The Home Energy Rating System (HERS) has been around since the 1980s when a group of states offered energy ratings and, along with the National Association of State Energy Officials (NASEO) and the U.S. Department of Energy (DOE), developed the Residential Energy Services Network (RESNET) in 1995. RESNET's task was to develop national standards for home energy ratings and to create a market for home energy rating systems and energy mortgages. Since then, more than 2 million homes have received HERS scores.
RESNET administers the national HERS system. This is carried out through a network of HERS Providers who are overseen by RESNET, follow a regimen of standards, report data back to RESNET, and are subject to a set of quality assurance standards. The HERS Providers represent RESNET in the field and are in turn responsible for all their certified HERS Raters. HERS Raters typically go through an extensive training process offered by RESNET-accredited training providers for a week or more to ensure that they have a sound building science understanding and familiarity with the software and all its uses. HERS ratings are recognized by the U.S. DOE, U.S. EPA, the IRS to access tax credits, local and state energy code compliance, lenders and many utility programs. HERS has also, historically been recognized by Freddie Mac, Fannie Mae and FHA Energy Efficiency Mortgages that allow the borrower to qualify for a mortgage with higher debt-to-income ratios in above-average scoring homes due to expected lower energy costs.
RESNET supports and oversees an integrated network of accredited program providers and software tools in support of HERS, including the following:
The HERS Index
The HERS score is based on a 0 to 100+ scale, where 0 is a net-zero home and 100 is a home that complies with the 2006 International Energy Conservation Code (IECC). Homes that use more energy than the 2006 IECC, score higher than 100, possibly up to 200 or more. The HERS score is primarily used for new homes, as it requires a larger number of data points and others that are more difficult to collect for an existing home (e.g., wall insulation R-value, window U-values). HERS ratings require a certified Energy Rater to collect about 150 on-site data points, measure building components, and conduct performance testing (i.e., blower door test and duct blaster test), and then enter the information into the accredited software. HERS ratings are typically done in phases, starting with an initial plan review, then verified in the field pre-insulation, and finally after completion. HERS ratings take multiple hours and generally cost $400 to $1000 depending on house size and complexity. Batch ratings for identical homes can be conducted for lower costs.
The HERS score can be used to achieve energy code compliance through the Energy Rating Index (ERI) compliance pathway in the 2015 and 2018 IECC energy codes. At the time of writing, it is the only eligible system for code compliance through the ERI pathway. These factors point to an increasing uptake of the HERS score in the new construction housing market segment, where it is the predominant system used in utility residential new construction programs to verify compliance with program standards.
Like the Home Energy Score, HERS is an asset rating. HERS assumes a standard thermostat schedule and average occupancy for appliances, plug loads and water heating.
Accredited rating software tools provide the calculations necessary to produce a home energy rating. The requirements to be an accredited rating software program are defined in Chapter Three of the RESNET Mortgage Industry National Home Energy Rating Standards at http://www.resnet.us/standards/RESNET_Mortgage_Industry_National_HERS_Standards.pdf.
At the time of writing this document, the following software tools were accredited by RESNET:
ICF International Beacon Residential Version 2-80-3
400 University Avenue
Toronto M5G 1S7 CA
Contact: Haider Kahn
Ekotrope, HERS Module Version V1.9.0, V2.1 & V2.2
50 Congress St.
Boston, MA 02109
Contact: Cy Kilbourn, Director of Engineering
EnergyGauge® USA Version 4.0, 5.1 & 6.0
Florida Solar Energy Center
1679 Clearlake Road
Cocoa, FL 32922-5703
Contact: Tei Kucharski
REM/Rate v14.6.4, v15.2, v15.3, v15.4 & 15.5
2540 Frontier Avenue
Boulder, CO 80301
Contact: Brian Christensen
HERS Rating Label Designs
Each RESNET accredited HERS software presents the HERS rating in different formats, reports and labels. Following are a few examples of some of the rating reports and label designs.
Figure 11: REM/Rate - Sample HERS Labels and Reports
Figure 12: Ekotrope - Sample HERS Labels and Reports
Figure 13: EnergyGauge USA - Sample HERS Label
ENERGY STAR Homes are certified through HERS software. An example of an ENERGY STAR certified new home label is presented below.
