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Board sheathing air-wash?

William Goodwin | Posted in General Questions on

I am remodeling a Victorian house with board sheathing in Vermont, I have added a second row of studs making my wall about 8″ thick. I am going to do airtight drywall.

The cellulose guys want a LOT to insulate, but I am concerned that if I use fiberglass, air-wash will get through the board sheathing into the fiberglass. Can I Tyvek the inside of the sheathing? (Tearing off the clapboards is not an option. It would clearly be labor-intensive, but I would do the work myself.

The attic is going to be really well sealed inside and out, so I’m less concerned about using fiberglass there.

Thoughts?

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    William,
    There is no practical way to install Tyvek on the inside of the sheathing.

    To improve the airtightness of your sheathing layer, you have several options:

    -- dense-packed cellulose;
    -- Owens Corning Energy Complete system or the similar Knauf system (Ecoseal);
    -- Flash-and-fill, using 2 inches of closed-cell spray polyurethane foam.

    Johns Manville claims it's possible to dense-pack blown-in fiberglass: "Dense-pack JM Spider for drill and fill" for retrofitting existing walls:
    http://www.specjm.com/files/pdf/BID-0108.pdf

    I don't know if this is marketing hype or a good approach.

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