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For those that have used perlite insulation.........

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by backemin, Jan 1, 2012.

  1. backemin

    backemin New Member

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    If you have used perlite insulation around your liner inside a masonry chimney.....what do you think? Are there any negatives/difficulties with it? What size granules did you use? How is it holding up over time? Where did you purchase it? I'm seriously considering it due to some tight liner clearances that all but prevent wrapping the liner.

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  2. Reaganomics

    Reaganomics Member

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    I used it for an installation last year and it seems to work fine.
    I only think the option that you will find is smaller granules it should not matter.
    Large bags were about 35-40 bux per.
  3. Prosecond

    Prosecond Member

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    I used vermiculite mixed 6 to 1 with portland cement. I used 10 bags@4 cubic feet and they were $13 bag. Bought it from a large masonry supplier. Only problem was it took a lot of trips up the ladder. It was heavy when mixed.
  4. Reaganomics

    Reaganomics Member

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    You are a better man than I.

    For my application about a short 20 ft flex into an older square chimney hole.
    We poured quite a bit down the hatch w/o Portland however after we filed the hole we poured some wet mix down the hole.

    I ran a last season with an older Lange no issues and just upgraded to the Summit Classic and that stove puts out a ton of heat.

    No issues whatsoever..in the future the removal wll be a groan but hopefully that wont be you doing the job.

    Cheers
  5. branchburner

    branchburner Minister of Fire

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    Check out other perlite threads regarding the issue of complying with approved insulation methods (loose perlite is not listed as an approved insulation by most liner manufacturers).

    Another issue is loose perlite sifting down from the liner - best to rely on more than just a block-off plate to prevent this. Either a perlite-cement plug, or a rock-wool plug, that loose perlite can not sift down through.

    Bags of the stuff are very inexpensive at masonry supply stores.
  6. Mr A

    Mr A Minister of Fire

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    I just tried looking into "approved" insulation methods. All I found was a statement of recommendation, and that insulation is not required. I have been looking into this myself last few days. Perlite is a good insulator, R-2.7 per inch, and certainly better than nothing. It is non combustible, and a lot less expensive than the bags they want to sell you for $80 that is the exact same thing. It seems to me that all they have done is take theirs down to UL and got a stamp of approval.
  7. branchburner

    branchburner Minister of Fire

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    I think this is about right. But I believe some liner manufacturers state there must be air space between the liner/insulation and the masonry. I think it is more of a technicality than a safety issue, but just something to be aware of if you (or your inspector, insurance co,. etc.) are a stickler for such things.

    Personally, I can't see what could be cheaper or easier than loose perlite. But I don't make the rules.
  8. pgmr

    pgmr Feeling the Heat

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    When used as a loose fill, it can settle over time. I assume the heating and cooling causes some movement in the liner. Save a half bag and check it after the first full season or so.
  9. Gark

    Gark Minister of Fire

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    +1 on the finer particles sifting & leaking down through the smallest crevices on the bottom of the stack. Had I known this when we used perlite, first pouring down a 'plug' of perlite/portland (a couple feet tall at least) would have stopped the leaking. We had to remove the perlite (big mess) because of leaks. It insulated the pipe great while it was in there.
  10. Realstone

    Realstone Lord of Fire

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    Don't you lose R value if the insulation medium settles?
  11. pgmr

    pgmr Feeling the Heat

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    Probably a bit. But the expanded pieces of perlite themselves are full of gas bubbles. You'd likely lose a lot more heat through the top of the pipe that's uncovered due to settling than the amount that gets through the perlite.
  12. Mr A

    Mr A Minister of Fire

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    I have been talking with a Mason. I think your statement refers to original masonry chimneys, not to adding in a stainless stell liner. RE:Masonry chimney with terra cotta lining-
    I am told there must be a space between the terra cotta liner and the outside masonry. The two materials have different expansion/contraction rates. I haven't heard back yet, but I assume in this type of chimney, if it is still in good shape, it has the space, otherwise it would have already crumbled down.
  13. branchburner

    branchburner Minister of Fire

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    I think the idea is that air space provides a thermal break, even with an insulated ss liner. The other concern, of course, is settling or other uneven contact between the liner and the insulating material. I have loose perlite around my liner, but for what it's worth, from p. 21-22:

