Three of the most common signs of leaking ductwork are energy bills that keep climbing, rooms that never hold an even temperature, and dust that keeps coming back. Any one of them is worth a closer look. Together, they make a leak more likely, though other causes are possible.
Leaks are common, and they add up. According to the U.S. Department of Energy, a typical home loses about 20 to 30% of the air moving through its ducts to leaks, holes, and poorly connected sections.
Leaking ducts are a problem we see regularly while inspecting systems across the Lowcountry. We hear the question ‘Do I have a leak, and is it worth fixing?’ often, usually after a high summer bill, so we put this guide together. At R&E Home Solutions, a family-owned, NADCA-member team that provides duct services in Charleston, SC, along with the inspections and duct repairs that catch leaks like these.
The Top 3 Signs Your Ductwork Is Leaking
1. Heating and Cooling Bills That Keep Climbing
If your bills rise in both summer and winter with no rate increase and no new appliance, leaking ducts are a likely cause. Air you paid to heat or cool is escaping into the attic, crawlspace, or walls instead of reaching your rooms.
The system then runs longer to hold the temperature you set, and that added runtime is what shows up on the bill. Charleston’s long cooling season makes the loss add up faster here than in a milder climate.
2. Rooms That Never Reach an Even Temperature
A room that stays warmer or cooler than the rest of the house often points to a leak. When air escapes along the way, less of it reaches the registers farthest from the unit.
Rooms at the end of a long duct run tend to feel it first, since they need the most airflow to keep up. A section of duct that has pulled apart at a joint can cause the same uneven result.
3. Excessive Dust and Declining Air Quality
If dust returns within days of cleaning, or your return vents are coated with it, your ductwork may be pulling it in. A leak on the return side draws air from the attic or crawlspace, and with it dust, insulation fibers, and humidity, then sends all of it through your rooms.
This is the sign that reaches beyond comfort and cost. It affects the air you breathe. Cleaning removes the debris a leak has pulled in, and our guide on the signs your ducts need cleaning covers when that step is worth taking, but sealing or repairing the leak is what stops the source.
Other Signs Worth Watching For
Apart from these 3 signs, pay attention to these as well:
- Whistling or hissing from vents or inside walls
- An AC or furnace that runs almost constantly without reaching the set temperature
- Weak airflow from some vents while others blow strongly
- A musty smell when the system starts, which can mean damp air is getting into the ducts
- Visible damage in the attic or crawlspace, such as torn, crushed, or sagging ducts
Why Duct Leaks Are Worse in a Humid Climate
Charleston stays humid for most of the year, and that changes what a duct leak does. A leak on the return side doesn’t just waste energy. It pulls damp air from crawlspaces and attics into the system, and that moisture can settle on duct walls and other components. Damp, dusty surfaces are where mold tends to grow, so here a leak can become an air-quality problem on top of a comfort and cost problem.
Storms add another factor. After heavy rain or flooding, mold can start growing in damp ductwork within 24 to 48 hours, especially in crawlspace homes. If you notice a musty smell, visible mold, or moisture around your ducts, an inspection should come sooner rather than later. If mold is suspected but you can’t find it, our mold inspection and testing can help confirm it.
How to Check Your Exposed Ducts Yourself
You can inspect the ducts you can see before calling anyone. Be careful in attics, which can be extremely hot, and wear a dust mask and gloves.
- Go where the ducts are exposed: the attic, basement, or crawlspace.
- Look at the joints and connections for gaps, loose sections, or ducts that have pulled apart.
- Check for dust streaks or dirty marks around seams, which often show where air is escaping.
- Turn the system on and hold your hand near the connections to feel for moving air. For small leaks, a lit incense stick near a joint will show the smoke pulled or blown away.
- Look for damage: torn insulation, crushed or sagging flexible ducts, or signs of chewing.
- Check where each vent meets the duct to make sure the connection is tight.
