One Ceiling Fan or Two?

[ShenKen]

Which is better for circulating the heat from a wood stove, a single fan centered on the stove, or two fans on either side?

We are in the process of building a new house, currently in the electrical rough-in stage. We plan to have a wood stove in the finished basement, located in a long-ish family room. The room is approx 16 ft x 28 ft, with the stove centered lengthwise and backed up against an exterior wall. We could place a single ceiling fan in the center of the room, or we could have two fans spaced 14 ft apart (7 ft on each side of the stove). In the cooling months, I am guessing that two fans would be more effective, but in the winter when we are trying to distribute heat, I'm not sure. Any input would be welcome as well as links to other resources.

Thank you!

 

[begreen]

That's not a large space to heat as long as the basement is insulated. I would not put in any ceiling fans unless the basement ceiling is unusually high. If it is standard 8' it may give a tall person a haircut.

 

[stoveliker]

And your can always add a fan on the ground in the cold corner blowing colder air slowly to the stove. It'll be replaced by warmer air flowing along the ceiling.

 

[ShenKen]

Thanks for the replies! I forgot to mention, the ceiling is 9 ft in that area, so we have room for ceiling fans. And yes, pretty well insulated: the walls are precast concrete with foam, and there is 2" foam under the concrete slab.

It would be nice if the stove would heat more than just that family room, although we won't be relying on that alone. The stairway to the main floor is about 30 ft from the stove. I believe what I am hearing around here is that ceiling fans won't be very effective to move heat across the room and up those stairs. I am hoping the heat will naturally travel up through the uninsulated basement ceiling to the main floor and maybe even the half story above that. I will attach a screenshot of the basement family room plan and some adjacent features.

 

[begreen]

With a 9' ceiling a centrally located, shallow profile, ceiling fan won't hurt. It can blow upward in winter to reduce drafts. For better heat up the stairwell, leave it as open as possible. Make the 87.5" wall an open railing instead of a dividing wall. For better heat transfer, don't insulate the basment ceiling.

 

[ShenKen]

I guess it's about a year later, and I have another question related to my original one. (The house is still not completed)

I'm thinking of putting a small fan in the basement ceiling in the corner of the room to the left of the stove. An opening could be boxed off between two joists, and grates installed in the flooring on top and in the ceiling on the bottom. Fan would be mounted in the joist bay. Perhaps a small inline fan such as would connect to a 4" duct (only here no duct would be used), wired through a variable speed switch on the basement wall. This in theory would blow the air from the main floor living room above, down into the basement, creating a loop carrying the air past the stove and over to the stairs at the far end, where it would flow up to the level above. See attached image.

Would this circulate the air effectively? Would it work better if the fan was pointing up instead of down? Or at a different location?

 

[begreen]

That setup will be fighting natural convection if blowing down. Hot air is going to want to rise through the opening near the stove and return via the stairwell. Note that the floor penetration will probably require a fusible link damper. Definitely fly this by the home inspector before cutting the hole.

 

[stoveliker]

I disagree with begreen. In my case I do something similar.
Except that I do have a duct to deposit the air from the living room floor onto the basement floor. It works great and I hear my whole home with it.

See this post for a longer description.

Post in thread 'Moving heat from basement'

May 1, 2023

I heat from the basement, and if I include my basement squre footage, I have 2500 sqft.
825 in the basement and 1700 above that. Late 70s. Brand new triple pane windows, fantastic sealing and insulation (R57) in the attic. Mediocre wall insulation.

My basement walls are insulated, but the floor is unfortunately not.

Heating my home above the basement is easy. Only when it gets to be 5 F do I have to push the stove (as in 8 hr reloads), still keeping my main floor around 70 F.

However, I second the comment above that heating from a basement benefits from consistency, i.e. you heat...

• stoveliker

• 

I do agree with the fusible link remark.

 

[begreen]

Didn't say it wouldn't work, just that it's fighting natural convection. Without the fan I suspect that it will behave as I noted.

 

[stoveliker]

The convection is no match for an inline fan; the fan running won't at all be affected/less effective because of some minor convection pressure differences.
If it would be, I'd change my system, make all kinds of holes with generators and generate power using the rising air...

Of course my system works with the convection (keeping the air temp stratified so that the warmest air goes up the stairs most easily).

 

[ShenKen]

That setup will be fighting natural convection if blowing down. Hot air is going to want to rise through the opening near the stove and return via the stairwell. Note that the floor penetration will probably require a fusible link damper. Definitely fly this by the home inspector before cutting the hole.

begreen: Thanks for the tip about the damper. I hadn't thought of it but I do believe the inspector would probably object to a damper-less hole.

I also see your point about natural convection. Do you think that in my situation upward flow would be better? One potential negative I'm envisioning with pushing air up is that then this end of the main floor will have both the warmer end of the air flow loop and have heat radiating up from the stove underneath. Therefore the other end of the house will stay cooler. So run my thoughts, but not sure if they are correct.

