitter (e.g. forced air vs. radiators vs baseboards vs. radiant floor) and the geometry of the space (including where the heat sources are, how effective they are in reducing stratification, and so on).

Let me think about it.

ChrisJ

hot_rod said:

hot goes to cold always. The rate of heat exchange is based on the temperature difference. With forced air the warmer the stratified air at the ceiling the greater the loss through the insulation.

That was always the "selling feature" of radiant floor heat, little to know stratifications, lowers the losses up top.

I guess the same applies for lowering your indoor temperature, less loss through the building shell, lower energy required.

So you're saying a ceiling fan will save money in the winter?
One thing I've been confused about for years is the claims you're supposed to reverse them in the winter. Why does the direction matter? In my case, reversing would cause the fan to fight the radiators convection.

I avoid running a fan in the winter because I'm pretty certain it screws up my perfect balance.

pecmsg

ChrisJ said:

hot_rod said:

hot goes to cold always. The rate of heat exchange is based on the temperature difference. With forced air the warmer the stratified air at the ceiling the greater the loss through the insulation.

That was always the "selling feature" of radiant floor heat, little to know stratifications, lowers the losses up top.

I guess the same applies for lowering your indoor temperature, less loss through the building shell, lower energy required.

So you're saying a ceiling fan will save money in the winter?
One thing I've been confused about for years is the claims you're supposed to reverse them in the winter. Why does the direction matter? In my case, reversing would cause the fan to fight the radiators convection.

I avoid running a fan in the winter because I'm pretty certain it screws up my perfect balance.

Blowing UP in the winter avoids the chilling effect of moving air over your skin. It washes the walls with warm air.

EBEBRATT-Ed

If you have normal height ceilings, they don't do anything except as 1 electrical inspector told me "All they do is blow dust around" I can only see a use in the summer or in the winter with high ceilings

hot_rod

ChrisJ said:

hot_rod said:

hot goes to cold always. The rate of heat exchange is based on the temperature difference. With forced air the warmer the stratified air at the ceiling the greater the loss through the insulation.

That was always the "selling feature" of radiant floor heat, little to know stratifications, lowers the losses up top.

I guess the same applies for lowering your indoor temperature, less loss through the building shell, lower energy required.

So you're saying a ceiling fan will save money in the winter?
One thing I've been confused about for years is the claims you're supposed to reverse them in the winter. Why does the direction matter? In my case, reversing would cause the fan to fight the radiators convection.

I avoid running a fan in the winter because I'm pretty certain it screws up my perfect balance.

If it somehow lowers the heatloss through the ceiling/ roof I would think so.
However it takes electrical power to run the fan, maybe it washes..

Not many ceiling fans that fit in a typical 8' room that I don't walk into, or duck under thinking I will run into it
You need some inches above the blades for them to work well, at least 8" according to installation directions on my dshop fan manual..

EdTheHeaterMan

I would be more interested in Jamie and ChrisJ's insight about the artistic movement started about 1848 by the poet and painter Dante Gabriel Rossetti and the painters John Everett Millais and William Holman Hunt, who is often credited with the group’s name, which indicates not a dismissal of the Italian painter Raphael, but rejection of strict aesthetic adherence to the principles of composition and light characteristic of his style

But that's just me!

Jamie Hall

Id have to say for starters (and I'm still thinking about this) that it would be just silly -- as well as useless -- in any room with a more or less normal ceiling height -- say less than 10 to 12 feet, in fact. Also, it would be not needed in any reasonably sized space with other air circulation -- forced hot air heat, mini[licts or ductless heat pumps, that sort of thing. Plenty of mixing without it.

On the other hand, in a space which is heated almost entirely by a convective source, such as baseboards which are all located on one side, and has a moderate to high ceiling, I can see that they might improve comfort, though whether they would save any money or not is doubtful. Particularly if all that convection was on an interior wall, and the exterior wall was poorly insulated. A very high ceiling -- say one of these cathedral ceiling great rooms one sees -- they might very well be helpful in improving comfort, and if the overhead is not so well insulated might well save some heat.

I can't see them helping much when a significant part of the heat is radiant -- like conventional hot water or steam radiators (though hot water at low temperature, like some more modern systems don't have the radiant heat, so they might).

With no theory at all, just opinions, folks!

