Using flexible ducts saves time, but careless installation can cause performance-related problems that are hard to find and even harder to fix after the drywall goes up. On most projects, HVAC ductwork is located in designated chases that maximize the efficiency of the airflow. But the path for the final branch of the ductwork tree—the one that runs from the trunk or plenum to the outlet register—is typically chosen by the subcontractor. Often, they find themselves competing to find space to run the ducts among all the wiring and piping already installed by the electrical and plumbing trades. Flexible ducts can speed installation by reducing the number of joints in a run and eliminating the need for elbows and offsets. They also easily conform to oval as well as round connectors. But the physical properties of flexible ducts that create advantages are also the source of potential problems if care isn’t taken during installation. A good first step, or course, is to make sure there