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Boiler Exhaust heat and moisture into attic

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jnbridges
jnbridges Member Posts: 1
edited January 22 in THE MAIN WALL
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Hi, my boiler vent was installed correctly and to code. The issue is the heat from the exhaust is running up the outside wall and back into my soffit vents, attic, creating moisture (see pics), frost etc. Can anyone give me my options for moving or extending the exhaust? UPDATE- I added the make and model of the boiler in the pics above.

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Comments

  • yellowdog
    yellowdog Member Posts: 286

    I'd like to see the install manual of the boiler to show that that is an approved way to terminate the exhaust. Is there a reason it cannot be re-piped to exhaust out the gable end?

    Ironman
  • hot_rod
    hot_rod Member Posts: 27,060

    It looks like it meets the required dimensions from windows, openings and the ground?

    Screenshot 2026-01-21 at 8.53.51 AM.png

    If you removed the 90 ell it would blow out a bit more, but wind may still push the exhaust vapors against the building. These concentric kits have exhaust straight out the end.

    Screenshot 2026-01-21 at 8.49.21 AM.png

    Besides fogged windows the siding will take a hit and fade over time.

    The very best way is through the roof.

    While you may not likes the looks it could run up the outside and ell out just under the soffit. The snorkle method

    \

    Screenshot 2026-01-21 at 8.54.51 AM.png
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Ironman
    Ironman Member Posts: 7,886

    What make and model boiler?

    If it’s 90%+, then the metal wall cap is not the proper termination.

    How about some pics of the boiler and the vent piping?

    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
    akaDigger
  • Ironman
    Ironman Member Posts: 7,886
    edited January 22

    Your flue gasses shouldn’t be cool enough to condense at the vent termination.

    What water temperature is the aquastat set to run the boiler?

    Was gas manifold pressure set to manufacturer’s specs with a manometer?

    The excessive zoning on that system may be causing short cycling which will lead to lower flue gas temperatures and condensation.

    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • kcopp
    kcopp Member Posts: 4,640

    That not a condensing boiler. Std 83% set up.

    the 90 downward is not helping matters at all.

    I would add a 6- 12" section w/ 45* on the end facing downward.

  • hot_rod
    hot_rod Member Posts: 27,060

    I think the manual shows the discharge with the thimble kit, without any fittings on the outside. But wind direction towards the house may still blow the exhaust against the siding

    IMG_1423.jpeg IMG_1424.jpeg
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream

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