LAS VEGAS -- Months before its scheduled opening, the first phase of CityCenter is getting national recognition for energy efficiency.

The U.S. Green Building Council awarded three Leadership in Energy and Environmental Design gold certifications to the Aria Resort and Vdara Hotel.

"It’s an achievement for CityCenter, a remarkable achievement for our company and a remarkable achievement for the green movement to do it at this scale,” said MGM Mirage Senior Vice President Cindy Ortega.

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Gold is the second-highest certification from the council, which evaluates buildings on several environmentally-friendly criteria including water efficiency and innovative design. The highest LEED certification is platinum.

MGM Mirage and its partner, Dubai World, have been touting the $8.5 billion resort complex as one of the most environmentally-friendly projects in the country.

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When it opens, high rollers will ride in a fleet of stretch limos powered by clean-burning compressed natural gas, while gamblers feed dollars into slot machines with built in air-conditioning units that cool from the floor upward.

CityCenter was even constructed using 97 percent of the debris left by the demolition of the Boardwalk Hotel.

“Being green is being conservative. You use less resources; you’re more caring in the way you do that and that usually translates into lower costs,” Ortega said.

Aria, the casino-resort at CityCenter, and Vdara, a 57-story condo-hotel tower are both scheduled to open in December.

Developers said they expect the remaining CityCenter buildings to also win LEED certification.