Chicago’s office market was named the greenest in the U.S. for the third year in a row as the green building trend continues to expand in the nation’s largest cities, according to the sixth annual Green Building Adoption Index by CBRE, Maastricht University and the University of Guelph.

The 2019 Green Building Adoption Index shows that 4,879 or 13.8% of all commercial office buildings across the 30 largest U.S. office markets are green certified—the highest total in the index’s history.

“Green” office buildings in the U.S. are defined as those that hold either an EPA ENERGY STAR® label, USGBC LEED certification or both.

Measured in square footage, 42.2% of total space across the top 30 office markets is green certified, up from 41.9% last year.

Chicago took the top spot for the third straight year, with 71.1 percent of its commercial office space being green certified. This was a slight increase from the previous year, when the Midwestern city recorded 69.8 percent.

Second-place San Francisco made significant ground, increasing from 64 percent to 67.5 this year, marking the largest percentage gain, along with ninth place Seattle, year-over-year.

Atlanta maintained the third spot with more than 59 percent of all space green certified, while Minneapolis moved up to the number four spot with 57 percent, passing Los Angeles, which now rounds out the top 5 at 56.6 percent.

Source: CBRE / The 2019 Green Building Adoption Index

“Green building continues to be a growing trend, as both tenants and owners seek the benefits of being associated with these properties,” said Spencer Levy, chairman of Americas Research for CBRE and senior economic advisor.

“Long-term, these buildings offer real cost savings, making them appealing to owners and investors alike. These buildings are also more attractive to tenants, as many corporate users seek out these properties for their operational and social benefits. As the market has proven, its popularity only continues to grow,” he added.