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  1. #1
    Mike Kramer's Avatar
    Mike Kramer Guest

    Default Attic insulation and water heater vent

    Hi all!
    Question for the experts: I have a gas water heater in the utility room that vents through the attic to the outside. There is a lot of blow in type insulation in the attic. Is it required to somehow keep the insulation away from the vent pipe? If so, how is this done effectively? Right now, it looks in my attic like the insulation is pulled away a little bit, but that of course is not a very sure way to keep a piece of insulation from ever touching that pipe.
    I will try to post a picture later. If anybody has a picture to illustrate a solution, that of course would also help a lot!

    Thanks for your help! What an awesome forum!

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  2. #2
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    Spring Hill (Nashville), TN
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    Default Re: Attic insulation and water heater vent

    Quote Originally Posted by Mike Kramer View Post
    Hi all!
    Question for the experts: I have a gas water heater in the utility room that vents through the attic to the outside. There is a lot of blow in type insulation in the attic. Is it required to somehow keep the insulation away from the vent pipe? If so, how is this done effectively? Right now, it looks in my attic like the insulation is pulled away a little bit, but that of course is not a very sure way to keep a piece of insulation from ever touching that pipe.
    I will try to post a picture later. If anybody has a picture to illustrate a solution, that of course would also help a lot!

    Thanks for your help! What an awesome forum!
    Yes, the insulation should not be in contact with the flue pipe. You want a 1" or more clearance between the flue pipe and anything else. The reason is that air needs to circulate around the pipe to keep it cool and if insulation is on it "hot" spots can develop which could cause a fire. The heat can actually be channeled to wood framing even though it is not near the flue pipe.

    Pulling the insulation away from the pipe usually works. Usually the insulation will stay in place once it is pulled back, unless it is disturbed.

    Scott Patterson, ACI
    Spring Hill, TN
    www.traceinspections.com

  3. #3
    Mike Kramer's Avatar
    Mike Kramer Guest

    Default Re: Attic insulation and water heater vent

    Thanks a lot, Scott!
    Now this is starting to make sense. From what you are saying, I conclude that the goal is not really keeping every piece of insulation from ever being in contact with the hot vent pipe, but to prevent heat build up that could ignite surrounding wood because of a lot of insulation around the pipe.
    Thanks,
    Mike.


  4. #4
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    Default Re: Attic insulation and water heater vent

    Depends on the venting material and type of appliance.

    Not just for the reasons you state.

    Hot spots and/or cold spots/rings on the material for example, development of condensation spots, prime and draft interference, deterioration of the venting material, and maintaining spacing from all combustibles for gravity/natural drafters is essential, etc.

    Maintaining separations and protection of the floor/ceiling and roof assemblies, manufacturer's specifications and instructions (vent, water heater, etc.) much more to be considered then just what you indicate.

    Insulation dams and maintaining spacing, support, stopping, blocking, breaking are SOP for s/w and b-vent. The required spacing/clearances and metal supports and stops also act as thermal isolation and sinks, insulation contact interferes.


  5. #5
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    Default Re: Attic insulation and water heater vent

    One of the easiest ways to ensure insulation kept back is to install a dam a few inches taller than the highest anticipated level of insulation. For a vent pipe, just a single wall sheet metal pipe (duct) a few inches larger in diameter than the pipe being protected is easy to install since it has a seam down the length of the pipe. Slip it around the pipe and if you really want to be sure it stays in place, cut a few dove tail slots in the end(s) of the pipe and bend the tabs 90 inward to form a spacer to the protected pipe.

    Jim Luttrall
    www.MrInspector.net
    Plano, Texas

  6. #6
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    Default Re: Attic insulation and water heater vent

    Oops, realize might not have been clear skipping modifiers for a unknown newbie poster: make that "breaking" as in thermal a break/space isolation; stopping and blocking as in draft and fire for the floor/ceiling assembly of the attic and the roofing assembly, "sink" as in heat sink/ability to throw heat off.

    Depends a LOT on what kind of venting material we're talking about for what TYPE of gas-fired water heating appliance we're talking about, i.e. PVC, SS, s/w, b-vent, etc.; storage type, tankless, category type, etc. Don't assume "gas" means natural gas vs. propane, etc.

    For all we know you have a DV tankless with concentric vent in a utility room directly below a short height attic area with a low slope roof.

    Welcome to the forum, please fill out your profile.

    Last edited by H.G. Watson, Sr.; 11-14-2010 at 10:33 AM.

  7. #7
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    Default Re: Attic insulation and water heater vent

    We just build a drywall box around the pipe. 1' foot high, 1' square. Fast, easy, keeps the insulation away from the pipe, gives it plenty of room.

    www.aic-chicago.com
    773/844-4AIC
    "The Code is not a ceiling to reach but a floor to work up from"

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