Chicago Bungalow Insulation – GreenBuildingAdvisor

I have a story and a half bungalow in Chicago (zone 5a) and have a partially finished attic space on the second floor. The 2×6 roof rafters are lacking insulation and the knee walls have fiberglass batts that are falling out. I have some good ideas from this site on how to insulate the knee walls, but am unsure how to insulate the roof rafters and avoid condensation. 

I’ve heard different recommendations on spray foam, cellulose, etc, but am unsure what the best solution is.

Any suggestions on what the best assembly might be to insulate the 2×6 roof rafters?