The biggest energy users in America are not cars and trucks - they're buildings.
Buildings use about forty percent of the nation's energy.
In 2000, the US Green Building Council introduced a program to certify "green" buildings, called LEED.
That stands for Leadership in Energy and Environmental Design.
A new version of the LEED standards was released yesrterday.
 But as the environment report’s Samara Freemark found, some critics see serious flaws in the program.