Past, Present, Future: Directions in Single-Family Energy Auditing and Retrofits
Firsthand feedback from those who currently work in the home performance industry must inform technical and policy discussions about the effectiveness of energy auditing, retrofit practices, and measurement of energy use and savings in retrofits of single-family homes.
To capture the insights and expertise of those in the field, the Washington State University (WSU) Energy program implemented an Assessment of Residential Research Measures scoping study. The purpose of the study was to improve the energy efficiency, durability, and indoor air quality (IAQ) of existing U.S. single-family homes. The study was developed and implemented by researchers at the WSU Energy program, with contributions and assistance from building scientists, practitioners, and other stakeholders in the home performance contracting industry.
Table 1. Portland Home
Table 2. Berkeley Home: Information Provided to Auditors
Table 3. Auditor Recommendations in Portland
Table 4. Auditor Recommendations in Berkeley
The study assessed
- energy audits, to identify ways to improve the audit process; and
- home improvement recommendations resulting from the audits.
- Single-family energy auditing and retrofits that focus on home performance contracting take a multidisciplinary systems engineering approach. This approach encompasses the home’s thermal envelope, IAQ, and HVAC system, and the work is often performed by home performance and low-income weatherization contractors. These contractors represent an emerging green jobs industry, poised to improve the energy efficiency, durability, and indoor environmental quality (IEQ) in millions of existing U.S. single-family residences.
- WSU worked with staff from DOE’s Building America teams and national laboratories, HUD, EPA, RESNET, ACI, ACCA, and ASHRAE to identify two initial project tasks that would address our research question. The first task was to conduct a round-robin auditing of a single home by multiple home performance contractors. The second task was to conduct a survey of building science stakeholders. This article describes how these two tasks were conducted, summarizes the initial findings, and provides a brief overview of other work included in the research.
Two energy audit round-robin pilot efforts were implemented at the ACI 2011 Home Performance conferences in Portland, Oregon, and San Francisco, California. These round-robins involved six auditors, who, working independently of one another, conducted energy audits and developed work plans on the two homes (see Tables 1 and 2). The researchers analyzed the differences among the six audits, and sought to identify the cause of those differences. The researchers then discussed potential means of promoting consistency in energy audits and presented their findings at the RESNET 2012 conference.
Over the last 15 years, a growing infrastructure of trained energy professionals who focus on residential energy performance has emerged. Government policy, utility program requirements, and market forces encouraged growth in this industry. Nationally, the most prevalent model consists of trained individuals certified by private nonprofit organizations (such as BPI and RESNET) that develop and maintain consensus standards within the housing industry. These organizations have joined other trades-based organizations (such as ACCA and North American Technician Excellence, which focus on HVAC), to offer quality assurance, guidance on best practices, and overall professionalism in the residential construction and retrofit markets.
To gauge the effectiveness of energy audits being conducted in the market, we asked trained professionals to conduct independent energy audits on the same house and compare the results. Conducting the audits in conjunction with the ACI conferences ensured access to a large pool of experienced auditors from different backgrounds working in a variety of markets. We saw the Portland event partly as a trial run for the event in Berkeley, where we anticipated wider national participation.
An expert panel evaluated both homes to establish a baseline for the existing conditions. The auditors who then conducted the tests were instructed to test and evaluate the homes only as they deemed necessary to characterize each home, and to prepare recommendations to improve its energy performance. In both cases, auditors were given utility energy bills for a full year, and feedback from the occupants about comfort, perceived IAQ, and occupant behavior.
At the Berkeley site, auditors were also asked to prioritize their recommendations based on budgetary limits of $8,000 and $16,000 respectively, and to create two separate proposals for upgrading energy performance.
Findings from the Portland House
Each of the six auditors who participated in Portland developed recommendations (see Table 3). The estimated costs and savings for each measure are broken out by auditor for the most commonly recommended measures. The savings estimates were based on modeling by the auditors in a variety of programs.
