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Chimney Questions

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by kmachn, May 25, 2012.

  1. kmachn

    kmachn Member

    Joined:
    Oct 27, 2010
    Messages:
    57
    Loc:
    St. Louis, MO
    I have two questions, both related to chimneys.

    1) We're hoping to install a Quadrafire 7100 fireplace before next heating season, and it is approved for both the air-cooled chimney pipe and the Class A pipe. Obviously, the Class A carries a MUCH heavier price tag but I am thinking that creosote buildup would be less likely since the air-cooled pipe would cool the exhaust fumes much more. Assuming good, seasoned wood and good burning practices, does anyone have experience (perhaps a chimney inspector) with creosote buildup in an air-cooled high-efficiency fireplace? Is this a realistic concern, or just a hypothetical/anecdotal worry?

    2) In a different maner, I have Class A chimney pipe on my EPA stove. I'm thinking about wrapping it with Roxul in the space through the attic. I realize it is not necessary to insulate the pipe, but to make a long story short I would like to keep the Roxul in the "clearance zone" to keep cellulose, etc. off the pipe. Just wondering if this would be a problem as far as too much insulation around the pipe. This would only be about the last 12-15 ft of the 23 ft of pipe, and only the space through the attic.

    Thanks in advance for the expertise

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  2. Wood Heat Stoves

    Wood Heat Stoves Minister of Fire

    Joined:
    Jun 12, 2009
    Messages:
    1,901
    Loc:
    Nevada City, California
    The warmer you can keep the inner chimney the less problem you'll have with creosote. I would opt for the Class A chimney for that reason on the Quadrafire. Anything it's listed for shouldn't be a saftey concern, though, as long as you burn dry, seasoned wood and sweep the chimney as needed.

    You do need to maintain a 2" clearance to Class A chimney and keep the attic insulation away from it. Most brands have attic insulation shields for that or you can enclose it in a wood chase with the proper clearance or use sheet metal around it. I don't see how wrapping it with a totally non combustible material would hurt but there are easier ways to accomplish keeping the insulation away.
  3. Greg D

    Greg D Member

    Joined:
    Nov 20, 2011
    Messages:
    14
    Loc:
    Eastern PA
    For what it is worth: I have the Quadrafire 7100fp connected to 28 feet of 8" air cooled stainless pipe inside of an exterior chimney chase that is insulated up to the roofline. When I did my own cleaning a few days ago, I found that the build up wasn't bad until the last few feet and inside the cap, and this was probably only becuase I burned wood that wasn't fully seasoned and only did one cleaning at the end of the season. A cleaning in the middle of the season and using drier wood will help me next winter. The 7100 is my favorite part of our house. quote="kmachn, post: 1125107, member: 15149"]I have two questions, both related to chimneys.

    1) We're hoping to install a Quadrafire 7100 fireplace before next heating season, and it is approved for both the air-cooled chimney pipe and the Class A pipe. Obviously, the Class A carries a MUCH heavier price tag but I am thinking that creosote buildup would be less likely since the air-cooled pipe would cool the exhaust fumes much more. Assuming good, seasoned wood and good burning practices, does anyone have experience (perhaps a chimney inspector) with creosote buildup in an air-cooled high-efficiency fireplace? Is this a realistic concern, or just a hypothetical/anecdotal worry?

    2) In a different maner, I have Class A chimney pipe on my EPA stove. I'm thinking about wrapping it with Roxul in the space through the attic. I realize it is not necessary to insulate the pipe, but to make a long story short I would like to keep the Roxul in the "clearance zone" to keep cellulose, etc. off the pipe. Just wondering if this would be a problem as far as too much insulation around the pipe. This would only be about the last 12-15 ft of the 23 ft of pipe, and only the space through the attic.

    Thanks in advance for the expertise[/quote]
  4. kmachn

    kmachn Member

    Joined:
    Oct 27, 2010
    Messages:
    57
    Loc:
    St. Louis, MO
    I feel like the Class A chimney would be the better investment, for the exact reason Wood Heat Stoves point out. I appreciate the input from Greg though because I really wondered about the actual performance of the air-cooled chimney pipe and his experience is exactly what I wanted to find out. I appreciate both views, I guess I will find out the exact cost difference and then decide if the additional cost for the Class A seems worth it.

    As for the chimney in the attic space, the attic shields they make don't quite go high enough for my particular application because the chimney pipe enters the attic at the bottom of a cathedral ceiling. Therefore, I am concerned about the insulation being above the attic shield...I'm just not comfortable with that. Building a chase is certainly the most logical option, but since the roof and ceiling are both angled and there is an offset/return, it would definitely take some real time and effort to plan, measure, cut and build the chase...all in the attic space. It's just not a straightforward situation, building a straight, vertical chase through the attic space. I thought if I could wrap it in Roxul and nothing was touching the insulation, then it would help me to "visualize" the clearance and just build around that. As long as no parts of my chase touched the Roxul, then I would be outside the safety clearances. It is true, there are probably easier ways of keeping the insulation away, but it sounds like this would at least be an option since it would not create any safety concerns related to over-insulation.

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