Aeroseal vs Hand Sealing vs Duct Replacement

Key Takeaways

Common Question	Short Answer
Is Aeroseal better than sealing ducts by hand?	For ducts you can’t reach, yes. Aeroseal seals leaks inside walls, floors and ceilings and measures the result, while hand sealing with mastic can be effective and costs less for fully exposed ducts. How Aeroseal works
Is it cheaper to seal ducts or replace them?	Sealing is almost always cheaper. At MaxSeal, Aeroseal costs $3,000–$3,500 per system, and manual repair of damaged sections starts at $450. See our price list
When is duct replacement the right choice?	When ducts are crushed, disconnected in many places, badly undersized, past their service life, or contaminated by pests or mold. How we repair ducts
Can Aeroseal fix a disconnected duct?	No. Aeroseal seals holes up to about 5/8 inch, so disconnected or crushed sections must be repaired by hand first. Duct repair
Do I need to replace ducts when I replace my HVAC system?	Not necessarily. Have the ducts tested first, and if they are intact and correctly sized, sealing them is usually the better value. Fix ducts before replacing HVAC
How much leakage does Aeroseal remove?	In MaxSeal’s data from 38 systems, leakage fell by an average of 86%. See the full study
How do I find out which option fits my home?	Start with a duct leakage and airflow test, which starts at $295 at MaxSeal. The consultation is free. Duct leakage test

1. Quick comparison

	Aeroseal (inside-out sealing)	Manual sealing (mastic / foil tape)	Duct replacement
How it works	The duct system is pressurized and a sealant mist builds up across leaks up to about 5/8 inch	A technician brushes mastic or applies UL-181 foil tape on joints they can reach	Old ducts are removed and new ducts installed
Reaches hidden ducts?	Yes, including inside walls, floors and ceilings	No, only exposed duct	Only where new ducts can be routed
Proof of results	Computer-measured leakage before, during and after (CFM25)	Usually none, unless a separate leakage test is done	Requires a leakage test in California (Title 24)
Typical time	Usually one day	A few hours to a day	1–3+ days
Disruption	Low: registers are temporarily covered	Low to medium: attic or crawl space work	High: access, removal, disposal
Fixes crushed or disconnected ducts?	No: large gaps are repaired by hand first	Yes, if reachable	Yes
MaxSeal price (2026)	$3,000–$3,500 per system, with multi-system discounts	Manual duct repair from $450	Usually the most expensive option, often several thousand dollars or more
Best for	Leaky but intact ducts, especially hard-to-reach ones	Small homes with fully exposed ducts	Damaged, undersized or failing duct systems

MaxSeal’s leakage and airflow test starts at $295, and the consultation is free. See the full 2026 price list.

2. What each option actually does

Aeroseal

Aeroseal pressurizes your duct system and blows in a mist of non-toxic sealant particles. As air escapes through a leak, the particles collect at the edge of the hole until it closes. Registers are blocked during the process so sealant only builds up at the leaks. Software tracks leakage in real time, so you get a printout showing where your system started and where it finished. In MaxSeal’s data from 38 systems, leakage fell by an average of 86% (see the full study).

Manual sealing

A technician applies water-based mastic with a brush or uses UL-181 rated foil tape on seams, joints and boots. ENERGY STAR recommends mastic or metal tape, and warns that ordinary duct tape “is not long-lasting.” Manual sealing is effective, but it is limited to what a person can physically reach. In most Bay Area homes, much of the ductwork runs through walls, between floors or under insulation.

Duct replacement

Replacement means tearing out the old ducts and installing new ones. It makes sense when ducts are crushed, disconnected in many places, badly undersized, past their service life (brittle old flex duct, for example), or contaminated by pests or mold. In California, new or altered ducts generally have to pass a duct leakage test with third-party (HERS) verification under Title 24. Check the exact requirements with your contractor or local building department.

3. Which one should you choose?

If your situation is…	Best option
Ducts are intact but leakage tests high, with lots of hidden runs	Aeroseal
Small system, all ducts exposed in an unfinished basement	Manual sealing
Ducts are crushed, torn, disconnected or rodent-damaged throughout	Replacement (then test)
Some damaged sections plus general leakage	Hand repair of damaged sections + Aeroseal
Replacing your furnace or AC and keeping the ducts	Test the ducts first, then seal them before the new equipment goes in
Rooms are uneven but you don’t know why	Duct leakage test + register airflow readings first

4. The hybrid approach most contractors use

Aeroseal seals gaps up to about 5/8 inch. Bigger openings, such as a disconnected boot or a torn flex duct, are fixed by hand first. Then Aeroseal seals everything else, including the hidden leaks. This combination usually costs far less than full replacement and comes with measured results.

5. Questions to ask before you pay for anything

What is my current leakage in CFM25, and what target will you guarantee or aim for?
Will you measure airflow at each register before and after?
What is repaired by hand, and what is sealed with Aeroseal?
Will I get the before and after report in writing?

Conclusion

Aeroseal, manual sealing and replacement each fix a different problem. Aeroseal reaches hidden ducts and measures the result, hand sealing covers the ducts you can reach, and replacement is for ducts that are damaged, undersized or contaminated.

Most homes with leaky but intact ducts get the best value from hand repair of large gaps plus Aeroseal. Test first so you choose based on numbers.

Get a Free Consultation or call (408) 400-3630.