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Double Wall vs. Triple Wall Class A Chimney

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by Johnny G82, Oct 3, 2013.

  1. Johnny G82

    Johnny G82 New Member

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    Hi,

    I am installing a Hearthstone Phoenix that will be vented out through an exterior wall (I realize that this is not ideal) and then up about 15' through a class A chimney. My question is, which type of class A chimney will perform best in terms of draft and creosote build up on the exterior? Double or Triple wall?

    I am considering using the AirJet chimney system, but want to make sure that a Triple wall chimney with no insulation won't cause increased creosote build up. Does anyone have experience with this pipe?

    http://www.continentalindustries.com/files/downloads/AJ-2100Brochure.pdf

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  2. DAKSY

    DAKSY Patriot Guard Rider Staff Member

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    It looks like a good product, but the diagram on Page 9 is WRONG. The THREE foot dimension is taken from highest point where the chimney exits thru (or passes along) the roof. Also, I'm not big on Galvanized exterior chimney pipe. I've seen too many instances where the Galvanizing has failed & the pipe has rusted. Your call, tho.
  3. dougand3

    dougand3 Minister of Fire

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    How much is the AirJet 15' chimney? Compare to Selkirk or Simpson double wall, insulated, SS.
  4. blwncrewchief

    blwncrewchief Burning Hunk

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    X2. I really would not want to spend the money to install a chimney that is a galvanized exterior. Especially for a wood stove. As far as the creosote issue since it is a ventilated air gap system cooler flue temps could be an issue and no way to predict without testing data. Since the system is ventilated it is a dynamic system relying on the design of the system versus an insulated double wall is pretty much a static design. It could be better or it could be worse. I would tend to stay with the tried and true insulated double wall SS unless you like to experiment.
  5. oldspark

    oldspark Guest

    Backwoods Savage likes this.
  6. begreen

    begreen Mooderator Staff Member

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    I'm not a big fan of triple wall chimney. Air Jet has a larger diameter pipe to do the same job as a more slender insulated double-wall pipe. And the air passages make wonderful homes for wasps and hornets. I would stick to the major brands for a wider variety of solutions, less bulk, stainless jacket and ease of getting parts. M&G DuraTech, Selkirk SuperVent or Ultra-Temp HT, or ICC Excel are much more common brands with good quality.
    Last edited: Oct 4, 2013
    WiscWoody likes this.
  7. bag of hammers

    bag of hammers Minister of Fire

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    They state that " Top of pipe must be 2 ft. higher than anything within 10 ft. of the chimney" which I believe is correct, but then in the diagram it says "if 10' or less, chimney must extend 2' above peak". I know this is just supposed to be an example where the peak happens to be exactly 10 away, but how often does that really happen? To my fuzzy brain, the picture at first glance sort of implies that if the chimney is 10' 1" from the peak, then it doesn't matter. Yeah it's kinda anal, but pictures speak louder than words. If I wrote the manual, I'd include a 2nd pic / example where the chimney is nowhere near the peak, just to drive the point home.
  8. Johnny G82

    Johnny G82 New Member

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    Thanks for all the replies. I should have specified in my initial post that they have a stainless steel option that I would go with. Overall for what I need this setup would price out around $800 which seemed to be about the same as Selkirk's Supervent, and quite a bit less than some of the other more popular brands. I liked the fact that the Air Jet pipe only needs to protrude 1" inside the interior wall since I'm trying to reduce the clearance from the wall to the stove as much as possible. I think most of the other systems that I've seen require 2" for Duravent and 3" or more for the other brands.

    It sounds like most of you agree that for an exterior application, I should probably go with an insulated chimney system, so I think that's what I'll do.

    Thanks for the good advice.
    Backwoods Savage likes this.
  9. begreen

    begreen Mooderator Staff Member

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    The clearances on the inside wall are determined by the distance of the connector pipe to the nearest combustible, ie: the wall.
  10. oldspark

    oldspark Guest

    Yea the link to the manual states standard 2 inch clearance to combustibles.
  11. dougand3

    dougand3 Minister of Fire

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    If the price is the same, I'd sure go with Selkirk Supervent. I put it in my house and am quite pleased with it.
  12. Johnny G82

    Johnny G82 New Member

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    Thanks everyone.

    I'm sorry if I confused you. The 3" that I mentioned above was in reference to the distance that Selkirk says the pipe must extend inside the room when installing the horizontal chimney through the wall. This would then connect to the single or double wall stove pipe from the stove.

    Since this pipe is stainless steel, it seems that this would look a bit awkward since it would be visible from the inside of the room. Has anyone run into this situation?

