After doing my insulation I delivered to a guy who does spray-on insulation, and found out that it was indeed cost-effective. It requires some work after the spray-on is done, to finish it and stuff, but it's actually very cost effective. Spray-on foam will cost more than a combination of foam board and canned foam you do yourself, but professional spray-on foam will save you about 4 days of insulating. To do the walls and ceiling of my Sprinter, dood said it would be in the $500 range. If I had known that, I might have gone that route in the first place. You'll still have to do a lot of shaving, cutting or sanding to finish it and then cover it with silver reflectix or something like the above liner, but it's a quick and easy way to efficiently get insulation into all the little nooks and crannys.