Passive house construction — that super-tight energy efficient design invented by the Germans — has gone from a niche concept to a mainstream one in the 10 years since the first passive house building went up in Maine. Passive house design "is like organic food," said Amy Hinkely, of the University of Maine architecture program and moderator of an Earth Day panel that discussed the status of he panel moderator. "It was once hippy, but now it's mainstream." "I didn't exepct to see the development and scale of passive house that's occurred over the past 10 to 12 years," said Matt O'Malia, of OPAL and GO Logic, of Belfast, which designed Maine's first passive house building, a small dorm on the Unity College Campus. "Initially, it was a very fringey thing."