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EETD Develops New Commercial Duct-Sealing Technology

Environmental Energy Technologies Division (EETD) researchers have invented an aerosol-based system for sealing ducts in large commercial buildings. The mobile aerosol-sealant injection system (MASIS) is based on an aerosol sealing device previously developed by EETD researchers for reducing energy losses through leaky ducts in residential and small commercial systems. MASIS incorporates two new, patented technologies that permit effective sealing in the larger, more complicated duct systems of commercial buildings: a series of compact aerosol injectors and a new atomizer that uses high-velocity heated gas to prevent clogging of the injection nozzle.

EETD scientist Duo Wang developed the new technology with assistance from Mark Modera, the scientist who developed the original sealing system for residential buildings. Carrier Aeroseal has licensed MASIS exclusively to seal ducts in commercial buildings.

Modera and colleagues first developed aerosol-based technology for sealing the ducts of heating, ventilating, and air-conditioning (HVAC) systems in residential and small commercial buildings during the 1990s. Their research showed that homes with leaky ducts in contact with outside air wasted, on average, 20 percent of all heating and cooling energy in the United States. They pioneered a system to seal these ducts remotely and inexpensively, using an aerosol that is injected through a home's heat register. The aerosol flows through the duct system, gradually building up flexible seals at holes, tears, and other leaks.

The team successfully tested the technology in the field and licensed it to a start-up company called Aeroseal, which was eventually acquired by Carrier Corporation. Residential duct sealing that uses the EETD technology is available through contractors trained by Carrier.

Addressing Leaky Ducts in Commercial Buildings

The research by Modera and his colleagues suggested that energy losses in the ducts of large commercial buildings are probably as large in scale as the losses in residential ducts. Although research to quantify the losses in commercial buildings is continuing, EETD scientists estimate that sealing ducts in commercial buildings could save large amounts of energy.

Large commercial buildings present special problems that the original residential duct sealing technology could not address. "The HVAC duct system in large buildings typically has a large trunk duct system and a number of smaller sub-duct systems connected to it," says Wang. "Trunk duct systems are longer and have a larger cross-section than residential systems, and they are connected to many branched duct systems. One problem is that large aerosol particles from a residential-scale duct sealer would fall out of the air stream too quickly to seal leaks effectively in these larger commercial ducts. Another problem is that the branch systems often contain heating or cooling coils that cannot be exposed to aerosol sealants.

"To increase the flow of aerosol sealant in larger ducts, we designed a sealing system that uses a number of compact aerosol injectors," Wang explains. "Several of these are installed along the trunk line of a commercial building duct, injecting aerosol simultaneously. This substantially increases the sealing rate of leaks in the duct system."

A New Aerosol Atomizer

The researchers also developed a new atomizer to adapt the original aerosol-based sealer to commercial buildings (see Figure 1). The residential system spray nozzle converts the sealant into an aerosol and sends it flowing into the duct system. The commercial system needed a nozzle that could inject sealant at a smaller spray angle and a higher flow rate than the residential system. Unable to find an appropriate commercially available nozzle, the research team developed its own design, the induced-cooling pneumatic atomizer, which provides the necessary particle size and flow rate at the correct spray angle, without clogging.

The prototype induced-cooling pneumatic atomizer is made with standard tube fittings.

Figure 1. The prototype induced-cooling pneumatic atomizer is made with standard tube fittings.

MASIS consists of a sealing-process monitoring system and portable injectors. In one design, each injector unit consists of an air compressor and a cart that carries an aerosol sealant injector wand, a liquid sealant tank, a peristaltic pump, a control box, and a dedicated toolbox. In another design, the injectors are all fed by a central station and are daisy-chained via umbilical cords.

To seal the trunk system, injectors are installed along the duct and run simultaneously. To seal the branch duct systems, injectors are installed downstream of the heating and cooling coils, which are usually located in variable air volume boxes. Each branch seals independently, and all of the injectors can operate simultaneously.

The induced-cooling atomizer is licensed to Carrier Aeroseal for aerosol duct sealing only. Licenses are still available for other applications, such as dehydration of products, drying of waste streams, and atomizing of liquids for industrial processes. Information about licensing is available from Lawrence Berkeley National Laboratory's Technology Transfer Department.

— Allan Chen

For more information, contact:

  • Duo Wang
  • (510) 486-6878 ; fax (510) 486-6658

Aerosol Duct Sealing Technology

Technology Transfer Department:TTD@lbl.gov

Technology Transfer: Available Technologies: Clog-free Atomizing and Spray Drying Nozzle

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