I am working on a reroof of an old building where we are going to add exterior foam insulation after removing the old roofing materials. I plan to vent the roof with 2x4s on top of the foam running from eave to ridge giving us a 1 1/2″ vent space followed by a new plywood deck and standing seam metal panels. The underside of the roof was recently sprayed with 4-5 inches of cc spray foam. After securing the old roof boards with screws, I plan to put a layer of #30 felt paper down followed by (2) 1 1/2″ layers of EPS foam – the idea being that those two materials will allow some drying potential up into the vent space.

Due to the design of the roof, which has massive overhangs, I plan to vent the intake at the eaves with a space between an upper and lower fascia board. It seems any venting calculations I’ve come across don’t pertain to this type of roof. Originally I had planned to bend stainless steel insect screen around spacers between the two fascia boards – but that sounded like a pain from the start. I’m considering using a plastic vent strip made by Cor-a-Vent that is designed just for this type of vent setup. It is a corrugated strip that is 1 inch wide and has 10 sq. in. NFVA [net free ventilation area] per foot. Any help figuring out if this will be adequate would be greatly appreciated. I’ve attached a photo of the building to show the scale of the roof.

Thanks!