Quick answer: The signs of leaky air ducts are a room that never quite catches up, dust back on the furniture two days after you wiped it, a register that whistles, and a bill climbing while your thermostat habits stay the same. In a Texas attic running past 130 degrees, every leak costs you twice: cooled air escapes on the supply side, superheated attic air gets pulled in on the return. A pressure test turns the suspicion into a number and a location, and most of what it finds is a straightforward duct repair, not a new system.
You changed the filter in June, you paid for a spring tune-up, and the hallway thermostat still reads 74 while the back bedroom sits at 80 with the door standing open. The condenser sounds healthy. The air at the nearest register feels cold on the back of your hand. The equipment is probably fine. What nobody has looked at since the house was framed is the couple hundred feet of ductwork running between the air handler and that bedroom, strapped to the rafters of an attic that spends a North Texas summer above 130 degrees. Every seam that has worked open up there is a hole you'd never tolerate in an exterior wall.
Four Signs of Leaky Air Ducts You Can Find Without a Ladder
Leaks don't announce themselves. They show up as small complaints that each have three other explanations, right up until you notice they cluster in one corner of the house.
- A room that never quite catches up. Usually the one at the end of the longest run, where leaks upstream bled off the pressure it needed to arrive with any authority. When the split follows floors, our guide to an upstairs that won't cool covers the rest.
- Dust back on the furniture two days after you cleaned. A torn return pulls attic air into what you breathe: insulation fiber, blown-in grit, and whatever the last roofing crew left behind. A duct cleaning clears what settled, but fresh dust keeps arriving until the tear is sealed.
- A register that whistles or hisses. That's air forcing through a gap it was never meant to pass, usually a boot connection working loose just above the ceiling.
- A hallway warmer than either room it connects. Often a supply joint that has come apart overhead, spending its air on attic insulation instead of your bedroom.
Any one of these on its own is worth a shrug. Three of them in the same wing of the house is a duct problem with a return address.
A Bill That Doesn't Match Your Thermostat Discipline
You held the line at 78 all summer the way ENERGY STAR suggests, nothing about how you run the system has changed, and the August bill still landed higher than last year. Leaking duct is the quiet explanation. ENERGY STAR puts the loss in a typical house at 20 to 30 percent of the air moving through the duct system, gone to holes, gaps, and connections nobody sealed properly. Your AC has no way of knowing, so it just runs longer chasing a number it keeps falling short of, and the meter counts every extra minute.
North Texas makes the arithmetic worse. That air isn't slipping into a basement where some of it might drift back to you. It goes into an attic that won't cool off much just because the calendar says September, while the return side pulls that heat back in through its own gaps. Your AC ends up cooling the attic on the way to cooling you. If the bill got your attention, our breakdown of high summer electric bills covers the other usual suspects.
Flex Duct Crushes, Kinks, and Comes Apart
Most DFW attics built in the last 40 years run flexible duct: a thin inner liner inside an insulated jacket, light enough for one installer to thread around trusses rigid metal could never follow. The tradeoff is that it damages easily and stays damaged. A roofer, a cable installer, or a homeowner after the Christmas boxes puts a boot in the wrong place and a run goes flat. A turn pulled too tight around a truss kinks it shut. Neither makes a sound. The register keeps blowing something, just half of what it used to.
The joints are the other weak point. Flex duct meets a metal boot or a trunk line at a connection made exactly once, by whoever was moving fastest on installation day. In the 1980s and 90s two-story homes around Carrollton, the trunk runs the length of the attic with the upstairs branches taking off at the far end, right where a strap nobody cinched down finally lets go. A branch fully off its boot dumps every cubic foot into the attic. That's the most expensive leak a duct system can have, and from inside the house it just looks like one room that quit.
Why Cloth Duct Tape Is a Punchline in the Trade
Every technician who works DFW attics has lifted a hatch and found gray cloth tape wound around a duct joint. It's the one product with duct in the name that should never touch a duct. That joint cycles between 55-degree supply air and attic air past 130 thousands of times a summer, and the rubber-based adhesive under cloth tape gives up first. Lawrence Berkeley National Laboratory ran 19 sealant samples through three months of exactly that cycling, and duct tape was the only thing that failed. Eleven of the tapes were leaking within days. Some fell right off the joint.
Unlisted cloth tape isn't an approved closure method under the mechanical code either, which is why it never shows up on a permitted install. What holds is mastic, a gray sealant brushed on like thick paint that cures flexible and doesn't care how hot the attic gets, backed with UL-listed foil tape on the bigger seams. It costs more and takes longer to apply. It also doesn't have to be redone in three years.
Pressurize the Ducts and the Guessing Stops
Hunting leaks by feel is how homeowners end up paying to seal the wrong joint. The honest answer comes out of a calibrated fan: pressurize the system, measure what it takes to hold that pressure, and a vague suspicion becomes a number. A technician then walks the attic under pressure and finds what that number was describing, the boot hanging loose, the run lying flat, the seam buried under blown insulation. Ask to see it, in the attic or on your phone, before anybody quotes a price.
Repair or Replace? How We Make the Call
A few crushed sections and a couple of joints that let go, in a system that's otherwise sound, is a repair. Mastic, new straps where the old ones failed, back in service the same day. The 1960s ranch homes in Richardson that picked up a room addition somewhere along the way are the classic version: the original trunk was never sized to feed the extra square footage, and the tie-in got done in one afternoon by whoever framed the room.
Replacement earns its keep when the leaks are everywhere at once. Duct original to a house pushing 25 years, flattened across half the attic or opening at a dozen points, is cheaper to redo than to chase one joint a summer for five years, and a redo is your only chance to correct undersized runs while the attic is open. We'll give you real numbers on both paths and say which one we'd pick if it were our house. Already holding somebody else's quote? Run it through our free second opinion calculator first.
Get Your Ducts Tested Before the Next Bill Lands
September is the right month for this in North Texas. The attic is still hot enough to make every leak obvious, and there's enough summer left to feel the difference before the first cool front. Book from the calendar on this page, contact us online, or call 972-421-8000 and talk to somebody who has been up there. Call-out and diagnostic are free, pricing is published upfront, and Stork's has been pulling leaks out of DFW attics for more than 30 years.
