Air ducts are responsible for a large portion of HVAC-related energy losses. According to the U.S. Environmental Protection Agency’s Energy Star program, 30% of heated and cooled air escapes from the ducts before it reaches its final destination. Some of the most common warning signs include hot and cold spots, odors, and low or no airflow. Loose ducts can be reconnected, and small cracks can be sealed with metallic foil tape. If the ducts are damaged, contaminated, or collapsed, it is usually time to call a professional. Trained AC technicians can also determine if the supply and return ducts are properly sized.