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Good idea to insulate old house with cellulose?

user-4053553 | Posted in Energy Efficiency and Durability on

I have a house that is well over a century old, its balloon framed and has no insulation in the walls, i am planning on getting dense packed cellulose, but i want to know if i am creating any moisture problems or other issues that should give me pause.

Its vinyl siding over original wood siding on wood planks with 2×4 framing and plaster and lath inside.

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  1. GBA Editor
    Martin Holladay | | #1

    The short answer to your question is no, you shouldn't worry that installing cellulose in your walls will cause any problems.

    The standard approach to insulating a house like the one you describe is to install dense-packed cellulose in the empty stud bays. In addition to providing R-value, the cellulose greatly cuts down on air leakage through the walls.

    In some cases, retrofitting insulation in walls has the undesirable side effect of increasing the frequency of exterior painting jobs on the siding. This side affect doesn't apply to houses like yours with vinyl siding.

    Finally, it should be noted that if you have any water entry problems -- for example, windows without adequate flashing that get lots of wind-driven rain -- it's possible for these problems, long ignored, to be more noticeable after your walls are insulated. Here's why: if your walls are uninsulated, lots of heat gets pumped through the walls during the winter (that's why your heating bills are high), and lots of air moves through the leaky walls. This heat and air can dry out the moisture that enters the wall due to flashing problems. If you insulate the walls, the moisture that enters due to flashing problems can't dry as fast.

    Don't worry too much about this possibility, but use common sense. If you know that your walls are damp, fix your flashing before proceeding.

  2. Expert Member
    Dana Dorsett | | #2

    The window & door flashing issue is the primary concern, but if you have sufficient roof overhangs (say, 1-foot of overhang per story of height, as a lot of older homes have) even that isn't a very serious concern.

    There are 100 year old houses even in cold climates (if Saskatchewan is considered cold) that were insulated with cellulose without vapor retarders of any type that are still going strong.

    You won't create moisture problems by dense-packing cellulose in there and may even mitigate it some, but it won't fix bulk water issues like flashing.

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