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  1. #1
    Join Date
    Nov 2009
    Northern Illinois

    Default Condensation / Furnace roof vent

    Hello all - been lurking around here for years, my first post!

    Anyway....I'm 2 years into my first home, so I'm still learning!

    We had a new furnace installed when we purchased, and I've been noticing some drip marks on the ceiling where the furnace (and fireplace) vents head up to exit the attic to their individual roof caps....which are both original to the house.

    In cooler weather, when the heat kicks on.....condensation forming and is running down the exterior of the duct into the attic, and also running all the way down the duct into the basement to the floor next to the furnace. Apparently there are two 'ducts' with the furnace inside the other. This is apparent at the roof cap, where the storm collar is around.

    I called my HVAC contractor, and he stated that a 6" duct is being used at the roof vent, and suggests a 4" "insert" being installed all the way from the roof cap to the furnace.....quoted me over $1,500! I'm out of work like the rest of America, so this is NOT in the cards!

    I have a 'hunch' that simply replacing the vent cap out on the roof may solve the problem.
    Any tips on looking at replacing this myself?
    Any other thoughts?

    Sorry for the long post!!!


  2. #2
    Join Date
    Jun 2007
    Fayette County, Ohio

    Default Re: Condensation / Furnace roof vent

    A newer furnace you probably do need a 4" chimney liner. You can buy and install yourself for a lot less money. To large a flue and the gasses condense rather than being expelled properly.

    Be sure you live your life, because you are a long time dead.-Scottish Proverb

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