Located in Des Moines, the 825,000-square-foot headquarters of Wellmark Blue Cross and Blue Shield is the largest LEED Platinum building in the worldwide -- as of March 2011. Compared with similar buildings, the Wellmark headquarters saves about 20 percent in energy costs and 50 percent in overall waster use. Among the technologies that the company used to earn its LEED Platinum points are daylight harvesting, low-flow water fixtures and a rainwater capture system, and under-the-floor airflow processes. Through 2010, Wellmark reported that its administrative savings from the facility were at least $10 million; it expects to realize another $10 million in savings over the next two to three years. (Photo courtesy of Wellmark)