This article was originally published in the January/February 1998 issue of Home Energy Magazine. Some formatting inconsistencies may be evident in older archive content.
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Home Energy Magazine Online January/February 1998
Not Your Daddy's Duct Sealing Method
By Gary Heederik
In the past, I, like many others, have diagnosed duct leakage with a Minneapolis Duct Blaster. The Duct Blaster pressurizes the heating and air conditioning duct system. Using a hand-held digital manometer, I can very accurately measure air loss in a duct system. Once I've done this, the next step is to reduce that air loss.
Using traditional duct sealing, leaks might go unsealed because they are small and hard to find, or because the duct run is inaccessible. With the use of a new technology that has just recently come to California, that hard-to-find leakage is easier to reach and repair in a cost-effective fashion.
This new technology--called Aeroseal-- is finally available to duct-sealing specialists. Once the duct runs are pressurized, Aeroseal blows in a sealant made up of polymers suspended in a water base. As the sealant crosses a warm air stream before entering the duct system, the warm air partially evaporates the water, allowing the polymers to collect and stick to leaks, attracted to the holes by the low pressure outside the duct system. Once the leaks are all sealed, the change in pressure notifies the Aeroseal equipment that the job is done, and the equipment shuts down.
In September, 1997, Aeroseal Incorporated approached my company, Consumer Energy Management Consulting Incorporated (CEMCO), to participate in a 60-day pilot program to test the Aeroseal product on older homes. I found this product works great on those homes as a cost-effective way to reduce duct losses and consumer energy bills. In general, the technology works well for sealing small leaks, but larger leaks still need to be sealed by hand.
At CEMCO, we have performed diagnostic testing services and repairs for the past several years and have worked on hundreds of homes. With the use of this product, we are able to seal ducts tighter at no additional cost. We can also further reduce leakage in a system that is already considered tight. Our target leakage rate after sealing a retrofit home with the Aeroseal product is approximately 25 CFM25. For a new production home builder this product offers tremendous value in assuring quality control, minimizing consumer energy bills, and reducing the risk of defect litigation issues arising from poorly installed ductwork.New Home Sealing The process is fairly simple for new homes. The sealing takes place when the ductwork is completely installed but the heating and cooling equipment is not yet set. First I perform a pretest to identify the leakage. Then I follow the same steps as for sealing an older home. Retrofit Home Sealing The process for sealing a retrofit home is a little more complex. I first do a preinspection on the home to make sure it is feasible to seal with Aeroseal. I look for such things as the type of duct work, indoor air quality, and any carbon monoxide (CO) problems. I check any gas appliance for high CO levels and positive flue gas drafts. For obvious safety reasons, if there are problems with air quality or appliance operation, I do not want to proceed further until these problems have been addressed. Once I have determined that it's safe to go ahead, I take the following steps:
The cost of sealing an existing duct system with Aeroseal is between $450 and $600, depending on what needs to be done, roughly the same as the cost of hand-sealing though less labor intensive. When sealing new homes, this product can be rolled into a total package of improvements provided to the builder, perhaps to qualify for the Environmental Protection Agency Energy Star Home Program (see New Software Helps Sell Energy-Efficient Homes, p. 7) or with the use of the Energy Efficient Mortgage Program (EEM).
Gary Heederik is the senior vice president of Consumer Energy Management Consulting Incorporated in Northern California.
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