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how to secure insulation to flute?

Post in 'It's a Gas!' started by wantboost, Jun 8, 2013.

  1. wantboost

    wantboost New Member

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    i just installed a gas fireplace. i was wondering how can i secure fireproof insulation to the flute?

    thx

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  2. begreen

    begreen Mooderator Staff Member

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    Do you mean the flue? Normally this is not required with a gas flue.
  3. wantboost

    wantboost New Member

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    yes flue. i wanna insulate it just to keep draft down etc???
  4. DAKSY

    DAKSY Patriot Guard Staff Member

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    What did you install, where did you install it & how is it vented? You will have to provide pics or a more detailed description in order for us to help you...
  5. wantboost

    wantboost New Member

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    its installed into a existing wood burning fireplace. iinstalled a lennox mpd vented out the back. i wanna insulate the flue opening.,??
  6. coaly

    coaly Fisher Moderator Staff Member

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    This is a direct vented unit. The inner pipe is the exhaust, cooled by the incoming air between the inner and outer pipe. There is a 3 inch clearance to combustibles at the top of pipe, 1 inch sides and bottom. Insulation on the outside of the outer pipe would not keep the inner pipe hotter like in a conventional chimney or liner and have no beneficial effect.
    Keep in mind the reason for the horizontal run and vertical rise required is calculated to maintain the exhaust draft needed to allow heated gasses to exit the combustion chamber inside the inner pipe. (see table in instructions) This rising of combustion exhaust is what puts the sealed combustin chamber in a negative pressure area allowing atmospheric air pressure to push into the intake area between pipes, supplying oxygen to the burner. Keeping the intake air hotter due to insulating the exterior of the vent pipe would have little to no benefit. Matter of fact, the hotter intake air would be expanded having LESS oxygen molecules per square inch than colder denser air. This would cause the mixture to be richer. As for "chilling" the firebox, the incoming air is going to be preheated by the exhaust inner pipe by the time it gets to the appliance anyway.
  7. DAKSY

    DAKSY Patriot Guard Staff Member

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    So you put a gas burning fireplace into a wood burning unit? Is the wood burner masonry & site-built or or is a ZC factory-built unit? I suppose, either way, if you can get into the woodburning flue, you can just grab some unfaced fiberglass insulation & jam it up in there. Make sure it's tight enough to stay on its own, otherwise, you'll need plumber's strapping or wire to secure it. To do the job correctly, you should also insulate the top of the chimney & cap it off with an aluminum plate & silicone it in place...That'll keep critters & water out.
  8. wantboost

    wantboost New Member

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    fireproof insulation? should i insulate the bottom of the flue also?
  9. DAKSY

    DAKSY Patriot Guard Staff Member

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    Unfaced fiberglass top & bottom...
  10. wantboost

    wantboost New Member

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    whats unfaced fiberglass?
  11. DAKSY

    DAKSY Patriot Guard Staff Member

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    "Unfaced" fiberglass is insulation. You don't want "Faced" fiberglass in that situation. It has a paper backing., Paper is flammable.
  12. s!MON

    s!MON Guest

    i'm surprised! Surely only a qualified Gas installer should be installing a gas fire. :confused:

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