Thanks bungeeii. I actually made contact with a spray company that had a certified Energystar auditor working with them. They did an energy audit today and took measurements to estimate the job. They estimated the following rebates, and will put these terms in the contract as stipulations before any work is done: 1. audit costs $400 with $125 rebated if the work is done. 2. $1000 govt rebate off the top for a thin barrier spray in the attic floor. I don't have the exact terminology in front of me, but it is basically a skim coat of foam onto which is blown cellulose or other for attic insulation. 3. up to 50% rebate ($5000 max) depending on the results of the energy audit. Because I have high efficiency furnaces and on-demand hot water, she says that I will rate at a 25%+ energy savings, which will put me at the 50% rebate from the govt. The rebate takes about 10 weeks. So, in their example, if the job costs $11,000, I pay $10,000 plus the $400 for the audit ($1000 "instant" rebate for the attic thing), then get $5000 + $125 back in 10 weeks. After my contractor subtracts out what he was charging me for fiberglass, I should net out at a very reasonable number. The people today were my third estimate, and I believe they were the most knowledgeable about the right thing to do. I'm just waiting till next week for their estimate. Thanks again, I think I'm finally getting the right game plan together!

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

"madpebs87 "plus then you might actually have to seal some of the holes in the ceilings." Wouldn't you do this anyway? You foam the roof deck/rafters, do nothing to the ceiling for insulation, why would you not seal all the plumbing/lighting etc holes that go up into attic? Great thread (bookmarked) giving me lots of info when i build in 3 years in coastal ga." been out of town so just getting to answer this. when the attic is vented, you absolutely want to seal all openings between living & attic space. when the attic is unvented & foam sealed, then you want air exchange between living & attic space. you can get this exchange from not sealing the openings that trades make & never seal, or seal it up tight and dedicate an exchange air pathway. problem is...seldom does anyone seal these openings, so adding a dedicated pathway is redundant. people think they built tighter than they actually did in my experience. but it is all just a guess until you blower door test to see what leakage actually exists. build tight, ventilate right, and TEST to find out what performance actually is. OP, I have to defer to folks in climates with basements, as we have too high of a water table in La. for basements. I have no hands on experience with basements, best of luck.

I'm glad to come across this thread because I'm also trying to figure out whether/how to add blown-in insulation to our attic, and possibly radiant foil. I hope I'm not derailing the thread by tacking on. Our home is a roughly 120 year old Victorian, and it also has a sprinkling of old insulation in the (sealed) attic, but nothing more. And when I say attic, I should clarify--we actually have a finished attic/third floor but the very peak of the attic, above the ceiling of the finished area, is unfinished. It's like a capital A, where the lower half is the finished portion and the upper half is unfinished. I'm sure there's proper terminology for that but I don't know what it's correctly called. We use the finished portion regularly, or at least we would if it didn't get very hot up there in both the winter and the summer. In the winter, we can counteract this by closing the HVAC vents so the attic is only heated by the hot air rising through the house, and that works well enough. But in the summer, we add two window units in addition to the house AC (to cool a space that's probably 400 sqft)--the window units are kind of a mixed bag because with the way they're installed, they let in a good portion of hot outside air around them through the window. We're contemplating replacing the window units with a minisplit system in the attic alone, but I feel like it's worth exploring all the various possible ideas to try to keep summer heat out of the finished portion of the attic before installing a whole new additional system. Any thoughts or ideas for me?