Ductwork Inspection & Repair Guide
How to inspect and repair residential ductwork — identifying leaks, insulation damage, and airflow problems that waste energy and reduce comfort.
The Hidden Energy Waster
Ductwork is out of sight and out of mind for most homeowners, but leaky or poorly insulated ducts can waste 20-30% of the energy your HVAC system produces. The EPA estimates that the average home loses $200-$400 per year through duct problems.
Signs of Ductwork Problems
Inspection Process
Visual Inspection
Access your attic, basement, or crawlspace and examine visible ductwork. Look for disconnected sections, crushed flexible duct, torn or missing insulation, and visible holes or gaps at connections. Flexible duct should not have sharp bends or be compressed — both conditions dramatically reduce airflow.
Pressure Testing
A professional duct test uses a calibrated fan (Duct Blaster) to pressurize the duct system and measure total leakage. Acceptable leakage is less than 6% of total system airflow. Many existing homes test at 15-25% leakage — indicating significant repair opportunities.
Repair Methods
Mastic sealant: A thick, paintable adhesive that permanently seals joints and small gaps. This is the professional standard — never use standard duct tape, which dries out and fails within 2-5 years.
Metallic tape: UL-listed aluminum foil tape (not cloth "duct tape") provides a durable seal for accessible joints. Apply over clean surfaces with firm pressure.
Aeroseal: A technology that seals ducts from the inside by injecting adhesive particles into pressurized ducts. The particles collect at leak points and build up to seal them. Effective for reaching inaccessible duct sections. Cost: $1,500-$3,000 for a typical home.
Insulation Requirements
Ducts in unconditioned spaces (attics, crawlspaces, garages) should be insulated to a minimum of R-8. Uninsulated ducts in a 140°F attic can lose 10-15°F of cooling capacity before air reaches the living space. Adding duct insulation costs $2-$5 per linear foot and pays back within 2-3 years through energy savings.
For accurate estimates on ductwork repairs and HVAC improvements, use the ModuBlox cost estimator to compare pricing from verified HVAC contractors in your area.