Spray foam against underside of roof deck? Or install vent baffles?
my location is zone 6.
my roof design is a cape: 5′ of rafters get insulated with sprayfoam from the plate to the intersection of the collar ties which form the “drop” ceiling and are also insulated.
My plan had been to install site built baffles in order to provide a 2″ airspace between the foam and underside of the roof deck. Rafter tails are exposed – no fascia and soffit, and the vents originate where the siding meet the roof deck and the vents dump into the short attic space. The ridge would be vented.
I’ve just had a foam installer out who is encouraging me to spray the foam against the underside of the roof deck directly omitting the vents and baffles.
I could go this route and instead provide gable vents.
My initial preference for the vented rafters arose out of my apprehension to seal off the bottom of the roof deck making it impossible to ever detect any roof leaks until damage occurs. With the 2″ space I can sight down the channels. I’ve included a sketch of the roof.
Am I wasting energy installing the baffles and vents and would I be further ahead just installing the foam against the roof deck?
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