CHICAGO—When CBRE Group, Inc. first launched a research project to study energy efficiency in US buildings, company officials expected to find that green buildings were a bicoastal phenomenon. But although San Francisco did rank second in the amount of commercial office space considered “green,” it was Minneapolis and Chicago which placed first and third, respectively, among the 30 markets studied for the 2015 Green Building Adoption Index, a joint project of CBRE, Maastricht University and the US Green Building Council.

The index charts the growth of ENERGY STAR- and LEED-certified space in US office markets. Although Chicago saw a reduction in the total number of certified buildings–287, down from 294 last year–the percentage of all square footage in those buildings increased to 63.4%. And the percentage of square footage in LEED-certified buildings was 38.5%, up nearly 7%. CBRE officials say this is most likely the result of ENERGY STAR–labeled buildings also achieving LEED certification.

“This is a first-tier market with a lot of high-profile owners and green-certified buildings also tend to be a big city phenomenon,” David Pogue, CBRE's global director of corporate responsibility, told GlobeSt.com.

Overall, Minneapolis led the green building index for the second consecutive year, with 70.4% of all commercial office space currently qualified as green, down from 77% in 2014. Atlanta and Houston swapped positions at fourth and fifth.

Pogue added that by implementing energy-efficient practices, small building owners can set themselves apart from the competition. The researchers found that 62.1% of office buildings in the US with more than 500,000 square feet are considered green. In contrast, only 4.5% of all US office buildings with less than 100,000 square feet qualified as green.

“It would appear that many smaller buildings in the majority of large markets still have an opportunity to be 'best in class' among their peer set by achieving these certifications,” he said.