Findings from the Portland house can be summarized as follows:
- Auditors disagreed about upgrading windows and doors, upgrading the domestic hot water, adding insulation to basement walls, and installing an attic radiant barrier.
- Most auditors agreed about air sealing the envelope, insulating the crawl space, sealing and insulting ducts, replacing incandescent bulbs with CFLs, and insulating the uninsulated laundry attic.
- Auditors all agreed on the need for better water management and drainage on the site.
- Estimated costs and savings for some measures varied greatly. Costs for crawl space insulation varied by a factor of almost three; costs for duct measures varied by a factor of three, and costs for air sealing varied by a factor of five. Estimated savings for these measures varied by factors of two to almost seven.
As of this writing the Portland homeowners have not yet decided which retrofits to make.
Findings from the Berkeley House
The eight auditors who participated in Berkeley were not asked to break out estimated costs and savings by measure. Rather, they were asked to prioritize their recommendations to meet two different budgets capped at $8,000 and $16,000, respectively (see Table 4). Auditor 1 only provided recommendations for a $16,000 budget. Auditor 4 only provided recommendations for an $8,000 budget. Any inconsistencies in the findings reflect the information submitted by the auditors.
Findings from the Berkeley house can be summarized as follows:
- Auditors agreed that health and safety issues were the primary concern at this site. The most important of these issues was the venting failure on the gas furnace in the crawl space.
- Auditors agreed on the need to air seal the envelope, upgrade the heating system, improve the floor insulation, and upgrade the hot-water system.
- Auditors disagreed as to the best type of heating system upgrade. Recommendations included a condensing furnace, a mini-split heat pump, and a hydroid combo system.
- Projected energy savings showed extreme variability, ranging from a 7.6% cost reduction to a 138% cost reduction—the latter with no apparent attempt to reconcile estimated savings with actual utility bills.
The owner of the Berkeley house chose to upgrade both the furnace and the water heater to condensing appliances, to close the crawl space, and to install perimeter insulation and an improved vapor barrier ground cover, at a total cost of about $10,000. The homeowner is also looking for ways to reduce the solar gain of the south-facing glazing.
Results of the Round-Robin Pilots
The results of the round-robins—admittedly based on a small sample—suggest that the home performance industry still has work to do to meet consumers’ expectations in the marketplace. Consumers want to know what a retrofit job will cost and what the resulting savings and benefits will be. The results of the round-robins were ambiguous with respect to these questions. The development of databases that track costs and savings for specific climates and specific house types could help to reduce the uncertainty. Standards, some still in development, at BPI and RESNET, address issues of quality assurance, energy savings estimates, and contractor certification. The implementation of these standards should continue to build consumer confidence.
The authors hope that the round-robin pilots will serve as a catalyst to improve energy auditing and retrofit practices. They have urged DOE and other organizations to support future round-robins with home performance contractor market actors such as RESNET, ACCA, and BPI. These future round-robins should evaluate many different program approaches to energy auditing and work plan development. If they are implemented nationwide, they can address variability in retrofit approaches based on differences in regional housing stock and/or climate. Feedback from round-robins will provide ongoing quality assurance to ensure that homeowners get relatively consistent, reliable, repeatable, and useful recommendations from the home performance contracting industry. The results could also be used as feedback to further inform the development of training programs and close the gap between instruction and practice.
Survey of Building Science Stakeholders
To obtain input from home performance experts, an energy audit diagnostic and measurement survey was conducted at the Building Science Corporation’s Westford Symposium, which was held in Westford, Massachusetts, August 1–3, 2011. The survey consisted of 13 questions about diagnostic measurements and analysis tools and post-retrofit information, including customer feedback, energy measurement, and ways to improve home energy performance. The survey was conducted online during and after the symposium. A total of 135 symposium participants responded to at least some of the questions, and of these, 118 completed the entire survey.
The results of the survey can be summarized as follows:
- Respondents rated the importance of 12 energy audit diagnostic measurements. All but 2 of the measurements were rated as important or very important. Lighting and appliance surveys were rated least important, while assembly area measurements, envelope leakage rates, the homeowner interview, utility bills, and combustion safety test were rated most important.
