To date, most LEED certifications in the U.S. have covered new buildings. By the end of 2009, about 46% of cumulative LEED certifications were under the LEED for New Construction (NC) program, with an additional 15% under the Core and Shell (CS) program. CS program certifies the “guts” of a new building project if the builder doesn’t have control complete control over the interior spaces.

In contrast, only about 31% of LEED certified space is under the Existing Buildings Operations & Maintenance (EB) program. (An additional 6% is under the LEED for Commercial Interiors (CI) program, which certifies spaces within new and existing buildings, as well as another 2% under specific LEED applications for schools, retail, and certain other types of buildings).