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45 foot Chimney Liner Advice - I Don’t Trust My Local Contractors Enough to let them design my liner

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by mnowaczyk, Feb 22, 2009.

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  1. mnowaczyk

    mnowaczyk Member

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    I believe I need 8" oval duct to get through my damper. Then I'll need an 8" oval to 8" round converter. At that point do I convert to 6"? Or Stick with 8" to the top of the 45 foot chimney? It looks like 8" material is at most $300 more. I'm assuming I've got room for 8".

    Do I use rigid or flex?

    My chimney looks like a straight shot after a slight angle on the first floor which would be lined with a 5 foot long 8" oval to 8" round stainless flex conversion. So I'm mostly trying to determine what to do with the top 35 feet of chimney liner. I think I'm locked into 8" oval positive connection, plus 8" oval-to-round.

    I assume Stainless Steel is the only way to go, right? Or is aluminum "B-vent" sufficient? It looks like a $500 difference. Granted I only want to do this once.

    Thanks,
    Mike

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  2. Hogwildz

    Hogwildz Minister of Fire

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    You should try and keep the liner same size as the outlet on the stove. If stove outlet is 6" then use 6" liner, if its 8", then use 8" liner.
    You could cut damper out enough to let round through, up to you.
    Round is better for draft then oval, bur with you height, it should draft real well.
    Stainless is the onlt way to go with the liner. Aluminum is a death wish and will not be code compliant, or sane compliant. If it son't melt all together. Keep doing your research, get the right facts and plan properly. Take your time, do it right & safely the first time.
    Make a list of things you want & need:
    Are you going to insulate?
    Install a lower block off plate?
    etc etc.
  3. mnowaczyk

    mnowaczyk Member

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    Thanks Hogwildz. I've since read the manual that says to use 8" liner.

    The postive connect kit comes with a damper plate. Is that what you mean by lower block off plate?

    Insulate? What's that all about? Insualte where? The chimney liner? The fireplace?
  4. Jimbob

    Jimbob New Member

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    A lower block off plate keeps warm air from rising up the chimney on the OUTSIDE of the liner.
    The insulation goes in the void between the liner and the masonary, if there's room.
    There are two types. One type is a blanket that wraps around theliner before it is installed.The second type is a granular type material that is poured in place AFTER the liner is installed (the block-off plate would keep material from pouring all over the insert).

    Here is a thread discussing insulation and a block off plate:
    http://www.hearth.com/econtent/index.php/forums/viewthread/34813/

    And here is how to make and install one:
    http://www.hearth.com/econtent/index.php/articles/making_a_block_off_plate/
  5. mnowaczyk

    mnowaczyk Member

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    Yeah. I'm pretty sure this is the same as a damper plate (I assume). One is supposed to come with the positive connection kit, or can be purchased for like $38. It's stainless and pre-cut for the 8" oval duct. I defintiely plan on using a damper plate.

    I'm not sure about the insulation. I like the idea of something to keep the duct from boucing around in there, but envision it would make installation more difficult. The mason who gave me the $5000 estimate said he'd pour CONCRETE down the liner. I like the idea of something less permanent in the event the liner needs to be replaced for some reason. However, it might also be nice to know the house won't fill with sand if something were to happen.

    Do you think this insulation is necessary? If the chimney is capped and covered at teh damper plate, that air should warm up with the chimney anyway. Air is insulation, right?
  6. LLigetfa

    LLigetfa Minister of Fire

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    Air, if trapped in small spaces is insulation but in a cavity where convection can move it, it has the effect of carrying away the heat.
  7. Hogwildz

    Hogwildz Minister of Fire

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    The plate that usually comes with kits is a top plate for the top of the chimney. This is a must!
    Then some, including myself add another plate at the bottom just below the old damper. This keeps the heat from rising up the chimney and gettins sucked up and let out by the masonry, hence keeping more of that heat into the home. Insulation is not a must unless your set up does not meet some criteria:
    The old tile lining must be intact and in good condition.
    If you have an exterior chimney most would recommend you insulate it.
    You have to make sure you have the room for insulation (if using the wrap type).
    With the height of your chimney, you may not need the insulation as long as the original liner is in good shape. If it is not, it will not meet code even with new liner unless it is insulated.
    Insulation helps keep liner warmer/hotter, which makes for better draft and less creosote build up due to the gases cooling sooner and condensing.

