Unvented to vented roof when have open cell spray foam against roof sheathing?

I have an approximately 100 year-old bungalow in climate zone 4A (Maryland).  It’s time to replace the roof (gable with front and back dormers).  The roof is unvented.  My question… I have an approximately 100 year-old bungalow in climate zone 4A (Maryland).  It’s time to replace the roof (gable with front and back dormers).  The roof is unvented.  My question…Read MoreGreenBuildingAdvisor