There are 40 companies across a wide spectrum of industries taking part in the U.S. Green Building Council’s Portfolio Pilot Program, which allows companies to create volume certifications like Marriott’s new green Courtyard prototype. Of the 40, roughly half are working on LEED for New Construction and the other half on LEED for Existing Buildings.

There are two other hotel companies involved, including Starwood and its Element brand. The extended-stay offering mandates LEED certification, but to this point, all the locations have been custom designed. The other company hasn’t publically announced its participation, but Marc Heisterkamp, the former USGBC director of commercial real estate who recently left for a position with Bank of America, says it is “one of the big companies” and will be a “game-changer.”

The unnamed company is working on a LEED for Existing Buildings volume certification, which would allow it to eventually certify “a very large portfolio of existing hotels by making them more efficient,” Heisterkamp explains.

Marriott hopes to have volume build prototypes for its Fairfield Inn, SpringHill Suites, Residence Inn and TownePlace Suites brands by the end of the year. Much of the work from the new Courtyard prototype will be taken and adapted to the other select-service brands.

The USGBC created the program to help reduce greenhouse emissions and energy dependence.