How to get R30 into 2x6 rafted ceiling?

[MachineMan]

One of my new rooms has a vaulted ceiling thats rafted with 2x6's with the roof directly on the otherside. Code says I need to insulated it with R30 and keep a 1" air gap on top. Impossible?? All the roll out R30 is 10" thick so that won't work and that rigid foam board cost big $$ and when stacked up to R30 value it won't leave a 1" gap. I need to figure this out before my inspection.

[Wgoodrich]

Install a ceiling joist sized for the span below the rafters low enough to create the 11" for the insulation.

Second choice is install 2x4s hanging off the rafters far enough below the rafter to create the 11" required using blocks to hang the 2x4 off the rafter as an expansion. As long as the rafter is sized to carry the ceiling and span the span required you will be fine this way also.

Good LUck

Wg