Despite increases in campus size and population, Yale has reduced its greenhouse gas emissions by 11.5 percent since 2005.

According to the 2011 update on the University’s greenhouse gas reduction plan, Yale is on track to achieve the reduction targets it set in 2005, according to University officials. The plan, originally conceived in 2005, announced Yale’s commitment to reduce greenhouse gas emissions by 43 percent of its 2005 levels by the year 2020 and to create a yearly progress report analyzing that goal, Sustainability Project Manager Keri Enright-Kato said.

“It’s a very aggressive goal that was set, but it’s one that is important,” said Thomas Downing, a senior energy engineer in the Office of Facilities.

The most common sources of these greenhouse gas emissions are Yale’s Central Power Plant and the Sterling Power Plant, which generate energy used primarily to heat, cool and ventilate buildings, Enright-Kato said. Downing said the Sterling Power Plant, which was recently converted to a co-generation facility — one that generates both electricity and heating or cooling for buildings — is now more efficient in taking raw fuel and converting it into usable energy for the buildings.

The University has also reduced greenhouse gas emissions through a recommissioning effort in which the heating and cooling systems of 90 buildings were “tuned up” to run at an optimal level, Downing said. These tune-ups were complemented by an initiative to vary temperatures in certain buildings depending on the season and time of day, he addded.

Yale’s energy saving measures also include a lighting retrofit project, which installed new light technology in older buildings, and window replacements, which are now multi-paned and seal better than previous ones, Downing said.

Since 2005, the University has increased the gross square footage served by its power plants — about 90 percent of campus — by 1,349,000 square feet. The majority of these new buildings meet the certification requirements for Leadership in Energy and Environmental Design, an internationally recognized program that aims to foster sustainable building development. LEED encourages the use of regional and recyclable materials in new projects through a rating system with certified, silver, gold and platinum levels. Downing said the University has voluntarily chosen to require that its new buildings achieve gold level certification with some additional energy efficient prerequisites. He added that he thinks buildings made sustainably are usually of better quality.

“For a very small additional cost, you’re going to get a building that is built better, and by the way, will actually save energy on the operating costs of it over time,” he said.

Enright-Kato said that while the greenhouse gas reduction initiative has made good progress, there is still work to be done in the next nine years.

“The goal is not looking as far away as it originally was,” she said. “As it gets closer, it gets more and more important to devote focus on reductions.”

Downing agreed and said he expects the University to continue its current path of reducing greenhouse gas emissions.

Beyond Yale’s campus, Christine Eppstein Tang, director of New Haven’s Office of Sustainability, emphasized the universal importance of reducing greenhouse gas emissions.

“I think it’s a very important issue for the whole country and the whole world, actually,” she said. “I think that Yale has been a leader among academic institutions in planning strategically for climate change, and I’m looking forward to seeing the implementation of that.”

The total U.S. greenhouse gas emissions rose by 7.3 percent from 1990 to 2009, according to the Environmental Protection Agency.