ChrisJ

EdTheHeaterMan said:

I would be more interested in Jamie and ChrisJ's insight about the artistic movement started about 1848 by the poet and painter Dante Gabriel Rossetti and the painters John Everett Millais and William Holman Hunt, who is often credited with the group’s name, which indicates not a dismissal of the Italian painter Raphael, but rejection of strict aesthetic adherence to the principles of composition and light characteristic of his style

But that's just me!

vhauk

heat rises. The theory is that a gentle push of the warmer air near the ceiling towards the floor would more equally distribute the available heat energy. But with radiators convection currents are important, maybe more important than moving already heated air towards the floor. Something one of my hvac instructors said has always stuck with me: “you cannot destroy heat, you can only move it.”  

Long Beach Ed

They are reversed in the winter to minimize the cooling effect of the draft that would chill anyone standing under them if they were blowing downward.

Lowering heating bills? Yeah, if you don't mind being cold.

reggi

@Motorapido

Every information source on earth claims that a ceiling fan in winter-mode rotation will lower heating bills

Perhaps if the original source was tracked down we can gain insight to their reasoning at the time ?

Just a quick search reference reversible ceiling fan appears Jan. 1916 though I didn't exhaust the criteria nor include warming.. but it may be a start

JakeCK

When I bought my house the ceiling light in the living room had long been removed and the box and switch plastered over. My house is also pretty drafty, especially because of all of the dinning room windows. You would always feel a bit of a chill rolling across the floor while up by the ceiling was pretty comfy. Now I had always wanted a ceiling fan in that room, mainly because no ac, and I will often push it until early summer before putting any window shakers in. So a few years ago I finally ran new 14-2 nmb, new boxes(yes I used an old work fan brace and box) and installed the largest diameter fan I could find. I believe it is a 60" with a short downrod. I have 8 1/2 ft ceilings so it doesn't hang very low. Even you overgrown sasquatches of human beings shouldn't hit your head on it. 

What I've found is that I love it just as much in the winter as summer. With it being such a large fan it can run at a very slow speed and still stir the air with out creating much in the way of a chill. Combined with the reverse direction you don't even feel the air movement unless you run it at a higher speed, you also don't feel any cool drafts along the floor anymore either, its almost as good as heated floors. I used to always suffer cold feet. That fan cured that problem. Both the dinning room and living room when that massive fan is moving slowing are a very even nice 72f from floor to ceiling. This is even measurable with the temp sensors I have placed in the house for the home automation. You can clearly see when that fan is turned on a moderate spike in temperature then a slow normalizing of it after a while and a delay in a call for heat by the thermostat. Does this save energy? Maybe, maybe not. But my feet are nice n' comfy with it on so I don't give a s* either way.

gmcinnes

Without calculations, but experientially, in domestic rooms with high vaulted ceilings, big slow fans improve my comfort.

When I've inhabited chalets with vaulted ceilings and sleeping lofts, I have felt much warmer in the loft than the ground level, unless the fan is on.

Have never felt a significant difference in 8 or 12 feet ceiling rooms though. Most of those rooms have smaller, faster fans too, which I think makes a difference. Really, small fans blow

“Life is so unlike theory.”
― Anthony Trollope

Motorapido

EdTheHeaterMan said:

I would be more interested in Jamie and ChrisJ's insight about the artistic movement started about 1848 by the poet and painter Dante Gabriel Rossetti and the painters John Everett Millais and William Holman Hunt, who is often credited with the group’s name, which indicates not a dismissal of the Italian painter Raphael, but rejection of strict aesthetic adherence to the principles of composition and light characteristic of his style

But that's just me!

Yet another reason I love the HeatingHelp wall more than any other mechanical forum that I haunt. We should start a sub-forum for steam-heat haiku. Here goes:

Gentle silent steam
The king of heat forever
Forgotten by most

Motorapido

I offer the following blend of objective data and subjective experience. Here are the facts of my environment: 2-story, 1,000 square foot house (vacation cottage deep in the woods of Northern Pennsylvania, a stone-throw from the NY state line). Heat source is a free-standing gas heater stove (looks like wood stove, burns NG, direct-vent), on first floor. First floor is largely wide-open and undivided. The gas heater stove has no blower fan. Heat circulates through first and second floor purely by convection. Over months of data logging during heating season, I recorded a pretty consistent 1.2 degree temperature differential between first and second floor, with second floor the colder floor. I installed a small ceiling fan in one of the two upstairs bedrooms yesterday. I ran it in winder-blade-rotation-mode from about noon yesterday until now. My temperature sensors indicate a 2.5 degree colder upstairs with the fan on its slowest speed, winter mode. That's the objective data. Running the fan in winter mode increased the temperature differential between upstairs and downstairs. The subjective data is that I feel colder with the fan on, even at its very slow speed. The air movement makes me feel colder.

