India, Oct. 9 -- In 2007, Leonardo DiCaprio produced and narrated The 11th Hour, a documentary about the state of the natural environment. A year later, in 2008, he did something a bit more personal. He bought a $3.67 million Manhattan apartment, according to Robb Report, in a building that runs partly on solar power. That building, the Riverhouse in Battery Park City, is a 32-story condo tower with a rooftop solar array. So what set it apart?

The story begins with the neighborhood itself, not the tower. Battery Park City sits on 92 acres of landfill in the southwestern corner of Manhattan. A 2004 paper, 'Charging the Battery: Energy Efficiency in Battery Park City,' explains what happened next. In the late 1990s, the Battery Park City A...