What size chimney?

[djblech]

I am building a house for a client and they asked me to put a chimney in for a future wood stove. The stove would be in the basement and the chimney is near the center of the house just off the ridge line. My question is, 6" or 8" flue size? If I had to guess on a type of stove I would say Englander 30, or Lopi Liberty type of stove. I think 6" would work for these, but would an 8" work better if reduced at the stove pipe? Just thought I would give you guys something to think about during the hot months.
Thanks
Doug

 

[Backwoods Savage]

Generally if you vent a 6" into an 8" you do not get enough draft. However, it has been done and some do get away with it. But you have a second problem and that is putting a stove in a basement. This is the most difficult for wood heat and most do have draft problems even using the proper size. Most will end up having to crack a window in the basement to get enough draw or draft.

Yet, this really doesn't address the problem and can't because you do not know for sure what stove will be used. You can probably calculate what size stove will be needed based upon the square footage of the home. Will they be heating 2 levels? 3 levels?

Now comes the bigger question: how do they plan on getting this hot air up into the house? It seems rather easy because we all know hot air rises, but it is not that simple. Most folks do have big problems trying to get that heat upstairs!

Here is another big problem. If that basement is not fully insulated, and that means all the walls too, most of that heat will be absorbed into the blocks or cement. If everything is insulated then that problem is solved but it is an added expense.

Good luck.

 

[cmonSTART]

Pretty much any stove will vent best when vented into a flue of the same size as the collar. It keeps the flue gases moving along quickly.

 

[Swedishchef]

I agree with everyone else, it's better to go with a 6 inch flue.

I currently have my woodstove in the basement. It does through my cement wall and the entire chimney runs outside (class A). I have some draft issues from time to time. Throughout the entire winter, I had 4 days where downdrafts were a problem. If I crack a window open (creating positive pressure), it reduces the problem dramatically.

However, I did try lighting a fire with a downdraft thinking "the birch bark burning heat will reverse the draft no problem". OMG was I WRONG. Smoke starting POURING out of the crack I left in the door, through the air intakes, everywhere. My wife was happy!

Long story short: 6 inch flue!

Andrew

 

[begreen]

I'm wondering more about the house seeing it is new construction. Just curious, why is this house being built with the stove in the basement? Is this a major family room area? Will the basement be well insulated? Is the stove just to heat the basement or are there wishes to heat the whole house?

 

[djblech]

I should have explained this at the beginning. The house is a 28x48 ranch style. It has a full block basement that is a walkout. The basement will be used as a family room at some point. With the walkout, hauling wood in should be easier. It also has an open stairway to the main floor. Gas forced air is the main heat source. The wood stove will be used when they are home, nights and weekends. They live on 40 acres with a ready access to the wood.
Doug

 

[Swedishchef]

Go with a 6 inch flue.

It sounds like they'll be using it to heat the basement when in the area. If you install a couple of floor grates (registers), the heat will be able to rise fairly well to the first floor from the basement. I have a 1250 square foot bungalow. My stove heats my basement and my main floor. Once the basement is warm, the heat rises, the floors gets heated and my main floor gets cozy.


Andrew

 

[begreen]

If they are building new, hopefully some common sense will go in at the planning phase like good insulation for the basement walls and having a central staircase with a wide opening. I agree with the 6" flue. That should cover all but a few stoves. With new construction, tight sealing and good insulation they should do ok.

 

[Swedishchef]

BeGreen,

I am in a newly built home (from last summer). I totally understand where you're coming from. For insulation in my basement, I sprayed 1.5 inches of polyurethane foam directly on the concrete (inside). Then I framed my walls and added 4 inches (R14) Roxul between the studs against the foam. The foam was also sprayed in my rim joists. My basement is air tight but my air exchanger fixes that problem.

I have a central staircase and am adding 2 floor registers in strategic locations on the main floor. Even without these registers my main floor heats well: once your floors get warm, the rooms warm up.

That's my experience with insulating basements!

Andrew

 

[Backwoods Savage]

One caution: make sure the home will meet code if you cut in some registers. The fire department might not be too hot on the idea.

 

[fossil]

6" flue...they'll have a zillion choices of very nice modern stoves from which to choose. Rick

 

[firefighterjake]

I should have explained this at the beginning. The house is a 28x48 ranch style. It has a full block basement that is a walkout. The basement will be used as a family room at some point. With the walkout, hauling wood in should be easier. It also has an open stairway to the main floor. Gas forced air is the main heat source. The wood stove will be used when they are home, nights and weekends. They live on 40 acres with a ready access to the wood.
Doug

Normally most folks here don't recommend basement installs, but it sounds as though this will be used as a family room which should mean it will be well insulated . . . and there will be a decent way to move the heat upstairs so they may be OK.

Like other folks I would suggest going with a 6 inch flue . . . it's the size that most modern woodstoves use and would give them the best choice in terms of draft and choice of stoves.