Willis Tower began undergoing the biggest restorative transformation in the building’s 43-year history, adding 300,000 square feet of new retail, dining and entertainment space, including Catalog, a five-story immersive neighborhood experience, as well as 125,000 square feet of tenant exclusive amenities and a 30,000 square-foot outdoor deck and garden to the building. As part of the over $500M redevelopment renovation, Willis Tower, owned and managed by EQ Office, achieved LEED for Existing Buildings certification. However, this was not your average certification. Willis Tower pursued both an initial LEED v2009 certification while simultaneously completing the recertification tasks for the latest update to the rating system, LEED v4.1, which emphasizes performance and tracks progress through the Arc platform. Willis Tower achieved the Gold level in both systems. Willis Tower utilized data from the same 12-month timeframe, establishing building performance baselines in both versions. This allowed the property to not only benchmark their current status but establish a platform from which to monitor future improvements. Willis Tower installed a new building automation system along with high-efficiency lighting systems with improved controls, HVAC exhaust and return damper improvements, all new air media and variable frequency drives, chiller modernization, expansive low-flow plumbing fixture upgrades, and replacement of automatic transfer switches, enhancing the electrical infrastructure integrity. Pursuing LEED certification prior to the expansive additions to the building, but during these many systems upgrades, allowed the site team to monitor changes while setting new operational baselines to best serve the building with its unique space types, employee counts, and operating hours. As Willis Tower continues to track annual performance through the LEED v4.1 Arc platform, they hope to witness score improvements not only in energy and water use, but to see increased occupant satisfaction scores in annual surveys, stemming not only from system improvements, but the future amenity expansion and ongoing sustainability efforts throughout the facility. “Willis Tower is a major destination in the heart of Chicago, and for more than 15,000 people, it’s also their workplace,” said David Moore, Senior Vice President and Portfolio Director, EQ Office. "As we redevelop this iconic Tower, we’re making a conscious effort to find ways to improve energy efficiency and reduce our environmental footprint. Earning the LEED Gold certification is a credit to our entire team for their hard work.