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Community and Q&A

How do you insulate rubble filled frame exterior walls?

ztyuv6vzBW | Posted in Energy Efficiency and Durability on

I have a house which was constructed c1800 with frame walls filled with rubble The exterior is wood siding and the interior walls are plaster on lath. I would like to make the home less drafty. Is it worth it to insulate the walls with spray foam or some other method? Is my money spent better insulating the attic or basement. Some details are: the roof is slate, the attic is uninsulated, the foundation walls are stone, the original windows have storms. We live in Central New Jersey. Your knowledgeable thoughts are appreciated.

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  1. GBA Editor
    Martin Holladay | | #1

    What kind of "rubble" was used to fill the stud bays? Stones? Dirt? Broken chunks of mortar? Sticks? Straw? All of the above?

    If you really want to insulate the stud bays, you would have to demolish the lath and plaster and empty the stud bays first. Once that work was done, you could use almost any type of insulation.

    If you don't want to open up your walls, you can install interior rigid foam on top of your plaster, followed by drywall. Or if you need new siding, you could install rigid foam on the exterior of your house, followed by vertical furring strips and new siding.

    Since each approach is disruptive and expensive, you may decide that it makes more sense to perform air sealing work rather than insulating.

    By the way, if you have an uninsulated attic, that's probably the first place to insulate -- before worrying about the walls. Install 18 or 24 inches of cellulose up there if you have the room. (Don't forget to air seal your ceiling before insulating, though.)

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