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Direct vent through wall or roof?

Debra_Ann | Posted in General Questions on

We are planning on installing a direct vent propane heater as a backup emergency heat source, and to provide toasty radiant heat in our living room on extra cold evenings. I’m trying to reduce roof penetrations, so I had planned to direct the exhaust pipe through the nearby exterior wall.

But I’m just now wondering if venting exhaust through the wall might send too much moisture up into the attic through the vented soffit above. Propane exhaust contains a lot of moisture, which is one reason why using unvented heaters inside a home can be a bad idea.

Our exhaust vent will be about 4-5 feet below the vented soffit. Does anyone know if that is far enough away to prevent the moisture from being sucked up into the attic?  I’ve seen a lot of photos of mold covering attic sheathing from humid bathroom exhaust air behind sucked into the soffits, and I’d like to prevent that in our own home.  I’m in climate zone 4A in Virginia.

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  1. etekberg | | #1

    A Bosch manual I have for an 80% water heater says 24 inch vertical clearance to ventilated soffit located above the terminal within a horizontal distance of 2 feet from the center line of the terminal.

    It has the code reference as "In accordance with the current ANSI Z223.1 / NFPA 54 National Fuel Gas Code"

    So I think you are good.

  2. Debra_Ann | | #2


  3. capecodhaus | | #3

    Were located in 4A Virginia also.

    I would think as long as you install the appliance following the manufacturers installation procedure, your all set for moisture concerns.. Most important Clearance to combustibles, proximity of doors/windows, roof overhangs etc..

    I removed an unvented propane heater from our living room, and installed a pellet stove in the basement instead, venting thru the daylight wall. It's only used for back up, powered by a small generator. In an ALL electric house i didn't want a propane bill. I also find pellet stoves easy to repair compared to a gas appliance.

  4. Expert Member
    Michael Maines | | #4

    Each gallon of propane burned releases a little less than one gallon of water. While that adds up indoors, for an intermittently used appliance, I wouldn't worry too much about moisture entering the attic as long as the roof is properly vented, and required clearances are met.

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