- Respondents most frequently identified assembly area measurements, lighting and appliance surveys, the homeowner interview, utility bills, and combustion safety tests as the diagnostic measurements they include in a basic audit.
- When respondents were asked whether or not we need to develop new audit measurements or techniques, slightly more than half (53%) said yes. The largest group of respondents said that we need to improve what we are doing by streamlining, simplifying, standardizing, and providing training. Three areas were identified as needing new measurements or techniques: air quality and health and safety (including ventilation, IEQ, combustion safety), heat loss through wall assemblies, and air leakage (including air infiltration, duct leakage). The responses suggest the emphasis should be on improvements rather than on new measurements.
- When asked what information from the audit is most important to homeowners, respondents most frequently identified energy cost savings and prioritizing what the homeowner should do (that is, making recommendations). Financing was mentioned in over half of the responses. Many responses also included one or more of the following: comfort, health and safety, durability, defects (that is, correcting problems), occupant behavior (that is, consumer education), building performance ratings, and IEQ.
- Respondents were asked what they charged their customers for an audit. Responses varied widely; costs were most frequently in the $300–600 range. The majority of respondents indicated that audit costs were subsidized by utilities (most frequent) by the local, state, or federal government or by contractors. A little more than half of the respondents (55%) said that the cost of the audit deterred homeowners from getting a retrofit.
Results of the Building Science Stakeholder Survey
One conclusion that can be drawn from the results of the building science stakeholder survey is that all the respondents see opportunities for improvement. While there was little consensus in the responses to many questions, the responses do reflect a very wide range of perspectives. This range of perspectives can be used to inform future work to improve home performance.
The grant that funded this study provided resources to develop a DVD entitled “Air Leakage in Homes.” This video gives builders, building officials, and homeowners an overview of opportunities to improve home energy efficiency by addressing air leakage in the home.
Recommendations and Conclusions
Information from the round-robin pilot, the stakeholder survey, and the input from the advisory group helped to inform technical and policy discussions regarding energy auditing, retrofit practices, and measurement of energy use and savings in single-family home retrofits. Other key recommendations resulting from this research are listed below.
More research is needed on the variance and other real-world uncertainties associated with the energy audit information used to develop work scopes.
A whole-house systems engineering approach is needed that focuses on energy savings, comfort, improved IAQ, durability, and health and safety.
Market research is needed that focuses on the nonenergy savings benefits of improved home performance. These benefits include greater comfort and improved health and safety. To encourage customers to invest in home performance improvements, we must first understand what those customers need and want. This may entail an energy audit that includes a home energy rating and/or an analysis of utility bills.
Auditors must make an effort to acquire and utilize utility billing history at the programmatic and/or individual home level. This will help to ensure that energy savings estimates are reasonable and realistic. This study identified a need for policy that allows easier access to that data.
Auditors need a variety of market-based approaches to home performance audits and work plan development that add value and improve market penetration while ensuring that home performance improvements are predictable and actionable.
The full report on which this article is based is available online for free at Washington State University.
Contact Michael Lubliner at firstname.lastname@example.org and David Hales at email@example.com.
Learn more about the WSU Extension Energy program.
Get more info about the Westford symposium.
Get a copy of the WSU Extension Energy program video “Air Leakage in Homes: The Invisible Thief."
In 2013 WSU implemented two additional round-robin tests. One focused on auditors using an EPS score in the Seattle retrofit market and the other focused on utility audits typical in the Denver market. Both included a HVAC/DHW combustion safety assessment. WSU hopes to have results available to the public in October 2013.
WSU is working with NIST and other stakeholders on the scoping and development of a guideline to assist in the implementation of round-robin testing as a feedback tool for home performance contracting trade organizations.
Also, WSU is seeking comments from Home Energy readers on: 1) the value round-robin testing may have as a QA tool; and 2) the areas of home performance contracting that you think could benefit from the round-robin process, as an important tool to assess reliability and repeatability. Please contact the authors with any feedback.
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