Circulating air

[BrianN]

While reading, and some times posting to these threads about circulating air, I had a thought while at work today, and couldn't wait to get home to try it.
It was in the -20 (-4) the other night. The down stairs was pretty warm, not as warm as I thought, but, better than last year.
Anyways, I have tried blowing air with a fan from my laundry room, which worked pretty good. I have also tried pushing cold air down from upstairs with a ceiling fan, but, the problem there is, the stairs are the only way for cold air to come down, and warm air to go up.
So, I was thinking, why not use the bathroom fan that is up stairs to pull the cold air outside, and have the warm air come up the stairs with no resistance with cold air trying to come down.
The minute I got home, I stuffed the stove, went upstairs and turned on the bathroom fan. To my surprise (kind of) the upstairs is now toasty, and a bonus, the down stairs living area is also toasty.

 

[Highbeam]

Good job, it must be the swiss in you. I just found out that I am mostly swiss.

 

[BurningBrutus]

Im gonna try this tonight, i turned my exhaust fan in the bathroom upstairs about 20 min ago, how long do you think it took your upstairs to heat up?

 

[Sully]

Do you think it was exhaust fan pulling warm air up stairs? Should see what results are with no fans at all, just letting the heat migrate up.

I have been wondering this about a fan in upstairs hallway. I thought same. It's pushing cold air down steps , how can the hot air come back up. I have not tried yet

 

[Oregon aloha]

You can do the same thing by just cracking a window. Warm air takes up more room then cool air so the warm air is always pushing for somewhere to go. Usually it has to push cool air that is heavy so the warm air is stuck. With the window open it helps the warm air push air out the window to make more room for the warmer air. Works for wherever your trying to warm, same level or not.
Wood heat warms things not the air, so the air needs to move to get and stay warm.

 

[dave_376]

I have never tried using the barthroom fan to help circulate hot air, but you are venting hot air. If the air up stairs is 60F and -4F out side you are losing 64 degrees of heat. I have a small fan at the top of the stairs sitting on the floor. , not a ceiling fan. That fan is angled to match the angle of teh stairs coming up. The fan blows cold air down and the heated air flows across the first floor ceiling and then up the stairwell. The difference is huge. I ceiling fan will push the colder air down to a degree but it will mostly mix the hot and cold air together more so than pushing the cold air back towards the stove.

 

[BrianN]

Im gonna try this tonight, i turned my exhaust fan in the bathroom upstairs about 20 min ago, how long do you think it took your upstairs to heat up?

After the first cycle (30 minutes) there was a noticeable difference. Not sure of the exact temp change as that is one place I do not have a thermometer. I will have to get one up there soon, to match nearly every other room in the house.

 

[BrianN]

Do you think it was exhaust fan pulling warm air up stairs? Should see what results are with no fans at all, just letting the heat migrate up.

I have been wondering this about a fan in upstairs hallway. I thought same. It's pushing cold air down steps , how can the hot air come back up. I have not tried yet

Yes, I have tried with no fans, with ceiling fans and with fans down stairs. Nothing seemed to heat up stairs. I will have to try to just crack a window like Oregon aloha mentioned. Or, what Dave does with the fan at the top of the stairs. Although, I don't know if the fan will work, as there is no outlet near the top of the stairs that will allow me to keep a fan there without tripping over the cord.

 

[My Oslo heats my home]

I don't have the same issues with moving the air up the stairs, but I do want to try your method just to see if it moves the air any faster for me. This should be fun, my wife will probably think "what the hell is he doing everytime he gets off the PC?" something new

 

[wenger7446]

Heat from our stove doesn't transfer well into our MBR. I will often use our MBR Bath fan (110 CFM) to create a negative pressure in the MBR area and it heat that area up nicely.
Keep in mind this is not efficient as you are sucking heated out outside, but it works.

 

[Oregon aloha]

Keep in mind a wood heater heats the thermal mass in your home. The air that comes in contact with that mass is heated so unless you lose that thermal mass you haven't lost any heat by letting the air move around or out. If you don't relive the air pressure caused by the air warming you can't get move warm air.