Upstairs has 8 foot gable ceilings (flat 8-foot-high ceiling in center, with ceiling then sloping down to knee walls). I agree with the observations offered on this thread suggesting that the winter-mode fan usage is beneficial primarily in large rooms with very high ceilings, and not so much in standard-ceiling, smaller rooms.

Maybe we could hire F. Lee Bailey to create a class action suit in which those of us who bought ceiling fans in hopes of improving our heating efficiency seek billions of dollars in compensation from the fan companies.

We will file the lawsuit with a haiku imprinted on the file cover:

Oh dear silent fan
Your promises have failed us
Now we want money

kcopp

Heat does not rise... hot air rises.
trying to use a ceiling fan to push heat down is like taking a beach ball and trying to push it to the bottom of a pool. It just does not want to go.
I have seen issue w/ rooms not heating well during cold snaps (zone would not reach temp) in a high ceiling room. Customer had a ceiling fan on. As soon as that was turned off the room would come to temperature.
Furthermore fans move air. Air blowing over your skin/ body is convective. That cools the body. This is one of the reasons that FHA is a poor heating system. Why would you want to have a fan cooling in the winter?
Turn it off and leave it off till June.

SteamingatMohawk

This will give you a headache.

https://www.hunterfan.com/blogs/hunter-blog/ceiling-fan-direction-for-summer-and-winter

You can't buy a pound of heat, but you can heat a pound of air, then try to put it where you want or mix it with other air..

My suggestion is to measure the temperature (i.e., heat in the air) in several locations in the room, both vertically and horizontally under both conditions.

In the absence of forced circulation, hotter air will stay where it is. Forced circulation will have some effect on the temperature distribution different from no forced circulation.

This discussion is like a Mobius strip...it has no beginning and no end. Google it.

I don't know how to make a haiku for this.

JakeCK

Talks cheap. Time to post up the evidence.

Clearly it made a difference.

JakeCK

And before someone tries to claim it must have been the outside temp that changed... You're right, it did, it got colder.

hot_rod

Around here 100F plus Utah, I know running my attic ventilation fans reduces my cooling load, AC runs less. Seems the same logic would apply to heating.

Isn't this the basis of heating and cooling load calcs, the ∆ between both surfaces of the wall or ceiling dictates the load.

ChrisJ

hot_rod said:

Around here 100F plus Utah, I know running my attic ventilation fans reduces my cooling load, AC runs less. Seems the same logic would apply to heating. Isn't this the basis of heating and cooling load calcs, the ∆ between both surfaces of the wall or ceiling dictates the load.

The only reason I've considered solar panels is to reduce my cooling load 

ethicalpaul

I think @ron has it right.

You MIGHT feel warmer because some warm air that would otherwise be at the ceiling is circulated down.

You MIGHT feel cooler because the warm moist air layer against your skin is being blown away by the fan and moisture evaporation will cool your skin faster.

You WILL see higher heating costs because the warm air of the room will have increased motion across the cold walls and windows.

I think the direction is irrelevant because wherever the air is getting pushed, other air will move to take its place so it's just air movement either way.

hot_rod

ethicalpaul said:

I think @ron has it right.

You MIGHT feel warmer because some warm air that would otherwise be at the ceiling is circulated down.

You MIGHT feel cooler because the warm moist air layer against your skin is being blown away by the fan and moisture evaporation will cool your skin faster.

You WILL see higher heating costs because the warm air of the room will have increased motion across the cold walls and windows.

I think the direction is irrelevant because wherever the air is getting pushed, other air will move to take its place so it's just air movement either way.

But Jakes data above shows just the opposite effect?

MaxMercy

My commercial building has 12' ceilings, and when it's reading 65 at the chest level thermostat, the temp at the ceiling is 75 or above. I ended up putting some table oscillating fans on the dividing partitians between sections (10' high) and leave them swinging towards the ceiling on low speed. I definitely shaved a few points on my gas usage.

ethicalpaul

hot_rod said:

But Jakes data above shows just the opposite effect?

I don't see fuel usage on that data, or am I misreading it? And i would be hesitant to use a couple hours of data to prove this.

dopey27177

There is a possibility that some people may be more comfortable with the ceiling fan operating.

maybe some fuel can be saved?
But running a fan 24/7 will eat up your fuel savings.

moving Air will cause the body to feel cooler because moisture leaving the body via the skin is evaporating faster because of the moving air. This effect will happen no matter the temp.

Jake

ChrisJ

I've been using a thermostat that tracks usage for years now.  I also get my gas bills every month that shows how much gas I used vs other times.

I also have the ecosteam that'll tell me actual run time.

I've never been able to successfully compare small changes because the weather changes so much.

