Heat Ducting for Wood Stove through basement

[vpuleo]

The new stove (https://www.hearth.com/talk/threads/62293/#953071) was a game changer last winter; it is definitely nice to have that space excessively warm, instead of excessively cool.

The next stage is to try to move some heat towards the opposite end of the house. I haven’t done much analysis on this, but I was leaving the two thermostats (on first floor - natural gas furnace forced hot water) at around 57 during burns and each room further away from the stove would be approximately 10 degrees cooler - if we got the woodstove room up to 85, the kitchen was 75, the dining area would be 65, the rest of the house would stay at what the thermostat was set for… a balmy 57. (fyi -I’m not concerned with the second floor)

Cathedral ceilings aren’t ideal for woodstoves, and I estimate that the temperature near the peak of the ceiling is around 100 degrees during burns. This is trapped heat and (I think) essentially wasted.

The plan is to add a vent near the top of the ceiling, run some type of duct through the wall into the basement. Continue with insulated duct work (through the unconditioned basement) to the front of the house. Put an inline fan to push/pull the hot air through the duct.

This brings up a number of questions… mostly in regards to sizing (fan and duct diameter), also what kind of losses I’ll see (temp at outlet). I want to start cheaply… maybe not even run a duct through the wall at first… I think that would likely be the hardest part but do have a plumbing gangway that may be easier to access/modify than a normal wall cavity.

I’ve seen posts on this topic… but not been able to find anyone with a working setup like this. Here’s one link with some calculations which look promising:

http://cr4.globalspec.com/thread/62365/heat-ducting-for-wood-stove

Any thoughts/experiences out there on pulling hot air through a duct and basement to another part of a house? Has anyone tried this???

Thanks!

 

[jeff_t]

Do you have a ceiling fan in the living room? Set it too blow up. Set a small fan on the floor blowing cool air toward the heat. What you are thinking about sounds pretty elaborate, and may not work that well anyway. I'd try the simple route first.

 

[vpuleo]

Thanks Jeff,

No ceiling fan... and I'm not really willing to put one in. I think they're ugly

I'd try a box fan, but I don't really love that idea either, it would have to be out in a hallway or some place in the way. Although this is probably a better first step to try, before putting a hole in the wall.

I'm really curious if anyone has tried the ducting, seems pretty logical to me...

 

[My Oslo heats my home]

Is your basement a full concrete walled basement? insulated floors? and a concrete floor?
I'm just trying to get an idea what the beasement is like. How about the basement space itself, is it an
open space?
I'm inclined to go with some of jeffs advice so far, a fan, or two blowing cold air towards the hot stove and
moving the heat towards the opposite end of the house. Make adjustments as you go.

In my home I have a centralized floor vent (1st flr to 2nd) just above the stove that moves warm air into
the second story. I have an 1880's styled farmhouse. At night I close the hallway door (front door) and turn
on the small inline fan in the floor vent. This keeps the second floor at about 72-78 degrees on the overnights.

You have a long narrow house plan with the stove located on one end. Could be tough getting that warm air
down to the other end.

 

[begreen]

Answered in the other thread. I suspect the duct losses will negate the heat gain. Suggest trying blowing air from the cooler section of the house toward the warmth (stove). Maybe use a second fan on the floor of the stove room pointed upward to circulate heat off the ceiling? (ceiling fan was nixed in other thread)

 

[vpuleo]

The basement is unfinished, insulation between the floor joists (the basement "ceiling") only - no insulation on the basement walls. Half of it has a concrete floor, half is dirt/gravel. All open space, and drafty. Seems like using insulated duct-work would help minimize heat loss in the basement. But not too sure...

 

[begreen]

Insulated ducts will reduce heat loss, but not minimize it. If you do this project, I would recommend running it in reverse. Same principal as the fan on the floor. Blowing the cooler air toward the hot will reduce the concerns about duct loss. Warm air will replace the cooler air at the far end of the house. But try the fan on the floor trick first and let us know the before and after temps in the sunroom and dining room. I think you will be pleasantly surprised.

 

[jimbom]

100 °F is kind of low to be using for hot air heat. I haven't lived with a hot air furnace for many years, but it seems to me the bonnet temperature on those is 140 °F .

The amount of heat you can move with air is approximately: BTU/hour = CFM * 1.08 * Δ T

So you would need to move about 1000 CFM of 100 °F air to get 33,000 BTU/hour to the other end of your house without taking in to consideration duct loses.

Thirty foot of duct with some elbows and fittings will require pretty good size duct and fan plus well insulated.