The magazine announced its annual rankings of the nation's most "eco-enlightened" universities or "Cool Schools" in its September/October edition.
Other top-five finishers include the University of Washington at Seattle, Middlebury College, the University of Vermont and the College of the Atlantic. In the report's three-year history, CU-Boulder remains the only Colorado institution to appear in the top 10 featured lineup of Sierra's green colleges.
"This ranking is not a surprise, but it is a wonderful tribute to the hard work of our students, faculty, staff and administrators," said Phil DiStefano, chancellor of CU-Boulder. "Over the course of the last nearly six decades they have made sustainability a campus priority, and have done the hard work to make it a reality."
The magazine compiled its results from a 39-question survey measuring sustainable practices and initiatives in the categories of academics, administration, efficiency, energy, food, purchasing, transportation and waste management. Bonus points, of which CU-Boulder received five, were possible for "green" activities not covered by the questionnaire.
CU-Boulder scored strongest in the areas of transportation and waste management, and its overall score was 100 - the highest possible rating - according to the evaluation performed by the official magazine of the Sierra Club, the nation's oldest and largest environmental nonprofit.