The 36-Year-Old Florida Study Every Duct-Sealing Pitch Quotes (and What It Really Found)

If you’ve sat through a duct-sealing sales pitch in Florida — or read a contractor’s website — you’ve seen the claim: sealing your ducts can cut cooling costs by nearly 20%.

That number is real. It comes from one specific study, conducted on Florida homes, published in 1990. Thirty-six years later, it’s still the backbone of the pitch. Here’s what the study actually measured, what it found, and where its numbers do and don’t apply to your house.

The Study Behind the Claim

The full citation: Cummings, J.B., N. Moyer, J.J. Tooley, Jr., and R. Dunsmore. “Impacts of Duct Leakage on Infiltration Rates, Space Conditioning Energy Use, and Peak Electrical Demand in Florida Homes.” Proceedings of the ACEEE 1990 Summer Study, Pacific Grove, CA, August 1990. Florida Solar Energy Center, FSEC-PF-217-96.

The full text is still hosted by the Florida Solar Energy Center at fsec.ucf.edu.

One detail worth flagging: the “-96” in the report number is FSEC’s catalog suffix, not the study year. The research is from 1990.

What It Actually Found

Three headline findings, quoted directly from the paper.

Cooling energy dropped 18%

“Air conditioner energy use decreased by 18.0% because of duct repair.”

Not 18% off your total electric bill — 18% off air conditioner energy use. In Florida, where cooling runs most of the year, that’s still a meaningful chunk of the bill, but it’s a narrower claim than most sales pitches let on.

Payback was under two years

“At an average cost of $200 per home, duct repairs have a simple payback of less than two years.”

More on that $200 in a moment, because it’s the most misused number in the study.

Return leaks were the big offender

“Return leaks were found to average 10.0% of air handler total flow.”

A leaky return duct doesn’t just lose cooled air — it pulls unconditioned air into the system before it ever reaches the coil. One in every ten cubic feet moving through the average air handler in these homes was leakage on the return side.

The sample sizes

Per the paper: “Testing for duct leakage was done in 91 homes.” “Duct repairs were made on 25 homes.” “Cooling energy use was monitored on 24 homes before and after duct repair.” So: 91 homes tested, 25 repaired, 24 measured before and after. Keep those numbers in mind for the limitations section.

The $200 Is 1990 Dollars

When a contractor quotes this study, the $200 repair cost almost always comes along for the ride — usually without a date attached. That figure is in 1990 dollars. Inflation-adjusted, it’s roughly $490 in 2026 dollars.

And even $490 is just the inflation-adjusted study average, not a quote for today’s market. We’re not going to invent a current duct-sealing price here — what your job costs depends on your duct layout, how accessible the ducts are, and how bad the leakage is. Get itemized quotes.

What does carry forward is the payback logic: the study’s repairs paid for themselves in under two years because the energy savings were large relative to the repair cost. If a quote you receive is many multiples of the work involved, the two-year payback math the salesperson is implying may not hold. Ask them to show the math with their price and your actual bills.

Why a 1990 Study Still Matters in Florida

The physics hasn’t changed, and the study’s setting is the reason it keeps getting quoted here specifically.

Florida is a year-round cooling market — air conditioning runs nine to twelve months in most of the state. Every hour the system runs, duct leakage costs you money, so the same percentage loss hurts more here than in a mild climate.

Humidity is the defining constraint of Florida HVAC. Latent (moisture) load matters as much as temperature. A return leak in a hot attic doesn’t just pull in hot air — it pulls in humid air the system then has to dehumidify, working the equipment harder and leaving the house clammier.

And the typical Florida duct system runs through unconditioned attic space, where summer temperatures are brutal. Leaks on either side of the system are exchanging air with about the worst environment in the house.

The Honest Limitations

Anyone quoting this study at you should also be willing to admit what it isn’t.

It’s 1990 construction. These were Florida homes tested and repaired 36 years ago. Duct materials, installation practices, and building codes have all changed since.

The sample was small. Repairs on 25 homes, before-and-after monitoring on 24. That’s legitimate field research, not a guarantee for your house.

18.0% is an average. Some homes in the study necessarily saved more, some less. If your ducts are already tight, sealing them saves you very little — which is why the study started by testing 91 homes for leakage before repairing any. Measurement first, repair second. Demand the same order from anyone pitching you.

Utilities Put Real Money Behind This Work

Here’s independent evidence the savings are real: utilities pay rebates for duct sealing. They only fund measures that measurably cut load. Examples from programs we track (verified July 2026):

• Georgia Power — Home Energy Improvement Program: duct sealing up to $400. The work must be done by a DET Verifier or Program Installer.
• Tucson Electric Power (TEP) — Efficient Home Program: duct sealing up to $300, through a participating program contractor.
• TVA EnergyRight (via north Alabama local power companies): $300 duct sealing rebate, with work completed by a member of TVA’s Quality Contractor Network.

None of those serve Florida — the Florida utility programs we track (FPL, TECO, JEA, OUC) currently center their HVAC rebates on equipment replacement rather than standalone duct sealing. But they show the pattern: where duct-sealing rebates exist, they typically require a program-approved contractor. Check your own utility’s current offerings before paying entirely out of pocket, wherever you live.

How to Use This When You Get the Pitch

1. Ask for measurement, not promises. The FSEC researchers tested for leakage before repairing anything. A contractor who wants to seal your ducts without testing them is guessing.
2. Ask about the return side. The study found return leaks averaging 10.0% of air handler flow — that’s where the money tends to be, especially with ducts in a hot, humid attic.
3. Anchor on the real numbers. An 18.0% average cooling-energy reduction, on 1990 Florida homes, after professional repair. Treat promises well beyond that with skepticism.
4. Run the payback math with today’s prices. The under-two-year payback came from ~$490 repairs in today’s dollars. If the quote is far higher, the payback stretches — make the contractor show you the math with your actual bills.