STEVEusaPA

vhauk said:

heat rises…

No it doesn't.

hot_rod

dopey27177 said:

There is a possibility that some people may be more comfortable with the ceiling fan operating.

maybe some fuel can be saved?
But running a fan 24/7 will eat up your fuel savings.

moving Air will cause the body to feel cooler because moisture leaving the body via the skin is evaporating faster because of the moving air. This effect will happen no matter the temp.

Jake

Unless the temperature of the air is above skin temperature. Most forced air systems feel warm. Heat pumps systems, not so much

gmcinnes

moving Air will cause the body to feel cooler because moisture leaving the body via the skin is evaporating faster because of the moving air. This effect will happen no matter the temp.

My wife's hairdryer begs to differ

I'd be interested to know if a 20' lofted ceiling, with a thermostat at a typical 5' or so, would be different from a typical room. The heat delta of the air between the ceiling and the thermostat is going to be larger than a 'normal' room. But then again, with the triangular roof shape, the volume decreases as you get higher, so maybe the smaller volume cancels that out. And, it depends on the temp. of the walls and windows that the force convected air is washing against, and how big an effect that has on cooling the air.

I think it's a very complicated question with a lot of context dependent values for the variables involved.
Mainly the height and shape of the room in question, the volume of air moving, and the speed of the air moving. I don't think it's a yes or no answer.

To me, the room @JakeCK posted a picture of is not one I think a winter fan would make much difference in (and it's not surprising it would make things worse) because the delta of the air between the thermostat and the ceiling must be very small.

JakeCK

ethicalpaul said:

But Jakes data above shows just the opposite effect?

I don't see fuel usage on that data, or am I misreading it? And i would be hesitant to use a couple hours of data to prove this.

I never claimed it affected fuel usage much. Overall average  temperature of the building shouldn't change much. Boiler run time averaged out might change a few seconds.

What I did say quite forcefully is that it does change the comfort of this house. It is old, it is drafty. There is always a slug of cool air rolling around the main floor until it finds it's way to the basement. That cool air gives me cold feet. And I find that particularly uncomfortable. The fan eliminates that. Arguing otherwise... Well if one believe that massive fan doesn't move around the warm air by the ceiling may I suggest you remove the fan from the heat sink of your PC. If you are using a PC. You obviously do not need it since fans apparently don't move warm air. I might add or rather warn this debate will be over quickly after that fan is removed.

Edit: I also want to add that those couple of hours were just the last few hours. I can turn that fan on and off all day and watch that same pattern occur in the graphed data. After doing it a dozen times and seeing it, being told it isn't real is akin to walking into a room and flicking the light switch to only be told it isn't the switch. Could it be coincidence? Sure anything is possible. But absent convincing evidence to the contrary I'm going to go with the simplest answer. Turning the fan on is moving the air and causing the sensors half way down the wall to report a warmer temperature. And I don't walk on the ceiling(I'm not spider pig), I walk on the floor. I'd rather feel the warm air down there.

JakeCK

gmcinnes said:

moving Air will cause the body to feel cooler because moisture leaving the body via the skin is evaporating faster because of the moving air. This effect will happen no matter the temp.

My wife's hairdryer begs to differ I'd be interested to know if a 20' lofted ceiling, with a thermostat at a typical 5' or so, would be different from a typical room. The heat delta of the air between the ceiling and the thermostat is going to be larger than a 'normal' room. But then again, with the triangular roof shape, the volume decreases as you get higher, so maybe the smaller volume cancels that out. And, it depends on the temp. of the walls and windows that the force convected air is washing against, and how big an effect that has on cooling the air. I think it's a very complicated question with a lot of context dependent values for the variables involved. Mainly the height and shape of the room in question, the volume of air moving, and the speed of the air moving. I don't think it's a yes or no answer. To me, the room @JakeCK posted a picture of is not one I think a winter fan would make much difference in (and it's not surprising it would make things worse) because the delta of the air between the thermostat and the ceiling must be very small.

The delta between the ceiling and about half way down is about 1f. The sensor for the dinning room and living room are both about mid way. T stat on wall, plus a multi sensor sitting on the fireplace mantle. The kitchen sensor is up by the ceiling above the cabinets(these are also motion, light, and humidity sensors) to prevent the cats from setting them off in the kitchen because cats love getting on counters. That said the delta between say 2ft off the floor vs say 6" is much pronounced. Again this is because of the air leaks. If It was possible to seal up this house like a new one this probably wouldn't be an issue. I can achieve almost the same result just by setting a box fan on low and have it blowing across the massive dinning room radiator from across the room. But the ceiling fan is nicer. 

