Recovering Lost Energy From Ductwork
October 15, 2007
Like other energy-saving measures, duct repair methods are finding more market acceptance among consumers, and for good reasons. The benefits include lower energy bills, decreased ecological impact, and improved comfort.
According to DOE’s Energy Star® program, typical residential systems leak 15-20 percent on the supply side and another potential 15-20 percent on the return side. “Even when the furnace or air conditioner is not running, duct leaks waste energy by contributing to the overall air leakage of the house,” states the “Improve Energy Efficiency with Aerosol Duct Sealing” report on the Website www.energystar.gov. “In new tight houses, duct leaks can account for 20-25 percent of total building air leakage.”
There are ramifications on the national level. “If 75 percent of the leakage in existing residential single-family homes were sealed, the nation would save approximately $7 billion dollars annually,” said Scott Morani, sales and marketing manager for Aeroseal, a division of Carrier, Syracuse, N.Y. “This does not even include multifamily buildings, commercial buildings, or new construction. As energy prices continue to increase, the [potential] national energy savings will only increase.”
INCREASED INTERESTIn the past, duct sealing may have been more difficult to educate consumers about. The basics could be explained, but it still couldn’t prevent a well-meaning homeowner from trying to fix his or her own ductwork using duct tape that is not an industry-recommended product, not to mention lack sealing with applied mastic, or proper repair of flex duct.
“Over the past year we have had a surge of new interest,” said Morani. “With energy prices increasing, consumers are becoming more interested in ways they can reduce energy usage in their homes and businesses. There has also been a movement for green homes and buildings that we are benefiting from.”
Researchers at Lawrence Berkeley Laboratories (LBL), Berkeley, Calif., are also optimistic about current attitudes toward duct repairs. “Both the housing and HVAC industries appear to have accepted the idea that thermal distribution inefficiency is a serious problem.”
The authors of the report “Energy Savings Potentials in Residential and Small Commercial Thermal Distribution Systems - An Update” cited the commercialization of aerosol duct sealing as “perhaps the most significant technology development in the ensuing 12 years… .”
Previous reports “found that it achieved 16-60 percent better air leakage reductions than hand sealing and potentially could reduce labor and repair costs by 30 percent. Modera et al., in the “Energy Effectiveness of Duct Sealing and Insulation in Two Multifamily Buildings,” Proc. 1996 ACEEE Summer Study on Energy Efficiency in Buildings, found that aerosol sealing was capable of sealing 80 percent of the leakage it encountered, assuming that catastrophic leaks such as disconnected ducts had first been repaired.
“The entire sealing protocol, including setup, supplementary conventional sealing, and cleanup, was found to take an average of 5.5 person-hours of labor, a significant saving over conventional sealing, which would have required an estimated 10.5 person-hours on average. The injection process itself consumed about 20 percent of this time.”
AEROSOL SEALINGAerosol-based duct-sealing technology seals duct leaks from the inside. Improvements to the mode of delivery make it more efficient for the contractor.
In general, all the registers are sealed off and the sealant is applied before the HVAC equipment is installed; or, the registers are sealed and the existing HVAC equipment is bypassed, states the Energy Star report.
“The duct system is pressurized with air and an aerosol vapor is injected. As aerosol-laden air is forced out through leaks in the ductwork, the tiny particles deposit in the gaps (not on duct walls), filling the leaks.”
According to Morani, Aeroseal has been successful in sealing metal, flex, ductboard, and building cavity ducts, in buildings ranging from single-family residences to large commercial structures.
There are limitations. “We do not recommend sealing ductwork that is underground or exposed to water,” he said. “Additionally, if the ducts have a uniform layer of dust on the bottom, we recommend having the ducts cleaned before sealing them.”
The company’s Generation II equipment can be used with 110-V electricity and seals approximately five to 10 times faster than earlier generation equipment, Morani said. “It has also been broken up into components that are connected with tubing, which makes it easier to get into confined areas.”
MANY BENEFITSDuct sealing products like Aeroseal are said to benefit contractors and their customers in multiple ways:
• There is less crawling around in cramped spaces (attics, crawl spaces) for contractors who are looking for and repairing leaks. “In fact, they can do other things during the automated injection process,” stated the Energy Star report. (Carrier’s instructions require a technician to remain with the machine during sealing.)
• Documentation of duct sealing can help reduce liability associated with HVAC system performance, and result in more satisfied customers for contractors and builders. Sealed ducts reduce the possibility of backdrafting from gas or oil appliances and fireplaces, Morani pointed out, and backdrafting is what introduces carbon monoxide, combustion gases, and smoke into living spaces.
• IAQ is improved because leaks are sealed in attics, unfinished basements, crawl spaces, and garages that would otherwise allow dirt, dust, moisture, pollen, pests, and fumes to enter the living space.
• Comfort is improved. “When ducts are properly sealed, they deliver conditioned air more effectively to all rooms, helping to ensure a more constant temperature throughout the home,” Morani said.
A recent survey from the Small Business Research Board (SBRB) stated that rising energy and fuel costs is the third-leading business issue. “Energy costs are beginning to impact the growth of our economy and impacting the prices of consumer products,” said Morani. “Simply put, the less energy we use, the less demand we generate, and this is a factor in keeping energy and product costs down.
“By reducing the amount of energy necessary to comfortably heat or cool homes or businesses, we are helping become part of the solution rather than being part of the problem.”
For more information, visit www.aeroseal.com, www.energystar.gov, www.ipasbrb.com, and/or www.lbnl.gov.
Publication date: 10/15/2007