The answer to 'ductwork freezing up' is that it is a common issue caused by a variety of factors, including low airflow, low refrigerant levels, and cold outdoor temperatures. Symptoms may include ice buildup on the ductwork, reduced air flow, and poor heating/cooling performance.
Some common solutions include checking and replacing air filters, ensuring proper airflow, and addressing any refrigerant leaks. In some cases, the issue may require professional HVAC service to diagnose and resolve the problem.