Duct Sealing vs. Replacement
Aerosol duct sealing injects a fine sealant into pressurized ductwork from the interior, closing small holes and seam gaps the aerosol can reach and bridge, verified in real time by pressure measurement. Manual sealing uses mastic or foil tape applied by hand to accessible joints and boots. Aerosol reaches interior and hidden leaks; manual work handles large, accessible, or oversized gaps aerosol cannot bridge.
When leakage is spread across numerous small gaps throughout the system rather than concentrated in a few accessible spots, aerosol sealing's interior, whole-system approach is often more practical than manually treating every joint.
A visibly disconnected boot or an open seam in the attic that a technician can reach by hand is often more directly and reliably closed with mastic or tape.
Ductwork buried behind finished surfaces cannot be reached for manual sealing at all — aerosol's interior application is the only practical way to treat leakage there.
Aerosol sealant is designed to close small perforations and seam gaps; a large disconnect or torn section exceeds what the material can span and needs mechanical repair or replacement first.
Sometimes the real issue is not which sealing method to choose but that the duct section is damaged or undersized, which neither sealing approach corrects.
Stick to what you can see, feel and hear. Leave electrical panels, refrigerant, combustion appliances and equipment internals to a licensed professional.
Aerosol sealing pressurizes the duct system and injects an aerosolized sealant that travels through the airflow and deposits at the edges of leaks as air escapes through them, building up until the gap closes. It is effective on small perforations and seam gaps distributed throughout a system, including ones that are physically inaccessible from outside the duct.
Manual sealing applies mastic or foil tape directly to a joint, seam, or boot connection by hand. It is durable and precise where a technician can reach the leak, and it is the right choice for larger gaps or specific problem connections that aerosol sealant cannot fully bridge.
Neither method changes the size, layout, or structural integrity of the ductwork. If a duct section is crushed, disconnected, or undersized, sealing — by either method — treats the leakage without correcting the underlying mechanical or design issue.
Duct Daddy specialises in duct leakage testing and duct sealing. We do not perform mechanical HVAC repair, refrigerant work or equipment replacement. Contact a qualified HVAC contractor if any of the following apply:
In homes across Southeast Louisiana with ductwork running through hot attics, both methods are commonly applied to attic-run systems, but accessibility and duct material condition — often worse after years of attic heat cycling — affect which approach fits a given section.
See the communities we serve.
A duct leakage test and inspection show whether your leakage is a candidate for aerosol sealing, manual work, or a combination of both.
What sealing can and cannot fix, and how to know if your duct system is a good candidate.
How to tell whether your duct system needs sealing, replacement, or neither.
The equipment and steps behind a duct pressurisation test, and what each reading measures.
How to read a CFM25 result — relative to what, judged against what, and what it can't tell you alone.
The specific failure points that develop in attic ductwork over time and at installation.
Browse every symptom in the troubleshooting center.
Schedule a duct leakage evaluation and get measured numbers for your home — not a guess.
