Ductwork Repair Cost: Sealing Leaks and Fixing Damage

Duct Repair Costs by Problem Type

Ductwork problems fall into several categories, each with its own cost range. Understanding what you are dealing with helps you evaluate contractor quotes and decide whether repair or full replacement is the better investment.

Disconnected joints and seams cost $150 to $400 per connection to repair. This is one of the most common duct problems, especially in flexible duct systems where joints can pull apart over time due to gravity, vibration from the HVAC system, or poor initial installation. The repair involves reconnecting the sections, securing them with mechanical fasteners or clamps, and sealing the joint with mastic sealant or UL-181 rated tape. A single disconnected joint can waste 10 to 20 percent of the air flowing through that branch, making this one of the highest-value repairs you can do.

Holes and tears in flexible duct cost $100 to $300 per damaged section. Small holes under two inches can be patched with mastic and reinforcing mesh. Larger tears or crushed sections usually require cutting out the damaged portion and splicing in a new section of duct. If the flexible duct is over 15 years old, the inner liner may be brittle enough that patching creates new tears adjacent to the repair, making section replacement the more practical option.

Rust and corrosion on metal ducts costs $200 to $500 per affected section. Surface rust can be treated with rust converter and sealed with mastic, but perforated sections need to be cut out and replaced with new sheet metal. Corrosion is most common at duct joints, where condensation collects, and in ducts running through high-humidity areas like crawl spaces and uninsulated attics. Widespread corrosion across multiple sections is a strong indicator that full replacement will cost less than a series of individual repairs.

Crushed or kinked flexible duct costs $200 to $500 to repair per section. Flexible duct that has been stepped on in an attic, compressed by stored items, or kinked at a tight bend restricts airflow to the rooms it serves. The repair involves replacing the damaged section and adding proper support straps spaced every four to five feet to prevent future sagging. If the duct was kinked at a turn, the technician may also need to install a turning vane or elbow fitting to allow a smoother routing path.

Duct Sealing Methods and Costs

Duct sealing is the most common and cost-effective ductwork repair. The Department of Energy estimates that the average home loses 20 to 30 percent of its conditioned air through duct leaks, making sealing one of the highest-return home improvements available.

Manual sealing with mastic costs $400 to $1,900 for a complete home, depending on the number of accessible joints and the total linear footage of ductwork. A technician physically applies water-based mastic sealant or metal-backed UL-181 tape to every accessible joint, seam, and connection point. This method is thorough for ducts that can be reached, but it cannot address leaks hidden inside walls, above finished ceilings, or in other enclosed spaces. Manual sealing typically takes four to eight hours for a standard home.

Aeroseal technology costs $1,500 to $6,900 and seals leaks from the inside out. The process involves temporarily sealing all registers, pressurizing the duct system, and injecting a polymer aerosol into the ducts. The pressurized air carries the sealant particles to leak points, where they accumulate and seal gaps up to 5/8 inch in diameter. The main advantage of Aeroseal is that it reaches leaks no technician can access manually, including those behind walls and in enclosed building cavities. The system also provides before-and-after leakage measurements that document exactly how much improvement the sealing achieved. For a detailed comparison, see our duct sealing cost and energy savings guide.

What an Inspection Costs

A professional duct inspection costs $150 to $500 and is the recommended first step before committing to either repair or replacement. The inspection includes a visual examination of all accessible ductwork, a duct pressure test that measures total system leakage, airflow measurements at individual registers, and a report on the condition of insulation, supports, and connections.

The pressure test is the most valuable part of the inspection. It measures duct leakage as a percentage of total system airflow, with new ductwork typically testing at 4 to 8 percent leakage and older systems ranging from 15 to 40 percent. Results above 15 to 20 percent indicate significant energy waste and comfort problems. Some utility companies offer free or subsidized duct testing as part of their energy efficiency programs, so check with your local provider before paying out of pocket. Our ductwork and energy audits guide covers what to expect from a professional assessment.

When Repair Makes Sense vs Replacement

Duct repair is the right choice when the damage is limited to a few specific locations, the ductwork is less than 15 years old, and the overall system is structurally sound. A few sealed joints or a replaced section can restore system performance for a fraction of what full replacement costs.

Replacement becomes the better investment when repairs would need to happen at multiple locations throughout the system, when the ductwork is over 20 years old and showing signs of widespread deterioration, or when the duct sizing does not match your current HVAC equipment. In these situations, spending $500 to $1,000 on repairs that will need to be repeated in a year or two costs more over time than a one-time replacement that gives you 20 to 25 years of reliable performance.

A useful rule of thumb is the 50 percent rule. If repair estimates total more than 50 percent of what a full replacement would cost, replacement is almost always the smarter financial decision because it gives you a complete new system with a full warranty rather than a patched older system with an uncertain remaining lifespan.