Visible Ductwork Leaks?

After 14 years crawling Tampa Bay attics, I can usually spot the leak pattern before I even pull out the flashlight. Tampa attics push past 130 degrees from May through September, and that heat does specific damage to specific parts of your duct system. Here is what we find on almost every job.

The first thing we see on older homes is shredded inner liner on flex duct. The mylar inside the flex run breaks down after 15 to 20 years of attic heat, and pieces of it actually flake off and end up sitting in the supply boots. From the outside the duct still looks fine, but the airflow is choked and conditioned air is leaking through the broken inner wall into the insulation jacket.

The second pattern is rodent damage to the outer R-4 or R-6 jacket. Roof rats, squirrels, and the occasional opossum chew right through the insulation looking for a warm nest. We pull soggy fiberglass out of three or four torn sections per house in older Carrollwood and Town N Country neighborhoods. Once that jacket is open, the inner core gets crushed and air dumps straight into the attic.

Third pattern is supply boot separation at the ceiling. Builder mastic dries hard after 10 years, the house settles, the AC vibrates 8 hours a day, and the boot pulls back a quarter inch off the drywall. You can feel the cold air with your hand from inside the room.

Fourth, we find collapsed trunk lines from improper hanger spacing. Code says support every 4 feet, but plenty of 1990s and 2000s installs went 8 to 10 feet between straps. The duct sags into a U shape and pinches off airflow.

Fifth pattern is duct tape patches that builders or handymen slapped on top of failing mastic joints. Cloth duct tape has zero business on HVAC ductwork. It dries out, peels off, and leaks worse than the original joint did.

Sixth, cracked sheet-metal connections at the air handler plenum from thermal cycling. The metal expands and contracts with every cooling cycle and after a decade the seams split open.

Seventh, round flex collapsing on long runs over support straps that cut into the jacket. Common on 25-foot-plus runs to back bedrooms.

Not every leaky duct system needs a full replacement. We rank the fix to the actual damage so you are not paying for more than you need.

Spot repair on flex duct using mastic and tie-strap runs $145 to $295 per location. Good fit when you have one or two visible tears on otherwise healthy 5 to 10 year old duct. We strip back the jacket, mastic the inner core, retape the joint, and re-insulate.

Boot reseal at the ceiling runs $95 to $195 per boot. We pull back the drywall trim, scrape out the dried builder mastic, lay fresh fiber-reinforced mastic, and re-set the boot tight to the drywall. Usually a 30 to 45 minute job per boot.

Aeroseal whole-system sealing runs $1,995 to $3,495 depending on system size. This is the option I recommend for homes with leaks scattered across the system or ducts buried deep where crawling is not practical. Aeroseal pressurizes the duct system, blows aerosol sealant from the inside, and the particles bridge gaps up to 5/8 inch. Typical 80 percent leakage reduction. No attic crawling, no demolition, done in one day.

Full duct replacement with R-8 insulated flex runs $2,500 to $4,500 for a typical 3-ton single-zone home. Right answer when ducts are 18-plus years old, multiple sections damaged, or insulation is already saturated.

Sheet-metal trunk line replacement runs $1,500 to $3,500. We see this on commercial conversions and older homes where the trunk has cracked seams across multiple joints.

Rodent damage requires pest removal first, $295 to $695 through a licensed wildlife removal company, before any duct repair makes sense. Patching ducts while rats still have access just means re-doing it in 6 months.

Every job starts with a FREE estimate and full attic inspection. We climb up, run the duct camera, pressure test if needed, and show you exactly what we found before quoting anything.