Does this seem a little extreme here in my zone 5/6 Ohio? My first floor has R19. It's over Code. But Building Science Corp.'s Dr. Lstiburek's rule of thumb is that for any home north of the Mason Dixon Line, follow the 10, 20, 40, 60 rule. That's R Value for, respectively, basement slab, basement walls, above grade walls and attic. If you're planning to stay for awhile and the labour is yours, there may be an economic payback. The space will definitely be more comfortable. My biggest fear is trapping water with too much insulation. At Roxul sales displays, they like to run a water fountain through a chunk of their product. The water runs right through and is not absorbed. will my basement still be the coolest part of my house in the summer? Well, mine have been. But that's probably because of the leakage of HVAC-cooled air into the basement, where the cooling equipment is also located. Is it ok to just add fiberglass insulation without a vapor barrier, and close up with sheetrock? Unless you're in an extreme cold climate such as northern Alaska, leave the poly vapour barrier out. All you need is painted drywall as a vapour retarder. in the rim joist, I have 1" of closed cell foam covering the entire rim joist. Should I add XPS boards and seal, or just add unfaced fiberglass there as well? Either one works. See illustration below from Building Science Corp. Info. Sheet 511, p. 2.

I'd take the fg out. It's just an invitation for mould. The cheapest diy way to well seal the rime joist area would be to use expanding foam or caulk followed by expanded or extruded polystyrene followed by 1/2" drywall. No special skills required. Just patience. Which, come to think of it, is probably a skill in itself! If you don't cover the foam with any of the approved materials, you take the risk of deadly fumes in a fire. I'm sure there are hundreds of thousands (maybe millions) of homeowners doing that. In a home I was building a few years back, a plumber accidentally set aflame just a tiny section of high-density spray foam, barely an inch circumference. Everyone working in the house fled the absolutely sickening and toxic fumes. As mentioned above if you just want to close the sill gaps, you can use the fireproof caulks. But if you're eventually covering them with drywall, any good caulk will do. For fireproof caulks, you'll have to hunt up a commercial building supplier. Or try the net. At least, I've not seen them in the Big Boxes near me. (See link for example.) Here is a link that might be useful: Fireproofing Caulks & Sealants

Open cell polyurethane spray on the underside of your roof will be way below the minimum recommended R Value for new wood framed homes, according to the US Department of Energy. If you have typical 2x6" rafters, you will only be getting R20 vs. the minimum recommended R30. actually 2x6 rafters are 5.5" filling the rafter bay with 6" of open cell foam meets the catherdalized insulation standard. foam covers faces of 2x's to minimize thermal bridging. see pictures linked in my previous post. Plus, unless the job includes sealing all the openings into the attic from the exterior, you will not be getting the full benefits of the insulation. (See linked document.) document linked is promoting rigid foam sheathing to exterior of roof. OP is applying foam to interior of attic at roofline. when roofline is foamed the air and thermal barrier is now at the roofline not the attic floor. leakage sites that were problematic with insulation at attic floor are no longer sucking (negative pressure) from the conditioned space below. Only if you have those leaks sealed and use closed cell foam does spraying the underside of the roof make economic sense. open cell is used in hot humid climates. not closed cell. Unless you have HVAC in your attic, you will likely be getting a much better return by insulating the attic floor as suggested above. Unless being the operative word... 90% of homes in the south have hvac in attic. and ductwork in the attic. putting equipment and ductwork under the insulation (foam on roofline) allows equipment and ducts to perform. putting foam on attic floor still puts equipment and ducts in 130 degree attic. Spraying R20 under your roof on the Georgia shores and calling that fine and dandy? I wouldn't have anything to do with either of these contractors. If you want an impartial assessment, read the linked materials or contact an energy consultant in your area. Resnet is a good source for an independent energy rater. best of luck op

Nothing about your home should keep you up at night. If concerns about using a particular construction material or method will do that, then don't use it. However, if we never applied any new materials, systems, and construction methods in residential construction, our homes would be no more comfortable and perform no better than homes built in the 1700's. We wouldn't have, for example, air conditioning, which makes living here in coastal Virginia much more pleasant in summer and which keeps certain contractors in the Houston area employed. The energy crisis in the 1970s gave rise to the use of house wraps and vapor barriers which caused plenty of unintended consequences. That doesn't make polyethylene or house wrap bad materials, it's simply that the building science wasn't established at the time. We continue to rely on the researchers to thoroughly test new ideas (and real world testing is better than computer simulations) to minimize, if not preclude, unintended consequences. When considering the use of the latest and greatest materials homeowners would be well advised to remember the old adage: The early bird gets the worm, but the second mouse gets the cheese!