Aeroseal Duct Sealing Technology: How It Works and What It Costs

Aeroseal is a pressurized injection process that seals duct leaks from the interior using aerosolized polymer particles, without requiring physical access to each leak point. This page covers the technology's mechanism, cost structure, applicable performance standards, and the scenarios where Aeroseal outperforms or underperforms conventional duct sealing methods. Understanding these boundaries helps building owners, contractors, and inspectors evaluate whether the process fits a specific system's failure profile.

Definition and scope

Aeroseal duct sealing is a patented process developed at Lawrence Berkeley National Laboratory (LBNL) in the 1990s and subsequently commercialized. The system injects a water-based vinyl acetate polymer aerosol into a pressurized duct system. Particles accumulate at leak edges — gaps, holes, and unsealed joints — building up a flexible seal without coating intact duct surfaces.

The technology targets leaks in the 0.02–0.5 inch (roughly 0.5–12 mm) size range. Gaps smaller than 0.02 inches are not meaningfully addressed because particles pass through or bridge insignificantly; gaps larger than 0.5 inches require mechanical or mastic pre-treatment before injection is effective, as particle bridging fails at that scale.

Aeroseal is applicable to residential, light commercial, and mid-size commercial systems. It is not rated for industrial high-pressure duct systems or ducts carrying exhaust streams from combustion equipment, where material compatibility and fire ratings apply under NFPA 90A (Standard for the Installation of Air-Conditioning and Ventilating Systems) and HVAC duct fire safety requirements.

Duct leakage testing performed before and after the Aeroseal process provides the primary performance metric. The ANSI/ACCA Standard 5 QI (Quality Installation) and ASHRAE Standard 152 (Method of Test for Determining the Design and Seasonal Efficiencies of Residential Thermal Distribution Systems) both establish baseline leakage measurement protocols relevant to this process.

How it works

The Aeroseal process follows a discrete sequence of phases:

  1. Pre-sealing diagnostics. Technicians perform a baseline duct pressurization test — typically using a blower door or duct blaster apparatus per duct pressurization test protocols — to quantify initial leakage in CFM (cubic feet per minute) at 25 pascals of pressure (CFM25), the standard test condition defined in ASHRAE 152.

  2. Register and grille blocking. All supply and return registers are temporarily sealed with foam plugs or tape to isolate the duct interior and force pressure and aerosol toward leak sites only.

  3. Injection equipment connection. A portable injection unit connects to the air handler opening or a single access point. The unit heats a water-based polymer solution and atomizes it into particles averaging 1–20 microns in diameter.

  4. Pressurized injection. The duct system is pressurized to approximately 25–50 pascals. The aerosol circulates through the duct network; particles carried in airflow accumulate at leak edges due to the velocity differential caused by air escaping through gaps.

  5. Real-time monitoring. The injection unit's onboard software monitors total duct leakage continuously. Technicians observe leakage reduction in real time on a display. Most residential systems reach target leakage levels within 1–3 hours of injection time.

  6. Post-sealing verification test. After the aerosol cures (typically within 30–60 minutes at ambient temperatures above 50°F), a second pressurization test documents final CFM25 leakage and the percentage reduction achieved.

The polymer sealant is listed by the manufacturer as meeting UL 181 standard requirements for duct system sealants — the same standard framework governing duct tape and mastic adhesives. Independent studies published by LBNL and the California Energy Commission (CEC) have documented average residential leakage reductions of 60–90% in tested installations, though results vary with system age, duct material, and initial leakage severity.

Common scenarios

Occupied buildings where duct access is restricted. In finished construction — ceilings, walls, and floors fully enclosed — conventional mastic or foil-tape sealing requires destructive access. Aeroseal bypasses this constraint because it operates through a single injection point.

Systems failing duct leakage tests during energy code compliance inspections. California Title 24, IECC (International Energy Conservation Code) 2021, and ASHRAE 90.1 all set maximum duct leakage thresholds. When a duct leakage testing result exceeds the allowable CFM25 value — typically 4 CFM25 per 100 square feet of conditioned floor area under IECC 2021, Section R403.3.3 (IECC 2021, ecfr.gov reference codes) — Aeroseal is one remediation path that avoids duct demolition.

Homes with high energy bills attributable to distribution losses. LBNL research (Modera, M., Field Measurements of HVAC System Efficiency in California) identified that duct leakage in typical US homes accounts for 20–30% of total HVAC energy consumption in systems with ducts running through unconditioned spaces such as attics and crawlspaces.

Pre-sale or pre-rental inspection remediation. In jurisdictions requiring duct leakage compliance testing at point of sale (including parts of California under Title 24 Part 6), Aeroseal is used as a rapid-remediation method to achieve code compliance without duct replacement.

Decision boundaries

Aeroseal vs. manual mastic sealing. Manual mastic application costs less per linear foot when ducts are fully accessible — an open basement or unfinished mechanical room context. Mastic applied by a qualified technician can seal gaps well beyond the 0.5-inch Aeroseal ceiling. For accessible systems with large joint failures or disconnected sections, duct sealing methods based on mastic and mesh tape are often the more economical choice. Aeroseal's cost advantage emerges when inaccessibility would require demolition to apply mastic manually.

Cost structure. Aeroseal pricing is set by contractors on a per-job basis. Nationally, residential installations have been quoted in the range of $1,500–$4,000 for a single-system home, depending on duct volume, access complexity, and regional labor rates. This range is not a manufacturer-set price; it reflects contractor market data reported by outlets including the Department of Energy's Building Technologies Office (BTO) program summaries. Commercial installations scale with system size and are priced separately.

Permitting and inspection. Aeroseal work that involves physical alteration to the duct system or HVAC equipment connections may trigger mechanical permit requirements under local amendments to the International Mechanical Code (IMC). Permit requirements vary by jurisdiction. HVAC duct permits and inspections provides context on when inspection is triggered. Where post-treatment duct leakage testing is a permit closeout requirement, the Aeroseal process's built-in documentation output (printed pre/post leakage report) typically satisfies inspector documentation needs.

When Aeroseal is not appropriate. The process is not suitable for duct systems with structural damage, disconnected sections, or significant air duct mold contamination. Physical remediation or replacement must precede injection in these cases. Systems with duct insulation requirements violations also require separate corrective action, as Aeroseal addresses air leakage only, not thermal losses through duct walls.

References

📜 4 regulatory citations referenced  ·  ✅ Citations verified Feb 26, 2026  ·  View update log

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