What is STL Air Pros The Premier HVAC Company?

The top-rated HVAC company in St Louis for home and business owners, providing expert HVAC diagnostics, maintenance, and new HVAC installation.

How do I know if my ducts are leaking?

Common signs are rooms that never reach the set temperature, weak airflow from some vents, and higher-than-expected energy bills. We can measure duct leakage directly with a pressure test, and in most St. Louis homes we find significant leaks at the plenum, takeoffs, and boot connections that mastic sealing will fix.

How much air should leak from my ducts?

Industry standards say total duct leakage should be under 10% of your system's airflow, and leakage to the outside (attic or crawlspace) should be minimal. Many older St. Louis homes we test are at 25–35%. Sealing that down can dramatically improve comfort and efficiency.

Can you add ductwork to a finished basement or addition?

Yes. We design and install duct runs for additions, finished basements, and bonus rooms — including the supply, return, and register layout. If extending the existing system isn't practical, we can also design a ductless mini-split to condition the new space independently.

Will sealing my ducts lower my energy bills?

In most homes, yes — often by 15–25% on heating and cooling. Leaky ducts waste conditioned air in unconditioned spaces and force your system to run longer. Sealing is one of the highest-ROI comfort upgrades you can make, and we measure the before-and-after so you can see the difference.

Ductwork

Ductwork Repair & Installation in St. Louis

Leaky, undersized, or poorly designed ductwork wastes up to 30% of your heating and cooling. We seal, modify, and design ductwork so every room reaches the temperature you set.

Call (314) 328-0008 Free Estimate

HVAC ductwork installation and sealing by STL Air Pros in St. Louis

Ductwork Services in St. Louis

Your ductwork is the delivery system for every dollar you spend on heating and cooling — and in older St. Louis homes it's almost always the weak link. The Department of Energy estimates that 20–30% of the air moving through a typical duct system is lost to leaks, gaps, and poor connections, which means your furnace and AC work harder and your rooms still aren't comfortable. We inspect, seal, modify, and redesign ductwork to fix the root cause of comfort problems. That includes sealing leaks with mastic, adding or rerunning supply and return runs to fix hot and cold spots, upsizing undersized returns that starve your system, and designing balanced airflow for additions and finished basements. We also test the results — measuring airflow and static pressure before and after so you can see the improvement, not just feel it.

Signs You Need Ductwork

If any of these sound familiar, it's time to give us a call.

Some rooms are always too hot or too cold

Weak airflow from certain vents

High energy bills with a relatively new system

Dusty rooms even with a clean filter

Loud whistling or popping from the ducts

Finished basement or addition with no ductwork

System short-cycles despite being properly sized

Visible gaps or disconnected ducts in the attic or crawlspace

What We Handle

Duct leak detection and mastic sealing

Supply and return duct modification and rerouting

Undersized return air upsizing

Ductwork design for additions and finished basements

Duct cleaning referrals and post-cleaning sealing

Airflow balancing and zone system installation

Duct insulation and wrapping

Static pressure testing and airflow verification

How It Works

Inspection & testing

We inspect visible ductwork, measure static pressure and airflow, and identify leaks, restrictions, and design problems.

Diagnosis & quote

We show you exactly what's wrong — leaky joints, undersized returns, poor layout — and quote a fixed price to fix it.

Sealing & modification

We seal leaks with mastic, modify or rerun ductwork as needed, and balance airflow to the problem rooms.

Verify the fix

We re-test static pressure and airflow so you can see the measurable improvement before we pack up.

Licensed & Insured NATE-Certified Techs 24/7 Emergency Service Upfront Pricing

Ductwork Services in St. Louis — Common Questions

What St. Louis Customers Say

Real reviews from homeowners across the metro who trusted us with their HVAC.

"Our AC went out on a 97-degree day and STL Air Pros had a tech at our house within two hours. Fixed a blown capacitor on the spot, explained exactly what failed and why, and the price was totally reasonable. Won't call anyone else."

Marcus Thompson

Webster Groves, MO · May 2025

Google

"Replaced our 18-year-old furnace with a new high-efficiency unit. The crew was on time, professional, and cleaned up completely. They also caught a small carbon monoxide issue with the old heat exchanger — probably saved our family from a serious problem."

Diane Reynolds

Kirkwood, MO · March 2025

Google

"I've used three different HVAC companies over the years and STL Air Pros is in a different league. Straight answers, no upselling, competitive pricing. My maintenance plan has caught two small issues before they became expensive repairs."

James Kowalski

Chesterfield, MO · January 2025

Yelp

Ductwork Services Across the St. Louis Metro

Dedicated ductwork services pages for cities across St. Louis, St. Charles, and Jefferson counties.

St. Louis Chesterfield St. Charles O'Fallon Florissant Kirkwood Ballwin Wentzville

Ready to Schedule Ductwork?

Licensed, insured, and ready to help across the St. Louis metro. Call now or request a free estimate online.

314-328-0008 Request an Estimate