The new rules require buildings to meet the basic certification standard adopted by the U.S. Green Building Council, which uses a points-based scoring system. The PDC says it hopes to have projects meeting an even higher environmental standard, and also hopes private developers will voluntarily adhere to the standards.

A certified green building earns at least 26 points out of a possible 64. Points are earned for upgrades to exterior and interior building materials, power and water use and erosion control, among other things. Projects may be exempted from the rule if, among other things, they can prove the costs are too extraordinary or that it would conflict with historic preservation efforts.

The PDC says it intends to continue financing larger projects for which its part would not total 10%. It stressed that in such instances the new green certification requirementwould be incorporated into development agreements. Changes to the new policy may still be made later in the year as business associations and developers weigh in on the issue.