    I highly recommend against pouring concrete around that new liner. If you need to service the liner or remove it for any reason, now you can't with concrete around it.
    Also, I think the concrete may secrete an acid which may eat away or prematurely age the liner? Think I read this here somewhere.
    If your considering insulating, go with the wrap or vermiculite type pour in. Or as some other have done, get some rockwool or other high temp rated insulation, and stuff it around the top few feet, and near the bottom above the lower block off plate. At 40' or so high, your going to have helladraft!

    One other note.
    If the old chimney is large enough inside, and fairly straight, you could do as I did and use insulated rigid double wall and just use flex at the bottom down to the stove.
    Works great, and easy to clean.
  8. mnowaczyk

    mnowaczyk Member

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    That's what I was thinking would be best: Rigid at the top 35 feet, and flex at the bottom ~10 feet. You agree? I would think flex would be much more likely to collect creosote than rigid.

    My draft is freaking rediculous. I could probably start a fire 3 feet into my living room and the chimney would suck it right up. I pull a log out of the fire twirl it around and never need to worry about smoke in the living room. Even when I had the insert in there (only a little over a day) I would often forget to open the damper on the insert, relying on the ~1"x10" heat chamber exhaust, and I'd often still not get smoke in the room.

    I just measured the inside, and once again, my chimney sweep if full of $h!t. He said I had nearly 50' of chimney, and I've got less just than 37 feet from the fireplace floor to the bottom of the peak ridgeline plank. I think I've got another 3-4 feet of chimney above that, so it's still probably more than 40'. Still a crazy draft.

    Do you know how chimney distance affacts the needed cross section? Would a longer chimney need a larger or smaller liner? (Just curious, I'm not going any smaller than 8".)

    Thanks for the tips like "vermiculite" and rock wool.

    My Next steps:
    - Get a contractor who will install the liner (I think my slate roofer wants the work, and will probably be very reasonable.)
    - Have him decide whether he wants to go flex, rigid, and if he wants to insulate. (I'm not htinking that I "need" it.)
    - Figure out which stove I'm going to be using going forward (trying to get my hands on an old Vermont Castings 0044 because it's probably better than my "Vermont Stove Company" Shelburne. Both look nice.
    - Order up the materials.


    I have to admit one other thing is at least interesting to me: The concept of heating water in the winter. I've got radiator heat, and I also need to replace my water heater. I'm looking at going with a tankless, and envisioning I could cut winter water heating costs by running some pipes through my firebox. :) I read a cool thread on that, but figure it's probably not worth it when I spend less than $60 per month on hot water. It would take an eternity to get a return on that investment. Maybe it makes more sense to look at some type of oil burner that combines hot water and radiator heat.

    This site forum has been EXTREEMLY HELPFUL and interesting. THANK YOU!!!!
  9. mnowaczyk

    mnowaczyk Member

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    So if the chimney is capped, and the damper plate is blockes off, that air aint going nowhere. Sure it might contribute to heating the brick. But what's the big deal with that? Is the fear that a cool(er) chimney liner is going to be more likely to collect creosote? The liner would be hotter with air insulation than if it was up against something non-insulating like the "concrete" a mason wanted to use. Right? If I were to use vermiculite as insulation, wouldn't the liner take longer to heat up? I guess there's logic behind it taking loger to cool down though too, right? When the fire cools, producing creosote, if the vermiculite keeps the liner warm, thne I'm likely to keep a strong draft and get less creosote condenstation on the liner. Is that the logic?

    It's an over 40 foot chimney with a crazy strong draft.
  10. Hogwildz

    Hogwildz Minister of Fire

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  11. Hogwildz

    Hogwildz Minister of Fire

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  12. begreen

    begreen Mooderator Staff Member

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    mnowaczyk did you mention what the stove / insert is? Is this the Vermont Stoveworks Shelburne? Could you add this to your signature?
  13. mnowaczyk

    mnowaczyk Member

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    BeGreen:

    Here's my new signature. More than you bargained for eh?
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