When my best friend decided to pick up and move to Chicago, I wasn’t heart broken. Instead, I remembered how the last time I was in Chi-town I had the opportunity to tour the largest design meccas in the United States–so large, it has its own zip code–the Merchandise Mart.

As the largest commercial building in the world, The Merchandise Mart welcomes millions each year to shop and tour its showrooms. When administrators decided to implement green policies in the 4.2-million-square-foot structure and apply for Leadership in Energy and Environmental Design (LEED) certification, they asked their employees for ideas.

The new green standards are paying off in a big way. In 2006, The Mart joined Clean Air Counts, a Chicago-based initiative to improve air quality, and has reduced pollution by more than 264,018 pounds―the largest reduction ever by a commercial building. Inside The Mart, and amid new construction, paint and building materials must contain low levels of VOCs (volatile organic compounds), potentially harmful to the environment. A stringent recycling program focuses on reusing and breaking down lightbulbs, batteries, paper products, construction waste, and more.

The Mart also maintains a site-management plan that mandates drought-tolerant plants and the use of environmentally friendly pest control. Efforts for more energy efficiency include a thermal cooling system and the latest lighting technology (to compensate for the extended hours required to illuminate showrooms). Tenants can even rent an I-Go hybrid car by the hour.

In 2007, The Mart earned LEED Silver certification for Existing Buildings (LEED-EB). Although it may not be shiny and new, the historic structure is a prime example of how it’s never too late for change.