Aerosol-Based Duct Sealing for Residential and Commercial Buildings

Summary

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.

Synopsis:

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.

Energy Savings: 20%

Energy Savings Rating: Limited Assessment What's this?

Level	Status	Description
1	Concept not validated	Claims of energy savings may not be credible due to lack of documentation or validation by unbiased experts.
2	Concept validated:	An unbiased expert has validated efficiency concepts through technical review and calculations based on engineering principles.
3	Limited assessment	An unbiased expert has measured technology characteristics and factors of energy use through one or more tests in typical applications with a clear baseline.
4	Extensive assessment	Additional testing in relevant applications and environments has increased knowledge of performance across a broad range of products, applications, and system conditions.
5	Comprehensive analysis	Results of lab and field tests have been used to develop methods for reliable prediction of performance across the range of intended applications.
6	Approved measure	Protocols for technology application are established and approved.

Simple Payback, New Construction (years): 3.7 What's this?

Simple Payback, Retrofit (years): 6.2 What's this?

Simple Payback is one tool used to estimate the cost-effectiveness of a proposed investment, such as the investment in an energy efficient technology. Simple payback indicates how many years it will take for the initial investment to "pay itself back." The basic formula for calculating a simple payback is:

Simple Payback = Incremental First Cost / Annual Savings

The Incremental Cost is determined by subtracting the Baseline First Cost from the Measure First Cost.

For New Construction, the Baseline First Cost is the cost to purchase the standard practice technology. The Measure First Cost is the cost of the alternative, more energy efficienct technology. Installation costs are not included, as it is assumed that installation costs are approximately the same for the Baseline and the Emerging Technology.

For Retrofit scenarios, the Baseline First Cost is $0, since the baseline scenario is to leave the existing equipment in place. The Emerging Technology First Cost is the Measure First Cost plus Installation Cost (the cost of the replacement technology, plus the labor cost to install it). Retrofit scenarios generally have a higher First Cost and longer Simple Paybacks than New Construction scenarios.

Simple Paybacks are called "simple" because they do not include details such as the time value of money or inflation, and often do not include operations and maintenance (O&M) costs or end-of-life disposal costs. However, they can still provide a powerful tool for a quick assessment of a proposed measure. These paybacks are rough estimates based upon best available data, and should be treated with caution. For major financial decisions, it is suggested that a full Lifecycle Cost Analysis be performed which includes the unique details of your situation.

The energy savings estimates are based upon an electric rate of $.09/kWh, and are calculated by comparing the range of estimated energy savings to the baseline energy use. For most technologies, this results in "Typical," "Fast" and "Slow" payback estimates, corresponding with the "Typical," "High" and "Low" estimates of energy savings, respectively.

Details

Aerosol-Based Duct Sealing for Residential and Commercial Buildings

Duct Sealing: Aerosol-Based vs. Conventional Taping

Item ID: 178

Sector: Residential, Commercial, Industrial

Energy System: 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)

Synopsis:

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 Example:

Baseline Description: Residential Unit with Electric Forced Air or Heat Pump Heating
Baseline Energy Use: 4.5 kWh per year per square foot

Comments:

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%

Comments:

Up to 40% (Aeroseal, 2014).

Best Estimate of Energy Savings:

"Typical" Savings: 20%
Energy Savings Reliability: 3 - Limited Assessment

Comments:

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 What's this?

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.))

Technical Potential:
Units: square foot
Potential number of units replaced by this technology: 1,348,026,943
Comments:

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
138 aMW
What's this?

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)

First Cost:

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

Comments:

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).

Cost Effectiveness:

Simple payback, new construction (years): 3.7

Simple payback, retrofit (years): 6.2

What's this?

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.

Comments:

While the technology saves energy, the simple payback may approach the warrantied life (10 years) of the technology.

Detailed Description:

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.

Standard Practice:

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.

Development Status:

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.

Non-Energy Benefits:

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.

Effective Life:

Comments:

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.

Competing Technologies:

Conventional manual sealing is a competitor in some instances, but cannot compete in the case of inaccessible ductwork.

Reference and Citations:

David Baylon, et. al., 09/18/2012. 2011 Residential Building Stock Assessment: Single-Family Characteristics and Energy Use
Northwest Energy Efficiency Alliance & Ecotope

I2SL, 07/29/2008. Aerosol Ductwork Sealing in Laboratory Facilities
Laboratories for the 21st Century

Mark Modera, 08/01/1996. Residential Field Testing of an Aerosol-Based Technology for Sealing Ductwork
American Council for an Energy-Efficienct Economy

LBL, 02/01/2003. Aerosol Duct Sealing Technology
Lawrence Berkeley Laboratory

H. Sachs, 11/10/2004. Emerging Technologies/Practices: Finding the Next Generation
Emerging Technologies/Practices: Finding the Next Generation

Mark Modera, 05/09/2008. Remote Duct Sealing in Residential and Commercial Buildings: Saving Money, Saving energy and Improving Performance
Lawrence Berkeley National Laboratory

Ecotope, 04/28/2014. Residential Building Stock Assessment: Metering Study
Northwest Energy Efficiency Alliance

U.S. Navy, 12/31/2013. Aerosol Duct Sealing
U.S. Navy, Naval Facilities Engineering Command (NAVFAC), Technology Validation Program (Techval)

Navigant Consulting, 10/01/2012. Energy Savings and RD&D Opportunities for Residential Building HVAC Systems
U.S. DOE Building Technologies Office

Rank & Scores

Aerosol-Based Duct Sealing for Residential and Commercial Buildings

2010 HVAC TAG (#3)

Technical Advisory Group: 2010 HVAC TAG (#3)
TAG Ranking: 22 out of 36
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.

2009 HVAC TAG (#2)

Technical Advisory Group: 2009 HVAC TAG (#2)
TAG Ranking:
Average TAG Rating:
TAG Ranking Date:
TAG Rating Commentary: