Bernstein Real Estate has broken ground on a unique development as its first ground-up project in 20 years.

At 211 West 29th St. in Chelsea, Bernstein is planning a 24-story, 55-unit multifamily building built to Passive House environmental sustainability standards. ZH Architects designed the building, which will have ground-floor retail. When completed, it will be the second-tallest Passive House building in New York, Curbed New York reports.

Passive House, or Passivhaus, is a concept that originated in Germany and Scandinavia in the late 1980s, focusing on passive elements of sustainability such as airtightness, effective window sealing, the elimination of thermal bridges, quality insulation and proper ventilation and heat recovery — with energy output benchmarks set by the Passive House Institute. Though popular for years in Europe, the Passive House standard has so far been applied to only a couple of dozen buildings in the United States, mostly single-family homes.

The tallest Passive House building in New York is Cornell Tech's dorm on Roosevelt Island, which stands 250 feet tall and cost $115M to build. Though Bernstein's project has increased the amount of stories from 19 stories to 24 to fit an additional 13 apartments into the project since initial permits were filed in 2016, the project's height remains 210 feet, the maximum allowable height under zoning regulations.

“This is Bernstein’s first ground-up development in over 20 years and we knew we wanted to do something special," Bernstein Director of Acquisitions and Asset Management Alex Bernstein said. "Even though the costs of building a Passive House are slightly higher, building something that was good for the community, environment and our tenants was a no-brainer.”

A final cost estimate for the project has not yet been reached.