The energy-efficient New Norris House in Norris, Tenn., was selected by the American Institute of Architects as one of the nation's top 10 examples of sustainable architecture and green design in 2013. (J. Miles Cary/AP)

The practice is called “greenwashing,” and home shoppers need to be on guard: It means a house is being marketed as environmentally friendly and energy-saving when it doesn’t deserve that description.

Greenwashing is a growing issue in real estate as multiple studies demonstrate that consumers are attracted to — and will often pay premiums for — homes that are highly efficient in saving on utility bills.

Just about everybody likes the concept of green, and builders and real estate agents increasingly use the term as a sales come-on. But experts say that, too often, what’s marketed as green isn’t what it purports to be when you take a close look.

Sandra Adomatis, an appraiser in Punta Gorda, Fla., who is nationally known for her expertise in valuing green properties, says, “Look in the MLS [multiple listing service] and you’ll see lots of homes listed as having green features,” but it may mean as little as “somebody put in some LED light bulbs or a couple of Energy Star appliances in the kitchen.”

In an interview, Adomatis described one listing she saw recently on a home built in 1959. It indicated that the house had a Home Energy Rating System (HERS) score of zero — signifying net zero energy use. (The HERS index measures a home’s energy efficiency and requires testing of the home’s performance by a certified HERS rater. The lower the score, the better.)

Adomatis knew it was unlikely that an older home would come anywhere close to such an impressive rating, so she asked the listing agent why she was marketing the house with a zero HERS score. Her response: “I don’t know what HERS is or how they score, so I just put in zero.” Wow.

Allison A. Bailes III, founder and president of Energy Vanguard, a home energy rating and consulting company based in Decatur, Ga., says, “Absolutely, [greenwashing] happens all the time. A lot of [builders] are doing things that are just standard” but they’re marketing them as green. He says he saw one company aggressively advertising its purportedly green homes, but most of the details didn’t amount to much. It was hype: Insulation R-values that met but did not exceed minimum local building code requirements; code-minimum HVAC systems; digital thermostats, which are commonplace; Energy Star appliances; and a long list of other unremarkable features. As for those appliances, Bailes noted in a blog, “if you’ve done any shopping lately, you may have noticed that it’s hard to find one that’s NOT Energy Star certified.”

Kari Klaus, chief executive and founder of Viva Green Homes of Arlington, Va., a new national listing portal exclusively for “eco-friendly” homes, says “greenwashing is a growing problem — clearly there’s a desire to jump on the train and use buzzwords” such as “green,” “sustainable” and “high-efficiency,” too often with little to back up the claims. Her website (at vivagreenhomes.com) carries free listings for homes certified by HERS, LEED, Energy Star, Built Green, NetZero and other programs as well as for noncertified homes that have some green features such as solar panels, geothermal systems, energy-efficient windows and doors, water conservation devices, etc.

When noncertified homes are listed on the site, the seller or agent must check off boxes indicating which green features the property offers. Viva Green Homes then produces a “Green Score” ranging from one to five stars to give potential purchasers a rough idea of how green the house is.

The site, which only recently emerged from a beta testing phase but already has more than 4,500 properties listed from across the country, also allows visitors to shop for specific features or high ratings by area.

So how can buyers and shoppers recognize a bona fide green house? Adomatis says you need to look for six essential elements:

●Site planning for the house that is sensitive to the immediate environment, minimizes tree destruction and is strong on managing water runoff.

●Energy efficiency throughout, including high-performance HVAC, lighting, insulation and appliances.

●Exceptional interior air quality through the use of advanced air filtration and exchange systems.

●Extensive use of nontoxic building materials.

●Water conservation efficiencies, such as water-saving toilets and shower fixtures and possibly some reuse of waste water.

●Ease of long-term operation and management.

The “house should work for you” thanks to the combination of green features and products, she says, “rather than you having to work for the house.”

Ken Harney’s email address is kenharney@earthlink.net.

To read more columns by Ken Harney, visit washingtonpost.com/people/Kenneth-R-Harney.