Principal Real Estate Investors is one of the “greenest” commercial real estate companies in the United States, according to Commercial Property Executive magazine. Principal Real Estate, the fourth-largest institutional real estate manager in the United States, tied with four other firms that ranked No. 8 on the real estate publication’s Greenest Companies list. They were ranked according to an environmental sensitivity index that measures companies’ participation in sustainable real estate activities such as employing people with specialized training, making plans for future sustainable building projects or pursuing Leadership in Energy and Environmental Design certification for projects. More than 90 percent of the office buildings under Principal Real Estate’s management have completed some type of green building project, upgrade or improvement.