    I am planning on installing a 1" air shield from the combustible wall, so my other question is if that 3" should be measured from the combusible wall or the air shield?
  13. bag of hammers

    bag of hammers Minister of Fire

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    In some setups the stainless chimney extends into the room. In my case, Selkirk Supervent that extends several inches down from the support box (for proper clearances from the stove pipe adapter to exposed beam, etc.). There are a few threads here on painting stainless chimney - I've thought about it and may paint it black one day but the look of the stainless actually doesn't bother me enough to get this on the priority list. It may be a different perspective in a horizontal install but I'd assume you can shoot some paint on the exposed part if it bugs you enough...?
  14. akbear

    akbear Member

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    In my case, whether it's right or wrong, I have this adaptor to transition from the chimney to the stove http://www.plumbersurplus.com/Prod/Selkirk-Metalbestos-258240-8-DSP-Chimney-Pipe-Adapter/272840/Cat/353?gclid=CKKaveXohboCFYw1QgodSWsApQ
    (well, a 6 inch size, I see this one linked is 8 ) and the stove collar on mine fits into the recess at least an inch or so. On the fires that I had so far, I haven't seen any temperatures either on the collar itself or the chimney that would lead me to be concerned with the setup which is why I've now set the magnetic thermometer on top of the chimney attached to the wall trim ring just to monitor it instead of using the IR gun on the pieces often. (the chimney is reflecting on the back of the stove at the bottom of the picture, so ignore that to save some confusion)

    IMG_1667.JPG
    Last edited by a moderator: Oct 7, 2013
  15. goofa

    goofa Burning Hunk

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    ok so if you have no clearance issues inside the home you can use single wall pipe up to the ceiling box or is it more logical to just use the double wall pipe?
  16. cableman

    cableman Feeling the Heat

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    If using the support box i think that has to be atleast 3" from the ceiling then keep the chimney pipe flush with the finish trim. Not sure of your set up but im in the process of installing mine on a small cathedral ceiling and im thinking thats how its gonna go!
  17. oldspark

    oldspark Guest

    Is that class A he has right up to the stove?
  18. akbear

    akbear Member

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    if you are talking about me, yes, it's class A where it comes out from the wall and the stove collar you are seeing (the transition piece or chimney pipe adaptor between the two which can not be seen), but it might also be notable that this is on a cookstove so by the time the exhaust has reached that point it has travelled across the top of the oven to the other side of the stove and makes a "P" shaped loop either down the back of the oven with the bypass open or down the side of the oven across the bottom and up the back side if the bypass is closed.
  19. Johnny G82

    Johnny G82 New Member

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    Thanks for your help everyone.

    I think the only question I have left is this:
    I am planning on installing a 1" air shield off the combustible wall that I am installing my stove in front of. It will have a 1" air space spaced out with strips of durock and vented top and bottom, with Durock attached to the strips. If Selkirk is saying the horizontal chimney pipe must extend through the wall and into the room 3", should I measure that 3" from the combustible wall or from the air shield surface (durock)?
  20. begreen

    begreen Mooderator Staff Member

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    The clearance measurement is always to the nearest combustible, in this case the combustible wall.
  21. Johnny G82

    Johnny G82 New Member

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    Ok, thanks begreen. The Selkirk installation manual was very vague because it only stated that the class A chimney coming through the wall and into the room must protrude 3" minimum. It seemed to me like this was to give proper clearnace for the transition from the class A to the double wall stove pipe, but wasn't sure how to handle the air shield being within that 3" minimum.

    Thank you!
  22. akbear

    akbear Member

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    Vague is the keyword, if you look at three different selkirk instruction manuals you often get three different distance recommendations as well in that off chance they have clearly spelled something out. For some reason or other they can't seem to co-ordinate the manuals or just don't care to update them when they've set out a new standard.

    One thing you might want to consider (mostly unrelated to the actual question) is putting up a radiant barrier over the studs before building out. I did that in my wall reconstruction and I was really pleased with the performance of that wall over the past winter before the stove was installed. In my case I used a class A blanket (the type like garage door blankets are made of, two layers of heavy foil sandwiching some sort of bubble wrap material) over the studs as a back to the air gap.

    I did also place a ring of the same rockwool type insulation that can go inside the thimble as well as in the corners around the thimble in the airgap surrounding the thimble as going through a winter with only a plastic grocery bag stuffed with insulation scraps I didn't want the metal thimble to be a conduit to bringing the cold into the wall to chill my interior walls or as a place for condensation to collect and drip into my wall (I have a canadian envelope, so basically I have an airgap all the way around). And that was the second thing that exceeded my expectations, I didn't have a drop of condensation on that trim ring all winter long.
  23. bag of hammers

    bag of hammers Minister of Fire

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    On my old stove with similar heat shielding set up - I picked up a couple lengths of metal furring strips - perfect air gap (I ran them vertical and a up couple inches from the floor) - no need to cut thin strips of durock, etc. Just something to consider...
  24. Backwoods Savage

    Backwoods Savage Minister of Fire

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    Welcome to the forum Johnny.

    You state that it is not ideal going through the exterior wall then up. In that case, me and many others have a bad setup! There is nothing wrong with doing this but you must know that the horizontal section must have a minimum of 1/4" rise per foot of horizontal. We went 1/2" or more per foot and have no problems. Our chimney is also short and should not work, but it does the task just fine.
  25. Johnny G82

    Johnny G82 New Member

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    Hi Dennis,

    I didn't mean to make the exterior chimney setup sound bad, only that everything I had read about it seemed to indicate that it was less ideal than going straight up inside :). I'm glad to hear it works well for you!
    Backwoods Savage likes this.

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