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  1. #1
    Join Date
    Jun 2014
    Posts
    2

    Default Insulating exterior walls - what to do about nails coming through from outside wall

    I am converting my garage into an art studio. I want to insulate and sheetrock the walls. There are hundreds of nails coming through from the outside between the wall studs. The nails will prevent the newly inserted insulation from completely filling the space. My house is 66 years old. 15 years ago I had the old siding removed and replaced with vinyl siding. The exterior walls are 1x6 or so, not plywood. Some of the nails are from the new siding, I assume, and some nails are probably from the previous siding that was removed. My question is - can I simply cut off the nail ends (easy with an angle grinder), or should I hammer the nails flat (very time consuming, hard on my arm and neck, hard on the exterior 1 by's). The wall studs are 16" center 2x4 (not 2x6). Because of the thin depth, I want as much r value I can get. I have considered blow-in foam, but cost prohibits this at this time.

  2. #2
    Join Date
    Dec 2007
    Location
    Tennessee
    Posts
    1,964

    Default Re: Insulating exterior walls - what to do about nails coming through from outside wa

    Those nails will not significantly affect the performance of fiberglass insulation. The fiberglass will simply surround them. A small gap between the fiberglass and the external sheathing is actually a good thing. Done properly, this will help keep the insulation drier and therefore more efficient. A 3% moisture level in fiberglass insulation reduces its R value by half.

    Install the insulation with the paper wings over the end of the studs instead of to the inside face as you see dome most often. Stapling the wins to the inside face and creating an airspace between the facing and the sheetrock actually hurts the insulating ability of the wall. You want to have as much of the insulation toward the inside as much as possible and no air gap between the ****r and the sheetrock.

    The kraft paper is a vapor barrier so unless the wings overlap each other a little, they do not do their job. Done correctly, the warm, moist air from inside your house will not be able to enter the wall cavity and the insulation where the moisture would condense and lower the R-vale and possibly cause mold and rot inside the wall cavity. The air entering the cavity would come from the outside.

    When the outside air is colder than the inside air, it will have less moisture in it. Even if the RH (relative humidity) is high, the total moisture, aka AH (absolute moisture) will be much lower as cold air cannot hold as much moisture as warm air. Air inside the wall cavity will warm up from some heat migration from inside the house. As it warms up, it rises and hopefully goes out the top of the wall near the roof. This will draw in fresh air from the outside at the bottom of the wall.

    The cold fresh air will warm up and the warming will drop its RH. The drop in RH will absorb any moisture that might be in the insulation, thus drying it out and making it more efficient. And the cycle continues. You do not want this cold outside air to get between your insulation and your sheetrock. That would make the sheetrock very cold and therefore the room will feel colder. That cold air will also bypass the insulation and carry heat from your room to the outside.

    Much is said and written about proper venting of attics, walls need the same type of venting, but not on the same scale as the attic. The vapor barrier reduces the need for as much venting.

  3. #3
    Join Date
    Jun 2014
    Posts
    2

    Default Re: Insulating exterior walls - what to do about nails coming through from outside wa

    Thank you for your prompt and informative reply. I will leave the nails, and I'll be sure to have the drywall contractor staple the flaps on the outside of the studs.

  4. #4
    Join Date
    Dec 2010
    Location
    Houston Texas
    Posts
    3,155

    Default Re: Insulating exterior walls - what to do about nails coming through from outside wa

    Thank you Keith for giving the proper instructions for hanging insulation !!

    YAY Go Team TOH

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