Here's a breakdown of the different certification programs.
HERS index
The Home Energy Rating System is an index measuring a home’s energy efficiency. An average home built to current industry standards for energy efficiency will have an index of 100. A lower score indicates higher levels of efficiency (for example, a home with a score of 70 is using 30 percent less energy than the average home). The opposite is true with homes that score higher than 100. This index is overseen by RESNET.
Energy Star
The Energy Star program is overseen by the U.S. Environmental Protection Agency. Products such as refrigerators, light bulbs, and furnaces can earn Energy Star certifications. Separately, homes can be Energy Star–certified through an independent inspection.
Indoor airPLUS:
This program is also administered by the EPA. Homes that go above and beyond the Energy Star requirements by incorporating additional features to combat moisture, mold, pests, and pollutants can earn this label.
LEED
The United States Green Building Council is the agency that bestows Leadership in Energy and Environmental Design certifications on environmentally friendly buildings and projects. The highest certification a building can earn is “LEED platinum.” Projects earn points based on numerous categories such as indoor air quality and water efficiency. More points add up to a higher certification level.
National Green Building Certification
Overseen by the National Association of Home Builders, this program helps residential building professionals develop and build sustainable projects. Buildings can earn bronze, silver, gold, or emerald certifications. At the Emerald level — which is the highest certification a project can earn — a building “must incorporate energy savings of 60 percent or more.”
Pearl Certification
Pearl Certification is a market-based firm approved by the U.S. Environmental Protection Agency (EPA) and the U.S. Department of Energy (DOE) to administer the Home Performance with ENERGY STAR® program for existing homes. The certification helps homeowners understand and improve their home's performance.
RESNET
The Residential Energy Services Network is a not-for-profit corporation that develops industry-wide standards and rules for energy efficiency ratings and certification systems for buildings. In addition to overseeing the HERS index (see below), RESNET certifies contractors of all types, including builders, roofing and siding professionals, and remodeling contractors.