Aerosol-Based Duct Sealing for Residential and Commercial Buildings
Duct Sealing: Aerosol-Based vs. Conventional Taping
An aerosol sealant is blown through ducts, plugging leaky ducts from inside the duct system without having to locate or access holes. This technology can be applied to both residential and commercial duct systems.
Item ID: 178
Residential, Commercial, Industrial
HVAC--Air & Fluid Distribution
Technical Advisory Group: 2010 HVAC TAG (#3)
Average TAG Rating: 2.6 out of 5
TAG Ranking Date: 06/29/2010
TAG Rating Commentary: FROM 2010 HVAC TAG RANKING SURVEY RESPONSES:
1. Leakage in commercial not nearly the issue it is in residential.
2. Certainly reducing duct leakage is important. If this is a good way to achieve it, great.
3. It has proven to be effective, though a little expensive in residential applications.
4. This seems difficult and expensive and would provide little benefit in buildings where ductwork is inside the conditioned space. This is more appropriate for residential buildings with ductwork in the attic or crawlspace.
Technical Advisory Group: 2009 HVAC TAG (#2)
Research have concluded that, for a typical residential home, 15% to 30% of the HVAC energy consumption is lost to duct leakage (DOE, Building Technologies Office). Over time, small holes and cracks form in the joints that connect ducts due to poor installation, physical movement, and thermal cycling (Navigant). Invented by Mark Modera of the Western Cooling Efficiency Center and developed by the Energy Performance of Buildings Group at Lawrence Berkeley National Laboratory in 1994, aerosol duct sealing has been used successfully in single-family homes for years, and has been installed in some 50,000 homes to date.
An aerosol sealant or adhesive in spray form is blown through ducts, sealing leaks from inside the duct system with minimal deposition on duct walls. Cracks and holes in the ductwork are sealed as the spray adhesive sticks to the edges of holes as the aerosol escapes from the duct. This technology can be applied to both residential and commercial duct systems. Sealing results in a greater percentage of supplied thermal energy reaching it's intended space, thus reducing both supplied thermal energy and fan energy consumption. Conventional duct sealing involves manually applying a sealant to the duct system from the outside of the duct. Ductwork is often concealed in commercial buildings, sometimes by permanent construction, which can make standard sealing methods costly.
This technology can be very cost effective, especially when compared to conventional sealing methods. Energy savings can be 15% to 35% and even 50% for special systems like laboratory hood systems. The viability of this technology for use in commercial applications will depend on many factors. In cases where most of the ducting is in the conditioned space, whether commercial or residential, savings will be much less, and it may not be cost effective. In many commercial buildings, ducting is in very inaccessible locations, making alternative means of sealing prohibitively expensive, so this may be the best method to use in those cases.
The sealant manufacturer currently provides a 10-year warranty on the seals. The actual life of the sealing is expected to be considerably longer than that.
Baseline Description: Residential Unit with Electric Forced Air or Heat Pump Heating
Baseline Energy Use: 4.5 kWh per year per square foot
NEEA's Residential Building Stock Assessment suggests that 5.3% of single family homes use electric forced-air furnaces. An additional 11.4% use air source heat pumps as their primary source of heating. Together, this data suggests that approximately 16.7% of single family homes have electrically heated systems with ductwork (David Baylon, 2012-09-18 Pg 52-55). The average energy use for a house with a forced air furnace is 6.85 kWh/sf-year. For a heat pump (heating use only) the value is 3.09 kWh/sf-year. The weighted average heating energy use is thus 4.28 kWh/sf-year. The mean region-wide energy use per square foot for central AC systems is 0.3 kWh/sf-year. An average all-electric home energy use is thus 4.28 kWh/sf-year + (11.4/16.7) x 0.3 kWh/sf-year = 4.48 kWh/sf-year.
Manufacturer's Energy Savings Claims:
"Typical" Savings: 20%
Savings Range: From 4% to 40%
Up to 40% (Aeroseal, 2014).
Best Estimate of Energy Savings:
"Typical" Savings: 20%
Energy Savings Reliability: 3 - Limited Assessment
Energy savings is obviously dependent upon the initial leakage level; however, the fraction of leakage sealed is fairly stable, ranging from 75-95% of the leakage encountered. Savings are also dependent upon the application, particularly in the large-building sector, due to the large variability in system designs and pre-retrofit performance.
Modera states that, based upon his experience, aerosol duct sealants can result in system energy savings of 10% for basement ducts and 15% to 20% for ducts located in attics and crawlspaces. The DOE Building Technologies Office assumes an energy savings of 10% for residential applications (Navigant Consulting, 2012). We assume 20% of heating and cooling annual energy use based upon an initial 30% duct leakage rate; a 90% leakage reduction through aerosol sealing; and assuming that 25% of the leaked airflow vents into conditioned space. (Savings = 0.75 x 0.3 x 0.9 = 0.20 x 100% = 20%). (Navigant).
Energy Use of Emerging Technology:
3.6 kWh per square foot per year
Energy Use of an Emerging Technology is based upon the following algorithm.
Baseline Energy Use - (Baseline Energy Use * Best Estimate of Energy Savings (either Typical savings OR the high range of savings.))
