vented or unvented for flat roof retrofit in an old row house?

I’m looking to insulate (and lower my heating bills) in my 100 yr old row house in Queens, NY, starting with my uninsulated, unvented cockloft attic space under a flat roof.… I’m looking to insulate (and lower my heating bills) in my 100 yr old row house in Queens, NY, starting with my uninsulated, unvented cockloft attic space under a flat roof.…Read MoreGreenBuildingAdvisor