Quick answer
Aeroseal fixes leaks; replacement fixes design. Aeroseal — a technology developed at Lawrence Berkeley National Laboratory with EPA and DOE funding — pressurizes your duct system with an aerosolized sealant that finds and plugs leaks from the inside, typically eliminating up to 90% of leakage, including leaks buried in walls and crawlspaces no hand can reach. It's remarkable at its job. But its job is holes: if your ducts are undersized, badly routed, crushed, or contaminated, sealing them makes tight ducts that are still wrong. The dividing question, as usual, is measured: what's your static pressure, and why?
- Aeroseal seals from the inside — LBNL-developed, EPA/DOE-funded research, typically sealing up to ~90% of leakage.
- It reaches what hands can't: leaks in walls, chases, and buried crawlspace runs — the leaks mastic can never touch.
- It cannot add capacity: undersized trunks and starved returns stay undersized. Sealing isn't sizing.
- On undersized ducts, sealing can raise static pressure — leaks were relieving it. Measure before AND after, always.
The decision, measured
Aeroseal when: the ducts are structurally sound and reasonably sized, but leakage testing shows real loss — the classic 'good bones, bad joints' system. Aeroseal when the worst leaks are unreachable — finished walls and ceilings make it the only practical sealing method. Replace when: static pressure measures above the equipment's rating due to sizing or layout, runs are crushed or failing, contamination is systemic, or asbestos wrap is in play (licensed abatement first, always). Often the sequence is both: replace the undersized trunk or starved return, keep the sound branch runs, and Aeroseal the assembled system tight. Design first, then seal — never the reverse.
How it works
What is Aeroseal, actually — and why is it clever?
The technology came out of Lawrence Berkeley National Laboratory in the 1990s, with funding from the EPA and Department of Energy, to solve a stubborn problem: most duct leakage hides where no technician can reach — joints buried in walls, runs snaking through closed chases. The process blocks your registers, pressurizes the system with a fog of polymer particles, and lets physics do the work: escaping air carries particles to each leak's edges, where they accumulate until the hole closes. The whole event is measured — you see leakage numbers before and after, typically showing the large majority of leakage eliminated. For a structurally sound system bleeding 25% of its air into a crawlspace, it's the highest-leverage duct fix there is, and it makes every service that follows (cleaning, filtration, new equipment) work better.
What can't it fix — and how can sealing even backfire?
Aeroseal seals the system you have. If that system is undersized for your equipment, poorly routed, crushed under a bathroom, or contaminated by pests, sealing it produces a tight version of the same problem. And there's a subtlety that separates careful contractors from product-pushers: on an undersized system, leaks function as unintended pressure relief. Seal them, and the blower now pushes everything through geometry that couldn't handle it before — measured static pressure can rise, further stressing equipment already near its ~0.5″ w.c. rating. This isn't a reason to fear sealing; it's the reason sealing must follow a static pressure evaluation. Right-size first (repair or replace what geometry demands), then seal the result into a tight, correct system.
Pros and cons, honestly
Aeroseal (aerosol sealing)
Pros
- Fixes leaks from pinholes to 5/8″ gaps, from the inside — verified by a before/after test
- Reaches inaccessible leaks: walls, chases, buried runs
- A fraction of replacement cost — ENERGY STAR pegs typical duct loss at 20–30% of conditioned air, and sealing recovers most of it
Cons
- Cannot add capacity, fix crushed runs, or remove contamination — sealing isn't sizing
- On undersized systems, static pressure can rise after sealing (the leaks were relief valves)
Duct replacement
Pros
- Fixes design: sizing, layout, routing, condition — per ACCA Manual D practice
- The direct fix for high static pressure caused by geometry
- Everything is new — including runs that were crushed, failing, or contaminated
Cons
- The full project — hard to justify when leaks were the only problem
- Overkill for a sound, right-sized system that just bleeds air at the joints
Key terms and context
This guide is written for heating & air decisions in the Puget Sound. It uses the same terminology you'll hear from inspectors, technicians, and permit offices.
The trap: sealing an undersized system tight
Sealing an undersized system is doing the wrong thing well. Leaks act as accidental pressure relief on bad geometry — seal them without fixing the sizing and your measured static pressure can actually rise, stressing equipment already near its rating. That's why every sealing recommendation follows a static pressure reading: if the number is already high, sizing comes first.
How we build this guidance
- Aeroseal claims per the LBNL-developed technology's published performance and our own before/after leakage tests — you see both numbers.
- Every sealing recommendation follows a static pressure reading, because sealing an undersized system tight is doing the wrong thing well.
- Leakage context per ENERGY STAR (typical homes lose 20–30% of duct air); design standards per ACCA Manual D.
Methodology: Technology history and performance per Lawrence Berkeley National Laboratory publications and manufacturer verification testing; decision criteria from field static pressure and leakage measurements.
Last updated: 2026-07-16
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Common questions
Is Aeroseal safe to breathe?
The sealant is a vinyl acetate polymer used for decades in applications from hairspray to chewing gum base, applied while the home's registers are sealed off, with the material curing inside the ducts. The developing science came from LBNL's indoor-air group — the same researchers whose job is protecting indoor air quality.
How long does Aeroseal last?
The sealant carries a 10-year warranty in residential applications, and LBNL durability testing projects far longer service life. It's a permanent repair by any practical definition — the seal doesn't relax or peel the way surface tapes do.
Why did my static pressure go UP after duct sealing?
Because the leaks were acting as relief valves for an undersized system — air escaped rather than fighting through tight geometry. Sealing removed the relief. This is precisely why we measure static before recommending sealing: if the number is already high, sizing comes first.
Is Aeroseal cheaper than replacing my ducts?
Substantially — it's a fraction of replacement cost, which is exactly why it's the right call for sound-but-leaky systems and the wrong call for undersized ones. The evaluation tells you which system you own; the price difference is why the evaluation is worth insisting on.
Sources & references
Equipment ratings, program details, and industry figures cited on this page are drawn from manufacturers and primary sources, linked below. Verify program status and requirements for your home where applicable.
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Aerosol duct sealing was developed at Lawrence Berkeley National Laboratory with EPA and DOE funding, sealing the large majority of leakage from the inside.
Lawrence Berkeley National Laboratory — Aerosol Duct Sealing ↗ -
In a typical house, 20–30% of duct air is lost to leaks.
ENERGY STAR — Duct Sealing ↗ -
Residential duct systems are sized to the industry design standard, ACCA Manual D.
ACCA — Manual D: Residential Duct Systems ↗ -
Residential air handlers and furnaces are rated for a maximum external static pressure — commonly 0.5 in. w.c. — printed in the installation manual.
Goodman Manufacturing — AVPTC Air Handler Installation Instructions ↗ -
How static pressure is measured and interpreted, and how excessive static degrades airflow and equipment operation.
National Comfort Institute — Measure and Interpret Static Pressures (via ENERGY STAR) ↗