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Applying liquid duct mastic sealant to sheet metal ductwork joints in a basement

How to Seal HVAC Ductwork Leaks with Mastic and Foil Tape

August 16, 202616 min read

Learn how to seal HVAC ductwork leaks using mastic paste and foil tape in unconditioned basements or crawlspaces. This step-by-step guide covers thermal auditing, duct repair, materials, safety checks, and insulation to restore airflow and lower utility costs.