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New Chimney liner

cekseniorceksenior Member Posts: 44
Hello everyone, I'm once again in need of some information. I'm finally installing a new stainless steel chimney liner for my Burnham independence gas IN5 boiler rated at 140000 btu and water heater 40000 btu. The company installing says they would like to put in a 6" liner. This leaves no room for a wrap around insulation. They said since its being installed through the existing clay lining this will act as an insulator. I do not want to go through the vermiculite type insulation for many reasons, so I will not even consider this option.

So is insulation absolutely needed in this type of setup or will it be ok without? Or are they're any other alternatives of course other than vermiculite?



  • Paul PolletsPaul Pollets Member Posts: 3,017
    edited March 2013
    Chimney liners

    It's nice to insulate the liner, as it increases boiler efficiency. Gas boilers can use an aluminum liner, but the SS liner will have a significantly longer life expectancy. If the chimney is within the house, insulating the liner is somewhat moot. If the chimney is exposed on an outside wall, insulation makes sense. Vermiculite contains asbestos. I'd be using an asbestos-free product, if you're going to insulate.
  • Bob HarperBob Harper Member Posts: 732
    liner installation

    At a total input of 180 mbh, a 6" liner would need to be over 20ft. tall per code. You are required to de-rate corrugated liners 20% off the top plus an additional 20% if there is an offset. The liner can not be smaller in diameter than your appliance collar, which is 6".

    Insulation is not required for the listing for the liner but is recommended. However, you can seal the top and bottom of the liner and create a dead air space around the liner as long as the rest of the flue around it does not leak like a sieve.

    All vermiculite chimney insulation is not allowed to have asbestos above a certain trace level per the EPA and it would be contained inside the chimney so I see no hazard to the occupants. You can install a 1/4" thick ceramic fiber foil backed insulation that only requires about 3/4" extra space on all sides. If this is too tight, seal the gaps top and bottom and be done with it.

    A smooth wall flex liner can buy you some capacity if you're tight to the code sizing.

    What are the internal flue dimensions, do you have mortar protrusion at the joints or mis-aligned tiles and how tall is the flue?
  • cekseniorceksenior Member Posts: 44
    edited March 2013
    Thanks for replys

    I personally have not been on my roof to see inside of the chimney. I got 3 estimates for the liner each with different recommendations. The company I hired is using a smooth wall flex liner. I remember 1 company saying the square clay tile flue was 8". The chimmney is approx 30'. It is on an outside wall.  Mortar protrusion at the joints or mis-aligned tiles has not been mentioned.

    I do like the idea of using dead air space as an insulator. Im sure they are going to seal the top but Im unsure how they would seal the bottom.

    One of the main reasons Im doing the liner is I noticed moss growing on the motar joints of the middle to upper part of 1 side of the chimney. It always also looks damp. Im assuming that there is allot of moisture toward the top of the liner not burning off becuase of short boiler cycles.

    Having the hot water loop off the boiler means that it never runs long enough for the whole chimney to heat up.

    I am hoping this helps with the overall health of my chimney. 
  • SWEISWEI Member Posts: 7,356

    Makes an awesome flue insulator, if you happen to have an applicator in your area.
  • Bob HarperBob Harper Member Posts: 732
    Air Krete as liner insulation?

    SWEI, do you know if anyone has tested or listed Air Krete as a chimney liner insulation? The problem could be corrosion. If you could provide data to the AHJ that there is no corrosion problem between AK and the various alloys of stainless steel liners then I wouldn't have a problem with it. BTW, I have a friend who is big into lime mortar restorations and mixes his own blend of vermiculite or perlite and lime mortar. It is accepted by the AHJ and historical commissions as well as the Nat'l Park Service.

    FYI, AK fascinates me with a number of applications so anything you have on this product I'm all ears.
  • SWEISWEI Member Posts: 7,356
    edited March 2013

    Magnesium Oxychloride (sorel cement) is used in steel refractories.  It starts to break down around 7,000F IIRC.  Someone with more chemistry background than I have should be able to describe the bonds involved, but they must be pretty good.

    AL29-4C is highly resistant to chlorides, so even if water gets in there I doubt it would cause much trouble.

    Bottom of page 13 of seems to indicate some kind of explicit approval.  I haven't looked at local approvals since the closest applicator is five hours away and Air Krete wants a huge upfront buy-in to become one.
  • cekseniorceksenior Member Posts: 44
    For those of you

    Who haven't insulated your liner are you experiencing any adverse ramifications from not doing so? It seems that most companies in my area are not even offering this option when installing stainless steel liners.
  • icesailoricesailor Member Posts: 7,265
    Wet Brick & Moss:

    It can be really important to weather seal brick chimneys that leak. Use a Silicone Based dealer for sealing brick. Thompson's water seal works well.

    Three or more coats work best and it will last for a few years. You can put it in a pump up garden sprayer and spray it on on a windless day. You can use the wand to reach areas out of reach. Try to cover shingles below with a drop cloth as the Silicone will bother shingles. You can use a brush or roller. The first coat will suck in like water. Do it until it is wet. If the moss is like roof moss, there is a product called "Spray And Forget" that works well on it. You spray it on and it slowly kills the moss. The rain washes it away. It is slow acting and takes time. But it works. If white efference is showing on the chimney, it needs to be sealed.
  • Bob HarperBob Harper Member Posts: 732
    edited March 2013
    uninsulated liners?

    First of all, I consider all my liners insulated. When you pack them tightly top and bottom they are air insulated with a dead air space. I have gone back on many connected to many various types of appliances and I've never found a failed liner. Every liner I've done has been an improvement in flow and draft. Even if the liner ever failed, the brand I use carries a transferrable lifetime warranty. Note that such warranties do not cover labor though. When I reline a very large internal dimension in relation to the liner OD, I do wrap these with a 1/4" foil backed ceramic fiber blanket. FYI, most liners used for heaters are 316Ti alloy and NOT AL29-4c.
  • cekseniorceksenior Member Posts: 44
    Liner installed today

    All went well and I feel they did a good job but 1 thing I noticed was they joined 2 pieces of liner together.

    The larger of the 2 pieces was approx 20 feet and the second was about 10 feet. Of course while seeing this I mentioned it right away becuase without doubt i know 1 continuous piece has to be better, but of course was told its ok.

    Is this a common practice or did they just cheap out on me??
  • icesailoricesailor Member Posts: 7,265
    Liner Lengths:

    There's a length limit that determines how much pipe can go into a box.
  • Bob HarperBob Harper Member Posts: 732
    listed liner connector/ adapters

    Almost all liner mfrs. have a tested listed chimney liner splice/ connector/ adapter for this purpose. If they used one tested and listed by this mfr. in accordance with the mfrs. listed instructions then it is the same and any other section of the liner. If they cobbled a splice together have them pull the liner and use the listed component. Did you take pics? 
  • cekseniorceksenior Member Posts: 44
    I didnt take pictures.

    I did watch him do it though. He said the connector he used was stainless steel. He slipped the connector into the pipe and secured it with screws. Then slipped the joining piece over the other end and secured it with screws. When finished I could not tell where the one piece ended and the other began. They butt up seamlessly.


    In all honesty if I wasnt watching vigilantly, or if they did it before they came I most definately would not have been able to tell.

    Im sure most people dont watch workers as they perform their tasks. I can gurantee there are thousands of liners out there done this way.

    How would a homeowner know???
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