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Thread: Vapor barrier boxes

  1. #11
    Join Date
    Jun 2013
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    Massachusetts
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    72
    Quote Originally Posted by pmoney44 View Post
    Good evening,

    State of Massachusetts

    I’ve been seeing a lot of these electrical boxes with so called vapor barrier.
    They are plastic boxes guessing for residential use but have a gasket around them. They seem to be very expensive compared to regular plastic boxes. In the state of Massachusetts does anyone know if these are a new code requirement for New residential construction or just a new way for suppliers to increase cost in the industry?

    What I understand they only have to be installed on the outside walls.

  2. #12
    Join Date
    Dec 2007
    Location
    NE Nebraska
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    38,252
    Quote Originally Posted by goldstar View Post
    There’s the obscure Code !!! It’s hard enough trying to keep up with the NEC and then an EI finds this one just to let you know he’s “up on the Codes”.
    Unless the inspector is a "combination inspector" IMO this is not a concern for strictly an EI. He may make a suggestion that another inspector is not going to accept something though.

    Quote Originally Posted by Knuckle Dragger View Post
    If the GC is using closed cell spray foam insulation in the walls when you don't need vapor barrier boxes. If they are using fiberglass then you will need vapor barrier boxes.
    Seems to me they are only required if the box is penetrating the "vapor barrier". Spray foam insulation - the vapor barrier is behind the box (most of the time anyway)
    I live for today, I'm just a day behind.

  3. #13
    Join Date
    May 2014
    Location
    Marlborough, Massachusetts USA
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    285
    Quote Originally Posted by kwired View Post
    Unless the inspector is a "combination inspector" IMO this is not a concern for strictly an EI. He may make a suggestion that another inspector is not going to accept something though.

    Seems to me they are only required if the box is penetrating the "vapor barrier". Spray foam insulation - the vapor barrier is behind the box (most of the time anyway)
    I'm not 100 percent sure but i believe it it is 2x6 construction with fiber glass insulation you may not need vapor barrier boxes either.
    Maybe someone here knows for sure.

  4. #14
    Join Date
    Aug 2009
    Location
    MASSACHUSETTS
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    38
    Quote Originally Posted by Knuckle Dragger View Post
    I'm not 100 percent sure but i believe it it is 2x6 construction with fiber glass insulation you may not need vapor barrier boxes either.
    Maybe someone here knows for sure.

    I’m under the impression they are needed in outside walls and ceilings. A colleague of mine was called out on it in another town in Massachusetts. I’m guessing he was referred to the building code. But I still haven’t received exact clarification. Guess I’ll have to contact AHJ.

  5. #15
    Join Date
    Aug 2009
    Location
    MASSACHUSETTS
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    38
    Quote Originally Posted by Knuckle Dragger View Post
    I'm not 100 percent sure but i believe it it is 2x6 construction with fiber glass insulation you may not need vapor barrier boxes either.
    Maybe someone here knows for sure.

    Got me???

  6. #16
    Join Date
    Dec 2007
    Location
    NE Nebraska
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    38,252
    Quote Originally Posted by pmoney44 View Post
    I’m under the impression they are needed in outside walls and ceilings. A colleague of mine was called out on it in another town in Massachusetts. I’m guessing he was referred to the building code. But I still haven’t received exact clarification. Guess I’ll have to contact AHJ.
    Where else would they apply to?

    This is not an NEC requirement, it would be an energy code issue I would think. Probably not the only way to comply, but likely the easiest way to comply.
    I live for today, I'm just a day behind.

  7. #17
    Join Date
    May 2018
    Location
    Jamaica and london
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    722
    I think too many inspectors watched Holmes on Homes and decided that should be correct. But, in the show, it looks like Holmes uses a vapor barrier in every single room, and uses tape over the staples etc... then wraps plastic around the boxes as well, taping that plastic to his barrier, and the only times he did not do that was when he used spray foam...

    AgIn, that was certain places in Canada. Not USA.

  8. #18
    Join Date
    May 2014
    Location
    Marlborough, Massachusetts USA
    Posts
    285
    I in gut jobs (remodels) I typically don't install VB boxes, but in all other new work yes, unless closed cell is used.
    If closed cell is used in the roof rafters then you don't need the vapor barrier boxes in the ceiling.
    I don't have code references this is just what I have figured out throughout the years through the GC and inspectors.
    When all else fails ask the AHJ.

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