Figure 14: ENERGY STAR Homes – Sample Label
The Market for HERS Ratings
HERS ratings originated for use with existing homes but are now used almost exclusively for rating new construction. Once the U.S. Environmental Protection Agency (EPA) decided to rely on HERS Raters to certify ENERGY STAR Homes in the mid-1990s, builders used ratings to market their new homes. Then, when the IRS began to recognize HERS ratings to verify tax credits, the use of HERS grew annually. Today, with the added recognition of HERS ratings in the International Energy Code Council (IECC) (called the “Energy Rating Index” by the code body) as an alternative path to verify code compliance, more than two million HERS ratings have been issued.
While HERS ratings can cost between $400 and $1,000 each, RESNET permits production builders to save rating costs by allowing HERS Raters to issue lower-cost sampled ratings. Sampled ratings can be issued for similar buildings while only inspecting and performance-testing a subset of homes. This can decrease rating costs significantly and has provided a market for production builders of efficient homes. In some cases, production builders choose to rate all their homes in order to promote the performance of their homes and to compete based on home energy efficiency as documented with HERS ratings.
HERS ratings are also used in utility residential new construction programs throughout North America. Utilities leverage market-based HERS Raters to work with builders to document utility program performance through HERS ratings and reward qualifying homes with incentives and marketing support.
HERS ratings have gained a foothold in the residential new construction market through program verification, code compliance and market competition. While HERS ratings are relatively expensive in comparison to a Home Energy Score assessment, they cost less than a fraction of a percent of the overall cost of building a new home.
While generally not used for existing homes due to rating costs, HERS can and have been used for existing homes. HERS rating modeling tools can be useful in evaluating energy savings from home upgrade options and determining cost-effectiveness. HERS have also been recognized for financing products to pay for energy upgrades and have historically been used in support of Energy Efficient Mortgages and appraisal adjustments to help with loan qualification. However, due to options with other less granular—and therefore less expensive-to-deliver—modeling tools, HERS ratings have tended to fall out of favor with existing homes, but remain the modeling and labeling tool of choice for new construction.
Training HERS Raters
Generating a HERS rating requires a Certified Home Energy Rater. A Certified Home Energy Rater, or Rater, is a person trained and certified by an accredited Home Energy Rating Provider to inspect and evaluate a home’s energy features, prepare a home energy rating and make recommendations for improvements that will save the homeowner energy and money. The path to becoming a Home Energy Rater begins with attending Rater Training classes offered by an accredited Energy Rater Training organization. The organizations are listed on the Residential Energy Services Network’s (RESNET) website at http://www.resnet.us/professional/programs/search_directory.
Training is required to become a certified Home Energy Rater and some training providers offer a portion of their training online. It is wise to begin preparing prior to attending rater training by studying the materials recommended by the training organization you have selected. Additional study materials are also listed at http://www.resnet.us/professional/rater/national_rater_test. All candidates must pass the national core competency tests including National Rater Exam, Work Scope and Combustion Safety Test, the RESNET Combustion Appliance Simulation Test and the RESNET Rater Simulation Practical Test. If the rater candidate does not pass the Rater test the first time, there are proctoring guidelines from RESNET that describe how to retake the test closer to the location of the rater candidate.
The final aspect of the Rater certification process is to sign a rater agreement with a RESNET accredited Rating Provider and complete probationary ratings. The Home Energy Rating industry is overseen by RESNET and is structured to ensure a high level of quality assurance. With that in mind, energy raters must work through a Rating Provider, who is responsible for their certification and quality assurance. The accredited Rating Providers are also listed on the RESNET website at http://www.resnet.us/professional/programs/training_providers. An accredited Rating Provider will assist new Raters in overseeing their required five probationary ratings. Rating Providers may require more than the minimum required five probationary ratings. After completing a minimum of five probationary ratings and passing all required Rater exams successfully, the Rating Provider will issue a document stating that the candidate has passed the course work necessary to become a HERS Certified Rater and may apply for a Rating Test Identification Number or RTIN. All of the required exams and the probationary ratings must be completed within 15 months. Candidates will need to sign a Rater Agreement outlining the responsibilities and obligations for both the Rater and the Rating Provider; this is detailed in the RESNET Standards. RESNET Standards require the Rating Provider to perform file quality assurance reviews on a minimum of 10% of all energy ratings and field quality assurance reviews on a minimum of 1% of the ratings for each rater. For more information, visit the RESNET website at http://www.resnet.us/professional/rater/what-is-a-hers.