By Kate McNeil

It may have added a lot to the cost, but Mother Earth took priority during Ethical Culture Fieldston School's biggest construction project since its opening in 1928.

From restricted flow showers and waterless urinals to rooftop gardens and sustainable African wood, every aspect of the three-year effort to build a new gym and a new middle school kept the environment in mind.

"This is the first plateau in a new thrust toward sustainability," said Peter Mott, the school's "green dean."

Mr. Mott, a former Fieldston biology teacher for 23 years and president of the New York City Audubon Society, took The Press on a tour of the new environmentally friendly facilities Monday afternoon. He has pressed the school for years to incorporate sustainability in its everyday practices, but he credited former head of school Dr. Joseph Healey for his determination to begin creating a "green" campus.

Standing in the faculty parking lot wearing a leaf green button down shirt, the expert birder pointed out a two-and-a-half acre forest area left undisturbed for the 75 species of migratory birds that visit Fieldston's campus every year.

Mr. Mott has studied the migratory patterns of these birds for a quarter of a century and said 20 of those species depend on the forest floor for survival. During the massive construction, no trees were lost and the school planted 450 native shrubs to enrich the woods.

Although the school grew in square footage, no parking was added to its grounds and several prime spots are reserved for carpoolers only.

The new gym and indoor pool are topped with light-colored roofs to reflect, not absorb, heat and reduce the "heat island effect" so familiar in New York City.

The 1,358-person capacity gym, opened in January, has a sustainably harvested maple floor. Inside the locker rooms, showers shut off after 70 seconds; low-flush toilets use only 1.6 gallons per flush and motion-sensitive lighting saves energy.

The middle school building is the crowning achievement of Fieldston's environmental movement. The school is seeking silver certification from the Leadership in Energy and Environmental Design (LEED) Green Building Rating