I hung the drywall in my garage with the help of a few friends. My ceiling height was 12 foot. Renting scaffolding with wheels was a big help and not that expensive. I also rented a drywall lift. Normal height range was up to 11 foot, but they rent an 18" extension. It worked good and was a big help. The only down side is that the extension also meant that we had to lift the drywall an extra 18 inches to get the drywall on the lift. I'm not sure what you use to lift drywall 15 feet, but I would think the scaffolding would be a big plus.