On my window van I used foil laminate iso foam, covered on both sides. Also took the time to wipe down metal & foam board with sprayed isopropyl alcohol to chase oil/silicone residues leftover from manufacturing.
We placed a 1/2" layer above/below windows and then added an 1" layer on top of below windows lower areas - used 3M 90 spray adhesive AND a thin bead of gunned foam-in-a-can around the face perimeter of each sheet as an air draft gasket, the 3M 90 when applied per directions will grab and hold while the foam cures, just keep massaging the panel to get it following the slight curves so both adhesives set under tension since all the panels have some curve/cup to them.
I did use the window and door gunned foam cans on the walls - thinking on using the true adhesive on the ceiling.
I grouted the panels flush with the window/door foam between layers, that's where the stuff excels, very minimum heave after the initial expansion and leaves a fine grain foam - if it's disturbed at all after applying it will collapse into coarse bubbles & voids so patient beads no double-taps of filling areas in while still wet.
There is a nook inside the stamped framing where the ceiling meets the floor, cutting 1/2" thickness strips just narrow enough to fit through the lightening holes and laying in three in parallel did a nifty job of insulating that section, plus leaves lots of room to stuff in more behind it.
I also bought shredded denim foil faced bats to add in to the top/bottom wall sections, Home Depot ships them, hopefully to total R-14 below and R-8 above for now. Also nabbed a roll of
http://www.dupont.com/products-and-...r-barrier-systems/products/Thermawrap-r5.html to use in the doors, stuff all the nooks and crannies with, and generally fill in voids as I piece together the built-ins...
As to quantity required - getcher tape measure out. And the sheet foam is fragile & the stuff ages exposed to weather & sunshine, next time I would not buy it all at once and maybe let the store keep it safe & protected until I needed it....