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  1. #1
    John Bernard's Avatar
    John Bernard Guest

    Default Fireplace combustion air from attic?

    I ran across this configuration for a gas fireplace combustion air vent that's terminating in the attic. Is this OK or does this vent have to terminate outside?

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  2. #2
    Ted Menelly's Avatar
    Ted Menelly Guest

    Default Re: Fireplace combustion air from attic?

    Combustion Air Sources

    Combustion air may be available for the woodburning appliance with no intervention or action may have to be taken to ensure adequate combustion air. We look at the different means by which combustion air is available.
    Passive Methods
    Passive combustion air delivery refers to non-mechanical means (no fan). There are two basic means of passive delivery of combustion air:
    1. All fireplaces rely to some extent on combustion air being drawn from the room and being replaced by infiltration through gaps in the building envelope. This is the sole source of combustion air if there is no outside air kit or powered air supply.
    2. Most factory-built fireplaces are designed with the capability of utilizing an outside air kit to provide air from outside directly to the firebox. The kits consist of ducting, connectors, and termination materials. The duct is connected to a removable plate, or knockout, on the firebox and extends to an approved source of combustion air (see above). There are also aftermarket outside air kits and methods for passive outside air.
    Research indicates that passive air supply methods may not always be effective since they depend on air pressure conditions inside and outside the house. In some situations, such as high wind, pressure may be lower at the weatherhood outside the house. Flow reversal of air and possibly combustion by-products and heat into the air inlet duct may occur in such conditions.
    Nonetheless, outside air kits may be required in some jurisdictions. Some recommendations that apply to the installation of outside air for combustion assemblies are:
    1. The entry point for the air should be located where it will be unlikely to be blocked by snow, leaves and other debris. (Manufacturers' instructions typically specify at least 12 inches above the ground.)
    2. The combustion air should never be taken from any area such as a garage, where combustible liquids or gases may be stored, used or could leak from tanks or other containers.
    3. The entry point for the air should never be located in an attic or located at a position above (higher than) the flue gas outlet.
    4. The length of the connecting air duct should be as as short and as straight as possible to avoid restriction to the flow of air.
    5. Duct materials should be in conformance with the manufacturer's instructions. The use of combustible material could be hazardous.
    6. Follow the manufacturer's requirements with respect to height and location of the air inlet.
    7. Always follow manufacturer's instructions when installing outside air components.
    Mechanical Methods of Combustion Air Delivery

  3. #3
    Join Date
    Feb 2008
    Chicago IL

    Default Re: Fireplace combustion air from attic?

    Cut and paste Ted's comment into your report.
    Beyond that my first line in the report would be, Unit NOT installed per manufacturer specifications, warranty, blah, blah
    Then I'd write it up as a potential catastrophic fire hazard (depending on how the configuration/connection is at the fireplace unit). Little fire in the fireplace becomes big fire engulfing the attic and roof structure as the flames race up the foil tube seeking oxygen.
    Don't downplay this one at all.
    "The Code is not a ceiling to reach but a floor to work up from"

  4. #4
    Join Date
    Jul 2008
    Snowbird (this means I'm retired and migrate between locations), FL/MI

    Default Re: Fireplace combustion air from attic?

    Quote Originally Posted by John Bernard View Post
    I ran across this configuration for a gas fireplace combustion air vent that's terminating in the attic. Is this OK or does this vent have to terminate outside?

    Okay, I have some concerns that haven't been discussed, so I'm going to point them out.

    You indicated a gas fireplace, but did not specify a factory built, a gas log kit in a masonry or converted solid fuel (such as wood burner), or a gas lighter.

    I see what appears to be a factory chimney or b-vent, rather large - without guard or firestop visible in attic - with pink apparently spun fiberglass insulation UP AGAINST it. It is difficult to determine if shadow and/or distance but appears to be wood (vertical orientation) up against (right) or within 1" of the factory chimney or vent.

    These are serious problems!

    I also see what appears to be foiled mylar DUCT folded upon itself in a conveluted fashion with a PLASTIC dryer or bathroom fan DUCT HOOD laying in the attic AGAINST the b-vent. The pictured duct is "combustible" and should not be exposed, let alone within 1" proximity of even a b-vent and this concentric foil duct is NOT a LISTED VENT. Even if the supposed "gas fireplace" is a sealed one/direct vent the pictured is not a listed vent for even combustion air. This is a problem!

    I see no screening or protection from drawing the pictured loose insulation INTO the supposed fresh air/make-up air/combustion air "duct".

    Factory chimneys and b-vents are SYSTEMS. They must be used and installed via manufacturer's instructions and in concert with the Standards applicable to their LISTINGS.

    You must begin with accurate descriptions of what you actually have "fireplace", "insert", "gas log set" or "lighter", check the data plates and manufacturer's instructions, and work from there.

    NFPA 54 (National Fuel Gas Code, or its ANSI Standard number) are often refered to by manufacturers of gas burning appliances and systems for same) as well as NFPA 211 regarding fireplaces, chimneys, etc.

    With such evidenced concerns, it would be reasonable to defer/refer a professional to inspect and review the entire set up as well as remediate. This includes a visualization of the entirety of the factory chimney/vent as it may have seriously deteriorated where encased in insulation. Without further information, it might also be warranted to alert the occupants/owners of a serious DANGER (injury, death, and/or fire) and/or to tag out, and possibly alert the NG utility as well as the local fire officials, its difficult to say, with the spoty info having been presented.


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