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  1. #1
    Join Date
    May 2014
    Posts
    3

    Default insulating and old house

    I am remodeling a 1900 farm house in Wisconsin and am wondering about weather to add a vapor barrier or not.
    the inside of the outside walls have plaster and lath on them with no insulation between that and the interior plaster and lath. I'm guessing they did this as a vapor barrier or type of insulation as they didn't have good insulation like we have today. my question is when I insulate should I install a plastic vapor barrier or use kraft faced insulation before the drywall is installed. I'm worried about trapping moisture in the walls. wont the plaster and lath on the inside of the outside walls and adding another vapor barrier to the inside walls under the drywall trap moister?
    Thank you

  2. #2
    Join Date
    Dec 2007
    Location
    Tennessee
    Posts
    1,700

    Default Re: insulating and old house

    I would love to help you out on this but you need to reread your post and edit it to make some sense. Right now you are saying there is no insulation between the lath and plaster and the lath and plaster and you want to put insulation between the lath and plaster and the drywall???

    But, you remove the lath and plaster from the interior side of the exterior wall. You can use kraft faced insulation or unfaced insulation. If you use unfaced, then add a layer of 6 mil vinyl on the interior side of the insulation and drywall over it. If you use faced insulation, staple the wings of the paper over the ends of the studs, not to the inside face as commonly (and may I say incorrectly) done. The drywall.

    You will not trap moisture this way. Moisture accumulates against colder surfaces. With a vapor barrier, the moisture will not get to the cooler surfaces where it can condense. Cold outside air entering the cavity will have much lower actual humidity (AH) so as it warms up inside the cavity, its relative humidity (RH) will actually decrease so condensation also will not occur, in fact, the insulation and the cavity will be much drier (lower RH) than either the interior of the house or the outside air, and the insulation will be more effective.

  3. #3
    Join Date
    Aug 2007
    Location
    Portland, Oregon, formerly of Chicago
    Posts
    1,737

    Default Re: insulating and old house

    Got to admit I was confused by the post too! Was the old lath and plaster removed or not?

    My first choice on an old air leak prone vintage home would be spray foam, but that is kind of pricey. A farm house of that age is very likely balloon frame and there is a LOT of air moving around the cavities.

  4. #4
    Join Date
    Dec 2010
    Location
    Houston Texas
    Posts
    2,919

    Default Re: insulating and old house

    The vapor barrier is normally applied to the hotter side of the wall assembly, so up north the vapor barrier is right under the drywall. If you are removing the lath and plaster, that is a fine time to re-wire, re-plumb, re-insulate, and re-frame any previous changes.

    Combining the remodel with your long range plan is a good idea if you don't want to rip the entire house apart.

  5. #5
    Join Date
    May 2014
    Posts
    3

    Default Re: insulating and old house

    Thank you everyone for your response. yes it does sound confusing how its written. I will try to clarify my original post. I have removed the old plaster and lath an found no insulation in the walls. here is the confusing part. their is plaster and lath on the back side of the exterior wall. some one took the time to put lath and plaster on the back side of the exterior wall. instead of insulation between the studs their is plaster and lath, than air space than the interior plaster and lath. (witch I have removed) so if you are looking at the exterior walls from the inside of the house you see studs with plaster and lath between each stud bay. when I insulate the walls and add a vapor barrier will their be any moisture problems.

    Thank you

  6. #6
    Join Date
    Dec 2007
    Location
    Tennessee
    Posts
    1,700

    Default Re: insulating and old house

    What is on the exterior of the house? Have you checked to wall thickness? Is it possible that you have a double wall construction? If you put a good vapor barrier on the inside, you won't have to worry about moisture, but if your exterior sheathing is too air tight, then the interior side has to be even tighter so a continuous 6 mil vinyl barrier would be best for you.

  7. #7
    Join Date
    May 2014
    Posts
    3

    Default Re: insulating and old house

    Thanks Keith,

    The outside of the house has 1x6's and aluminum siding with what I think is tar paper between the wood and aluminum siding. it sounds like the thicker plastic vapor barrier you suggested is the way to go.

    Thank you

  8. #8
    Join Date
    Jun 2014
    Posts
    1

    Default Re: insulating and old house

    I'm doing a similar project on a farmhouse in Michigan. What R-Value are you going with for the insulation?

    Jeff

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