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Community and Q&A

XPS vs professional spray foam for basement rim joists

Rain952 | Posted in Energy Efficiency and Durability on

I live in SE Michigan and recently had an energy audit done on our home we purchased 6 months ago; And have since discovered a whole bunch of issues.

The house was built in 1978 with a poured concrete foundation, and the rim joists were insulated with paper backer fiberglass insulation. After removing several of the panels mold and moisture were discovered 🙁

My question is: is there a difference in performance between DIY XPS/great stuff vs professional installed spray foam? We are trying to keep costs down and I am an average DIY’er

And second, should the joists be given time to dry out longer then when moisture is visible?


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  1. GBA Editor
    Martin Holladay | | #1

    1. It's best if you can wait for weather conditions to change, and for the rim joist to dry out, before you insulate the rim joists.

    2. A do-it-yourself job with rigid foam can be just as effective as a spray foam job. But the quality of the job depends (in either case) on the conscientiousness of the installer.

    Here are links to two articles you may want to read:

    Insulating rim joists

    Basement Insulation — Part 2

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