My client has two bedrooms with vaulted ceilings, 4/12 pitch, exposed 4×4 rafters 3-1/4″ thick, under 1″ tongue and groove boards. The ceilings are unvented and the home is located in Southern California.

My plan was to fill the cavities with Hunter H Shield panels 2 1/2″. Thereby leaving a 3/4″ gap of dead air. Then running full sheets of 3/4″ Rmax R-Matte Plus-3 unde the rafters. Then taping the seams of the Rmax with Tyvek housewrap tape, to try and air seal as much as possible.

Also, there are 4 fiberglass jboxes in roof that will be getting LED surface lighting installed. I was planning on using fireblocking foam to surruond the jboxes.

2.5″ Hunter polyiso=   R15.3

3/4″ dead air          =    R2.77

3/4″ Rmax              =     R5

Total Rvalue          =    23.07

What do you guys think?