to stop dams from forming in the first place is to keep the attic cold
When fiberglass batting is installed between the attic’s rafters, he said, there should be a two-inch air space between the underside of the roof and the insulation, to allow air to circulate. Homeowners should check the area where the roof meets the exterior wall and the attic floor for cracks or holes through which warm air from below can enter
best way to “super-insulate” the attic is with sheets of rigid foam insulation