Green building is gaining popularity among the nation’s counties, according to a new study by the American Institute of Architects.

Since 2003, the number of counties with green building programs has grown from eight to 39 – an increase of 487.5 percent. The study, “Local Leaders in Sustainability: Green Counties,” surveyed 200 of the most populous counties in 2008, where nearly 169 million Americans live.

Among the findings:

• Nearly 43 million people live in counties with green building programs.
• The eastern region of the country has the most green building programs.

The report reviews best practices and the diversity of approaches to promoting sustainability. It highlights a handful of counties in particular for their experience and expertise. They include: Alameda County in California, Hennepin County in Minnesota, King County in Washington, and Montgomery County in Maryland.