Con Edison never looked so cool.

The energy company's cutting-edge “green roof” on its Long Island City facility is an environmental hole-in-one, a Columbia University study shows.

The LIC venture is one of several so-called “cool roofs” - whitewashed or green, plant-covered roofs designed to deflect or trap sunshine - that Con Ed has installed around the city to improve energy efficiency and reduce carbon emissions.

In 2008, Con Ed began growing plants on a quarter-acre rooftop section of The Learning Center, a training and conference center located at 43-82 Vernon Boulevard. It's now covered with 21,000 plants. They help retain heat inside the building during the winter, and block it out during the summer, producing significant savings on heating and air conditioning costs.

The university study, which was led by Stuart Gaffin, a research scientist at Columbia's Center for Climate Systems Research, found the plants reduce winter heat losses and summer heat gains from heat flowing into the building by 37 percent and 84 percent, respectively.

The study did not focus on other factors, such as insulation and windows, which contribute to a building's overall energy consumption.

The energy savings were measured against two different sections of rooftop space that were installed at the Con Ed facility as part of the study: a traditional dark roof, which absorbs summertime heat, and a white-washed cool roof, which deflects the sun's rays.

Con Edison has installed almost 250,000 square feet of white roofing, and has plans to whitewash an additional 220,000 square feet of roof space by the end of the year.

The method - and Long Island City itself - drew national attention last year when Mayor Michael Bloomberg and former Vice President Al Gore helped paint the neighborhood's YMCA roof white at a ceremony launching the city's own white roof program.

“This study by one of the world's top universities confirms the benefits of our cool roofs programs,” said Saddie Smith, Con Ed's vice president of facilities. “We strongly encourage building owners to consider cool roofs, whether white or green. They save energy and they're good for the environment.”

Smith noted that the more energy-efficient green roofs are also more expensive. Even so, Gaffin said the study proves cool roofs technology isn't entirely out of reach.

“Ultimately the goal of this effort is to provide the best science so we can inform the various policy choices and cost-benefit estimates for energy conservation,” he said.