Commercial real estate services firm CBRE and Maastricht University in the Netherlands have released their annual Green Building Adoption Index study, according to Bisnow. The study named Chicago the top U.S. city for sustainability.

The Green Building Adoption Index evaluates the top 30 office markets in the country, taking into consideration factors like LEED-certified buildings and Energy Star certifications. Chicago earned the top spot because 66 percent of its office building space is considered green, according to the report. Chicago outpaced the previous year’s leading city, San Francisco. Chicago’s green office building space increased 6.5 percent compared to last year. 

Chicago was also among the top cities because it has put in place sustainability benchmarks. The 2016 Chicago Energy Benchmarking report found that the properties reporting their energy use were able to reduce use by 4 percent, which translated to $11.6 million in yearly energy savings. 

Chicago will likely stay at the top of rankings like this one as the city continues to pledge resources to sustainability projects. Earlier this year, Mayor Rahm Emanuel announced plans to transition all city-owned buildings to renewable energy by 2025. If the plan comes to fruition, all of Chicago’s public schools, park district buildings, government buildings, and Chicago Housing Authority buildings will be powered by renewable energy sources.