How successful has the U.S. Green Building Council‘s (USGBC) LEED program been in bringing green building to the commercial sector? Exactly two billion square feet of successful, according to a recent announcement [PDF] – with seven billion more coming down the pike.

A number of factors converge in LEED’s popularity with the commercial sector – among them, energy efficiency and publicity. Because commercial buildings leave the lights on longer and require more of their HVAC systems than residential structures, green building systems can pay for themselves in short order (and serve to lower operating expenses thereafter). Also, that lovely glass plaque announcing a building’s LEED status to the world has proven attractive to many companies looking to build a brand and gain favor with green-minded customers.

These factors, combined with LEED’s flexibility in scoring, has led the certification to worldwide renown since it was launched in 2000. The USGBC is currently certifying two million square feet of commercial building space every day across more than 130 countries. There are nearly 50,000 commercial projects are currently participating in LEED today, comprising nine billion square feet of construction space.

The program has proven successful in terms of home certifications as well, though to a lesser extent. A total of 23,000 homes across the U.S. have earned certification through the LEED for Homes program, with around 86,000 more in the pipeline. On this count, however, LEED certifications are not the only game in town, as the National Green Building Standard (NGBS) is currently on track to duplicate and perhaps even exceed LEED’s success in the residential building sector, having racked up around 4,000 certifications in its first three years.