Condensation Coming from Vent
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  1. #1
    Join Date
    Feb 2004
    Posts
    9

    Hmm

    My father-in-law is complaining about a lot of condensation coming thru one of his a/c vents in the bedroom. Above the room (in the attic) is the furnace, so the duct is a short run. The furnace is about 18yrs. old but has been maintained & runs well. All of the vents are open in the house. From inside the attic, there appear to be no leaks around the duct or around the vent itself...why all the condensation suddenly? Do you think there is some kind of obstruction somewhere? Drain line problem?

    thanks,
    mark

  2. #2
    Join Date
    Nov 2001
    Posts
    1,874
    There must be a bare spot in the insulation around the duct work or boot in the attic.

    The cool air inside the duct, coming in contact with the warm moist air of the attic, will cause moisture to form.

    How is the attic vented ?
    If you try to fail, and succeed.
    Which have you done ?



  3. #3
    Join Date
    Feb 2004
    Posts
    9

    Hmm Condensation Coming From Vent

    The attic is vented primarily by a ridge vent & intermittent soffit vents....a power vent was eliminated when the roof was replaced. The advice on eliminating the power vent was because although it pulled the warm air out of the attic it was also pulling a/c through cracks/crevices which of course in turn would make the a/c come on...a vicious cycle I guess you could say.

    thanks for the info....I'm going over to his house to take a look at the vent/duct.

    mark

  4. #4
    Join Date
    Nov 2001
    Posts
    1,874

    Re: Condensation Coming From Vent

    Originally posted by lynmar
    it was also pulling a/c through cracks/crevices which of course in turn would make the a/c come on...a vicious cycle I guess you could say.

    thanks for the info....I'm going over to his house to take a look at the vent/duct.

    mark
    Attic fans aren't that powerfull, to produce a negative pressure in the house.
    I think someone was to lazy to mess with it.
    If you try to fail, and succeed.
    Which have you done ?



  5. #5
    Join Date
    Feb 2004
    Posts
    9

    CONDENSATION COMING FROM VENT

    Well, there's 50% out there that would disagree with you; as an ex-home inspector I'm of the 50% that says power vents are a waste of money - they do in fact pull enough to start the whole negative pressure aspect. Plus, the xtra electrical expense involved too. The attic originally had one power vent (located at the far end above master bdrm)plus the intermittent soffit vents...that in itself was not enough ventilation. This is a large house...when it came time to replace the roof, based on the ventilation formula, two power vents (one at each end)were advised as needed OR a complete ridge vent (but not both)....he chose a ridge vent instead....forget about those squirrel cage vents...what a ripoff! Once again, if the ventilation is properly sized/installed, etc...not including power vents there should be no problem....my house is a 3000 sq.ft. home...I have a ridge vent & continuous soffit vents...no problems.


  6. #6
    Join Date
    Nov 2001
    Posts
    1,874
    Do you have supply runs in your attic ?

    And No an attic fan cannot produce a vacum in a house.

    It pulls air in through the soffit, and or gable vents.
    How the hell can it pull through the cracks in a house.
    Theres far to much air available from free areas, to pull through closed areas, or cracks.

    Now, if you mean a whole house fan then sure, but an attic fan, no way.
    They are a step above fart fans.

    I've never met a whole house inspector that knew much about HVAC, You may be different, and if so thats fine.
    But as a whole, Those type inspectors are not trained to the extent I feel that they should be,
    Atleast the ones I've seen,

    I've condemed 3 furnaces that were given the ok by inspectors.
    They just don't know what they are looking for, or should be looking for during an inspection.
    Theres more to a furnace then dust on the burners.

    But this is about your in-laws cieling, and since he doesn't have an attic fan, then theres no point in discussing it.

    But the pipe has to be getting attic air somehow.

    If you try to fail, and succeed.
    Which have you done ?



  7. #7
    Join Date
    Nov 2004
    Posts
    2,927
    Originally posted by lynmar
    the duct is a short run. Do you think there is some kind of obstruction somewhere? Drain line problem?

    thanks,
    mark
    If it is a very short duct ,you might be getting water blow off the coil.That could be from clogged drain or just seasonal (humid) conditions.

    Put a shop vac on the end of drain line and try to suck out the obstruction.

    Try to find and stop any inflitration of outside air.
    Sometimes there are compounding complexities of multiple variables that are not intuitively obvious

  8. #8
    Join Date
    Feb 2004
    Posts
    9
    In defense of Home Inspectors, we are not licensed HVAC contractors...we inspect a home for clues for possible safety violations, damage, in need of repair, etc...you get the picture. It's like going to the doctor & getting a physical except that we do a house. If we suspect that the furnace has never been cleaned or there are no service records available, I'm going to write it up as needing a complete evaluation by a certified licensed HVAC. YOU make the call if it should be condemned....unless I see an incredible obvious un-working hunk of junk in front of me.

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