Insulation

Closed Cell Foam Insulation (ccSPF), per article in Coastal Contractor Magazine, Jan/Feb 2008
-superior thermal performance to fiberglass batts (frequently compromised by stuffing into small spaces)
-R-value of 6.5-7/inch
-limited to 5" thick sprayed overhead
-absorbs negligible amount of water; effective secondary rain barrier; only FEMA-approved insulation for flood-resistant construction
-controls diffusion
-air barrier qualities
-expands to fill voids in hard-to-insulate areas
-adds structural integrity to the frame
    + University of Florida research demonstrates an effective bond of sheathing to framing with 3" of foam.  Effect is same benefits of increasing nailing schedule from 6/12 to 6/6.  Using only foam to glue down the sheathing nearly equals (178-209 psf) 8d common nails (205 psf) installed at the 6/6 schedule.
(1/2" OSB on 2x4 framing @ 24".)
    + "fillet method" = 3x5" bead of ccSPF in corners between sheathing and the roof framing.  Effectively doubled uplift resistance of baseline assembly of 2x4 framing on 24" centers (1/2" OSB, 6/12 nailing.)
    + Wall A: Conventional wood-framed walls + 1/2" OSB + housewrap + siding = failure to withstand impact required by ASTM E1886 and E1996 missle test, which hurls a 9 lb 2x4 at 50 ft/sec. 
        Wall B: 1/2" OSB sheathing + 1" foam insulating sheathing + 2" ccSPF between 2x4 studs = pass.
        Wall C: 1" foam insulating sheathing + housewrap + ccSPF (no OSB) = better than wall with housewrap and OSB.