First, let me own my novice DIY status and say I screwed up. I bought a new house last year in the Indianapolis area and immediately went to work finishing the basement. The builder attached batts of insulation to the top half of the poured concrete walls to just below grade, but that's all. I framed the walls just off those batts -- so several inches from the foundation. Didn't consider any other insulation as I assumed like a novice that I'd just insulate the stud cavities after everything was done. It's only recently I've become aware that the preferred option is rigid foam attached to the concrete walls for moisture control. I've now got a 2000 sf basement fully framed with electrical run and I'm wondering what my best and most cost-effective course of action is for insulation. Thanks for any advice!

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    Is there a moisture concern? The foam approach certainly isn't a requirement if you have generally dry soil. – isherwood May 21 '20 at 14:36
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    @isherwood it's a basement in central Indiana. It's guaranteed to have moisture problems. You drill a well around here by hamming a piece of pipe a foot or two into the ground and putting a pump handle on top. (close enough) Reference: 30 year resident. OP & I are darn near neighbors. – FreeMan May 21 '20 at 15:13
  • A few pics would help. I have ideas about tipping walls out of the way to get foam in, but it's hard to say with only general information. – isherwood May 21 '20 at 15:17
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    Thanks for the quick replies, everyone! To answer some questions: As FreeMan mentioned, there's definitely outside moisture issues. I've got no specific mitigation system installed. Just a standard sump pump that does run a good amount after rain. I've never seen water inside the basement, but it's only been a year. My dehumidifier keeps the whole space under 50%, though. Here's a link to photos showing two different walls. They all pretty much look the same with fiberglass on the top half and also shoved into the rim joists I just noticed. photos.app.goo.gl/1Kq5uGx6XoicXFBJ9 – IndyGopher May 21 '20 at 16:06
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    One additional piece of info I found out is that my builder used a waterproofing membrane outside called Tuff-N-Dri Hydra-Guard or something. I don't believe they used the insulating board on top of that, but I'm looking into it. Would a membrane like that make any difference in what I do inside the walls? – IndyGopher May 21 '20 at 20:23

Just wanted to come back and say my plan is now to remove the fiberglass insulation from the top half of the wall, cover the walls with foam foam board insulation (EPS) by threading sheets through the studs and at the large openings for my egress windows, then reuse the fiberglass in the stud bays (along with more I'll need to purchase). This approach has been recommended to me on several forums in order to minimize condensation on the cold concrete walls when warmer air from inside hits it -- especially in winter. For about $1000, it seems the smart thing to do, albeit a bit of a pain to get all that foam delivered and installed. But this is a large basement that will have a lot of living space, so it's obviously best to do it right. Thanks for replies all! Any further input is certainly welcome!

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