HERS testing is a process that evaluates the features and systems of a house to determine the building’s overall energy efficiency. Using the Home Energy Rating System (HERS), it tells you how the house compares to others like it and can guide you in deciding where to make improvements.
Why Your Home’s HERS Rating Matters
HERS testing can benefit you whether you’re planning to upgrade, sell, buy or build a house. In many locations, it’s a requirement for new constructions, remodeling, and renovations to ensure the building meets current energy efficiency standards. If you’re budgeting for upgrades, HERS testing helps you find your home’s biggest energy efficiency weak points. Taking care of these issues first will give you the best return on your investment.
If you’re preparing to sell, knowing your home’s HERS rating helps you calculate the selling price by factoring in the cost of future energy bills. Proof of the home’s energy efficiency is a good selling point, too. Investing in energy efficiency upgrades, such as air sealing and adding insulation, before testing can help you achieve a good rating that attracts buyers.
When you’re building a new home or buying an existing one, the HERS rating lets you know what to expect in terms of future energy bills and upgrade costs. A home with a good HERS score typically costs a little more upfront compared to average homes, but the investment will pay you back with lower energy bills and greater comfort.
HERS got its start in 2006, when California set ambitious goals to reduce greenhouse gasses. That year, the Residential Energy Services Network (RESNET) created the HERS Index to help homeowners and buyers reduce their energy use.
The process involves running tests on features such as the heating and cooling system, appliances, walls, and windows to evaluate the energy efficiency of each. Data from these tests are combined to calculate a rating from 0 to 150 on the HERS Index. A score of 100 is the standard home, known as the HERS Reference Home, which is based on the 2006 International Energy Conservation Code.
The lower the HERS rating, the more energy efficient the house. Every point of the rating represents a 1 percent difference in energy efficiency compared to the HERS Reference Home. A rating of 100 means the house is up to code. Most newly built homes achieve a rating of around 100.
For homes a few decades old that haven’t been upgraded much, 130 is a typical rating. That means the house is 30 percent less efficient than the HERS Reference Home. For a very old, inefficient house without upgrades, the rating can theoretically reach 200 or even higher, meaning it uses twice the energy as the Reference Home.
With a HERS rating of 85, which is at least 15 percent more efficient than the standard, a home meets the EPA’s requirements for the Energy Star label. Most new homes built with a little extra attention to energy efficiency meet this requirement.
At around 70, or 30 percent more efficient than the standard, you’ll find new or upgraded older houses that have a few energy efficiency improvements, such as extra attic insulation, a high-efficiency heating and cooling system, and storm windows.
Serious attention to green building can reduce the rating to 50 or lower. Homes with these ratings have features such as all modern, high-efficiency appliances, optimal insulation throughout the building, and high-efficiency windows and doors.
A net-zero energy home, which produces as much renewable energy as it consumes, gets a HERS score of 0. Achieving this score requires not only having energy efficient features, but also a means of producing renewable energy, such as solar panels.
What to Expect from HERS Testing
A HERS test must be performed by a RESNET Certified HERS Rater. All your heating, cooling, and ventilation systems should be fully operational when the testing starts. The process usually takes between two to four hours, during which the rater performs both visual inspections and diagnostic testing on the parts of your home that affect its energy efficiency.
- Heating and cooling system – The rater will note the system’s efficiency rating and ensure that it’s running optimally. This includes verifying the refrigerant charge and assessing the thermostat.
- Vents and ductwork – Done along with tests on the heating and cooling system, this involves measuring airflow velocity and testing for duct leakage.
- Water heating system
- Attics, foundation, and crawlspaces
- Ceilings and roof
- Exterior walls, windows, and doors
- Floors over unconditioned spaces, such as over the garage or cellar
Other tests include the blower door test to measure the building’s airtightness and check for leaks, as well as use of infrared (IR) scanning to spot areas of energy waste due to insufficient insulation.
The HERS rater compares test data from your home to a version of the HERS Reference Home that’s the same size and shape as yours and located in the same climate and general environment. From this, they’ll determine where your home scores on the HERS Index.
If your home scores above average, meaning it’s less efficient than most, consider making some repairs and upgrades to improve your comfort and save money. Use your test results to find your home’s biggest energy leaks and perform a cost-benefit analysis of possible improvements. Many raters even provide a list of upgrade recommendations with a cost-benefit analysis of each as part of the HERS testing process.
For new constructions, you’ll need a preliminary projected HERS rating. To calculate this, a certified HERS rater uses computer modeling to gather data based on how the house will perform if built according to plan. This data is used to calculate the projected HERS rating. During construction, the HERS rater checks in to ensure the house is being built as planned. Once the house is built, the HERS rater runs tests and collects data to confirm the projected rating.
By telling you how your home’s energy efficiency stacks up against modern standards, HERS testing helps you prioritize upgrades and remodeling work, and guides you in setting a selling price. Pay close attention to the results, and you’ll find ways to enjoy your home more while saving money.