Good links there, and similar to what I already know. I'm going to use 1" at a minimum and will likely have additional batting (not fiberglass) in the stud bays. The real questions are around the scoring of XPS and if there's a significant difference in benefit between 1" and 2" (R5/R10 values aside). I'm talking vapor permeance, etc.

You need to check with your housing authority - they may have a minimum - R10 or R15. I'm in Minneapolis - zone 4 - I went with a total of R15.

Installed top/bottom plate. Bottom plate pressure treated, with tar paper on basement floor - no direct contact with cement.

I went with 1.5" x 48" wide XPS (pink stuff) against the wall - no studs yet (this makes a thermal break). Used PL300 to glue it to the wall - don't need a lot - one tube does 3 - 4 - 48" sheets.

Then put 2x4's flat, 16" OC (you can get XPS scored 16", use a serrated bread knife to finish the cut), with 1.5" XPS between them - for a total of 3" XPS - R15.

Take your time to make sure that the studs will fall in the center of the drywall joints. You may have to add additional 1x2's or 2x4's for the dry wall butt joints.

Basement Insulation Basics

Just an aside: my 1950's home had the old style basement windows. Replaced them with glass block - a lot more light once you get rid of the window frame and storm window. I found the glass block windows come pre-made. I ripped the windows out, including the frame. Installed the glass block windows with shims. Used a little foam to hold it in place. Next day, removed the shims, and foamed the rest of the opening. I framed around the window, before insulating, so I could do sheet rock 'returns'. Also what gives more light, is if you angle the bottom of the window 3" or 4" rather then make a right angle window sill.

Thanks, Geoffrey. I've checked with my city and they don't enforce insulation in basements at all but recommend following DoE guidelines. That's R-5 continuous and R-13 for cavity-fill (zone3 non-coastal). That suggests I'll be fine with 1" continuous XPS. For purposes of simplicity of outlets, plumbing, etc. I'll be doing a traditional perpendicular-to-plane 16"OC walls. That'll give me 3.5" for batting. Roxul claims R-15 for that thickness (of which I'm skeptical, but I digress) and that'll give me better noise attenuation than the foam will (yeah, the one thing foam doesn't do better than batts)

Interestingly, the space I need to insulate is about 640 sq/ft. That much 1" XPS at retail is almost the same price at the equivalent square footage of the rock wool, but only 1/3 the rated R-value. Putting them together with all penetrations sealed and adding sheetrock will give me a "rating" over R-20. Not bad for Georgia. I wonder if I'll need to run the HVAC down there or just get a larger dehumidifier :)

If you could easily get a supply on one end of the room and a return on the other, that would be ideal.

I had to screw 2x2's on all my joists to go over conduit and water pipes.

Made a '10" deep ladder' soffit. Cut 2x2's 10" rungs on table saw, screwed to 8' 2x2's - made - 3 - 'ladders' and screwed them to the joists - worked out great.

What I do for my outlets is I use a big 4" square box, and then a mud ring - you can get single or double gang in a variety of wall thicknesses. Gives you a lot of space for the wire and outlets

I'll be replacing the HVAC that serves the basement and main level (1200 sq/ft each) and will need to be really careful about accurate load calcs. I may only end up needing a few small supplies and an in-wall return near the unit to help with moisture control.