Signs Your Ductwork Is Leaking Air
Duct leaks don't announce themselves the way a broken AC does. There's no error code, no sudden no-cooling moment — just a slow drain on comfort and money that's easy to chalk up to "that's just how this room is" or "our bills are just high in summer." Industry studies regularly find that 20-30% of conditioned air escapes through duct leaks in a typical home before it ever reaches a room.
Here's how to spot it.
| Sign | What it usually means | Urgency |
|---|---|---|
| One or more rooms always warmer/cooler | Supply duct leak or disconnection to that room | Worth checking |
| Higher energy bills than expected | System running longer to compensate for lost air | Worth checking |
| Dusty air or musty smell from vents | Return leaks pulling in attic/crawlspace air | Worth checking |
| Whistling or rushing sound at registers | Air escaping through small gaps under pressure | Soon |
| Visible disconnected or crushed flex duct | Significant leak or total loss to that branch | Address soon |
| Hot/humid attic air noticeable indoors | Major return leak pulling attic air directly in | Address soon |
Suspect a duct leak?
We pressure test and inspect duct systems throughout Bay, Walton and Washington counties.
Uneven room temperatures
This is usually the first thing people notice — a bedroom at the end of the hall or a room over the garage that's always a few degrees off from the rest of the house, no matter what the thermostat says. While this can have other causes, a leak or disconnection in the supply duct feeding that room is one of the most common. More on how supply ducts work.
Higher than expected energy bills
If your system has to run longer to make up for air that's escaping into the attic before it reaches your rooms, that shows up on your electric bill. This is easy to dismiss as "just summer," but if your bills feel high relative to your system's age, size, and your usual habits, ductwork is worth ruling out alongside the equipment itself.
Dust and musty smells
Leaks aren't only on the supply side. If return ducts have gaps, your system can pull air from the attic or crawlspace directly into your home's air supply — bringing dust, insulation fibers, and sometimes a musty smell with it. More on dusty homes here and musty smells here.
Whistling or rushing sounds
A whistling or hissing sound near a register, especially when the system first kicks on, can be air being forced through a small gap under pressure — similar to air escaping a balloon. It's often one of the easier leaks to find because you can sometimes hear roughly where it's coming from.
Visible damage in the attic
If you're comfortable looking in your attic (and it's safe to do so), look for flex duct that has come loose from a register boot or plenum connection, sections that are crushed or kinked, or duct tape that has dried out and peeled away from joints — standard cloth duct tape degrades in attic heat over time and is one of the most common points of failure, despite the name.
What to do next
If one or two of these signs sound familiar, it's worth a duct inspection. A technician can do a visual check of accessible ductwork and, if needed, a pressure test to find leaks more precisely. Sealing accessible joints and connections is often a same-visit fix and one of the better dollar-for-dollar investments in home comfort — sometimes more impactful than upgrading the AC itself. If sections need to be replaced, here's what that typically costs.
Some rooms always hotter than others?
Let us pressure test and seal your ductwork.
📞 Call (850) 235-8834Frequently asked questions
How do I know if my ductwork is leaking?
Common signs include rooms that never feel as cool as others, higher than normal energy bills, dusty air from vents, a whistling sound near registers, and visible gaps, disconnections, or loose tape on ducts in an attic or crawlspace.
How much air can leaky ductwork waste?
Industry studies commonly find that 20-30% of conditioned air is lost through duct leaks in an average home, especially when ducts run through unconditioned attics. That is air you are paying to cool that never makes it into your living space.
How much does it cost to fix leaky ductwork?
Sealing accessible duct joints and connections typically runs a few hundred dollars. Repairing or replacing damaged sections of ductwork costs more depending on how much needs to be replaced and how accessible it is, often $300 to $2,000 or more for partial replacement. See full cost breakdown.
Can I seal duct leaks myself?
For ducts you can safely access, sealing visible gaps with mastic sealant (not standard cloth duct tape, which degrades) can help. But many duct leaks are at connections that are hard to reach or identify without a pressure test, so a professional inspection finds more than a visual check alone.
Will sealing my ductwork lower my energy bills?
In most homes with meaningful duct leakage, yes — sealing reduces how much conditioned air is wasted, which means your system doesn't have to run as long to maintain the same comfort level.