Sorry to start another basement insulation thread but I'm trying to determine the most cost effective way to properly insulate my basement.
I've read the Building Science's site. It seems 2" of xps against the concrete would be one of the best solutions. But 2" xps is really expensive and I have a plumbing drain pipe that hangs down in the top foot of my concrete wall and it only give me at most 1" between the concrete and the pipe.
Since I'm limited to 1" xps and Roxul. Would it be OK to drop to 3/4" xps and Roxul? I didn't want to get condensation on the front of the xps because it wasn't thick enough. My local Lowes sell 3/4" xps for almost $10 a board less than 1". The 3/4" has a R-value of 3.8 vs 5 for the 1"
I also have I-Joists and lots of obstructions in my rim joist bay (bolts for deck ledger, electric, etc). Is it OK to only use Roxul in the rim joist or should I cut xps and then roxul? I was also thinking with the money I save doing 3/4 and roxul I could do spray foam in the rim joist. The spray seems like it would be the easiest way to effectively seal my rim joist.
I have about 3-4.5 feet of exposed concrete, the rest is underground. 9 feet floor to ceiling in basement.
I live in Montgomery County Maryland and supposedly it's in the mixed-humid zone 4. R10 continuous or R13 framed.
Thanks in advance for the help!