    "Just as with clay flue lining, stainless steel liners
    require space between the liner and the
    surrounding masonry wall to limit temperatures
    on the chimney exterior. However, in order to
    pass the stringent limitations of UL 1777, most
    stainless systems must use some form of solid
    high-temperature insulating material rather than
    an air space. When they were first introduced,
    many stainless liners were insulated with a loose
    fill of vermiculite or similar material. This is no
    longer allowed because of concern for settling and
    sifting of the material into the flue. Listed
    stainless liners must provide a specified amount of
    space around the liner to allow the proper
    thickness of insulation."

    http://www.csia.org/Portals/0/CSIA_ChimneyFires_Causes_Effects_&_Evaluation.pdf
  14. Mr A

    Mr A Minister of Fire

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    That is good information. UL 1777 refers to the zero clearance standard, . I am strictly referring to insulating SS liner through existing masonry chimney, and attempting to save some $$. The statement "However, in order to pass the stringent limitations of UL 1777, most stainless systems must use some form of solid high-temperature insulating material rather than an air space." says to me, using a perlite/cement mixture complies with the standard.
    Have you checked your perlite filled chimney for settlement?
    I read somewhere perlite is 6% better insulator than vermiculite, and resists settling, as with vermiculite. I am forming my theory that vermiculite is used in the commercial mix because the granules are smaller than horticultural perlite, providing more insulating value by eliminating voids of insulating material throughout the mix. Vermiculite absorbs water, so the commercial mix is probably treated with something to avoid water retention. Perlite does not absorb water, but concrete grade perlite, (small sand size granules) seems hard to find. I found some but I will have to drive to the perlite processing plant 100 miles away to get it. In my correspondence with a Schundler Company representative, I received this response regarding using perlite in a lightweight insulating concrete mix to insulate ss liner-
    "Typical mix designs are 6 parts perlite to 1 part Portland cement. There is
    a concrete aggregate particle size but frankly, for this application, you
    can use any garden variety grades (super-coarse or a blend with fines)
    provided it is not treated with anything.
    Hope this helps.
    Good luck,
    Vikki @ Schundler"
  15. branchburner

    branchburner Minister of Fire

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    I have not - it's not really a concern for me.

    Have you checked all your local masonry supply stores? Even if they don't stock perlite, they may be able to order it.
  16. Realstone

    Realstone Lord of Fire

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    A number of years back, and for a number of years I was a self-employed mason in the chimney restoration business. I always left a space between the brick and the flue liner, silicone caulked the flue tile joints and place a weep vent in the brick to allow ventilation of the cavity I left between the clay flue liner and the brick. After having demolished several old chimneys that were filled solid between the brick and the flue and saw how damp the masonry was, I was convinced that this was the way to go. It is freeze-thaw cycles with damp masonry that causes the damage, IMO. Having read your post, I felt somewhat pleased to know that I was doing it right.
  17. laynes69

    laynes69 Minister of Fire

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    I wanted to use perilite, but ended up using vermiculite. I used I believe a grade 5 vermiculite or very coarse for most of the chimney. Towards the top I used fine for it was all I could get at that time. It's been almost 2 seasons and out of a 32' chimney, it's settled about a foot at the top. I have a stainless cap over the masonry and I can remove it. During the course of the burning season I have checked it and it's stayed dry. I wanted a course material so it wouldn't compact. I did debate the 6 to 1 mix, but after speaking to the maker of the liner and sweeps they didn't recommend a cement insulation. They explained the expansion was different for rigid liners over flex. If I had the space I would have used a blanket, but things were tight. Before the rigid liner and vermiculite the chimney would remain warm, it's now the same temp as the outside. There's little to no heat transfer to the bricks.

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