Should I use rigid foam plus fiberglass insulation for a finished basement? (re: PA UCC/”2018 I Code series”)
jmk396
| Posted in Building Code Questions on
My local township follows PA UCC codes which in turn follows “2018 I Code series”.
If I understand correctly, that requires basement walls to have R15/R19.
I was planning to use 1″ rigid foam (R-5) + fiberglass insulation (R-13) but I don’t think that meets code?
Does that mean I need 2″ rigid foam (R-10) + fiberglass insulation (R-13) for a total of R-23?
(I’m trying to learn myself the correct method because I’ve had 5 contractors each telling me different things and requirements…)
If I use rigid foam + fiberglass, do I need unfaced insulation?
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I'm not familiar with PA code, but in NY, prescriptive basement requirements are for R15 insulation. It's common practice to attach foam to the concrete walls (sealed/taped) to create an air/vapor barrier and keep the inner surface of the foam warm enough to prevent condensation from forming. The minimum thickness of the foam will be determined by your climate zone (probably 1.5 or 2" for your area). You can then frame and insulate an interior wall with unfaced batt insulation to get the remaining R-value that you want/need. Any moisture in the wall can dry inward. The same method would typically be applied to the rim joist.
Thanks very much for the reply.
My climate zone is 5A but I can't find a minimum thickness mentioned anywhere.
The only thing I can find is the R15/R19 insulation requirement (ie. R15 continuous vs R19)
In climate zone 5, you would need r-5 or r-7.5 rigid foam depending on the total r-value of the wall assembly (see attached chart). You might also want to look through this post…
https://www.greenbuildingadvisor.com/question/basement-watercondensation-issue