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  1. #1
    Join Date
    Jan 2009

    Default Excessive attic moisture

    We renovated my 1923 Bungalow home in 2004 by adding a new second floor. During the renovation we installed 2 zone air conditioning. On the second floor we have been experiencing condensation like dripping from the diffuser in our master bedroom closet. All diffusers/vents were closed for the winter. The dripping in the closet seems to correct itself by mid-December.

    This winter I found excessive moisture within the Air Handler in the attic. The moisture is found everywhere in the air handler Ė wiring and fan chambers. This winter season has been so bad that the water alarm for the drip pan under the air handler went off. I have also noticed drops of moisture on the roofing nails in the attic.

    Iíve done everything I can think of to fix the problem, including opening as many covers, plugs and drainage outlets in the air handler to get more ventilation in it. But iím worried because I now see mold growing on my 4 year old air handlerís fiberglass. I've also painstakenly covered each diffuser with window shrink wrap, to see if this is where moisture was originating.

    Our new roof has deep soffits. These soffits are 14 inches deep of free ventilation Ė my contractor used continuous perforated vinyl soffit material.

    Using the 1/150 formula I calculated how much ventilation I actually needed for an attic with 1050 square feet; I came up with 7 square feet (my home is 25 x 42). My ridge vent extends only 14 feet and is ventilated using GAF COBRA Ridge Vent. If Iíve calculated correctly, my roof has an unbalanced ventilation by a factor of 9 to 1, and is over ventilated.

    I'm wondering if balancing the Soffit ventilation area to match that of the Ridge (14í x 14.1 net free = 197.4 square feet), is the answer.

    I would appreciate some advice as to if I am understanding this problem correctly and what may be my alternatives. Additionally, I am concerned my air handler will need extensive cleaning to correct the mold problem. My 5 year old has asthma and this problem has given me great concern.
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