How Much Does Air Duct Replacement Cost in St. Louis? [2025 Data]

In St. Louis, where muggy summers and brisk winters push your HVAC system to its limits, ductwork plays a vital role in home comfort. Replacing worn or inefficient air ducts ensures consistent airflow and helps lower your energy bills. On average, air duct replacement in St. Louis, MO, costs $724, with most homeowners spending between $376 and $1,072. Several factors influence the total price, including materials and layout. Here's how much you can expect to pay—and why.

Air Duct Replacement Cost Factors 

Air duct replacement isn’t one-size-fits-all. In St. Louis, older brick homes may present more challenges than modern builds in Chesterfield or O’Fallon. Whether you're replacing all the ducts in a multi-level house or just a few runs during a renovation, local labor rates, duct access points, and Missouri's four distinct seasons all factor into the final cost.

Size

The size of your home directly affects air duct replacement costs. Larger homes require more materials and labor to replace the entire duct system. On average, the cost ranges from $2,000 to $5,000 for a small- to medium-sized home. However, duct replacement can run as low as $1,400 for smaller homes and as high as $9,000 for larger homes. Here’s how the size of your home affects duct replacement costs:

Duct Location

If only specific sections of your ductwork need replacement, such as in a renovation project, costs will depend on the location of the damaged or worn ductwork. Replacing ducts in hard-to-reach or concealed areas—like attics, basements, ceilings, walls, or crawl spaces—can increase labor costs. Here’s how the location of the ducts could affect their cost:

Duct Material

The material you choose for your replacement ducts affects both their cost and longevity. Flexible ducts for retrofits and tight spaces are the most commonly used duct material in St. Louis, MO, while sheet metal is a top choice for longevity and airflow efficiency, especially in larger homes or new construction projects. 

Sheet metal ducts are durable but pricey. Flexible ducts, on the other hand, are more affordable but may need to be repaired or replaced sooner. Here’s a breakdown of air duct replacement costs based on the type of air duct:

HVAC Pro Costs

You should hire an HVAC pro in St. Louis to handle this job. Full duct replacement projects may require two or more technicians over one to three days. Expect higher rates for work in homes with hard-to-access ductwork, such as those built before 1950 in neighborhoods like Benton Park or The Hill.

For an accurate estimate, it’s best to get multiple quotes from licensed professionals in your area.

Labor Costs

HVAC pros in St. Louis charge $75 to $125 per hour. Service call fees start around $100, and rates may increase if you need work done during extreme weather. Summer heat waves and cold snaps in January often drive up demand, so plan ahead if possible to avoid seasonal surcharges.

Permits and Regulations

In St. Louis City and St. Louis County, ductwork replacement requires a mechanical permit. Permit fees start at $100 to $150, depending on project size. These permits ensure your ducts meet local building codes and pass inspection, which is particularly important if you plan to sell your home.

Licensing and Insurance

In Missouri, HVAC professionals must register at the local level rather than hold a single statewide license. In St. Louis, many HVAC companies are certified through municipal licensing boards and must comply with local regulations. Reputable contractors will also carry liability insurance and workers’ compensation coverage—be sure to confirm credentials before hiring.

Local Climate Considerations

St. Louis’s humid summers and frigid winters place extra stress on duct systems. Ducts in unconditioned attics or basements are vulnerable to condensation, which can lead to mold or rust. Local pros often recommend insulating ducts during replacement to prevent air loss and moisture damage, particularly in older homes with unfinished basements or tight crawl spaces.

Additional Pros to Consider Hiring 

While your HVAC contractor will handle the bulk of the air duct replacement work, there are situations where additional professionals may be needed—especially in older or custom-built St. Louis homes. Here’s who you might need on your project team:

• General contractors: If your ductwork is hidden behind walls, ceilings, or under flooring—as is common in historic homes around Lafayette Square or Shaw—you may need a general contractor to manage demolition, framing, and finish carpentry. This is especially likely if you're upgrading from outdated galvanized ducts to more efficient materials.

• Mold remediation specialists: St. Louis’s humid climate, paired with older homes that may have moisture issues in basements or crawl spaces, can create conditions for mold growth. If your HVAC pro discovers signs of mold in or around your ducts, it’s critical to bring in a certified mold remediation specialist to address the problem before new ducts are installed.

• Insulation contractors: Proper insulation around ducts is essential for keeping energy bills in check—especially in unconditioned spaces like attics or crawl spaces. Insulation pros can ensure new ductwork is sealed and wrapped according to Missouri energy code standards.

• Electricians: If duct replacement requires moving or working around electrical wiring—especially in homes with finished basements or complex HVAC zoning systems—an electrician may be needed to reroute lines or install additional circuits safely.

• Asbestos abatement specialists: In older St. Louis homes, particularly those built before 1980, you might encounter asbestos insulation on or near ductwork. If suspected, you’ll need a licensed abatement contractor to safely remove the material before work can proceed.

Hiring the right pros ensures your duct replacement goes smoothly and complies with local building codes and safety standards. Ask your HVAC contractor if any additional specialists are recommended for your home.

Does Air Duct Replacement Increase Home Value?

Replacing ductwork at your St. Louis home can yield a return on investment (ROI) of between 50% and 75%. New ductwork enhances HVAC performance and lowers monthly bills, which can be particularly beneficial in regions like Missouri, where there are significant temperature swings.

In competitive neighborhoods such as Clayton or Kirkwood, where buyers are more likely to expect updated systems, new ductwork can help your home stand out. Plus, a well-sealed duct system can make your HVAC run more quietly and efficiently—another plus during those humid St. Louis summers.

How Angi Gets Its Cost Data

Home is the most important place on earth, which is why Angi has helped more than 150 million homeowners transform their houses into homes they adore. To help homeowners with their next project, Angi provides readers with the most accurate cost data and upholds strict editorial standards. We survey real Angi customers about their project costs to develop the pricing data you see, so you can make the best decisions for you and your home. We pair this data with research from reputable sources, including the U.S. Bureau of Labor Statistics, academic journals, market studies, and interviews with industry experts—all to ensure our prices reflect real-world projects. 

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