When Discussing Efficiency Upgrades, the HERS Index Helps
How low can your HVAC work go?
Quality home performance contracting and HVAC work involve plenty of measurement and verification. So what’s one more metric?
In this case, the HERS Index is more for the general public’s consumption, as opposed to, say, a static pressure reading. Homeowners, and perhaps especially home shoppers, can use a HERS rating to compare current conditions and get a sense for likely energy costs or possible upgrade priorities.
The HERS Index scale is a little different than most. A score of 100 means a home is dead-on average in its energy efficiency. (“Average” reflects the performance of a RESNET reference home, a “designed-model home of the same size and shape” as the home in question. RESNET is the industry body that oversees the HERS Index in the U.S. Its longer-term goal is a net-zero residential sector by 2040.)
So a home can score over 100, but not in a good way. A home with a 140 score is 40 percent less energy efficient than average.
On the other hand, a home with a HERS rating of 70 is 30 percent more efficient than the RESNET reference home. Therefore, a perfect score on the HERS index is … zero. A nice, round, emissions-friendly number.
The level of performance earning a score of 100 would theoretically shift toward the better over time, as the average home’s energy efficiency improves.
TUNE UP AND GET DOWN: The HVAC system, building envelope, and observed air leakage throughout a home all contribute to its HERS rating, where scoring 100 is hardly A+ work and scoring zero is the ultimate.
BEHIND THE RATING
The condition variables that contribute to a home’s HERS rating according to RESNET are right in line with typical home performance contracting targets and goals.
- All exterior walls (both above and below grade)
- Floors over unconditioned spaces (like garages or cellars)
- Ceilings and roofs
- Attics, foundations and crawlspaces
- Windows and doors, vents and ductwork
- HVAC system, water heating system, and your thermostat
- Air leakage of the home
- Leakage in the heating and cooling distribution system
Becoming a RESNET Certified Home Energy Rater requires training by an organization listed on the organization website’s (https://resnet.us) training provider page. Some of the training may be available online, depending on the particular provider.
The pivotal part of the certification process is passing several national core competency tests. These include a National Rater Exam, Work Scope and Combustion Safety Test, the RESNET Appliance Simulation Test, and the RESNET Rater Simulation Practical Test.
The RESNET site offers additional information on certification, assurance reviews, and recertification, along with a list of associate courses and library of infographics and videos.
COUNTING ON EFFICIENCY
Unlike professional associations, RESNET and its resources take a largely public-facing approach. Its web presence promotes the HERS Index to consumers and offers a rolling list of energy efficiency tips, a case study, a search function for “Energy Smart Builders,” and more.
The index itself is less of a technical tool than a way to quantify high-performing homes and the collective deficiencies of homes with more serious issues. It is new enough that successful home performance contracting companies may not incorporate it at all at this point.
However, RESNET reports that 2.6 million homes have received HERS ratings, with 159,000 of those taking place this year.
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