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  1. #1

    Attic ventilation for a gambrel roof?

    Our home was built in 1960. We moved in 4 years ago with a relatively new roof. We have since had issues with ice dams and mold in our attic. We've had several roofers come to inspect and advise. It is our understanding that we have several issues:

    1. Not a true ridge vent
    2. No soffit vents
    3. poorly flashed valley where the addition meets the main house

    We do have two gable vents.

    The plan is to put in a new ridge vent, add soffit vents and install a power vent with therm/humidstat. The mold will be removed and we are replacing all of the insulation.

    Questions:
    1. Is this adequate or too much/too little?
    2. What size power vent would be recommended for 800 sq ft.?
    3. Any other considerations?

    Thanks for the comments!

  2. #2
    Join Date
    Jul 2006
    Location
    Virginia
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    4,665
    i would consider foaming the attic then you dont need the ventilation.or the insulation

  3. #3
    Join Date
    Jun 2010
    Location
    Philadelphia PA
    Posts
    2,190

    That style roof

    is used to make the "attic" a potentially habitable space. Are your ceiling joist strong enough to support a real attic use? If so then call a real insulation contractor because foam, although at first blush a really good thought, may stop you from using the attic in the future as habitable unless you cover so as to reduce fire hazard. And if you are going to cover and use then conventional fiber glass may be the answer.
    Don't have the answer, just another question
    You have got to learn from other people's mistakes! Because God knows you don't live long enough to make them all yourself !!!!!!!!

  4. #4
    Join Date
    Sep 2009
    Location
    Arnold mo
    Posts
    3,967
    Find someone that is BPI or RESNET certified and has experience to come out and perform an energy audit of your home. The ice dams are likely forming due to air leakage from your conditioned areas that is blowing right through your insulation and is warming your roof up in that area, but it then re-freezes as it gets out to the eaves. Without proper training in Building Science, as are BPI & RESNET certified people, even experienced insulators will likely not know how to remedy problems such as yours.
    An answer without a question is meaningless.
    Information without understanding is useless.
    You can lead a horse to water............
    http://www.mohomeenergyaudits.com

  5. #5
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,290
    Most "ridge vents" are junk, good luck finding a "true ridge vent" that actually works.

  6. #6
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    +1 on spray foam. No need tobastadize the soffits and roof and punch more holes in it and burn electricity trying to vent it. As for a habitable space. There are coatings that can be applied later if needed.

    You will need to still fix the flashing of course.

  7. #7
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,188
    gable vents
    ridge vents with soffit vents
    and pav's..

    that is every method of venting an attic
    with the exception of passive vent (whirlybird)

    doesn't sound like anyone is solving the problems
    but instead throwing every ventilation strategy known
    into your home.
    I'd get better opinions for your home.

    best of luck..
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  8. #8
    Join Date
    Jul 2008
    Location
    Rochester NY
    Posts
    4,729
    Quote Originally Posted by catmanacman View Post
    i would consider foaming the attic then you dont need the ventilation.or the insulation
    +2. Very least air seal attic penetrations.

    On the moisture, jumping to treatments without diagnosing cause? Where is the moisture coming from? Where is the heat coming from?

    Moisture doesn't magically appear on your roof deck, it gets delivered there. Likely your fart fans dump shower steam into your attic, along with other plumbing and wire penetrations delivering humidified air from your furnace. Mold more predominant in attic adjacent to bathrooms?

    Its this heat which causes ice problems. Gable vents allow free exit path for air to leave after delivering heat and moisture to your roof, allowing a continuous supply of fresh heat and moisture.

    Cure your problems once and for all and see your energy bills go down or treat by removing heat in winter and see them go up.

    If you add venting don't be surprised if the ice doesn't resolve itself, as more venting may mean more area for heated air to exfiltrate up and out of your house. Oh, and if you have comfort issues, expect more venting to make them worse.
    Which makes more sense to you?
    CONSERVATION - turning your thermostat back and being uncomfortable. Maybe saving 5-10%
    ENERGY EFFICIENCY - leaving your thermostat where everyone is comfortable. Saving 30-70%

    DO THE NUMBERS! Step on a HOMESCALE.
    What is comfort? Well, it AIN'T just TEMPERATURE!

    Energy Obese? An audit is the next step - go to BPI.org, or RESNET, and find an auditor near you.

  9. #9
    Join Date
    Sep 2009
    Location
    Arnold mo
    Posts
    3,967

    Preventing wet attics video

    This is a link to a great video on how to prevent wet attics. http://ecw.mediasite.com/mediasite/S...75f089096f9b1d
    An answer without a question is meaningless.
    Information without understanding is useless.
    You can lead a horse to water............
    http://www.mohomeenergyaudits.com

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