I'd like to finish my attic and turn it into a bedroom loft.

The ridge height is 8'2", and it's a 32 degree slope, so I should be fine for ceiling height as far as code is concerned.

My problem is that my rafters are 2x8, so I only have 7 inches to insulate, unless I tack on a 2x2 or 2x4 to each rafter to extend the depth. Only issue there is that I'd be cutting pretty seriously into ceiling height by doing so.

I'm in Virginia, so I'm looking at a min R value of 38 to meet code (I think?). I'd also like not to be hemorrhaging heat/AC even if I do meet code, so if I could put a bit more in, before I started diminishing my insulative return, for not much more money, that'd be good too.

I've got 720 square feet of roof underside I'd be looking to insulate, however, and the stuff ain't cheap.

I'm looking at an Amazon listing for a closed cell kit that advertises 600 square feet of coverage at 1" thickness with an R value of 6.6 per inch, and it's 900 bucks.(!)

What's my strategy? 2ish inches of the stuff for ~3 grand, then a less insulative but much cheaper stuff for the last 5 inches?