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    QBenji's Avatar
    QBenji Posts: 5, Reputation: 1
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    #1

    Jun 1, 2010, 12:45 PM
    Moisture in a vaulted ceiling
    I have insulated my valuted ceiling by spraying 1.5" of 2lb. Sprayfoam on the inside of the roof and then filled between the rafters with R-20 fiberglass bats and covered it with 6 mil poly then drywall. This was done per an inspectors request. BUT I have a huge moisture issue!!
    On the shaded side of the roof water beads up on the top and bottom of the fiberglass and on the foam. From what I have seen on TV I don't think I should use a poly vapor barrier on the inside because the roof is sealed with sprayfoam.
    I hope the cure is to remove the plastic!!
    Your input would be greatly appreciated.
    ballengerb1's Avatar
    ballengerb1 Posts: 27,379, Reputation: 2280
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    #2

    Jun 1, 2010, 06:52 PM

    What is causing the high humidity in your room? You need to insure good air circulation. I am a bit confused, if your drywalled over everything how can you see the fiber glass?
    KBC's Avatar
    KBC Posts: 2,550, Reputation: 487
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    #3

    Jun 1, 2010, 07:31 PM
    The finish taping isn't done then?That's why you can see this moisture?

    What do you have for venting the roof line?I understand the need for insulation,there are products for roof tops on vaulted rooms which eliminates the need for much interior insulation.

    If the roof isn't breathing,the interior air, being cooler,verses the outside air,being much hotter, will cause condensation, especially if the roof can't let the heat out.same goes for the opposite, hot inside and cold outside.
    QBenji's Avatar
    QBenji Posts: 5, Reputation: 1
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    #4

    Jun 1, 2010, 08:12 PM
    Quote Originally Posted by ballengerb1 View Post
    What is causing the high humidity in your room?? You need to insure good air circulation. I am a bit confused, if your drywalled over everything how can you see the fiber glass?


    I didn't have the ceiling completely drywalled.
    I live in Atlantic Canada and our humidity is generally high so it's a bit of battle to keep it down in the house.
    QBenji's Avatar
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    #5

    Jun 2, 2010, 09:23 AM
    Quote Originally Posted by KBC View Post
    The finish taping isn't done then?That's why you can see this moisture?

    What do you have for venting the roof line?I understand the need for insulation,there are products for roof tops on vaulted rooms which eliminates the need for much interior insulation.

    If the roof isn't breathing,the interior air, being cooler,verses the outside air,being much hotter,,will cause condensation, especially if the roof can't let the heat out.same goes for the opposite,,hot inside and cold outside.
    That's correct, the taping has not been done yet.
    The roof and soffits are sealed with the sprayfoam whitch eliminates air movement.From what I've seen and heard,I should not need a vapor barrier behind the drywall when the roof is sealed with sprayfoam, the roof is treated like a regular sprayfoamed wall. Having the vapor barrier behind the drywall just traps the humidity in the insulated cavity I would think.
    I guess having the drywall taped and painted would help a lot as well.
    Does this theory seem correct?
    ballengerb1's Avatar
    ballengerb1 Posts: 27,379, Reputation: 2280
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    #6

    Jun 2, 2010, 09:59 AM

    If the cavity was solid foam then no plastic needed. However, you added fiber glass, as I recall, and the plastic behind the drywall stops room moisture from getting into the fiber glass. I think you are pictureing the moisture traveling into the cavity from the shingle side, vapor barrier protects from the inside moisture.
    21boat's Avatar
    21boat Posts: 2,441, Reputation: 212
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    #7

    Jun 2, 2010, 10:52 AM

    I do believe that Canada requires 6 Mil Plastic tuck taped, I also remember that your insul there is unfaced because paper faced in your Geo its not a good enough vapor barrier due to Geo's high moisture.

    I don't know why the inspector didn't pick this up but you you Can't have TWO Vapor barrier's. When that spray foam went on that became the vapor Barrie's in itself. Now you added Fiber insul and then trapped that with the Plastic barrier. This is no different when a person adds insul to the attic ceiling and uses faced as opposed to unfaced and the add faced vapor barrier creates the same problem.

