Aeroseal Duct Sealing: An Honest Guide

What is Aeroseal and how does aerosol duct sealing work?

Aeroseal is a method for sealing duct leaks from the inside using an aerosol. The registers are temporarily blocked and the duct system is pressurized with a fan, then a fine mist of sealant particles is introduced into the airstream. Where air is escaping through a crack or gap, the moving air carries those particles to the leak, where they accumulate at the edges and gradually bridge the opening until it closes. The particles stay suspended and only deposit where air is leaving the system, so they seal the leaks rather than coating the duct interior. Because the process works from inside the ductwork, it can reach leaks buried in walls, ceilings, and floors that would be difficult or destructive to access by hand. It is a sealing technology, not a cleaning method.

What does a before-and-after leakage report show?

The defining feature of aerosol sealing is that it is measured. Before the process begins, the equipment quantifies how much the duct system is leaking by measuring airflow while the system is pressurized. As sealing proceeds, that leakage figure is tracked in real time, and when the process finishes you receive a report comparing the measured leakage before and after. This turns an invisible problem into a documented result: you can see the reduction rather than take it on faith. That measurement is genuinely valuable, and it is a fair thing to insist on. A sealing job that cannot show you a quantified before-and-after is missing the very thing that makes the method credible. When we refer, we point toward providers who deliver that report as a matter of course.

Where does Aeroseal shine?

Aerosol sealing is at its best on existing duct systems riddled with small and medium leaks in places you cannot easily reach. Ductwork routed through finished walls, above ceilings, or under floors often leaks at seams and connections that would require opening up the house to seal by hand. Because the aerosol travels to the leaks on its own, it addresses many of these at once without demolition. It is also well suited to systems with numerous distributed small leaks, where hand-sealing each one would be impractical. ENERGY STAR notes that sealing and insulating ducts can improve the efficiency of a heating and cooling system, and reducing leakage means more of the conditioned air the system produces actually reaches the rooms it was meant for. Distributed, hidden leaks are exactly the problem the aerosol approach was designed to solve.

Where does hand-applied mastic still win?

Aerosol sealing is not the answer to every leak. Large, obvious gaps, a disconnected duct, a wide-open joint, or a hole you can put a finger through, are better closed by hand with mastic or mastic-and-mesh, because the aerosol is designed to bridge small openings, not span big ones. Accessible ductwork in a basement or crawlspace, where a technician can physically reach the seams, is often sealed effectively and durably with mastic at lower complexity. The honest framing is that the two approaches are complementary: many good sealing jobs hand-seal the large accessible defects first and use the aerosol for the small, hidden, distributed leaks that hands cannot reach. Be wary of any pitch that treats aerosol sealing as a universal fix; the leak's size and location should decide the method.

Is Aeroseal the same as duct cleaning?

No, and conflating the two causes real confusion. Duct cleaning removes debris from inside the ducts; aerosol sealing closes leaks so conditioned air stops escaping. They solve different problems and are measured differently, cleaning by verified source removal, sealing by a before-and-after leakage number. In fact, sealing is generally done on a system that is already reasonably clean, because you do not want to seal over a duct full of debris. If a single proposal bundles cleaning and sealing, that can be perfectly legitimate, but you should see each one scoped, performed, and documented on its own terms. Knowing they are separate services helps you evaluate whether you actually need both, one, or neither, rather than accepting a combined package on faith.

How durable is aerosol duct sealing?

The sealant is designed to remain in place at the leak edges after it cures, so the closures are intended to last rather than being a temporary patch. Providers typically offer a warranty on the sealing work, which is worth asking about and reading. Durability in practice depends on the condition of the ducts going in: sealing works best on ducts that are structurally sound, and it is not a substitute for replacing ductwork that is collapsing, badly corroded, or crushed. Aerosol sealing addresses leaks; it does not rebuild a failing duct. So the reasonable expectation is a lasting reduction in measured leakage on ducts that were sound enough to seal, backed by a documented result and a stated warranty, not a permanent guarantee on ductwork that needed replacement in the first place.

What questions should I ask an Aeroseal provider?

Lead with the measurement. Ask whether you will receive a quantified before-and-after leakage report, since that documented result is the method's core value. Ask how they will handle any large or accessible leaks, and listen for an answer that includes hand-sealing the big defects rather than relying on the aerosol for everything. Ask about the condition of your ducts and whether any runs are too damaged to seal and should be replaced instead. Ask what warranty covers the work. And ask whether the ducts should be cleaned first, so you are not sealing over debris. A provider who welcomes these questions and answers them concretely is demonstrating the same evidence-first approach the whole field should follow, and it is what we look for when we connect you to a local technician.