Commercial Aeroseal Duct Sealing With Measured Verification
Duct leaks waste conditioned air inside walls and ceilings you can't open. Aeroseal seals them from the inside — and proves it with a before/after leakage report. On one Service-Tech commercial project, measured leakage dropped 94%.
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What Aeroseal Duct Sealing Is
Aeroseal is a computerized aerosol duct-sealing process that closes leaks from the inside of the duct system. A non-toxic sealant is aerosolized and injected into pressurized ductwork; the particles stay suspended in the airstream until they reach a leak, where escaping air carries them to the gap's edges. They accumulate there — building across holes up to roughly the size the manufacturer specifies — until the leak is closed. The system measures duct leakage continuously, so you watch the leakage number fall in real time and receive a printed verification report when sealing is complete.
Service-Tech Corporation delivers Aeroseal as part of our Commercial Air Duct & HVAC Cleaning practice. Most of what ranks for this topic is written for homeowners; this page covers what the process looks like in commercial buildings, healthcare facilities, and campuses — where the ductwork is bigger, the ceilings are full, and tearing out finished construction to patch duct joints is rarely an option.
Why Duct Leakage Is a Building Performance Problem
In a commercial building, duct leakage rarely announces itself. It shows up as symptoms facility managers chase for years:
- Starved distal zones. The rooms farthest from the air handler never hit setpoint because supply air escapes upstream.
- Pressurization failures. Healthcare isolation rooms, labs, and clean spaces depend on precise pressure relationships; leaky duct undermines them silently.
- Runaway fan energy. The system moves more air to deliver the same comfort, and VAV boxes hunt against a supply that isn't what the controls assume.
- IAQ complaints. Return-side leaks pull unconditioned, unfiltered air from plenums, mechanical rooms, and cavities directly into the airstream.
- Comfort complaint churn. The endless hot-call/cold-call cycle that consumes maintenance hours without ever finding "the" problem.
If these symptoms persist after balancing and controls work, leakage is the untested variable. Sealing addresses the cause rather than compensating for it. Commercial offices, hospitals, and universities — where duct runs are long and access is worst — see the clearest gains; more building types are on our industries page.
Clean First, Then Seal: The Right Sequence
Aeroseal bonds at the edges of leaks, which means the sealing surface matters. Sealing a duct system that is loaded with dust and debris is poor practice — and it wastes the one moment when your ductwork is fully accessed and controlled. As a duct cleaning firm first, Service-Tech runs the sequence the way it should be run: NADCA-standard source-removal cleaning, then aerosol sealing into clean duct, in one coordinated scope. Facilities with heavy systems can fold in industrial air duct cleaning ahead of sealing. One mobilization, one containment setup, one report covering both hygiene and leakage — a pairing a sealing-only franchise or a cleaning-only vendor cannot offer.
How a Commercial Aeroseal Project Runs
Here is the process from the applicator's side, so you know what to expect in an occupied building:
- 01
Pre-test
We isolate the duct section, temporarily block registers and diffusers, and pressurize the system to measure baseline leakage — a hard number, not an estimate.
- 02
Protection of terminal equipment
Coils, VAV components, and devices that should not receive sealant are blocked off or bypassed per the process specification.
- 03
Injection
The aerosolized sealant is introduced under controlled pressure and temperature. The computer tracks leakage continuously as particles close each gap from the inside.
- 04
Verification
When leakage reaches target, injection stops and the system generates the certificate: baseline leakage, final leakage, and the reduction achieved. On one Service-Tech commercial project, that report documented a 94% reduction in duct leakage.
- 05
Restoration
Blocks come out, registers are reinstalled, and the system returns to service — typically the same visit, with no demolition and no repainting.
Work is staged zone by zone, so an occupied building keeps operating while sections are sealed.
"Is This Smoke and Mirrors?" — An Honest Answer
Skepticism about aerosol sealing is reasonable: you cannot see the leaks, and you cannot see the fix. The answer is that you do not have to take anyone's word for it. The process is measurement-bracketed — a pressurized leakage test before, continuous measurement during, and a verification report after. Either the cfm of leakage fell or it did not; the printout is generated by the system, not written by the salesperson. That is a stronger evidence standard than most duct repairs can offer, where a technician tapes a joint and everyone hopes. Keep the verification report with your TAB records — it is auditable proof of the building's duct performance.
When Sealing Makes Sense — and When It Doesn't
Aeroseal is the right tool when leaks are distributed, inaccessible, or both: duct above hard ceilings, risers in shafts, long runs through occupied floors, systems failing a leakage test before commissioning or code sign-off. It is the wrong tool in some cases, and we will tell you so at assessment:
- Large accessible defects. A disconnected joint or crushed section is a mechanical repair, not a sealing job. Aerosol sealant closes gaps, not open ducts.
- Certain industrial exhaust. Process exhaust carrying grease, chemicals, or combustible dust has its own codes and cleaning obligations; sealing is evaluated case by case and sometimes ruled out.
- Systems that mainly need balancing. If leakage tests low but comfort is poor, the money belongs in TAB and controls, not sealant.
Sealing also pairs well with the rest of an HVAC hygiene program: restored airflow exposes weak heat transfer, so many clients schedule HVAC coil cleaning in the same project, and buildings under life-safety audit cycles add fire damper inspections while systems are open and accessible.
