Duct leakage: the hidden cost in your crawlspace.

A typical home loses 20–30% of its conditioned air through duct leaks — air you've already paid to cool or heat, escaping into places you don't live. In Georgia, the problem is worse than the national picture, because our ducts so often run through the two harshest environments a house has: attics that exceed 130°F in summer, and damp clay-soil crawlspaces. You pay for duct leakage every month on your Georgia Power bill, but it never appears as a line item — which is exactly why it goes unfixed for decades.

Our techs have been in Metro Atlanta attics and crawlspaces since 1972, and leaky ductwork is among the most common — and most commonly ignored — problems we find. Here's how leakage happens, what it actually costs you beyond the bill, how to spot it, and the honest cases where sealing isn't worth the money.

What is duct leakage, exactly?

Your duct system is a pressurized air-delivery network: supply ducts push conditioned air out to the rooms, return ducts pull house air back to the air handler. Duct leakage is any gap in that network — unsealed joints, disconnected takeoffs, punctured flex duct, poorly sealed boots where ducts meet floors and ceilings — that lets supply air escape before it reaches a room, or lets outside air get sucked into the returns.

Both directions cost you. Supply leaks dump cooled air into the attic or crawlspace. Return leaks are sneakier: a return running through a Georgia crawlspace that pulls in musty, humid air is feeding that air to your system to be cooled, filtered, and breathed. Leakage also unbalances the house — rooms served by leaky runs get starved, which is one reason a duct problem often masquerades as an equipment problem.

Why do ducts leak in the first place?

Ducts rarely leak because of one dramatic failure. They leak because of accumulation:

• Original construction shortcuts. Much of the two-story housing stock built across the northern Atlanta suburbs in the 90s and 2000s — Cumming, Suwanee, Alpharetta, Marietta — got ductwork installed fast, with fabric duct tape or minimal mastic at the joints. Tape adhesive is the first thing a hot attic destroys.
• Heat cycling. A 130°F attic in July and a 35°F attic in January expand and contract every joint, season after season, working connections loose over 20 or 30 years.
• Physical damage. Flex duct crushed under stored holiday boxes, runs snagged during a cable or security-system install, boots knocked loose by pest-control or insulation crews, and rodent damage in crawlspaces.
• Sagging and disconnection. Flex duct supported by failing straps droops, kinks, and eventually pulls off its collar entirely. A fully disconnected run — blowing conditioned air straight into the attic — is something our techs find more often than homeowners would believe, sometimes years after it happened.

What does duct leakage actually cost you?

The power bill is only the first layer:

• Energy you never use. If a quarter of your system's output leaks out, your system runs meaningfully longer to deliver the same comfort — through a Metro Atlanta cooling season that already runs 2,000-plus hours.
• Equipment wear. Those extra run hours are compressor cycles and blower hours you're spending on the attic's comfort. Leaky and restrictive ducts also raise static pressure, which strains blower motors — duct condition is one of the quiet factors behind why some Georgia systems die years early.
• Humidity and air quality. Return-side leaks pull humid, dusty, sometimes moldy air from crawlspaces and attics into the airstream. In our climate that's a double hit: the system must work harder to wring out moisture it imported itself, and the house can stay clammy even at the right temperature — a problem that overlaps with whole-home humidity control.
• Comfort you blame on the equipment. The hot bonus room over the garage, the bedroom at the end of the run that never cools — these are often duct problems wearing an equipment costume. Homeowners sometimes replace a system to fix a symptom the new system inherits on day one.

How do Georgia attics and crawlspaces make it worse?

Location multiplies the penalty. A duct leaking 20% inside conditioned space loses air to rooms you live in — inefficient, but partly recovered. The same leak in a Georgia attic loses that air to a 130°F oven, and every degree of that heat radiates back into thin-walled flex duct, warming the air that does make it to the registers. Crawlspaces add moisture: our clay soil holds water, crawlspace air stays damp much of the year, and return leaks down there import that dampness directly. The national 20–30% figure is an average; duct systems running entirely through unconditioned Georgia spaces are set up to do worse.

How is duct leakage measured and actually fixed?

Measurement first: a duct blaster test temporarily seals the registers, pressurizes the duct system with a calibrated fan, and reads exactly how much air it takes to hold that pressure — that number is the leakage. It turns "your ducts probably leak" into a figure you can weigh a sealing quote against, and a follow-up test after the work proves what you paid for.

Fixing it is less glamorous than most home upgrades, which is part of why it gets skipped. The durable approaches are mastic — a thick, paint-on sealant brushed over every joint, collar, and boot, which cures into a permanent flexible seal — and UL-181-rated foil tapes engineered for ductwork (unlike the fabric "duct tape" whose adhesive a 130°F attic destroys in a few summers). For duct systems with many small, inaccessible leaks, aerosolized sealant blown through the pressurized system finds and plugs gaps from the inside. Priorities in a typical Georgia job: reconnect anything fully separated, seal the boots and takeoffs where leakage concentrates, mend or replace damaged flex runs, and re-support sagging duct so the fix lasts. In our experience the biggest wins usually come from a handful of ugly failures — a disconnected bonus-room run, a return gap in the crawlspace — rather than from hundreds of pinholes.

When does duct sealing not pay back?

Sealing is high-payoff work, but not always. Honest cases where we'd tell you to wait:

• Ducts that test reasonably tight already. If a duct blaster test shows modest leakage, chasing the last few percent costs more than it returns. Spend the money on attic insulation or a maintenance plan instead.
• Ductwork that's beyond sealing. Crushed, undersized, or badly degraded runs need repair or replacement, not sealant over the top. That's ductwork repair territory, and pretending otherwise wastes the sealing budget.
• A system replacement is imminent. Don't seal in isolation this year and replace equipment next year — combine them, so the new system is sized for the tightened ducts and commissioned against them. Duct condition is one of the four big factors in what an installation actually costs, and handling it inside the same project is almost always cheaper than two separate jobs.
• You're selling soon. Duct sealing pays back over years of utility bills. If you're leaving in twelve months, the next owner collects most of the return.

How do you find out what your ducts are doing?

Start with the symptoms: uneven rooms, weak registers, high summer bills, recurring dust, musty startup smells. Then get eyes on the ductwork — a technician in the attic and crawlspace can spot disconnections, failed tape, and crushed runs quickly, and a duct blaster test can put a hard number on total leakage if you want one before spending. If the evidence points to leaks, our duct sealing team can scope what sealing (or repair) your specific duct system needs and be straight with you about the payback.

Duct leakage is the rare home problem that's invisible, fixable, and paying interest against you every month it waits. If your system seems to run forever without the house feeling right, look at the delivery network before blaming the equipment — in Georgia, the ducts are guilty more often than they get charged.