They are only huricane hangers by name, they are to insure that there are enough nails in the rafters to prevent all kinds of problems and with climate changes who knows.
The fan-fold (1/2") may have a perm rating of 1.1 Perms; http://www.google.com/url?sa=t&rct=j...52434380,d.cGE
For your location, Zone 6; http://energycode.pnl.gov/EnergyCode...sp?state=Maine
With over 1 perm at sheathing, you are vapor semi-permeable and require asphalt faced paper, SVR, or v.b. paint next to the drywall, Fig.4a: http://www.buildingscience.com/docum...nd-wall-design
Don't use poly when a Class 2 will work; http://www.buildingscience.com/documents/information-sheets/info-sheet-310-vapor-control-layer-recommendations/
Been the same for many years; "A polyethylene vapor diffusion barrier and air barrier should only be
very cold hygro-thermal regions. If it is used in other regions it reduces
potentials to the interior more than it reduces wetting potentials from the
interior." From; http://www.google.com/url?sa=t&source=web&cd=22&ved=0CBQQFjABOBQ&url=htt p%3A%2F%2Fwww.buildingscience.com%2Fdocuments%2Fre ports%2Frr-9910-wood-durability&ei=L1JYTMG1LoyksQO_obC3Cw&usg=AFQjCNGKC c1gz_HCcZylkv71jEkZUZC98Q
ADA the drywall; http://www.buildingscience.com/documents/information-sheets/air-barriers-airtight-drywall-approach/
Gary: I stand corrected but some of your links don't work. Just to be clear, are you saying it is not required, or he should not do it?