I just had the roof on the back half of my house replaced to help detour ice damming but the roofer was stressing insulation and getting done so that it doesn't ice dam. The patio is an addition, low slope roof put directly on the existing roof in three places where it is properly pitched. The ice either dams right where the old and new roof meet, or in the gutter. The regular roof has shingles and the patio roof now has a rubber roof. The question is should I use spray foan insulation right to the underside of the patio roof or try to do regular pat insulation in the rafters and work on proper ventilation of the small area between the ceiling rafters and the roof. The room is of substantial size 15×20 and you can enter it from three different areas of the house. The heating is with a baseboard electric heater that does a very good job. The area now has vents that are left over from the old roof section under the overhang but are at the same level as the soffit vents. I really just want to do what is needed to keep the roof from leaking into this patio. It has been a long standing problem with this house since the pation was added on.