Spray foam insulation
Sorry to cross post but I'm a bit in a hurry to find out what differences there are between the expensive two part closed cell foam you'd pay someone to do (icynene or polyurethane) and the Great Stuff you get in a can.... which I believe is also closed cell?
All I have is a 3 x 12 area, about 3-4 inches deep and the quotes are as you might imagine quite high.
BTW, why do all estimates come in increments of $500 or $1000 these days? It used to be 10-12 yrs ago that estimates reflected actual costs and increments of time, so I'd get estimates like $400, or $700, or $800 for stuff. Now they all round up.