I'm in the process of designing/planning to finish our walk up attic, i need a little guidance on planning for insulation. Here's my plan and correct anything that doesn't work: Currently there are 2x8 rafters, 24" oc, starting where the knee walls will meet the rafters up to where the ceiling will be i'm going to staple rafter vents and use R30 Roxul, cover that with a vapor barrier, and then drywall. The 2x4 Knee walls will be roxul r15 with a vapor barrier and then drywall The 2x8 ceiling will be roxul r30, vapor barrer, and drywall I've gone back and forth on just using fiberglass batts, but in order to fit r30 I would have to add 2x4's to the current rafters, this won't work the planned ceiling height for the shower, and i would have to cut down doors because of height. Thoughts? does this work?