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Community and Q&A

1926 Tudor basement finishing project

swee0099 | Posted in Green Building Techniques on


Our house is a 1926 Tudor located in Minneapolis. I am in the process of finishing the basement. Planned insulation is 2″ rigid (polyiso or XPS) with 2×4 stud wall. I am only air sealing the rim joist due to the fact my floor joist are half buried in concrete.

My question: there is not much clearance behind our boiler, so I was planning on leaving a void of insulation and stud wall behind it. There would have to be a void on the wall above the boiler as well, as the flue attaches to the chimney in that area. The boiler and water heater will be in an isolated mechanical room. Will this plan lead to any potential problems?

Thanks in advance.


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  1. GBA Editor
    Martin Holladay | | #1

    Leaving one section of your basement wall uninsulated won't lead to any problems, except one: your energy bills will be a little bit higher than they would be if you could insulate 100% of the basement wall.

  2. Expert Member
    Dana Dorsett | | #2

    Is the 2x4 wall going to have any fluff between the studs?

    IRC 2015 code min for MN would be R15 continuous insulation, which takes more like 3" of foam, or 1-2" of foam + 2x4/R13. For dew point control on the above grade section of wall with a fluff + foam solution it's better to stick with the 2" of foam rather than dial it back to the minimum R7.5 prescriptive for zone 6 above-grade walls. See:

  3. swee0099 | | #3

    Thanks Martin and Dana.

    I'm not quite installing yet. Still rewiring, tucking plumbing and all of the other stuff you never think of to do it right! I'm sure I'll be back with more questions.


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