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  1. #1
    Join Date
    Oct 2008
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    3

    Default Insulation on TOP of an attic floor...

    I have an 200 yr old oil heated house in Connecticut with an unfinished attic that currently has blown in insulation (Perlite & Vermiculite) between the rafters. Have no idea if there is a vapor barrier up there.

    The entire attic has a floor, and a thick one, 3/4 particle board, another 1/4 plywood (previous owner(s)). Don't want to disturb the vermiculite (possible asbestos), so I don't want to touch the flooring.

    Probably R20 or so up there now, have seen recommendations of R49. Can I just lay some R38 up there on the existing floor? Will it improve the situation or just trap moisture?

    Thanks in advance,

    John

  2. #2
    Join Date
    Aug 2007
    Location
    The Great White North
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    4,045

    Default Re: Insulation on TOP of an attic floor...

    You should be fine putting more insulation on top of the floor.
    If you decide to use fiberglass batt insulattion just make sure you do not use faced batts.


    Hopefully this helps.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  3. #3
    Join Date
    Oct 2008
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    3

    Default Re: Insulation on TOP of an attic floor...

    Canuk, that is the answer I'm hoping for, but I'm confused about your specification to used unfaced batts.

    Isn't the inch thick floor the insulation would be sitting on a vapor barrier itself (if so, what's another 0.05 inch)?

  4. #4
    Join Date
    Aug 2007
    Location
    The Great White North
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    4,045

    Default Re: Insulation on TOP of an attic floor...

    Isn't the inch thick floor the insulation would be sitting on a vapor barrier itself (if so, what's another 0.05 inch )?
    No .... it's semi-permable barrier .... meaning vapor ttransmission is likely.

    The reason for the unfaced batts is the floor in the attic is considered a vapor semi-premable barrier as well as the kraft paper face.

    In the event warm moist air from the living space leaks through the first layer of existing insulation ..... it needs to transfer through the flooring above and through the insulation on top and into the attic space itself.

    Otherwise it will be trapped between the flooring and the faced insulation which is not a good thing.

    Hope this helps.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  5. #5
    Join Date
    Oct 2008
    Posts
    3

    Default Re: Insulation on TOP of an attic floor...

    Canuk, thanks for the advice!

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