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Insulation the basement joist parallel with basement wall

Andrew207 | Posted in Green Building Techniques on

There is a lot of information on how to insulate basement joists, but it’s hard to find information about insulating the last basement joist that runs parallel with the foundation wall on the gable ends. Does the basement joist along this side of the house also require rigid foam or spray foam insulation?

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  1. GBA Editor
    Martin Holladay | | #1

    Yes, every rim joist need to be insulated. If you have 15 inches or 23 inches of space to work, it's pretty easy. If the gap between the first and second joist is small -- say, only 1 to 4 inches -- your best approach is to fill the entire gap between these parallel joists with two-component spray foam.

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