Downtown Bethesda soon could become the first “green” community in Montgomery County, with large swaths of energy-efficient buildings, more trees, and landscaping that would better control and clean stormwater runoff.

Through a pilot program that would be part of the area’s next 20-year development plan, Montgomery planners say they will try to ensure that one of the county’s most urban areas and biggest job centers becomes more “sustainable” as it grows.

Under the plan, two to three areas within downtown would be designated as “high-performance districts” with broader and more rigorous standards in three areas.

The “environmental” piece could include more environmentally friendly high-rise office and condo buildings, perhaps with renewable energy sources such as solar panels, and surrounded by more trees and green space. The “social” goal eyes more public gathering spots and better-connected paths to encourage walking and cycling. The “economic” goals could include more affordable housing and retail space.

Tina Schneider, a senior environmental planner for the county, said planners want to “push the envelope” to make downtown Bethesda a “really vivacious, desirable place that’s seen as being innovative and technically advanced.”

“It would be doing more good for the community and the ecosystem rather than doing less harm,” Schneider said. The designated areas, she said, would “function in a way that’s not depleting our resources but perhaps even improving them.”

The idea of planning entire neighborhoods or communities, rather than individual buildings, around the idea of environmental and economic sustainability is part of a growing trend nationwide, planning experts say. While cities in Europe have embraced the idea for years, they say, it began gaining momentum in the United States about five years ago.

Cities such as Baltimore, Phoenix and Philadelphia have embraced or are exploring the concept. Since last year, the District has had an “ecodistrict” in a 15-block area of Southwest just south of the Mall, where planners are trying to revitalize an isolated area of mostly federal buildings into a more livable neighborhood.

This year, four towns in the Bladensburg area of Prince George’s County became a state-designated “sustainable community.” The towns catch and clean more stormwater runoff than the county requires, run some government buildings on solar and wind power, and have urban farms and gardens.

“We’re environmentally sensitive because we’re so close to the water” of the Anacostia River, said John Moss, Bladensburg’s town administrator.

In downtown Bethesda, Schneider said, planners are considering two to three potential sites for “high-performance districts.” Those include Woodmont Triangle and the area around the Bethesda Metro station. The 20-year Downtown Bethesda growth plan covers both sides of Wisconsin Avenue, from about Bradley Lane on the south to just north of Battery Lane.

Schneider emphasized that the plan is preliminary, and many details have yet to be worked out. A key question: Whether developers and county environmental and permitting officials will buy into a proposal that ultimately must be approved by the County Council. If the idea works, Schneider said, it could be expanded to other parts of the county.

Tim Eden, managing partner for Chevy Chase-based developer Starr Capital, said he doesn’t see how Montgomery environmental standards could get much more stringent. By the time developers meet state and county regulations, such as for green roofs and stormwater runoff, most buildings meet the requirements for a silver LEED certification as a “green” building, he said.

Developers already design environmentally friendly buildings because investors routinely require LEED certification as part of the financing terms, Eden said. Developers also cater to tenant demand, including from many millennials who want “green” buildings for their offices or homes. Developers are convinced, he said, that the marketability, environmental benefits and long-term savings in lower water and energy bills offset higher construction costs.

Developers in Montgomery also absorb the costs of meeting county requirements that new residential buildings have bike racks, bike storage areas and up to 15 percent of units as “moderately priced” housing.

“The development community is already meeting fairly strict standards for environmental sustainability,” Eden said. “I don’t know what else we could do, frankly, to raise the bar.”

Schneider said planners are beginning to seek developers’ input on what the new “high-performance districts” might entail. She said any new standards probably would be encouraged, rather than required, by offering developers tax breaks or additional density.

If done correctly, the districts could make downtown Bethesda a “green urban model,” said Veronique Marier, executive director of Bethesda Green, a nonprofit public-private partnership of businesses, government and residents that promotes sustainable living practices.

“I think this plan is a good start that we can support, so we can push the envelope to a greener Bethesda,” Marier said. “The trick will be to make sure there are the right incentives for developers.”

The Montgomery planning board is scheduled to review a draft of the Downtown Bethesda sector plan in April.