According to government estimates, commercial buildings account for more than 60 percent of the country’s electricity consumption and generate 30 percent of all GHG emissions. And though new green commercial buildings are regularly being built, this New York Times piece notes that they are only a tiny fraction of the nation’s estimated 4.5 million commercial properties, many built long before the notion of sustainable design. So many companies, such as Adobe Systems, CB Richard Ellis and Citigroup, are retrofitting older buildings to lessen their carbon footprint.

A 2006 Green Building Council study found that by retrofitting buildings, owners can save on average 90 cents a square foot annually. When property manager Cushman & Wakefield retrofitted Adobe Towers, Adobe spent $1.4 million, but the company says it earned that money back in savings in less than 10 months. As a result, “We’re seeing building managers, developers and property managers wanting to come in and talk to us,” said Randy Knox, director of real estate at Adobe.

In Europe, the Dutch firm OVG specializes in retrofitting older buildings, and business, as a result, is booming.