Insulation fastener placement is normally specified at 6" from the board edges with a tolerance of +/- 1.5". Recent testing accomplished by FM Global reveals that variations in fastener placement can significantly reduce the wind uplift resistance of the system. FM test results found that moving the fasteners from 6" to 12" from the board edges can reduce the uplift resistance as much as 1/3 of its original value.

Placement does matter and allowing the fasteners to be arbitrarily moved for convenience of installation can significantly reduce the system wind uplift resistance.