    You should NEVER mix and match insuls if at all possible. Ether all Foam and no ventilation is required, or all fiber and each rafter needs to vent/breath. The other problem is if fiber insul get 5% of moisture in it then it losses 95% of its insul properties. If it was me I would shave sprayed and completely filled up the rafter cavities .

    The insul Gain is tremendous
    QBenji's Avatar
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    #8

    Jun 2, 2010, 05:31 PM
    Quote Originally Posted by 21boat View Post
    I do believe that Canada requires 6 Mil Plastic tuck taped, I also remember that your insul there is unfaced because paper faced in your Geo its not a good enough vapor barrier due to Geo's high moisture.

    I don't know why the inspector didn't pick this up but you you Can't have TWO Vapor barrier's. When that spray foam went on that became the vapor Barrie's in itself. Now you added Fiber insul and then trapped that with the Plastic barrier. This is no different when a person adds insul to the attic ceiling and uses faced as opposed to unfaced and the add faced vapor barrier creates the exact same problem.

    You should NEVER mix and match insuls if at all possible. Ether all Foam and no ventilation is required, or all fiber and each rafter needs to vent/breath. The other problem is if fiber insul get 5% of moisture in it then it losses 95% of its insul properties. If it was me I would shave sprayed and completely filled up the rafter cavities .

    The insul Gain is tremendous
    I definitely agree with you that there should not be two vapor barriers.
    I don't think the inspector is familiar enough with the use and function of spray foam insulation.
    So if I eliminate the poly vapor barrier you think I won't be able to use the fiberglass batts along with the spray foam?
    21boat's Avatar
    21boat Posts: 2,441, Reputation: 212
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    #9

    Jun 2, 2010, 08:36 PM
    Quote Originally Posted by QBenji View Post
    So if I eliminate the poly vapor barrier you think I won't be able to use the fiberglass batts along with the spray foam?
    I wouldn't use the batts at all especially in your Geo. As you probably know spray foam is 3 times more expensive but pays off is quick in heating and cooling.

    I forget who it was last year or so here that had a vaulted ceiling and I talked him into all foam. He got back later and was so pleased on how easy it was to heat. Think , a vaulted ceiling is a heat loser because of height. So to compensate for that you should use top Grade insult.

    Compare Spray Foam | McGlaughlin Spray Foam Insulation

    Your situation

    Your fiber insult may already be bad because of moisture in it. ( Risky) I'm sticking to my guns here, either all fiber glass with baffles to peak or all foam not mixing it. I'm curious who came up with the mixing of insuls?


    Can you recycle the batts after it dries out to save elsewhere...
    QBenji's Avatar
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    #10

    Jun 3, 2010, 09:27 AM
    Quote Originally Posted by 21boat View Post
    I wouldn't use the batts at all especially in your Geo. As you probably know spray foam is 3 times more expensive but pays off is quick in heating and cooling.

    I forget who it was last year or so here that had a vaulted ceiling and I talked him into all foam. He got back later and was so pleased on how easy it was to heat. Think , a vaulted ceiling is a heat loser because of height. So to compensate for that you should use top Grade insult.

    Compare Spray Foam | McGlaughlin Spray Foam Insulation

    Your situation

    Your fiber insult may already be bad because of moisture in it. ( Risky) I'm sticking to my guns here, either all fiber glass with baffles to peak or all foam not mixing it. I'm curious who came up with the mixing of insuls?


    Can you recycle the batts after it dries out to save elsewhere...
    I was pretty sure that going all foam was going to be what I have to do.
    Now it's just a matter of finding the money for it.
    The batts only had moisture on the top and bottom surfaces. I have pulled it all out and have had a dehumidifier runnong in the room and they are all dried out.(only took a couple of days) I will be using them in my basement.

    The government out here gives grants to people who renovate and bring their homes up to high efficiency standards,it certainly does not cover all the cost but every little bit helps.Of course you don't get any money back until you are done and pass their tests.If it isn't good enough you are out of luck.
    The guy that came out and did the "before" test is the guy that makes the recommendations.
    21boat's Avatar
    21boat Posts: 2,441, Reputation: 212
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    #11

    Jun 3, 2010, 08:14 PM

    I'm glad to hear you making the best move here. Good luck on your project!!

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