I’m building my first ICF home in climate zone 5a and am concentrating heavily on energy efficiency due to high electrical rates in our area. I’m wanting to utilize an unvented roof with 5 1/2″ of polyiso on the roof deck and air permeable insulation under the roof deck. My roof structure (tobacco barn style) utilizes fairly shallow trusses. I wanted to dense pack 10″ of  cellulose under the roof deck which is one of the few jobs I will contract out on the build. My insulation guy said netting webbed trusses is tricky and suggested loose fill in the truss bays. My concern is settling of the loose fill which would create an air gap under the roof deck (possible moisture trouble and local code dictates the insulation must be against the roof deck).  My goal is at least an R-60 roof so would I be better using the loose fill, netting the trusses for dense pack, or maybe installing unfaced glass batts against the roof deck? **update** For clarity the roof style is high pitched (12/12) in the center of the home and sheds to 4/12 either side of  the home. My polyiso  satisfies the code requirements for exterior rigid board (R20 min) in my climate zone and i was trying to follow a formula I found in an older GBA article which used dense pack under the decking.