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Stack Insulation Raining Down

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by gwmiller, Dec 4, 2013.

  1. gwmiller

    gwmiller Member

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    Hello, I have a jotul 550 that is located in the center of my living area. My chimney stack is masonry block with a clay liner that had to be broken/removed in order to make room for my insulated stainless stack.

    I was having major issues with attic air coming down the chimney and out into my living room through the gap between the surround. The chimney liner connects directly to the top of the stove and runs to the top of my chimney.

    Over the summer, a contractor poured insulation from the top of the chimney in order to 'plug' the area between the stainless liner and the rough masonry block in order to stop the attic air from down drafting into my living room. He stuffed fiberglass insulation above the stove and then poured the insulation in. It stopped the attic air and all was well until I started using the stove.

    Now I can hear the pebbles dropping onto my stove while the stove is heating up/cooling down. Not a tiny amount either, it is piling up against the top of my stove and the flue pipe. To make matters worse, the insulation is falling into the space between the top of my stove and the box (where the air flows) and being blown out into my living room.

    I had the contractor come back to address it, but all he did was put a small strip of fiberglass around the bottom of the flue and (to my dismay) taped it to my flue pipe with metal tape. Needless to say, I just pulled the surround to see why insulation is still blowing out and found the tape has failed (big surprise!) and there is a mountain of insulation laying on the top of my stove.

    My question is, is it a good idea for me to stuff mineral wool insulation (rockwool) up into the space above the top of the stove and completely fill that void? (stuffed from the top of the stove all the way up as far as can go).
    While i'm at it, can I also stuff rockwool on the sides/back of the stove to fill the gap between the stove and the 'fireplace'? I've attached some pics to hopefully help you visualize what I am talking about.

    Thanks!

    insulation falling into this gap:
    photo 2.JPG
    looking up:
    photo 3.JPG
    looking up from the side of the stove:
    photo 4.JPG
    overall view with surround removed:
    photo 1.JPG

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  2. weatherguy

    weatherguy Minister of Fire

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    He should have installed a metal block off plate, not too hard to do, a lot of us did it ourselves. Do a search here on block off plates and have him come back and do it right.
  3. EatenByLimestone

    EatenByLimestone Minister of Fire

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    Don't waste your time with the contractor again. Get some sheet metal and make your own block off plate. He had his chance to get referrals and blew it.

    Matt
  4. webby3650

    webby3650 Master of Fire

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    I don't understand what the purpose of the poured in insulation is? That liner has wrapped insulation already, no need for the loose fill!

    Attic air is not able to get into the chimney unless you got some major problems. The liner should have had insulation stuffed around it at the top and a top plate sealed down, preventing cold air from coming down the chimney.

    I have a friend that is dealing with the same issue, it will never stop trickling down if you don't make a tight sheet metal blocking plate with stove cement filling what little gape is left.
  5. webby3650

    webby3650 Master of Fire

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    I didn't install my friends liner by the way.<>
  6. gwmiller

    gwmiller Member

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    the reason for the insulation is to plug the gap between the outside of the insulated liner and the masonry block chimney structure. when they build my house they did not seem too concerned about the joints between the masonry block stack (there are big gaps up in the attic on the outside of it) and instead they relied on the clay tiles to create a sealed stack. because the clay tiles were essentially removed, air was being drawn from my attic whenever my kitchen exhaust was running. The top of my chimney is sealed down, but that just stops outside air, not chimney.
    I've read through the how to's on making a block off plate but I have no idea how to seal the edges. If you look at the pic below, you can see that the bricks on the back wall of my fireplace have been removed, so there is no even area where the metal can sit.
    Thats why I figured I would just get a bunch of mineral wool and stuff that whole cavity, including the area where the bricks are missing. Is there any reason why I should not go that route? photo 1.jpg
  7. EatenByLimestone

    EatenByLimestone Minister of Fire

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    Shoving mineral wool into the area will not stop the convection currents. A sheet metal barrier will.

    Here's what I'd do:

    Use 2 pieces of 2x4 to make a sheetmetal brake. Like this, except use a hammer or rubber mallet to tap the metal over.



    Anchor it right into the brick with your preferred method. I'd use tapcons because I have a lot of them already in my garage.



    Seal the edges with this:

    http://www.dap.com/product_details.aspx?BrandID=9&SubcatID=2

    Around the liner itself I'd use a furnace cement which can withstand higher temps such as this:

    http://www.amazon.com/MEECOS-120-Furnace-Cement-Fireplace/dp/B000VZS0ZQ

    I wouldn't sue the DAP around the liner as I don't think it's rated to that temp. I wouldn't use the furnace cement around the edges as it really doesn't expand and contract any and the DAP will.
  8. gwmiller

    gwmiller Member

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    Thanks eaten, but what can i do about the back edge, where the bricks are missing? Its totally uneven, is it worth putting up a metal plate if there is a 2"+ gap along the back edge?
  9. webby3650

    webby3650 Master of Fire

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    It's easier to fill a 2" gap with insulation than an entire damper opening.
  10. EatenByLimestone

    EatenByLimestone Minister of Fire

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    Fill it with insulation as Webby suggested and then caulk over it to seal and stop air movement. You'll notice the stove perform better also since the contractor didn't address air moving inside the insulation. He only slowed it down.