What Commercial Aeroseal Sealing Costs
Commercial sealing is priced by system: duct volume, zone count, access, and baseline leakage all drive scope. Free estimate — quote after site assessment. Travel is factored into the quote across our 150-mile service radius from each office. Because the pre-test produces a real leakage number before any sealing begins, you decide whether to proceed with data in hand.
What Leaky Ductwork Costs You If You Wait
Every month a leaky system runs, you pay to condition air that never reaches an occupied space — fan energy, heating and cooling energy, and maintenance hours spent chasing comfort complaints that balancing cannot fix. In healthcare and lab settings the stakes are higher: pressurization failures are compliance findings, not comfort issues. Duct leakage never improves on its own; joints only loosen with age and vibration. A measured pre-test is the cheap way to find out how much of your airflow you are losing.
Find out exactly how much air your duct system is losing — then watch the number fall. Free estimate, quote after site assessment.
Measured, Not Estimated
The reason to seal from the inside is that the result is measurable. The system is pressurized, leakage is quantified before the work, the sealant is introduced as an aerosol that deposits at the leak edges until they close, and leakage is measured again afterwards. You get a before-and-after number rather than an assurance.
- The verification is the product. Computerised leakage measurement at both ends of the job. One Service-Tech project on an Ohio facility recorded a 94% reduction in measured duct leakage.
- What sealing does not fix. It closes leaks; it does not clean a dirty system. Sealing a contaminated duct traps the contamination behind the sealant, so cleaning to the NADCA acceptance figure of 0.75 mg per 100 cm² comes first.
- Liner condition decides eligibility. A liner that has begun to delaminate needs encapsulation or replacement — sealant is not a repair for shedding fibre.
- Where it pays. Buildings where the plenum and duct runs are buried, inaccessible or spread across floors, and where the alternative is opening ceilings to reach joints by hand.
- The energy connection. The U.S. Department of Energy attributes 25–40% of commercial heating and cooling energy to contamination and airflow restriction; leakage is the part of that you can close permanently.
Before Sealing: What the Survey Has to Establish
- Cleanliness first. Sealant applied to a contaminated run traps the contamination behind it. The system is cleaned and verified to 0.75 mg per 100 cm² on the NADCA Vacuum Test before any sealing.
- Borescope the runs. Interior condition beyond arm's reach decides eligibility; a camera on a rod answers it in minutes.
- Baseline the leakage. The system is pressurized and leakage quantified as a measured figure, not estimated, so the post-seal result means something.
- Check the liner. A liner shedding under light pressure is encapsulated or replaced. Sealant is not a repair for delaminating fibre.
- Open the plenum and terminals. Registers, diffusers and the air-handler plenum are opened so the aerosol reaches the leaks rather than depositing at the first restriction, and everything is reinstated and re-tested afterwards.
- Interval context. NADCA guidance is annual on air handling units and every 1–2 years on ductwork; sealing is a one-time capital improvement on top of that cycle, not a substitute for it.
In Short
- Clean and verify first: 0.75 mg per 100 cm² on the NADCA Vacuum Test, with capture at HEPA 99.97% of particles at 0.3 micron.
- Then baseline: pressurize and measure leakage as a figure rather than an estimate.
- Measured result: one Service-Tech project recorded a 94% reduction in duct leakage, and duct life extended by as much as 10 years.
- Reassemble to spec: MERV 8 or better, relative humidity held between 30–60%, ASHRAE 180 as the programme basis.
- Interval context: annual on air handling units against every 1–2 years on ductwork; NFPA 90A and NFPA 90B govern the installation.
- The economic frame: the DOE attributes 25–40% of commercial heating and cooling energy to contamination and airflow restriction.
Frequently Asked Questions
Does Aeroseal actually work, or is it marketing?
The process is measurement-bracketed: a pressurized baseline leakage test before sealing, live computer measurement during, and a printed verification report after. The result is a hard before/after number generated by the system itself. On one Service-Tech commercial project, the verification report documented a 94% reduction in measured duct leakage.
Is the sealant safe for occupied buildings?
The sealant is applied inside the duct system under controlled conditions, with registers blocked and the work zone managed section by section. It is designed to bond at leak edges rather than coat duct interiors, and buildings remain occupied while zones outside the active work area operate normally. We review the manufacturer's product and safety data with your team before work begins.
Can you seal ducts without opening walls or ceilings?
Yes — that is the core advantage. The sealant travels through the airstream and closes leaks from the inside, so duct above hard lids, inside shafts, and behind finished construction is sealed without demolition. Access is only needed at injection points and terminals.
Should ducts be cleaned before they are sealed?
Yes. Sealant bonds most effectively at clean leak edges, and the sealing project is the ideal moment to address duct hygiene since the system is already isolated and controlled. Service-Tech performs NADCA-standard duct cleaning and Aeroseal sealing as one sequenced scope — clean first, then seal.
When is Aeroseal not the right solution?
When the defect is a disconnected or crushed duct (a mechanical repair), when certain industrial exhaust codes rule it out, or when testing shows leakage is low and the real problem is balancing or controls. Our assessment includes a measured pre-test, so the recommendation is based on data — and we will tell you if sealing is not the answer.