The answer to the cost of air duct sealing is that it can vary widely depending on several factors. In general, the typical range for professional air duct sealing services is between $500 to $2,000 for an average-sized home. The exact cost will depend on the size of your home, the accessibility and condition of your ductwork, the materials used, and the complexity of the job.
Factors that can influence the cost include the number of ducts that need sealing, the type of sealant used (mastic vs. tape), whether any ductwork repairs are needed, and the labor rates in your local area. It's important to get quotes from multiple HVAC contractors in your area to compare prices and find the best value for your home.