It's iconic, and now it's certified green. The Empire State Building has been awarded LEED Gold for Existing Buildings certification as further recognition from the $550 million Empire State ReBuilding program. The 2.85 million-square-foot building is celebrating its 80th anniversary while nearing completion of its renewal and repurposing to meet the needs of today's businesses. It's is one of a small number of National Historic Landmarks to earn the designation, which was established by the U.S. Green Building Council (USGBC) and verified by the Green Building Certification Institute (GBCI).

The retrofit was conducted by Johnson Controls and real-estate services firm Jones Lang LaSalle. It's guaranteed to reduce the building's energy consumption by more than 38 percent and should save $4.4 million in energy costs annually, representing an approximate three-year payback of the cost of implementation, said the USGBC in a press release.

The improvements also reduce carbon emissions by an estimated 105,000 metric tons over 15 years. In Jan. 2011, Anthony Malkin of the Empire State Building Company agreed to buy carbon offsets totalling 55 million kilowatt hours per year of renewable energy, making the Empire State Building carbon-neutral.

“LEED certification is one of the top criteria for many tenants today, and it reinforces the strong business case we have made for a cost-effective energy retrofit that lowers tenant occupancy costs,” said Dana Robbins Schneider, vice president of Jones Lang LaSalle and program manager of the energy retrofit, LEED feasibility assessment and application process. “We have continued our work with building ownership with LEED-level new tenant installations and tenant-based energy efficiency programs, which are now being documented in a new program with the Center for Market Innovation of the Natural Resources Defense Council.”