Potential number of units replaced by this technology:
There are 4,023,937 single family houses in the Northwest region (Ecotope, 04/28/2014 Pg 12). About 16.7% have electric forced air furnaces or air-source heat pumps (for heating use) with the average house size being 2,006 sf. The square footage for houses where this technology may be employed is approximately 0.167 x 4,023,937 x 2,006 = 1,348,026,943 square feet.
Regional Technical Potential:
1.21 TWh per year
Regional Technical Potential of an Emerging Technology is calculated as follows:
Baseline Energy Use * Estimate of Energy Savings (either Typical savings OR the high range of savings) * Technical Potential (potential number of units replaced by the Emerging Technology)
Installed first cost per: square foot
Emerging Technology Unit Cost (Equipment Only): $0.50
Emerging Technology Installation Cost (Labor, Disposal, Etc.): $0.00
Baseline Technology Unit Cost (Equipment Only): $0.20
The cost of aerosol sealing averages $350-$500 per system in residential new construction (comparable to conventional sealing methods). In existing homes the cost averages $1,000-$2,000 per system (50-100% more than conventional sealing; however 33-50% more leakage is typically sealed by aerosol sealing). The cost in existing homes is elevated due to the increased effort required to block off outlets and isolate duct runs already in service with the building occupied. In larger buildings, costs are quite variable due to the large variability in system types. For existing commercial construction, aerosol sealing is often the only viable alternative, often costing less than 1/3 the price of conventional sealing (due to the inaccessibility of the duct system, and/or the large disruption associated with manual sealing). A study of 121 Sacramento area homes yielded an average cost of aerosol duct sealing of $1,000 (in 2004 dollars). Assume a retrofit cost of $0.50/sf (Navigant, for US DOE Building Technologies Office, 2012).
Simple payback, new construction (years): 3.7
Simple payback, retrofit (years): 6.2
Cost Effectiveness is calculated using baseline energy use, best estimate of typical energy savings, and first cost. It does not account for factors such as impacts on O&M costs (which could be significant if product life is greatly extended) or savings of non-electric fuels such as natural gas. Actual overall cost effectiveness could be significantly different based on these other factors.
While the technology saves energy, the simple payback may approach the warrantied life (10 years) of the technology.
The aerosol duct sealing technology was invented and developed by the Energy Performance of Buildings Group at Lawrence Berkeley National Laboratory in 1994. This technology internally seals leaks in air distribution ducts by injecting a fog of aerosolized sealant particles into a pressurized duct system. The key to the technology is to keep the particles suspended within the air stream without depositing on the duct surfaces until they reach the leaks, where they leave the air stream, deposit at the leak edges, and seal the leaks. Aerosol particles are directed toward, and deposit at, the leaks because:
• All supply and return grilles are temporarily sealed, so that all the airflow passes through the leaks;
• Small aerosol particles are kept suspended in the airflow by continuous air movement;
• As the air stream makes a sharp turn to exit through a leak, the particles collide with and adhere to the leak edges; and
• Using adhesive solid particles allows the built-up seal to span leaks as much as 5/8" across.
Conventional duct sealing involves manually applying a sealant to the duct system, typically from the outside of the duct. Ductwork is usually concealed, sometimes by permanent construction. For this and other reasons, the standard sealing practice can be quite costly.
The technology was first commercialized for the single-family residential market in 1999, and was first commercialized in the large-building market in 2003. Roughly 50,000 single-family residences have been sealed to date. There are several residential HVAC dealers currently providing the service in the Pacific Northwest.
Saves space, simplifies power cabling, saves capital cost and reduces weight.
End User Drawbacks:
High perceived cost. Testing should probably be done on how this affects indoor air quality and to see if the aerosol material is getting into the airstream.
Operations and Maintenance Costs:
No information available.
The aerosol duct sealant was tested for longevity at Lawrence Berkeley National Laboratory, where they could not find any failures after four years of continuous testing. Based upon that testing, the manufacturer currently provides a 10-year warranty on the seals. The actual life of the sealing is expected to be considerably longer.
Conventional manual sealing is a competitor in some instances, but cannot compete in the case of inaccessible ductwork.
Reference and Citations:
Baylon, et. al.,
2011 Residential Building Stock Assessment: Single-Family Characteristics and Energy Use
Northwest Energy Efficiency Alliance & Ecotope
Aerosol Ductwork Sealing in Laboratory Facilities
Laboratories for the 21st Century
Residential Field Testing of an Aerosol-Based Technology for Sealing Ductwork
American Council for an Energy-Efficienct Economy
Aerosol Duct Sealing Technology
Lawrence Berkeley Laboratory
Emerging Technologies/Practices: Finding the Next Generation
Emerging Technologies/Practices: Finding the Next Generation
Remote Duct Sealing in Residential and Commercial Buildings: Saving Money, Saving energy and Improving Performance
Lawrence Berkeley National Laboratory
Residential Building Stock Assessment: Metering Study
Northwest Energy Efficiency Alliance
Aerosol Duct Sealing
U.S. Navy, Naval Facilities Engineering Command (NAVFAC), Technology Validation Program (Techval)
Energy Savings and RD&D Opportunities for Residential Building HVAC Systems
U.S. DOE Building Technologies Office