2 lb density spray foam is a closed cell product that offers an R-value of 7 per inch (the most of any insulation) and acts as a vapor barrier at two inches thick. With foams ability to seal and insulate nothing else will give you the comfort and quality of life that poly urethane foam will offer.
Spray foam eliminates those drafts caused by seams, and plumbing or electrical penetrations. Much higher R-values may be attained in vaulted ceilings by using 2lb foam so you do not have
to sacrifice comfort for the beauty of vaults.
Areas such as joist ends and rim joists that are nearly impossible to adhere a proper vapor seal with conventional insulation are done so much more efficiently with 2 lb foam. Decks and cantilevers sprayed with foam will not leave that cold spot on the floor we so hate to stand on.