Homeowners usually call NILOV about the equipment first — the AC isn't cooling, it's running nonstop, the bill went up. A large share of those calls end with the same finding: the compressor, coil, and blower are all doing exactly what they should, and the actual problem is the network of ducts carrying that conditioned air from the unit to every room in the house. Ductwork doesn't fail the way a bad capacitor does, with one obvious moment where it stops working. It shows up sideways, as a pattern in how the house feels rather than a single dramatic breakdown.
None of the seven signs below guarantees a duct problem alone. Seeing two or three together, or the same one consistently over weeks rather than one hot afternoon, is worth checking before you spend money assuming the equipment is at fault.
Seven Signs Your Ductwork — Not Your AC — Is the Real Problem
1. Some Rooms Are Always Hotter (or Colder) Than the Rest
A thermostat makes one decision for the whole house based on the temperature at its own location, usually a hallway. If a back bedroom at the end of a long duct run, or a room with more western sun exposure, consistently runs several degrees off from what the thermostat reads, that gap is rarely about the equipment. It comes down to how much conditioned air is actually reaching that specific room compared to the others — which is a duct sizing, duct leak, or restriction question, not an AC question.
See One Room Hotter Than the Rest for how NILOV narrows down whether a specific room's duct run is the cause.
2. Airflow Is Strong at Some Vents and Weak at Others
Hold your hand up to two or three vents around the house. If one delivers a noticeable stream of air and another barely moves a curtain, that's not a coincidence. It's a sign that air is being lost or blocked somewhere between the unit and the weaker vent. A leaky joint, a crushed flexible duct run, or a duct that was undersized at installation can each produce this exact pattern, and each one calls for a different fix.
For a closer look specifically at this symptom, see Weak Airflow From Vents.
3. Your Electric Bill Has Climbed and the AC Seems to Be Running Normally
Leaky or undersized ductwork forces the system to run longer to deliver the same comfort, because a share of the air it conditions never reaches a room. The equipment isn't malfunctioning — it's working harder and longer to compensate for air lost along the way. If your bill has trended upward over a season or two without a clear cause, and the AC otherwise seems to run the way it always has, ductwork is worth ruling out before assuming the unit itself has degraded.
A system fighting duct leaks or excess resistance doesn't just cost more to run — it puts more hours on a blower motor and compressor than the same comfort level should require. See High Electric Bill for more on how this shows up on a statement.
4. A Whistling or Hissing Sound Comes From a Vent
Air moving through an opening that's too small for the volume trying to pass through it makes noise, the same way wind whistles through a narrow gap. At a register, that usually means the vent opening or the duct feeding it is undersized for the airflow the system is pushing toward it, or that something is partially blocking the opening from inside the duct. It's rarely dangerous, but it's a clear, audible sign that air isn't moving through that run the way it was designed to.
5. You Can See or Feel Duct Damage Near an Attic or Crawlspace Access Point
Most homeowners never look at their ductwork directly, but if you've had a reason to glance near an attic hatch or a crawlspace access panel, a few things are worth noting: a duct that's visibly sagging or pulled loose from a boot, flexible duct with a crushed or kinked section, or insulation that's wet, torn, or missing along a run. Any of those is a direct, physical cause of airflow loss right at the point where you happened to see it.
A quick glance near an easily and safely reachable access point is fine. Don't climb into an attic or crawlspace to inspect ductwork further — a Louisiana attic in summer routinely climbs past 130°F, and a crawlspace brings its own hazards with tight clearance, uneven ground, and pests. NILOV can inspect duct runs safely and thoroughly.
6. Dust or Debris Blows Out When the System Kicks On
A duct leak on the return side of the system — the side pulling air back into the equipment — can draw in attic insulation particles, crawlspace dust, or other debris from whatever space the ductwork runs through, then push it right back out through your supply vents along with the conditioned air. A puff of dust or a musty smell right when the system starts a cycle is worth paying attention to. It points to air being pulled into the duct system from somewhere it shouldn't be.
