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Outside air kit question?

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by ohlongarm, Dec 3, 2012.

  1. ohlongarm

    ohlongarm Minister of Fire

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    Will an outside air kit compensate for a chimney that is at manufacturers minimum requirement.In this case my chimney is 14 feet counting from where the pipe connects to the stove to the chimney cap.I'm looking for a better draft in shoulder season,no problem when 20's arrive,or would I be better off adding 4 more feet somehow to the chimney.

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  2. Backwoods Savage

    Backwoods Savage Minister of Fire

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    I'm not so sure it would help with that but it would not do any harm for sure. The nice part is that you are not drawing all that air for the stove from inside the house. Realizing that when that air leaves, it has to be replaced by other air and that comes from the outdoors so is cold.

    When we had an OAK, most times it seemed to work okay but in certain wind conditions we did not like the result.
  3. MnDave

    MnDave Guest

    It depends on how much make-up air you already have near your stove. If your house is tight and the make-up air in your utility room is far away or you keep that door closed and the door is tight to the floor, then you would probably benefit greatly from an OAK.

    Plus you would be less likely to use heated air to fuel the stove, a win-win.

    MnDave
  4. MasterMech

    MasterMech Guest

    Hard to go wrong with adding 4 ft to your chimney. That'll improve draft in any situation. The OAK will do little to improve draft. The OAK will however prevent the stove from creating cold drafts in the house.
    chimneylinerjames and jjs777_fzr like this.
  5. jjs777_fzr

    jjs777_fzr Feeling the Heat

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    I'd definitely add to the existing 14' of chimney.
  6. chimneylinerjames

    chimneylinerjames Feeling the Heat

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    I agree, adding to the height of the chimney will always improve draft.
  7. Wood Duck

    Wood Duck Minister of Fire

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    I don't see how the outside air kit would improve draft. If anything I think it would hurt draft because it makes the path for air entering the stove more difficult - instead of air simply entering the stove through the air intake vent, the air must instead be pulled through a tube then into the air intake vent. If improving your draft is your goal, I'd go with the additional chimney height. If eliminating cold drafts into the house then try the outside air kit. I have an outside air kit, but it was installed when the stove was first installed so I can't say if it helps or hurts the draft (theoretically it must hurt, but how much?)
  8. chimneylinerjames

    chimneylinerjames Feeling the Heat

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    Well the outside air kit would help if the house was sealed up very tight and basically draft free. Then the stove would be starving for air and reducing the draft. But if the home isn't fairly new most likely there will be plenty of drafts in the home.

    one test you can do to see if an OAK will help is crack open a window near the stove, it will have the same effect as an OAK. If it helps drastically with the draft, then you have your answer, you need one. If not don't bother with one.
  9. Dakotas Dad

    Dakotas Dad Minister of Fire

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    More than one member with a finicky stove has done a dance of joy to discover what 4' more chimney can do for your draft...
    northernontario likes this.
  10. Joful

    Joful Minister of Fire

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    When compared to the volume of any normal house, and the minimum air changes per hour to keep your living space healthy (mold, bacteria, etc.), you will find it swamps the make-up air requirement of any stove 10:1. That said, appliances such as large range hoods, clothes dryers, oil or gas furnaces, and radon ventillation systems can rob enough of that air that there is sometimes a legitimate need for an OAK.

    Unfortunately, when the OAK inlet is located on the leeward side of a house in any wind, you may find it creates more of a problem than it solves. I believe this is to what Dennis was referring when he stated, "in certain conditions we did not like the result." This can be a problem if your wind doesn't always blow from the same direction, or if you're unable to locate the OAK on the typically-windward side of the house.

    Wood Duck's theory about the OAK actually creating more resistance to draft may be a good one. I've seen it written before, and some actually recommend providing make-up air near the appliances most likely to use it (range hood, dryer, etc.), rather than at the wood stove. Of course, that only aggravates the problem of feeling cold draft in rooms not directly adjacent to the stove.

    However, before getting into a long debate over the merits and need for an OAK, have you performed the exceedingly simple test to determine your need for one? Open a window in the room with a stove. Does your draft improve dramatically?
  11. ohlongarm

    ohlongarm Minister of Fire

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    I tried the test doesn't increase dramatically but noticeable. Now my stove has never failed to fire off with the door closed under any burning conditions encountered,so I'm leaning towards extending the liner 4 feet next year how would one go about doing that,can the steel liner just be extended where it connects to the chimney cap?Thanks for the replies.
  12. chimneylinerjames

    chimneylinerjames Feeling the Heat

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    You could use a liner coupler and install 4' of chimney block/brick and use the same top plate and cap.
    Or you could buy and anchor plate with a liner coupler on the bottom of it and extend the chimney using Class A pipe.
  13. northernontario

    northernontario Member

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    I have to agree with what people are saying. I started out with 15' of chimney (thru the wall... 15' up). Second year I added another 3'... helped a bit, but also could have been better seasoned wood. This fall I added another 3'... so I'm now at 21'... what a difference! I can actually throttle the stove back now and not run wide open all the time.
  14. Joful

    Joful Minister of Fire

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    Yep. You want a class A anchor plate. Allows flex liner below and class-A above. You may want to add a roof brace to support the class A extension.
  15. semipro

    semipro Minister of Fire

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    Though I'm a big proponent of OAKs in most circumstances I don't think adding one is likely to help your draft.

    Insulated flues tend to get hotter and draft better. I didn't read how yours was constructed but adding insulation might help.
  16. MnDave

    MnDave Guest

    If I am not mistaken, your stove has a 8" outlet. Do you have an 8" flue all the way up? That 8" makes for a slower draft.

    If it is easy to put on 4 more feet then I would go for it.

    I just installed a new stove. One change I made was to the stovepipe. I used 2 - 45 degree elbows instead of 1 - 90 degree. Too much horizontal can stall an updraft. My horizontal was about 3 feet, now it is less than 2 feet.

    I also added an OAK. I use a torch to warm up the flue before I light. I run that torch until I can feel that the first foot of pipe is warm.

    I have had easier starts but again it is a new stove so other variables.

    Letting your stove run hotter in the shoulder seasons may be all you need to do.

    MnDave

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