1. Welcome Hearth.com Guests and Visitors - Please enjoy our forums!
    Hearth.com GOLD Sponsors who help bring the site content to you:
    Hearthstone Soapstone and Cast-Iron stoves( Wood, Gas or Pellet Stoves and Inserts)
    Caluwe - Passion for Fire and Water ( Pellet and Wood Hydronic and Space Heating)

Is insulation needed on my flex liner?

Post in 'The Pellet Mill - Pellet and Multifuel Stoves' started by Rowdysdad, Aug 13, 2013.

  1. Rowdysdad

    Rowdysdad New Member

    Joined:
    Mar 18, 2013
    Messages:
    95
    Loc:
    The beautiful Ozarks. SW Missouri
    I've decided to use a 4" x 20' Flex King Pro liner in my centrally located masonry flue.

    The Mt. Vernon manual shows insulation only in the damper area, not on the flex liner itself.

    The Flex king Pro brochure suggests using an insulation kit with the liner.

    Is insulating below the chimney cap and using a block off plate and insulation in the damper area sufficient?

    Is the insulation really necessary on the liner?

    Suggestions please for the best setup.

    Thanks in advance for any advise/comments. All are appreciated.

    Helpful Sponsor Ads!





  2. smwilliamson

    smwilliamson Minister of Fire

    Joined:
    Dec 28, 2009
    Messages:
    3,890
    Loc:
    Southcoast, MA
    i say no its not needed, others disagree
  3. Rowdysdad

    Rowdysdad New Member

    Joined:
    Mar 18, 2013
    Messages:
    95
    Loc:
    The beautiful Ozarks. SW Missouri
    Could you explain your reasoning for it not being needed?

    I'm sure others may disagree but I would also like their opinions of why it should be insulated. I'm not trying to stir the pot, There is a lot of knowledge and experience on this forum and I'm just trying to get educated.

    Again, thanks for taking the time to reply.
  4. smwilliamson

    smwilliamson Minister of Fire

    Joined:
    Dec 28, 2009
    Messages:
    3,890
    Loc:
    Southcoast, MA
    Pellet stoves with induced draft don't need insulation to keep the vent hot For them to draft. Pellet stoves hove very low emissions while running so there is nothing to condense in a cool liner.
  5. Don2222

    Don2222 Minister of Fire

    Joined:
    Feb 1, 2010
    Messages:
    6,968
    Loc:
    Salem NH
    The Mt. Vernon manual shows insulation only in the damper area, not on the flex liner itself.
    To keep the room air that was just heated from wafting up the chimney, I highly recommend Roxul fireproof insulation on the damper shelf and around the liner

    The Flex king Pro brochure suggests using an insulation kit with the liner.
    Chimney manufacturers are really pushing insulation as another item to sell.

    Is insulating below the chimney cap and using a block off plate and insulation in the damper area sufficient?
    Insulation in the damper area in a center chimney is sufficient.
    Block off plates were designed for wood stove pipes that connected the wood stove to the chimney. This is an old method.
    Nowadays liners go all the way up to the top of the chimney and are sealed at the top. This makes blocking plates not necessary unless stated in the appliance manual or by the town inspector. The inspector should go by the manual but you can always check with him to make sure.

    Is the insulation really necessary on the liner?
    I would suggest insulation around the liner on outside chimneys and uninsulated chases up the sides of the house. In this case the cold temps can cool the warm gases in the liner and cause the liner to plug up sooner and may create more frequent cleaning.
    Inside center chimneys that are warm really do not have this issue.

    Suggestions please for the best setup.

    Thanks in advance for any advise/comments. All are appreciated.

    Just my 2 cents
  6. Rowdysdad

    Rowdysdad New Member

    Joined:
    Mar 18, 2013
    Messages:
    95
    Loc:
    The beautiful Ozarks. SW Missouri
    Don2222,

    Thanks for the reply.

    So, Roxul in the damper area only. Would Lowes or Home Depot have Roxul ?

    I plan on using a tera- cota collinear cap uptop for the 4" flex vent and the 3" oak termination.
  7. Don2222

    Don2222 Minister of Fire

    Joined:
    Feb 1, 2010
    Messages:
    6,968
    Loc:
    Salem NH

    Our Home Depot started to carry the Roxul. Some lumber yards carry it too.

    That is what we use. We run a 4" SS liner for the exhaust and 3" liner for the fresh air.
    Then the Roxul for the insulation on the damper shelf and you have a top notch fireplace install.
  8. Rowdysdad

    Rowdysdad New Member

    Joined:
    Mar 18, 2013
    Messages:
    95
    Loc:
    The beautiful Ozarks. SW Missouri
    Alrighty. Thanks!
  9. Rowdysdad

    Rowdysdad New Member

    Joined:
    Mar 18, 2013
    Messages:
    95
    Loc:
    The beautiful Ozarks. SW Missouri
    Anyone else have anything to ad?
  10. smoke show

    smoke show Guest

    good luck!
  11. Rowdysdad

    Rowdysdad New Member

    Joined:
    Mar 18, 2013
    Messages:
    95
    Loc:
    The beautiful Ozarks. SW Missouri
    Thanks Smoke show.

    Believe me when I say that I need all luck, help, advise and comments I can get when it comes to setting up my AE correctly.
  12. chazcarr

    chazcarr Feeling the Heat

    Joined:
    Jan 22, 2012
    Messages:
    315
    Loc:
    Wolcott, CT
    Take pics please, I am doing the same project right now
  13. iron stove

    iron stove Feeling the Heat

    Joined:
    Sep 14, 2009
    Messages:
    478
    Loc:
    Central CT
    Yes, would love to see how liner install goes. Might be doing one in the future here too.
  14. The Maine Stove Guy

    The Maine Stove Guy New Member

    Joined:
    Jul 31, 2013
    Messages:
    41
    Loc:
    Bangor, Maine
    Great Answer! For what it's worth Rowdy, we have tons (no pellet pun intended) of different units installed in our area using un-insulated liners with no problems. It's not an outside exposed chimney, I doubt you will have any problems. Good Luck!!
  15. john193

    john193 Minister of Fire

    Joined:
    Jan 11, 2010
    Messages:
    911
    Loc:
    Southeast PA
    According to code, at least here in PA, you dont need an insulated liner/pipe when going through an existing chimney. Insulating the chimney cap and damper would be sufficient enough to block the cold air from coming down or the hot air escaping out.

    I use a 3 by 17 ft liner on my Mt. Vernon insert and this year I blocked off the damper area with unfaced fiberglass insulation. People have varying opinions on this method, so dont take my post as an endorsement, but just an FYI.

    As a side note, my SS flex liner is single wall uninsulated (i believe 6mm thick) and the hottest I've measured it right at the stove connection was 260F.

    There area few threads about the topic on hearth.com if you want to further read up about it.

    http://www.hearth.com/talk/threads/when-is-it-ok-to-not-insulate-liner-block-off.84047/

Share This Page