Aeroseal Frequently Asked Questions


Aspen Air Duct Cleaning is an approved Aeroseal Dealer, licensed and ensured, and a member of the National Air Duct Cleaners Association (NADCA) and National Organization of Remediators and Mold Inspectors (NORMI). Following are some of our most frequently asked questions.

Aeroseal Frequently Asked Questions

Why should ducts in commercial buildings be sealed?  How much energy does the sealing process save?  How does Aeroseal work?  These are the questions we hear a lot and you’ll find the answers below.  If you have any other questions please do not hesitate to contact us – we’re here to help!

Why should ducts in commercial buildings be sealed?
Duct sealing in commercial buildings cost-effectively saves energy, improves air balance and thermal distribution (comfort and ventilation), and helps comply with building codes and specification for air distribution effectiveness.

How much energy does the sealing process save?
Energy savings are different for each building and HVAC system and obviously depend upon the initial air duct tightness. The Aeroseal Energy Savings Excel spreadsheet can be used to estimate the savings for most types of buildings.

In smaller commercial buildings with air ducts outside the insulation barrier of the building, energy savings can be as much as 30% of HVAC energy use. In large buildings Aeroseal duct sealing can reduce fan-system energy use by as much as 40% and reduce heating and cooling costs by as much as 10%.

As a rough estimate, simple paybacks typically range from 3 to 7 years. In some cases building owners have recovered the investment in Aeroseal duct sealing in less than 18 months.

Is the sealant used in Aeroseal safe?
The sealant material has been certified to UL1381, the industry standard for aerosol duct sealants. It is tested to rigorous requirements for flammability, smoke inhibition, mold growth and durability. The sealant has no OSHA Exposure Limit and no special precautions are required during application. It cures in less than two hours and meets LEED requirements for low VOC emissions.

The dried sealant material is primarily vinyl acetate polymer (VAP), which has been used in chewing gums, latex paints and hair sprays.

How long will the seals last?
The sealant has a life of over 30 years. Scientists at Lawrence Berkeley National Laboratory tested the performance of Aeroseal seals for 4 years under accelerated conditions, and were never able to observe a failure. This corresponds to 100,000 cycles under more severe temperatures and pressures than are found in duct systems.

How do I know if the ducts in my building need to be sealed?
The duct leaks can be uncovered several ways. Aeroseal has developed a simple survey (link) that can accurately predict if an air distribution system is leaking excessively. Another method is to review a Test and Balance Report and compare the flow at the HVAC system supply or return fans and sum of the flows measures at the supply diffusers or return grilles. Testing a sample of duct sections for leakage is an accurate way to identify if ducts are too leaky. Aeroseal technicians regularly perform this test.

How does the Aeroseal process work?
The Aeroseal process seals duct leaks from the inside, using small sealant particles that deposit at the leaks without coating the interior of the duct system.

This is accomplished by pressurizing the duct system with a fog of sealant particles sized to stay suspended in the air until they try to exit the duct system. By blocking all of the intentional openings in the duct system (i.e., diffusers or grilles), all of the sealant-laden air is forced out through to the leaks. As the duct pressure causes the particles to accelerate through the leaks, they stick to the edge and build upon each other until the leaks are sealed. By constantly monitoring the duct pressure and flow, the process-control computer calculates and the displays the remaining leakage in real time. When the sealing is finished, a complete minute-by-minute record of the process is printed, stored on the local computer, and then uploaded over the internet for archival on the Aeroseal server.

How large of a leak can be sealed?
Aeroseal recommends sealing the leaks up to 5/8 inches across. Leaks more than one inch across can be sealed, however the sealing rate varies with the size of the leak times itself. In other words, the sealing time for a 1″ leak is 64 times longer than that for a leak 1/8″ across.

Practically speaking, leaks larger than about 5/8″ across are better suited to be sealed manually if possible.

What types of ducts can be sealed?
Aeroseal is capable of sealing all types of ductwork. It has been successfully applied in rigid metal and flexible air ducts. It has been applied in duct with internal insulation. It has also been installed in duct systems fabricated of ductboard, drywall or masonry blocks.

Aeroseal avoids sealing through VAV boxes or fire/smoke dampers.

What about VAV boxes and fire/smoke dampers?
Aeroseal generally avoids blowing sealant materiel through VAV boxes or fire/smoke dampers, however laboratory and field testing have shown that under the right circumstances this can be done without adverse consequences.

Under no circumstances can sealant material be blown through VAV boxes with reheat coils. Should it be more practical to blow sealant through VAV boxes or fire/smoke dampers, it is recommended to consult with the engineers at Aeroseal LLC.

Do ducts need to be cleaned prior to sealing?
Extremely dirty ducts should be cleaned.  We recommend that the technician assess the condition of ducts prior to beginning to Aeroseal process.

Can I clean my ducts if they are sealed by Aeroseal?
Ducts of all material types can be successfully cleaned after they have been sealed with Aeroseal.

