The 4-1-1 on Efficiency Rating Systems
September 28, 2013
All things sustainable in one place.
Understanding how to measure sustainability becomes more difficult as more groups and organizations establish more codes, systems and guidelines. All that being said, wouldn’t it be nice to have this information in one place? Well, here it is.
Below you’ll find a quick and easy-to-digest synopsis of a number of the most popular “green” ratings. We hope this helps in your search to understand all things sustainable.
Energy Factor (EF) – The overall energy efficiency of a water heater, which is based on three measurements:
- How efficiently heat is transferred to the water;
- The percentage of energy lost from cooling unused, stored hot water—in the case of traditional tank-style water heaters this is referred to as standby loss; and
- The amount of energy consumed between active and standby mode uses.
A rule of thumb: the higher the EF, the more efficient the model.
Home Energy Rating System (HERS) Index – According to the Residential Energy Services Network (RESNET), HERS is the industry standard for measuring a home’s energy efficiency. It’s also the nationally recognized system for inspecting and calculating a home’s energy performance. HERS ratings are based on a number of variables, including:
- Amount and location of air leaks in the building envelope
- Effectiveness of insulation within walls and ceilings
- Floors over unconditioned spaces, such as cellars and garages
- Attics, foundations and crawlspaces
- Windows and doors
- HVAC systems, water heaters and thermostats
A rule of thumb: the lower the value, the more efficient the home.
LEED® (Leadership in Energy and Environmental Design) for Homes – Developed by the U.S. Green Building Council, this system requires third-party verification. A LEED®-certified home incorporates efficient green homebuilding techniques and features. The rating scale is based on points earned for meeting specific green building conditions, such as specifying energy-efficient tankless water heaters, direct-vent wall furnaces and condensing boilers.
Other determining factors include: building and design, location, landscaping, materials and resources, waste management, indoor environmental quality, various water and energy efficiency aspects, as well as awareness and education of the homeowner on basic operations.
A rule of thumb: the higher the LEED score, the more efficient the home.
ENERGY STAR® Program – Probably the most commonly recognized rating on this list is the ENERGY STAR program, which was initiated by the U.S. Environmental Protection Agency (EPA) in 1992. It assists homeowners in their efforts to save money and protect the Earth with efficient commercial buildings, industrial plants, products and new residences—the last two qualification requirements being the most pertinent to homeowners.
- For Products: Products must be third-party certified based on testing in EPA-recognized laboratories. Qualifying products include select appliances, electronics, computers, building products, lighting and fans, heating and cooling systems, and water heaters.
- For New Homes: The home has been inspected, tested and verified to meet strict requirements set by the EPA.
A rule of thumb: Check the ENERGY STAR @ Home Tips to better understand your next applicable product purchase, and the possible savings you and your family can expect.
Annual Fuel Utilization Efficiency (AFUE) – A measurement of thermal efficiency for furnaces and boilers. It helps determine the actual, season-long average efficiency of a piece of heating equipment by measuring the amount of heat actually delivered to the house compared to the amount of fuel supplied to the furnace or boiler. For example, if a gas boiler has a 90 percent AFUE rating, it is converting 90 percent of the energy from its fuel into heat.
A rule of thumb: the higher the rating, the less energy/heat is lost.