Most ductwork is hidden inside walls and ceilings, so this only covers part of the system. Still, what you find on the exposed sections is a good early hint about the rest.
What to Do When You Find Ductwork Leak
The right fix depends on how bad the leaks are:
- Sealing works for small leaks and gaps, using mastic or metal-backed tape rather than standard duct tape, which does not last.
- Repair handles worn or damaged sections, often a targeted replacement of one run.
- Full replacement makes sense when ductwork is badly deteriorated or the wrong size for the system.
When to Act Faster
Most duct leaks are not emergencies, but a few situations call for faster action:
- A musty smell or visible mold. Moisture is getting into the system, and the longer it sits, the more it spreads.
- Signs of pests. Droppings, nesting material, or chewed ducts should be handled promptly.
- Leaks near a furnace or water heater. Poor airflow around fuel-burning appliances can affect how safely they vent. Keep working carbon monoxide detectors on every level of your home, and call a professional if you suspect a problem.
Have Your Ductwork Inspected by Professionals
Leaking ductwork rarely fixes itself, and in a humid climate it tends to get worse. Catching it early protects your energy bills, your comfort, and the air in your home.
When you schedule an inspection with R&E Home Solutions, we check your ducts, show you where the leaks are with photos, and explain your options before any work begins. Estimates are free. If your ducts are in good shape, we’ll tell you that too. We serve Charleston, James Island, Mount Pleasant, Daniel Island, Johns Island, Summerville, and nearby areas.
To schedule, call (843) 886-1658 or book online.
Frequently Asked Questions
What is a return duct, and why do leaks in it matter?
Your system has two sides. Supply ducts carry conditioned air to your rooms, and return ducts pull room air back to the unit for heating or cooling. A leak on the return side is the one that hurts air quality most. Instead of drawing clean room air, it pulls in dusty, humid air from the attic or crawlspace and sends it through the system. That is why return-side leaks often show up as extra dust and stuffy air.
Does air duct cleaning fix leaking ducts?
No. Cleaning removes the dust and debris that leaks have pulled into the system, which helps your air, but it does not seal the leak. A leak still needs sealing, repair, or replacement. The two often go together, since one inspection can find both. Our guide on how professional air duct cleaning works explains what a cleaning covers.
Can I seal duct leaks myself?
You can seal small gaps on exposed ducts with mastic or metal-backed tape. Standard duct tape is worth avoiding, since it does not hold up over time. Hidden ducts in walls and ceilings, along with larger or disconnected sections, need a professional, because those are where most of the loss happens, and they are hard to reach safely.
How do professionals find air duct leaks?
When the problem is out of sight, a technician has several ways to locate it:
- Visual inspection of accessible ducts, connections, and the HVAC unit
- Duct leakage testing, which pressurizes the system and measures how much air escapes
- Smoke testing, where harmless smoke shows exactly where air is leaking
- Thermal imaging, which can reveal temperature differences that point to leaks
How much does it cost to fix leaking ducts?
It depends on the fix. Sealing small leaks is the least expensive. Repairing a section costs more, and replacing ductwork is the largest job, priced by how much duct is involved and how hard it is to reach. An inspection gives you a firm number for your home before any work begins.
What are the Causes of Duct Leaking?
Most leaks come from a handful of everyday causes, and none of them mean you did something wrong.
- Age. The tape and sealant on duct joints dry out and crack over time. In homes 15 or more years old, this is the most common reason we find.
- Poor sealing at installation. Many ducts were never sealed well to begin with, or were closed with regular cloth duct tape, which tends to fail within a few years.
- Sections that have come apart. Vibration and settling can loosen connections. Work in the attic, like a cable installer moving things around, can pull a duct loose without anyone noticing.
- Pests. Mice and squirrels sometimes chew through flexible ducts, especially in attics and crawlspaces.
- Moisture. In a humid area like Charleston, damp crawlspaces break down duct materials and tape faster.
