All right science geeks; gather 'round. Got a home heating question for you.

So what's the deal with running your ceiling fans in reverse during heating season?

I get that warm air rises, and I get the value of trying to circulate it back down to the floor where the people are (especially with, say, a vaulted ceiling). But for the life of me I don't understand why it makes a difference what direction the fan is running.

It seems to me that either way the fan rotates it will set up a perfectly useful convective loop from ceiling to floor. I don't get why 'they' say to run it in reverse during Winter.

What do you think? It's early; have some coffee and get back to me :grin:

No geek answer here. It just has to do with comfort.

From a scientific point of view, either way will do a perfectly fine job of equaling out the temperatures between floor and ceiling, but in the summer when you are trying to cool you don't mind air blowing directly on you. However, in the winter having air blowing directly at you provides a cooling effect, which is opposite what you are trying to achieve.

... Ok, that did go way far more geek than I anticipated

What he said. Glad he got to the geek before me!

Ok, I thought about it first and *then* googled "why reverse fan in winter" and this explanation popped up #1, with drawings:
https://www.dansfancity.com/techhelp/wntrsmmr.htm

What he says makes sense, but I also think it ymmv with the shape of the room and positioning of the fan (in center, off center, etc.). Their pictures look like a best case scenario, in terms of getting the convection current going.

For the record, I had never heard of changing the direction of the fan at all, (and when I read this, thought it had to do with pushing cold air up vs. warmer air down) so as my daddy always said, "It's a rare day you don't learn something new."

It's common practice aroung these parts to do it.
The prevailing Theory I have is that it makes the most sense to force the Warm Air down along the Walls and to the Floors Edges because those are the Parts of the House that would be the coldest being that they are the ones closest to the Outside.
It might not make as much sense if you have multiple Rooms in a Larger House, but in a 650sqft. Building like my tiny huge Living Room one Bedroom House it seems to make perfect sense.

I think any difference could be described as bs. If you are moving the same amount of air it should not matter.


Mark Koelsch
Sent from my iPhone using Rocketry Forum

TopRamen said:

It's common practice aroung these parts to do it.

Click to expand...

I never had ceiling fans until we bought our house here in California...my wife doesn't "believe" in fans, so we basically never run them.

I definitely think they help in the summer, but it has to be real cold for me to want to run the heat...I love the house interior at 64 F, or even lower...gives me a chance to wear all the wool sweaters and LLBean stuff I accumulated during my years on the East Coast.

Anyway, I definitely can see it being useful...anything that would get a good convection current going would definitely be more efficient at heating the air in the room.

That said, I have not actually used my Cieling Fan, Winter OR Summer in years.
I do have a different Fan, which moves much more Air and has a Remote Control that I sometimes turn on to move the Air around.

From the sunny south.....

I run my ceiling fan forcing air down in summer months at higher speeds to get the "fan" cooling effect. [wind chill]
The room seating is under the fan.

Now keep in mind many of us down here have 11-12ft ceilings, so during summer the cool air stays low anyhow.

But in winter the warm air collects in the upper 3-4 ft of room, just reversing the fans and running them on low does 2 things,
recycles the warm air collected above, & re-circulates it with out having a draft.[if fan on low]

Modern room with 8ft ceilings really don't gain much either way, but when you increase your volume [12ft] by 25-30 % big difference .

So summer ..run on high, to "feel" the breeze.
Winter reverse low,just to "bring " down the heat, collected at ceiling level with out creating a draft

Same for many modern houses with vaulted & tray ceilings which really collect the warm air.

You change direction according to where the heating/AC outlets are in order to pull hot air down in the winter and push cool air up in the summer. End of thread - everyone else can go home.

It's pretty much been answered, but having answered this exact same question this past Thursday for someone else, here's my HVAC based answer:

Summer: The fan should blow-down in the summer for cooling effect. That's about all it helps with. The significance of it is that you can actually raise the thermostat temperature a set number of degrees based on the velocity (cooling effect) of the fan, while still making the air "feel" like the same temperature. There's a chart used in HVAC that shows exactly this.

Winter: Since air stratifies, specifically warm air rises and settles at the ceiling, you want to blow air UP in the winter. That way, the air hits the ceiling, runs across to and down the walls. This De-stratifies the air, bringing the warm air back down.