Shut down the system to avoid air pressure pushing through while you're working.
This also prevents dust or adhesive fumes from entering the living space.
2. Inspect and Clean the Damaged Area
Wipe down the duct using a dry cloth or mild degreaser.
Remove any rust, dust, or condensation using a wire brush or sanding pad.
Let it dry completely.
3. Cut and Remove Damaged Sections (If Needed)
If the hole or tear is too large, cut out the damaged portion with metal snips.
For small punctures or tears, you can patch directly over them.
4. Apply Aluminum Foil Tape
Use UL 181-rated aluminum foil tape for air ducts.
Seal over the damaged area or seams at least 1 inch beyond all edges.
Press firmly and smooth out wrinkles to ensure airtight adhesion.
5. Seal with Mastic Duct Sealer (for Long-Term Durability)
Using a brush or gloved hand, apply HVAC-grade mastic sealant over the taped area.
Cover all edges and overlapping tape.
Let it dry fully (typically 24 hours) before turning the system back on.
6. Re-Insulate the Duct (if previously insulated)
Wrap new R6 or R8 insulation around the patched area.
Use insulation tape or zip ties to secure.
If the original duct was flex duct, seal the outer vapor barrier as well.
7. Check for Leaks
After 24 hours, turn the system back on and inspect for any air leaks using:
Your hand (feel for airflow)
Incense/smoke test
Or a pressure test if available
✅ TOOLS & MATERIALS CHECKLIST
Aluminum Foil Tape (UL 181-rated) – Used to seal small cracks, tears, and seams on ductwork. Provides a strong, heat-resistant, airtight seal.
Mastic Duct Sealant (HVAC-grade) – A flexible, long-lasting paste applied over tape and joints to create a permanent air-tight seal. Ideal for irregular surfaces.
Wire Brush or Sanding Sponge – Cleans off rust, debris, or old adhesive to ensure proper bonding of sealant or tape.
Utility Knife or Metal Snips – Used to cut out damaged sections of metal ductwork or trim insulation as needed.
R6 or R8 Insulation Wrap (for insulated ducts) – Wraps around ductwork to maintain temperature efficiency and meet code requirements.
Insulation Tape or Zip Ties – Secure insulation wrap around the duct after patching. Helps maintain the integrity of the vapor barrier.
Clean Cloth or Degreaser Wipes – Used to remove dust, oil, or condensation before applying tape or sealant.
Gloves (nitrile or work gloves) – Protect your hands from sharp edges, mastic, and insulation fibers.
Safety Glasses or Goggles – Prevents debris, insulation, or mastic from getting into your eyes during cleaning or sealing.