Can Aeroseal be used to seal air leaks in exhaust duct systems serving Type I (grease) commercial kitchen hoods?
We do not recommend Aeroseal to seal air leaks in exhaust ducts serving commercial kitchen grease & heat removal hoods (Type I hoods).  The sealant is not listed or rated for use as a duct sealant for these types of systems, and harsh cleaning chemicals used to clean the ducts could remove or degrade the performance of any seals.

Don’t see the answer to your question? Let’s talk!

Source: Aeroseal

Please contact Aspen Air Duct Cleaning at 1-800-931-6653 for an Air Duct System Inspection and to learn more about how sealing air duct leaks can improve indoor air quality and reduce energy costs. Or email

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Duct Leakage Testing is a Must

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A recent survey of the building construction industry by the Building Commissioning Association (BCA) on the issue of duct leakage resulted in some startling statistics. Seventy-five percent of the approximately 300 respondents felt that duct leakage contributes substantially to energy loss in commercial buildings. And, 74% of the respondents also believed most of the buildings in the U.S. have significant duct leakage (greater than 15%). Duct leakage can significantly increase the energy consumption of a building, leading to increased energy bills for the owner. It increases energy costs and can result in occupant discomfort and lower productivity. This combination can transform a building intended to be a high performing building into a building that is not. So, what can be done to combat duct leakage? Test early and test often.

As a commissioning provider for high performing buildings, we observe many instances of duct leakage in both new and existing buildings. The top factors for duct leakage issues are inadequate sealing of duct joints and access doors or panels, which are related to quality of duct installation workmanship, and over-pressurization of the air distribution system resulting in duct seam separation, which is related to HVAC system control. Many owners do not include commissioning, which can identify performance issues such as lack of testing requirements in the design specifications and building performance issues that occur during the design, construction, and operational phases of a project.

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Where new building codes (2010 and later) have been adopted, some duct leakage testing requirements exist. However, many states have yet to adopt the newer codes. While these new codes are beginning to require duct leakage testing, they only require 25% of the high- and medium-pressure duct be tested. As a result, duct leakage testing appears to be hit or miss when it comes to newly | Duct Leakage Testing is a Must… 1 of 2 12/6/2016 3:03 PM constructed buildings. Though a project designer can specify the required sealing level for each duct type, the only way to verify the effectiveness of the duct sealing is by duct leak testing.

It is important that design professionals specify duct leakage testing and have the commissioning provider observe duct leak testing of high- and medium-pressure ductwork in accordance with SMACNA’s HVAC Air Duct Leakage Test Manual. It is also important that the commissioning provider evaluate the building’s controls.

Allowable duct leakage rates specified are around 10%. However, for high performing buildings, designers may elect to reduce the allowable leakage amount in an effort to further reduce the energy consumption of the air moving systems. By specifying SMACNA duct leakage testing for medium- and high-pressure air duct systems integrated with commissioning in their projects, design professionals can be confident that their building will meet the high performing requirements of the owner.

The survey by the BCA also noted that a majority of respondents felt duct leakage is most prevalent in existing buildings. This should come as no surprise to individuals in the building industry. Many of the existing buildings that are prime candidates for services such as energy audits or retro-commissioning were built 15 or more years ago. Even if duct leakage testing was performed when the buildings were constructed, the sealant materials can be either near the end of their useful life or have begun to deteriorate, which leads to increased duct leakage.

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Typical building maintenance programs do not include observations and maintenance of the duct sealants, and even if they did it would be nearly impossible for all seams and joints to be evaluated, let alone resealed from the exterior. What is the answer? Very cost-effective products that can be applied to the interior of the air distribution system that can seal most air loss paths. Maintaining a sealed air distribution system should be included in a building’s operation and maintenance (O&M) budgets, similar to sealants for the building enclosure. This is a simple way for building owners to keep their buildings’ energy consumption low.

If owners elect to have energy audit or retro-commissioning services performed on their building, they should require that these professionals evaluate the leakage of the existing ductwork. This can provide the owner with a low-cost energy measure that can potentially have a very low payback period.

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It is clear to the building industry that duct leakage is an issue. For buildings looking to be labeled as high performing buildings, it can be a significant issue. Therefore, it is imperative that engineers require duct leak testing and that commissioning providers ensure duct leakage is minimized. The simplest way to stop or significantly reduce duct leakage is to require testing and verification of the air distribution and exhaust systems’ installation and HVAC control function through the design and commissioning process.

Source: Aeroseal; authors H. Jay Enck, Member ASHRAE, HBDP, BEAP, CPMP, CxAP, LEED Fellow, cofounder/chief technical officer and David Cantrill, P.E., Member ASHRAE, BEAP, CCP, branch manager/commissioning authority/project manager, both with Commissioning and Green Building Solutions, Inc.

Aspen Air Duct Cleaning is an approved Aeroseal Dealer, licensed and ensured, and a member of the National Air Duct Cleaners Association (NADCA) and National Organization of Remediators and Mold Inspectors (NORMI).

Please contact Aspen Air Duct Cleaning at 1-800-931-6653 for an Air Duct System Inspection and to learn more about how sealing air duct leaks can improve indoor air quality and reduce energy costs. Or email

nadca-logo    normi-logo

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