North Texas duct systems lose 20-30% of their air into a 140-degree attic. The signs, how leakage is measured, and why duct sealing is not duct cleaning.
The average duct system in a North Texas home loses somewhere between 20 and 30 percent of the air it carries. That air doesn’t vanish — it leaks out of joints and seams into a 140°F attic, which means you are paying to air condition the space above your ceiling. It is the single most expensive defect in most DFW homes, and almost nobody can see it.
In much of the country, ducts run through conditioned basements. Leaky duct in a basement leaks cold air into a space that’s part of the house — wasteful, but not catastrophic. North Texas has no basements. Our ducts run through vented attics, which are the hottest place on the property for four months of the year and among the coldest in January.
So the same leak that’s a minor inefficiency in Ohio is, in Plano, a direct exchange of the air you paid to cool for 140°F attic air pulled in on the return side.
That last two matter for more than comfort: a leaking return pulls unfiltered attic air — insulation fibers, dust, whatever else is up there — and distributes it through the house.
These get conflated constantly, and they are unrelated jobs.
| Duct Sealing | Duct Cleaning | |
|---|---|---|
| What it does | Closes leaks so air reaches rooms | Removes debris from inside the ducts |
| Affects your bill | Yes, measurably | No |
| Worth doing | In almost every DFW home | After renovation, pest issues, or visible contamination |
Duct cleaning is a legitimate service for the right problem. It is also the most aggressively upsold service in this industry, frequently pitched to homeowners whose actual problem is leakage. If someone quotes cleaning as a fix for high bills or uneven rooms, they are selling you the wrong job.
A duct blaster test pressurizes the duct system and measures how much air escapes. That gives a number — leakage as a percentage of system airflow — instead of an opinion. Paired with static pressure readings at the air handler, it tells you whether you have a leakage problem, a restriction problem, or an undersized-duct problem, which need three different fixes.
A visual inspection in the attic catches the worst offenders: disconnected boots, unsealed plenum joints, flex duct crushed under storage or sagging into a long unsupported run.
Mastic — a thick paste brushed onto joints and seams — at every connection: the plenum, the takeoffs, and the boots where duct meets ceiling. Ceiling boots are the most commonly skipped and among the leakiest, because they sit at the drywall line where nobody looks.
Duct tape, despite the name, is not the material for this. It dries out and releases in attic heat, usually within a couple of seasons. If a previous contractor taped your joints, they have probably already failed.
Ahead of a new thermostat, ahead of a higher-SEER replacement, and usually ahead of adding insulation. There is no point buying more efficient equipment to push conditioned air into your attic more efficiently — and if you’re planning a system replacement, sealing first can genuinely change the size of the equipment you need.
We inspect, test, and seal duct systems across Dallas–Fort Worth, and we’ll show you the readings rather than describe them.
Call 214-900-2533 or see our air duct services. If it’s one floor rather than the whole house, see upstairs hot, downstairs cold.
AC Installation & Replacement · Air Duct Sealing, Repair & Replacement · Smart Thermostat Installation · All HVAC services · Find your city
Kenny founded Absolute Comfort Mechanical after more than 20 years in the Dallas–Fort Worth HVAC trade, because he was tired of watching homeowners get sold equipment they didn't need. He still runs diagnostics himself and reviews the technical advice published on this site.
Fall HVAC Checklist for Dallas-Fort Worth Homes · Thermostat Not Working? What to Check First · Preparing Your HVAC for a Texas Hard Freeze · Heat Pump vs Gas Furnace in North Texas · How to Check an HVAC Contractor's License in Dallas · How Long Does an AC Unit Last in North Texas? · All articles
Absolute Comfort Mechanical HVAC — licensed, insured, family-owned, serving the Dallas–Fort Worth metroplex. Call 214-900-2533 for 24/7 AC repair, heating, cooling, and commercial refrigeration service.