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  1. #1
    Join Date
    Jan 2011

    Default siding bowing- roof exhaust vent

    We have 2 areas on our siding that are bowing. Directly above these areas on the roof are exhaust vents. We have noticed they have ice at times and wonder if this is causing our problem. The vents go through the attic and we think they are fine but why is there ice forming outside? How is the warm air getting out to create this? Also why does it appear to be affecting the siding and the wood under it to bow outward?
    Need some help

  2. #2
    Join Date
    Aug 2007

    Default Re: siding bowing- roof exhaust vent

    Kinda hard to see from this far away, but my guess is the exhaust vents are allowing snow/ice to melt and this water is finding its way behind the siding and re-freezing via an ice dam forcing the siding away from the wall creating the bulge.

    I would first look in the unheated space that the vents pass through to see if they are leaking air before they get through the roof. Then I would look for water leaks around the roof penetrations for these vents to see if water is running along the roof sheathing to the wall and running down the outside wall refreezing. Then I would check to see if water is running down the fascia and getting caught in the soffit at the roof line and running back to the outside wall and dripping and re-freezing behind the siding.

    If you could post a pic or two of the area it may help diagnose it.

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