Contemplating a second wood stove, seeking advice on building chimney chase

[Eric Miller]

I’m new to wood burning, just installed a wood stove this year and I love it. I would like to install a second stove in hopes of heating my entire house with wood (two stories about 3500 sq ft). The new stove would go in my insulated basement at the opposite end of the house from where my current stove sits on the main floor. To do this I need to add a chimney so I am thinking I could build a square chase that runs straight from the basement to the attic and install a Duravent class A chimney in this chaseway. In addition, I would like to construct an air shaft right next to the chimney chase. The chase would measure about 16" square and the air shaft would be about 16 x 20 inches. I am thinking I could use a fan in the air shaft to move warm air from the basement up to two second floor bedrooms where the airshaft would terminate. The cold air returns for my second floor heat pump will be located in these two bedrooms so I’m thinking I could just run the heat pump's blower fan on low to circulate this air around the second floor.

In the end, I'd like to use as little fossil fuel as possible to heat my house. I've considered other alternatives but the wood stove seems to be the most practical …

GeoThermal heatpump - $$$

Wood Furnace - This is a possibility but they appear to be less efficient then a wood stove and emit more pollution. Also, a furnace is not “pretty” like a nice cast iron wood stove.

Pellet Stove or furnace – I’d have to buy pellets but I can get wood for free minus my labor (which I enjoy).

Outside Wood Boiler - Too inefficient and too smoky.

Gasification Wood Boiler and thermal storage tank - I must admit, I am very attracted to this type of system but it is very expensive. If I lived further north it might make more economic sense for me but the fact is that Maryland winters aren’t typically very cold. The big advantage of this system is its ability to store heat for latter use and also the fact that it can provide domestic hot water. Considering the minimum $10K extra a system like this would cost, it’s kind of hard to justify the $. However, if I factor in the price of a solar hot water system to the price of the 2nd woodstove option then the price difference for the gasification boiler doesn’t look as drastic. This could still be an option.

Assuming I opt for the second wood stove …

1) How would a chimney chase be constructed? Is framing lumber and drywall appropriate or must it be shielded in any way? Duravent specs just show that there must be a 2 inch air gap between the chimney and any combustible surface. I could install the chimney outside the house but I know it will perform better inside the house envelope and the finished result will look nicer.

2) Are there any safety concerns related to the airshaft – fire codes, that sort of thing? And, as with the chase, is framing lumber and drywall appropriate?

3) Any special issues with a tall chimney? This one would be somewhere around 30 feet or more by the time I get from the basement to two feet above my roof peak. Is there such thing as too much draft?

Before I would start on this project I will verify everything is compliant with my local code. I just want to run a sanity check to see what I am overlooking. Thanks to everyone.

 

[RonB]

Welcome to the forum Eric. The majority of heat that is made by a stove in the basement will primarily heat the basement first and then secondly the floor above it. (I have one large stove in my in my Ranch style house basement). I am not so sure that trying to heat the second story floor from a basement stove will work. Do you have a large hallway on the second floor that would accept a stove?
Other random thoughts: Heard 2 stoves are a lot of work. Might work better to exhaust the cold air from the bedrooms letting warm air naturally "loop" back into the room. Geo-thermal is efficient and relatively inexpensive (I have one but choose to heat with wood). Can't an Outside Wood Burner be run more efficiently as to not belch smoke? Wood furnace makes more sense in your application. Tall chimneys draft good. Is your basement a walkout? If not, then lots more work getting the wood into the basement. Also, most new stoves do require a fair amount of user input--lots of trips up and down the steps to track temps, fire progress, and low smoke startups. Don't be afraid to do some searching in the archives about your issues.

 

[begreen]

One more thought. If ever there was a fire in the basement, that air chase would be a mighty chimney delivering the flames to the 2nd floor in seconds. Not a pretty thought, but possible.

 

[Redox]

This sounds like what I did when I installed the new stove. I moved the stove closer to the center of our split level house but kept it in the family room. I ran the flue up through the bedroom close to the peak and ran a 12" galvanized pipe up to the 2nd floor heat pump return right next to the flue paying attention to the clearances all the way. I framed this out with metal studs as an extra precaution and used 1/2" wall board to finish it. I plan on using the space between the floor joists to move the return away from the stove when it is done, but right now, the return is right over the stove. I don't think it meets code right now, but it does work very well. I only run the downstairs fan at night to spread the heat around and let the upstairs zone cycle normally. I keep both zones set at about 65F and neither zone runs unless the outside temperature drops below about 20F. I think I have conservatively cut our heat bill down to about $100/month in a 3000 sf house with one stove. You should feel the cold air running down the stairs!
I think I read somewhere the return has to be about 10 feet from the stove, and it will be when I get done with the addition. I might also invest in a couple duct smoke detectors to shut down the heat pumps in the event of fire. I thought about putting a pellet stove somewhere upstairs, but this is working so well right now, I probably won't. The new flue is inside the house and is about 24 feet long. I get very good draft; much better than the old outside chimney on the insert.

 

[Eric Miller]

Thanks for the info guys.

I've considered a stove on the second floor but don't have a good place for it. In addition, getting the wood up there would be a hassle too. My basement is a walkout so getting the wood down there is not an issue.

Creating a fire hazard is also definitely among my list of concerns and partly what motivated me to seek advice here. I definitely don't want to do anything that is not safe.

Reading of Redox's success with a similar setup is encouraging. Metal studs are a good idea, as is moving the air shaft inlet away from the stove.

I will call my county permit office and see if they can offer any advice relating to applicable codes.

 

[begreen]

If you go this route, be sure to install a fire damper with a fusible link in the air duct.

redox, code says a return air duct must be at least 10 ft. away from the woodstove.

 

[Eric Miller]

BeGreen, a fire damper is an excellent suggestion - thanks. I didn't know there was such a thing but I am more familiar with the idea now after a couple of Google searches. If I go with this basement wood stove, I'll need to find a source for the fire/smoke damper and figure out how to connect it to a smoke alarm.