Seeing as Brooklyn is the artisanal, organic heartbeat of New York City, it should come as no surprise that the latest trend in sustainable building is spreading across the borough. Passive buildings, built to "passive house" standards imported from Germany, are popping up all over the place, and they have an intrigue not found in plain ol' LEED-certified buildings. It's not that they look exotic, necessarily, but they function entirely differently from traditional buildings. Passive houses are all about insulation, so they are virtually airtight and use up to 90 percent less energy to heat and cool, making standard heating and cooling systems completely unnecessary. From single-family homes to affordable housing complexes, dozens of developments across New York City have adopted the eco-friendly building techniques.