GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Daylight basement and rigid foam questions

jedispork | Posted in General Questions on

I’m located in northern IL. House is 1240 square feet not counting the basement. I have vinyl siding and was only recently wrapped when it was replaced. Basement is a daylight type with one side being half way above ground. In other words about 25% of the basement is above ground. Builder left it with unfaced yellow fiber glass covered with a vapor barrier and the foundation walls exposed.

It was very damp before adding a dehumidifier and I wasn’t sure if the insulation was getting dirty or moldy and had some spots on the osb behind the insulation.

I tossed all of the fiber glass including between the joist bays. Then I cut 2 inch xps to fit between the studs and rim joist area and locked them in with can foam.  Then about half the basement was finished into a simple room. There is only half inch xps against the foundation with the framing against that in the finished area. I heard so many bad things about mold and fiberglass insulation that I didn’t want any of it.  Is it worth tearing apart to add more foam?

I would like to add more insulation to the above ground stud bays that I can still access. I was thinking of adding another layer of eps in the stud bays. Should it lay flat against the xps or would it be ok with a air gap provided by the previous foam around the xps sheets?

I know it should be covered with drywall as well. I’ve also thought about buying  more 4×8 sheets of foam and simply screwing that with the drywall to the back of the stud bays but it would leave an air gap.

I don’t feel like framing the rest of the foundation walls simply for adding insulation but might in the future.  I know it saves on heating costs but does it make cooling more expensive in the summer?



GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |