Insulating attic with air gap?

[ishiboo]

I'm wondering, I have a really nice attic space I was planning on blowing R-60 into. Instead, I was considering doing R-38 between the roof rafters and R-19 in the ceiling (floor joists of the attic), which would give me a total of R-57... close to where I want to be. This would allow me to cover the floor in OSB so I can store stuff and get around up there.

If I insulated the ceiling with a foil below the R-19, would this give me adequate performance? Or would all the heat end up sitting in the attic?

 

[Ricktick]

IF it looks like my garage attic, the soffit vents and rafter baffles are open to the space between the ceiling and the roof so the roof insulation would not help the finished/heated space below. Like you I added some storage flooring and made a sandwich of 1/2 inch OSB with 2 inch rigid foam between, and batts between the rafters under the flooring. I don't recall the r value of this but it seemed like a reasonable compromise.