California will become the first state in the nation to require new homes and businesses to be energy efficient.

The California Building Standards Commission unanimously voted to adopt the green building code July 17.

Commission chairwoman Rosario Marin says the energy and water efficiency standards will help the state cut its greenhouse gas emissions.

The rules are voluntary for now, but become mandatory in 2010. They also apply to new hospitals and schools.

Craig Noble, a spokesman for the Natural Resources Defense Council, says the standards are a good step but could be tougher.

He says about 75 California cities and counties already have more stringent green standards.