Performed underground air duct repair for a 4" insulated ductwork system connecting the home to a detached garage. Excavated to expose the damaged section caused by root intrusion. Cut away and removed cracked ducting and foam insulation. Installed a new 4" rigid aluminum duct section using UL181 listed water-based mastic sealant at joints. Wrapped repaired area with R-8 insulation and sealed vapor barrier jacket. Backfilled with compacted gravel and soil. Restored airflow to detached garage while preventing moisture/air leakage issues underground.