At the edge of the Prospect Heights neighborhood in Brooklyn, near the Barclays Center, a new development is pushing the edge of sustainability and green construction. R-951, a series of three 1,500-square-foot, open-loft style apartments that went up this spring, are some of the city’s first Passive House-certified and net-zero buildings, bringing solar-powered living to a medium-density section of New York. According to architect Paul Castrucci, “It’s important for me not to be wasteful and use more fuel for many reasons, so I’ve been designing more energy-efficient buildings. This is the most aggressive so far. With the solar array on the roof, it’s like each apartment has its own solar system.” Castrucci showed us the spacious interior, which despite its green bonafides still captures the airy, open feel normally associated with urban living.