    Look around the 2-3 minute marks. I'd ignore the tape, it doesn't have to be pretty.

    Matt
  11. WriteNoob

    WriteNoob Member

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    Just curious. Is that vermiculite that they used? It seems awfully fine grade, for such an application. Granted I'm miles from being any kind of expert, but I'd think that a grade that fine might also filter through any gaps or cracks in the attic area of the chimney, itself? Not trying to worry anyone. Just wondering if that's the standard for the application.
  12. EatenByLimestone

    EatenByLimestone Minister of Fire

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    I was worried about vermiculite and asbestos also, but it doesn't look like any of the vermiculite I've seen. Maybe it's perlite?
  13. begreen

    begreen Mooderator Staff Member

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    When installing the block off plate seal the folded down edges to the brick with a bead of silicone.
  14. gwmiller

    gwmiller Member

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    the insulation is called chim-mix, i believe it is vermiculite and mortar based. i was left with the impression that, once installed, it would become rigid (like concrete).
    apparently that is not the case.
    im going to try and fabricate some kind of block off plate and probably just stuff rockwool in the gap that remains. thanks for all the advice!
  15. branchburner

    branchburner Minister of Fire

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    I wonder if he mixed it wrong, and that's why it's crumbling - seems it should have set up and provided the airtight seal that a blockoff plate also provides.
  16. gwmiller

    gwmiller Member

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    In case anyone is interested, I ended up stuffing the entire space with mineral wool and then I installed a block off plate made from some sheet metal from home depot.
    I fastened it to the metal header on the front…. luckily there were two holes already drilled in the steel header on the ends. I did not remove the stove during the install so I was unable to drill holes in the header over the stove as I could not get the drill in the space. I got a few rare earth super magnets instead to hold up the front end.
    I did end up fastening the back end using tapcon screws.
    There was still a gap surrounding the opening int the block off plate, so I wrapped the bottom of the flue (between the stove and block off plate) with mineral wool and then used some sheet metal and a large duct clamp to hold it together.
    For the areas on the back of the fireplace cavity where the bricks had been removed, I just cut out mineral wool blocks to fit in the gap.
    Now I'm just waiting for cooler temps to roll in to see what kind of difference this set up will make…
    some 'after' pics are attached:
    IMG_1627.JPG IMG_1622.JPG
  17. EatenByLimestone

    EatenByLimestone Minister of Fire

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    I'm sure you'll notice a difference. You did a good job!
  18. bag of hammers

    bag of hammers Minister of Fire

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    Fiberglass stuffed against the liner? Is this something another (better) contractor would do? I suppose roxul or similar may be a bit harder to come by in some places, but I'd expect a contractor to have the best parts for the job.

    I don't know much about inserts or block off plates but just from the visual it looks like you took your time and did a really nice clean job. I 2nd the idea of not doing any more work with the original contractor.

    fwiw - a small right angle drill (or adapter) is a nice addition to the toolbox for tight spot situations such as this :). I've run mine (cheap box store unit) until I almost blew it apart, it saved my a$$ a couple times.
  19. EatenByLimestone

    EatenByLimestone Minister of Fire

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    Mineral wool isn't fiberglass. It's made from spinning molten rock. I think the base material is the slag from making steel, but I could be wrong on that.

    Matt
  20. bag of hammers

    bag of hammers Minister of Fire

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    I've used a lot of Roxul, gw used it to fix the problem which is good, I'm just a bit curious (worried) about the fact that the OP's contractor stuffed fiberglass up around the liner When he did his work - is this safe?
  21. EatenByLimestone

    EatenByLimestone Minister of Fire

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  22. weatherguy

    weatherguy Minister of Fire

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    Looks good gw, good idea with the magnets, wish I would have thought of that when I did mine.
  23. gwmiller

    gwmiller Member

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    when i initially had my stove installed, my liner was wrapped with insulation (i think it was foil faced ceramic fiber) with a stainless mesh. the wrap ends about a foot or two above the top of the stove (you can kind of see it in the original pics).
    i was a little concerned about the fiberglass, so as a precaution i removed any fiberglass that was in contact with the exposed metal flue and then stuffed the remaining empty cavity with mineral wool.
    just for my own amusement, i cut a 6" square of mineral wool and put it in my stove once it got up to a nice temp. after 10 minutes, it looked exactly the same as when i put it in.
  24. bag of hammers

    bag of hammers Minister of Fire

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    Sounds like you got everything buttoned down. Yeah I was soldering some copper pipe outside once and I took the torch to a roxul scrap - didn't phase it at all.

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