I originally asked this question within another thread titled
"Basement Heating Options." I noticed that the thread was quickly becoming more about insulation rather than heating, I decided to post my situation with updated questions in this new thread with an appropriate title.
I'd also like to apologize in advance if it seems like I am asking the same question different ways or if I keep changing my mind. The more I read about basement insulation, the more my head spins.
Background:
I have a Cape Cod style home built in 1951. I live in southern New York, climate zone 5. The foundation is made from concrete block. The house had water infiltration problems when I first moved in 8 years ago. Since then, I have installed an interior perimeter drainage system below the slab and a sump pump.
I currently have a moisture issue in one corner of the basement after several days of heavy rain. I plan on digging down and sealing the exterior foundation wall with tar extending out about 5-6 feet from the corner. I will also regrade and extend the downspout 10 feet from the house.
Question:
What combination of insulation should I use for my basement?
I started by insulating my rim joists with 2” XPS as described in
this article from Family Handyman. Based on the reading that I’ve done and the recommendations in the previous thread (thank you Ballenger), I want to go with XPS rigid foam boards glued directly to the foundation. My building inspector said that I need to have at least R13 insulation in the walls, so the 2” XPS alone (R10) is not enough.
This second article from Family Handyman says to use ¾” XPS on the walls, frame, and later fill with fiberglass.
Then I came across two articles from Building Science Corporation.
The first BSC article says using 2” XPS along with R13 fiberglass works very well at controlling moisture when used with spray foam on the rim joists and another 2” of XPS below the slab. But I don’t have anything below the slab and used XPS on the joists instead of spray foam.
If I’m reading
the second BSC article correctly, it says that using 1” XPS with R13 fiberglass can also be effective at controlling moisture as long as the sheet rock is covered with vapor barrier paint and a dehumidifier is located in the basement. But… the article states that “some variations not recommended” and the article does not explain what that means.
So, will 1” XPS (with fiberglass) be thick enough for moisture control or will I need to go with the 2” XPS?