Q: Why Should Ducts in Commercial Buildings Be Sealed?
A: Duct sealing in commercial buildings cost-effectively saves energy, improves air balance and thermal distribution (comfort and ventilation), help comply with building codes and reduces cross contamination between different zones in the building (i.e., smoking vs. non-smoking, bio-aerosols, localized indoor air pollutants).
Q: How Much Energy Does the Sealing Process Save?
A: Energy savings are different for light commercial vs. large commercial buildings and obviously depend upon the initial duct leakage level. The Aeroseal Energy Savings Excel spreadsheet can be used to estimate the savings for both types of buildings. For ducts above an insulated ceiling in a light commercial building, energy savings should be 10—30% of HVAC energy use, and peak electricity-demand reduction is generally a higher percentage. In a large commercial office building with a VAV system, energy savings and demand reduction should be 20—40% of fan-system energy use and 5—10% of cooling energy use. As a rough estimate, excluding any of the non-energy benefits of duct sealing, simple payback times typically range from 1 to 4 years, and return on investment between 30% and 70%.
Q: How Do I Know if the Ducts in My Building Need to be Sealed?
A: The existence of duct leaks in your building can be uncovered several ways. One way is to examine Test and Balance reports, comparing the total flow through the grilles with the total flow through the air handler, or by looking for systematically low flows at grilles that are far from the fan. Another way is to test a sample of duct sections for leakage, a test that DuctMedic’s Aeroseal technicians perform on a regular basis.
Q: How Does the Aeroseal Process Work?
A: 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.
Q: Who is Aeroseal?
A: Aeroseal is a fully owned subsidiary of JMD Corporation that holds an exclusive license from the University of California for the aerosol-based duct sealing process patented by Lawrence Berkeley National Laboratory.
Q: Is the Sealant Material Safe?
A: The sealant material consists of a water-based solution (65% water) prior to application. The dried sealant material primarily contains two chemicals, vinyl acetate polymer (VAP) and 2-ethyl-1 hexanol (2E1H). The vast majority of what is left in the duct system is VAP, which has been used in water-based paints, adhesives, and hair spray. VAP has been used in chewing gum, and has no OSHA Exposure Limit. 2E1H is a common industrial solvent and is not considered toxic by OSHA. A review of the literature showed no ill effects after long-term exposure to concentrations of 200 ppm. The largest concentration of 2E1H measured in test houses was 1 ppb (200,000 times smaller), during Aeroseal injection. The sealant is UL-listed for smoke generation and flame spread (UL 723 0,0), and additional testing by UL showed no signs of mold growth or erosion.
Q: How Long Will the Seals Last?
A: 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. Aeroseal and the sealant manufacturer warrantee that seals will last at least 3 years in commercial application.
Q: How Large of a Leak Can be Sealed?
A: 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.
Q: What Types of Ducts Can be Sealed?
A: Aeroseal is capable of sealing all types of ductwork, however the sealing rate varies with the type of ductwork. Sheetmetal ductwork seal most quickly, and internally lined ductwork seals most slowly.
Q:What about VAV and Fire/Smoke Dampers?
A: Aeroseal generally avoids blowing sealant material 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.