 

[stoveliker]

I would not suck air away from the stove room. That's asking for trouble.

 

[stoveliker]

Btw, I initially did have a hole in the floor right above the stove for convective transport up. It didn't do anything measurable.

 

[ShenKen]

I disagree with begreen. In my case I do something similar.
Except that I do have a duct to deposit the air from the living room floor onto the basement floor. It works great and I hear my whole home with it.

See this post for a longer description.

Post in thread 'Moving heat from basement'

May 1, 2023

I heat from the basement, and if I include my basement squre footage, I have 2500 sqft.
825 in the basement and 1700 above that. Late 70s. Brand new triple pane windows, fantastic sealing and insulation (R57) in the attic. Mediocre wall insulation.

My basement walls are insulated, but the floor is unfortunately not.

Heating my home above the basement is easy. Only when it gets to be 5 F do I have to push the stove (as in 8 hr reloads), still keeping my main floor around 70 F.

However, I second the comment above that heating from a basement benefits from consistency, i.e. you heat...

• stoveliker

• 

I do agree with the fusible link remark.

This is what I'd really like to do, except that this will be a finished basement and a duct or chase would not be desirable (aesthetically). I wonder how much less effective the downdraft would be without the duct to get it right down on the floor.

It does seem to me that just the addition of an opening in the floor at the end of house opposite the stairs end should help some in creating a loop, whether the flow is up or down.

 

[stoveliker]

My basement is finished. I ran the duct between the joists to the side wall, where I put everything in a chase down. Having the fan at the bottom also cuts down a lot on fan noise (over having it mounted in a floor)

I don't know how much less effective it'll be.with no duct down. If the stairs are farther away it will be less of a problem; you're mixing air but near the stairs it'll be more stratified than near the fan - and more so the larger the distance is between fan and stairs.

Yes, a loop is better than merely only the stairs (where mixing of cold air descending and warm air rising would create turbulence and mixing leading to less warm air reaching the upper floor). Separate the cold and warm air flows is a good thing. Plus having a cold return away from the warm supply will create a flow spreading the heat better on the upper floor.

 

[begreen]

Note when placing the hole and running this by the inspector that a return air duct can not be closer than 10 ft per mechanical code.

Second, basements are frequently negative pressure zones. That may affect the best made plans. It might be worth considering how to bring fresh outside air to the stove for an OAK connection. That may affect where the stove is located.

 

[ShenKen]

I don't know how much less effective it'll be.with no duct down. If the stairs are farther away it will be less of a problem; you're mixing air but near the stairs it'll be more stratified than near the fan - and more so the larger the distance is between fan and stairs.

Not sure I completely understand about the difference in stratification and how it might affect air flow. Would you mind elaborating a bit more? (when convenient)

The fan spot is about 14 ft from the stove, and the stairway is about 29 ft farther on, so it's around 43 ft from the fan location to the stairs.

 

[stoveliker]

If warm and cold air mix, it will result in the air at the ceiling of the lower floor be less warm. That is the air that will go up to the next floor, but it's less warm.

When you blow (fan) cold air into the lower room near the ceiling it'll mix with the warm air, cooling the warmest air you have before it has a chance to go up to the next floor.

But that mixing effect will decrease with increasing distance from the fan/mixer.
So the farther away from the mixer the location is where the warm air goes up, the less mixed it'll be, and thus the warmer the air will be near the ceiling - which is the air that will rise up.

This is thinking of a fan, no duct, blowing colder air into the stove room.

If your air flow loop would be fan (blowing downwards), 14 ft, stove, 29 ft, stairs (complemented by the half on the upper floor running from the stairs back to the fan),.that would work okay I think

 

[ShenKen]

If warm and cold air mix, it will result in the air at the ceiling of the lower floor be less warm. That is the air that will go up to the next floor, but it's less warm.

When you blow (fan) cold air into the lower room near the ceiling it'll mix with the warm air, cooling the warmest air you have before it has a chance to go up to the next floor.

But that mixing effect will decrease with increasing distance from the fan/mixer.
So the farther away from the mixer the location is where the warm air goes up, the less mixed it'll be, and thus the warmer the air will be near the ceiling - which is the air that will rise up.

This is thinking of a fan, no duct, blowing colder air into the stove room.

If your air flow loop would be fan (blowing downwards), 14 ft, stove, 29 ft, stairs (complemented by the half on the upper floor running from the stairs back to the fan),.that would work okay I think

Thanks for that explanation - makes sense.

 

[dvellone]

My cabin is two story 16’ x 22’, with a 10’x12’ single story off one side, and the stove is is in the main first floor space at one end and in a corner and I have a ceiling fan around 6’ away from the center of the stove set on low and running constantly that circulates the heat beautifully. The 10x12 addition is a bathroom and it gets heated perfectly, and the fan prevents the heat from overheating the second floor.