Yesterday, the EPA announced the first set of multifamily properties to earn the Energy Star certification, marking the sustainability giant’s first foray into the asset class.

Energy Star worked with Fannie Mae for three years to develop a multifamily certification system, which began this September, EPA Energy Star commercial buildings manager Mike Zatz, above, tells us. “We’ve been in other commercial sectors for 20 years,” he says. “Multifamily had tremendous untapped potential for energy savings." One third of the population lives in the US’ 500,000 multifamily buildings, spending $22B annually on energy (that’s risen 20% over the past decade). The benchmarking tools and Energy Star score allows owners to see how their buildings stack up against peers, and it makes the rental proposition more affordable for prospective tenants since they’re generally paying their own energy bills, he says.

The class of 17 properties certified (shocking stat: five are old-timers, built before 1920) are owned by some industry giants, like AvalonBay and TIAA-CREF, and most are located in major metros that have made cutting greenhouse gas emissions a priority, Mike says. Some cool features: River City in Chicago (above) incorporates Chicago River water into the building’s cooling system to save on energy costs; affordable property Castle Square Apartments in Boston is doing the country’s largest deep energy retrofit (while allowing residents to stay in their apartments during the process); and Eco Modern Flats in Fayetteville, AR, found some killer savings via solar hot water, closed-cell insulation, white roofing and more.