 

[wenger7446]

Keep in mind a wood heater heats the thermal mass in your home. The air that comes in contact with that mass is heated so unless you lose that thermal mass you haven't lost any heat by letting the air move around or out. If you don't relive the air pressure caused by the air warming you can't get move warm air.

Thanks for the reply. Doesn’t the air being removed from the home need to be made up with replacement air from outside (presumably colder then the air that is existing) then that colder air will remove heat from the mass (the house)?

 

[DMB]

I don't know if I'm right here but this is my take on the subject. A wood stove running well is pulling in so much air heating it and recycling it back into the room that it would completely overwelm any heat lost by cracking a window. I don't think you would want to leave the window cracked 24/7 but it would certainly seem like a legitimate way to move the air in your house. You are getting rid of warm air but the point is that when say 62 air leaves your house there is warmer air following it to fill that space.

 

[Grisu]

Keep in mind a wood heater heats the thermal mass in your home. The air that comes in contact with that mass is heated so unless you lose that thermal mass you haven't lost any heat by letting the air move around or out. If you don't relive the air pressure caused by the air warming you can't get move warm air.

But first the stove has to heat the air in order to be able to heat the thermal mass of the rest of the house (minus heat radiated by the stove). The heat capacity of air (or gases in general) is relatively low. That is the reason it takes a pretty long time to heat up the thermal mass of the house and why air is actually a pretty good insulator when there is no airflow. Nevertheless, pulling cold air into the house and pushing warm air out at the other side of it will lose heat. Using the ideal gas law air density goes from 1.2250 kg/cubic meter at 15 C (59 F) to 1.1839 kg/cubic meter at 25 C (77 F). That is a difference of ~3.5% of air that needs to be removed in order to keep the pressure between inside and outside in equilibrium. That is not a whole lot and would be done by the standard air exchange happening in a house anyway during the hours the stove heats up the air. What the OP did was creating a draft not releasing the pressure artificially.

 

[Andy S.]

I plan to try the exhaust fan, too. I've also considered a different twist on the idea of running the HVAC fan to circulate air. I would close off the floor registers in all but the stove room and close off the return air from all but the MBR (for example). I think you'd need to tweek it to get the proper balance, of course, but it would probably work pretty quickly.

 

[Bagelboy]

I've never heard of opening a window. So Oregon, what your saying is if the side of the hous opposite my stove is colder, just crack a window? Also, do you leave it cracked or wait til the room warms up and then close it?

 

[Oregon aloha]

Leave it cracked as long as your heating. Just like your chimney draws air so dose that window. It's pulling the air though the house. Still air can't get warm with wood heat. Wood heat, heats objects and the air moving against the objects warms the air. That's why it takes a long time to warm a house from a cold start, but once the house is up to temp it holds with very little fire in comparison. If you have a very drafty house then you may pull cool air in, but your doing that already.

It's a zig zag from the stove room to our laundry room though the family room. Without the window cracked the laundry room gets very cold as it is also insulate from the house. Someone (me) thought if you insulate the walls to the laundry room and put a solid core door on it, it would keep the noise out the the house.

 

[Andy S.]

Im gonna try this tonight, i turned my exhaust fan in the bathroom upstairs about 20 min ago, how long do you think it took your upstairs to heat up?

I tried it last night with a small fire. It increase the temp in my MBR 3* in 30 minutes (using comparison IR readings on the wall). I'm looking forward to testing it when it is cold.

 

[Winged Pig]

I have a split foyer and the wood stove is in the basement. Our downstairs room gets nice and warm and the heat goes up the stairs with no forced (fan) air. I would like to get more of the heat upstairs, so I've been thinking about putting a fan in the wall from the basement (front of the house) to the foyer. The basement area adjacent to the foyer does get pretty hot as the air seams to get trapped in there. My thinking is that the hot air will go into the foyer and up to the rest of the house.

Anyone done anything like this to circulate air? Good idea, or waste of time?