7. An Added-On Room Has Never Quite Matched the Rest of the House
A room addition, converted garage, or bonus room tied into the original ductwork is only as comfortable as the duct capacity feeding it — and that capacity was almost always sized for the home's original footprint, not the square footage added later. If that room has never felt as comfortable as the rest of the house since the day it was finished, that's not a mystery to keep troubleshooting indefinitely. It's usually a sign the duct run feeding it was never sized for the extra load in the first place.
Attic Ducts vs. Crawlspace Ducts: Two Different Failure Patterns in Acadiana
Where your ductwork actually runs through the house changes which of the signs above are most likely, and why. Most homes built in and around Lafayette in recent decades are slab-on-grade, with ductwork run entirely through the attic. Older homes, and some raised or historic homes throughout Acadiana, sit on a pier-and-beam foundation with ductwork running through the crawlspace underneath the house instead. Both routing methods work fine when the ducts are in good condition, but they fail in different ways.
| Routing Type | Typical Homes | Common Failure Pattern |
|---|---|---|
| Attic ducts | Most slab-on-grade homes built in recent decades throughout Lafayette, Broussard, and Youngsville | Heat gain through duct walls in an attic that can top 130°F in summer; duct material and insulation degrade faster after years of extreme heat and UV exposure near the roof deck; any leak loses conditioned air into the hottest space on the property |
| Crawlspace ducts | Older, raised, and pier-and-beam homes common in older Acadiana neighborhoods | Ground moisture and standing water after heavy rain can soak duct insulation and promote rust on metal fittings; the enclosed, damp space is also more accessible to rodents and insects, which can chew through flexible duct or nest inside it |
A homeowner troubleshooting airflow problems in an attic-duct home should think heat and UV exposure first. A homeowner with a pier-and-beam crawlspace should think moisture and pest activity first. Knowing which kind of home you have helps you describe the right details when you call, and helps NILOV know what to check first once we're on-site.
Common Mistakes Homeowners Make Diagnosing Airflow Problems
A few assumptions come up often enough to name directly.
- Assuming a duct problem always means visible damage. Most duct leaks are small gaps at joints and connections that were never sealed well to begin with. They don't look dramatic, and plenty of real airflow loss happens along runs that look completely intact from what little you can actually see.
- Closing vents in unused rooms to "help" other rooms. This adds resistance to the whole system instead of redirecting air where you want it, and can make an existing airflow problem worse rather than better.
- Blaming the thermostat or the equipment first. A perfectly healthy AC unit connected to leaky or undersized ductwork will still deliver an uncomfortable house, no matter how new or efficient the equipment is.
- Waiting for one dramatic sign before calling. Most duct problems build gradually. Two or three of the milder signs above, present consistently, are just as meaningful as one obvious one.
- Sealing a visible gap with standard cloth "duct tape." It dries out and fails quickly under the heat cycling inside an attic or the humidity inside a crawlspace, often within a season.
Plenty of the ductwork NILOV finds to be the actual source of a comfort or bill complaint shows no visible sign anyone would have caught by looking. That's the whole reason a real evaluation measures airflow and pressure instead of relying on a walk-through alone.
What a Professional Duct Evaluation Actually Checks
When NILOV comes out for airflow or comfort complaints, the goal is finding the actual restriction rather than guessing at a fix. That typically involves three things:
- Static pressure testing — measuring the resistance air is meeting as it moves through the system, and comparing it to what the equipment was actually designed to handle.
- Visual inspection — checking accessible duct runs, joints, boots, and connections in the attic or crawlspace for disconnection, damage, crushed sections, or wet or missing insulation.
- Airflow measurement at registers — comparing what's actually coming out of each vent, room by room, against what the system is supposed to deliver there.
Together, those three checks usually explain most of the signs on this list at once, and point to whether the fix is sealing, resizing a run, correcting a return, or something else — instead of sealing one visible gap and hoping the rest of the house improves along with it.
See Humidity, Ductwork & Airflow for more on how NILOV approaches this across a full system, or Ductwork & Airflow Problems for a deeper look at what causes duct problems in the first place.
NILOV serves homeowners throughout Lafayette and the surrounding communities, whether your ductwork runs through a hot attic or an older crawlspace. NILOV is open 24 hours a day, 7 days a week, so if two or more of the signs above sound familiar, reach out whenever it's convenient and describe what you're noticing room by room.