Some years back I was building "forts" with my son using the dinning room chairs, blankets and pillows. At some point the arch between the dinning room and living room was blocked by a wall of blanket covered chairs and pillows. After a while I noticed the living room was considerably warmer. That is until that slug of cool air built up and spilled over the chairs. You could feel the air flowing over it like you could feel water spilling over a dam. When I take it all down it was like a torrent of cool air rolling across the room. 

You can feel the same effect in a car. Take a hard right turn(if driving in the UK make a hard left turn) all the cooler air by the floor boards will wash over you as centripetal force moves the cooler heavier air out while the lighter warmer air is displaced by it.

If you are incapable of feeling this then that is a problem with sensory.

JakeCK

STEVEusaPA said:

heat rises…

No it doesn't.

Lol

Smart a**. You could have at least clarified for him that heat always goes from hot to cold. Nature abhors a vacuum. But because of the interesting interaction between gravity, and density warmer air rises, while cooler air falls.

And for extra credit start to explain that is what contributes to a lot of our weather patterns on planet earth.

ethicalpaul

JakeCK said:

I never claimed it affected fuel usage much. Overall average  temperature of the building shouldn't change much. Boiler run time averaged out might change a few seconds.

What I did say quite forcefully is that it does change the comfort of this house. It is old, it is drafty. There is always a slug of cool air rolling around the main floor until it finds it's way to the basement. That cool air gives me cold feet. And I find that particularly uncomfortable. The fan eliminates that. Arguing otherwise... Well if one believe that massive fan doesn't move around the warm air by the ceiling may I suggest you remove the fan from the heat sink of your PC. If you are using a PC. You obviously do not need it since fans apparently don't move warm air. I might add or rather warn this debate will be over quickly after that fan is removed.

Edit: I also want to add that those couple of hours were just the last few hours. I can turn that fan on and off all day and watch that same pattern occur in the graphed data. After doing it a dozen times and seeing it, being told it isn't real is akin to walking into a room and flicking the light switch to only be told it isn't the switch. Could it be coincidence? Sure anything is possible. But absent convincing evidence to the contrary I'm going to go with the simplest answer. Turning the fan on is moving the air and causing the sensors half way down the wall to report a warmer temperature. And I don't walk on the ceiling(I'm not spider pig), I walk on the floor. I'd rather feel the warm air down there.

Sorry I'm not trying to fight but the title of the thread is asking if it affects the fuel bill. I said in my reply that it might make people feel warmer or cooler, depending, but that the fuel bill will be higher. I will respectfully stick with that.

Hot_water_fan

We’re forgetting about the thermostat location! Even if a fan does save energy in a room, if that room has a closed door and a distant thermostat, does it make a sound? 

JakeCK

We heat our houses to stay comfortable. If we can can increase comfort at a lower temperature money will be saved...

Or as is often experienced when energy retrofits are undertaken with old houses initially there is a reduction in energy usage for the first year. But often after the second year energy usage rebounds. Why is this? Is it because the insulation or air sealing failed with in a year? Or is it because the home owner can now stay more comfortable with out increasing costs over past years?

JUGHNE

A hardware store owner told me that he had a lady complain that the ceiling fan he sold here did not make the room warmer, she ran it for an hour and the blades never even got warm to help heat the room.

gmcinnes

not really. when you find something is complicated it's often because there's not a full understanding of the subject, something was misinterpreted, or missed, or you're being misled or not being truthful.

'complicated' was a bad word choice. I meant complex. It's a complex system in the mathematical sense. It's very hard, if not impossible, to predict the outcomes with certainty even if the first principles are easy. That's not a real world problem though.

It's too far down the rabbit hole and around the mobius strip

Paul Formisano

Increased air velocity increases the convection coefficient and energy transfer from air to surfaces increases.  That means more rapid energy loss from the heated space to the wall will result from using a fan.  

However, the air will mix and become less stratified with the fan on, which will make the dry bulb temperature at lower elevations in the room increase when the fan is on, and also make the dry bulb temperature decrease at higher elevations as the colder lower air gets mixed with it.  Depending on the vertical location of the thermostat, the new room temperature could increase or decrease at its location.

Meanwhile, the wet bulb temperature (we humans are like wet bulbs because we perspire) will decrease when air velocity increases, due to the latent heat of evaporation becoming sensible on the skin surface. So it will feel colder in moving air compared to still air of the same temperature if the air temperature is lower than body surface temperature.

So, with a fan on, you’re more likely to use more energy to heat your home, but depending on the geometry of your room and your thermostat location, and your location relative to moving air, it could make you feel warmer or colder.

I’m a Professional Mechanical Engineer with a lot of thermal design experience.