Hi Martin….I am building in zone 5 and have chosen to spray the roof deck with closed foam backed with open cel. There will be no air coming in through the soffits since the foam fills the roof joist cavity above the plate on the outside walls. My question is regarding the roof joist tails beyond the exterior walls. My intention was to close those soffits with cedar without any venting considering there will be no way for air to get out if I allowed it to get in. Is this an acceptable practice? or should I install a continuous vent on the underside as usual….assuming air will move in/out from the underside?

I fear after seasonal temperature changes that the tails could warp if they cant breath.

Thanks