A properly insulated attic and a well-ventilated roof will help you reduce heat loss and moisture condensation in the winter as well as reducing heat retention in the summer. The bottom line is that a properly installed roofing system will help you conserve energy and reduce your Utility Hydro Bills.
Further, Adequate ventilation and insulation in your attic will also help reduce the possibility of ice-dams from occurring. Ice-dams are caused by uneven roof temperatures and melting snow.