Sealing Leaky HVAC Ducts

When a renovation of an elementary school revealed substantial leakage in a portion of ductwork, a pilot program to evaluate a sealing technology was put into action..

With 14,000 buildings under its domain, LAUSD continuously pursues energy efficiency solutions. When a renovation of an elementary school revealed substantial leakage in a portion of ductwork, a pilot program to evaluate a sealing technology was put into action.

Adrian Tylim, former sustainability initiatives officer for LAUSD, discusses the project.

By Facility Executive Staff

Please give an overview of the facility involved in this project.

This project involved one of LA Unified’s active K-6 elementary school buildings. The school currently serves more than 1,000 students and includes classrooms, a library, computer lab, and administrative offices. The duct sealing was limited to the supply and return ductwork serving the building’s administrative offices, and the return duct serving the four kindergarten classrooms.

HVAC ducts
The aerosol-based sealant from Aeroseal is blown into the interior of the duct system. By sealing from the inside, the sealant “finds” and seals leaks throughout the entire duct system. (Photo: Aeroseal)
What were the motivating factors to pursue this project?

The initial interest in Aeroseal technology was related to our need to meet building code requirements. At the same time, we saw this as a potential avenue for substantial energy and cost savings. Our test and balancing (TAB) experts determined that the ductwork had leakage rates well above specifications. Accessing the ductwork and sealing those leaks using traditional duct sealing methods would have required substantial demolition to the existing building. The time needed and the disruption that would be caused by the demolition, along with the costs of rebuilding made this option impractical. If it worked as promised, the Aeroseal technology seemed to be the answer.

How did you research the options available in the market? And, how did you arrive at the final decision to implement Aeroseal?

I first learned about Aeroseal duct sealing technology while attending a local tradeshow. Our staff of engineers and sustainability professionals is always on the lookout for new and better ways to manage the 14,000 building structures within the school district. This innovative approach to duct sealing had the potential to do both.

We had several subsequent meetings with Aeroseal representatives as we investigated the technology to ensure it was safe as well as effective. This included a rigorous approval process conducted by our office of education health and safety (OEHS). It also included a review of research conducted by Lawrence Berkeley National Laboratory where the technology was first developed. There was also a review of the associated MSDS documents. And we solicited information from other school districts, hospital administrators, and commercial building owners where the technology was applied.

There were several aspects of the technology that made it particularly appealing.
  1. Highly effective: The research we reviewed found it to be 95% effective at sealing duct leaks.
  2. Non-destructive: There was no other viable means of accessing the existing ductwork hidden behind walls, under insulation, and other building infrastructure.
  3. It took the guesswork out of success: The computerized process monitors the leakage rate while it is sealing. At the end of the sealing process, the system generated an accurate “before and after” report that documented the results. There was no need to follow up with additional TAB measurements.

Once approved at that level, we identified the LAUSD 93rd Elementary School for a pilot project.

Please share the project timeline.

The initial research and approval process spanned about one year. We then began the planning phase, where the Aeroseal representatives met with our engineers and planned out a course of action. Over the course of a few months, we put the project out to bid, selected Penn Air Group [in Los Angeles] as our Aeroseal contractor for the job. They conducted site visits and developed a final plan of action.

The actual sealing process took just two days to complete from start to finish. On the first day, the supply and return ducts serving the administrative offices were sealed. On the second day, we sealed the return duct serving the kindergarten classrooms. On the first day of sealing, there were several district personnel on hand to witness and evaluate the process, including school administrators, maintenance and operations staff, inspectors, and engineers. The sealing portion of the project was conducted over two days of winter break when the building was relatively unoccupied.

What have the results been?

First, the technology was very effective. Post-testing showed that leakage rates were reduced by about 92%. This got us well within code requirements. Reducing that amount of leakage has got to have a significant impact on energy use. We are in the process of calculating exactly how much we will be saving as a result, but we feel confident that it will be enough to provide a two to three year return. With 930 schools in the district—more than 14,000 buildings overall, the energy saving potential of effective duct sealing easily represents hundreds of thousands of dollars in reduced utility costs.

Any other comments on this project, or lessons learned?

There were many skeptics on hand to witness the process as it was being applied to the school building, but everyone came away impressed with how well it worked. The bottom line is that there simply wasn’t any other viable means for tackling this problem.

Visit the Los Angeles Unified School District website at To learn more about Aeroseal, visit

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