Of the trillion dollars that we lose each year in wasted energy, as an architect I miss the following product as roofs are primary heat and cooling loss in our country:
Sandwich panel of R=80 with solar PV as integral part of surface.
Sandwich made of nailable rigid panel on top equal to 5/8" plywood, two layers of foil 3/8" apart under, foil faced poly iso layer of R=60 and with foil underlayer at the bottom for vapor barrier and attached to eq of 1/2" plywood.
The odds and ends pieces that are common in each job would be solid ISO with foil on each and every side for vapor control, sides field applied.
The goal would be to have 40% of energy loss technically taken care of in an average building, and thus leave the easier task of walls and windows to next years entry.
As a result, the solar only has to do 40% less work to keep the house PASSIVE.