The U.S. Green Building Council, FTSE Group and NAREIT are developing a green-property index for investors. It is meant to give retail and institutional investors a new way to invest in sustainability. "We've been tracking the U.S. REIT space for 18 years and have recently been hearing more from our clients about which companies own LEED-certified or Energy Star-certified assets," says Keven Lindemann, CFA, CAIA, director of SNL Real Estate.