In their high-profile campaign against climate change, California lawmakers have set goals for curbing carbon emissions from cars, factories and power plants - and now they are taking aim at homes and offices.

"Studies show that buildings, like the ones you and I sit in, are responsible for 40 percent of greenhouse gas emissions," said Assemblyman Ted Lieu, D-Torrance, by telephone Monday.

Adam Dondro, legislative aide to Assemblyman John Laird, D-Santa Cruz, said: "It's a huge piece that needs to be addressed."

Laird and Lieu co-wrote legislation this year to establish statewide building regulations that would help create new tracts of energy-efficient homes, beginning in 2013. The legislation, Assembly Bill 1058, would direct the state Department of Housing and Community Development to write new building codes that require efficient homes.

Lieu also wrote Assembly Bill 888 to require efficient commercial buildings starting in 2013 as well.

Both bills passed the Legislature and are sitting on the desk of Gov. Arnold Schwarzenegger, who was at the United Nations on Monday urging worldwide action on global warming. Many scientists say they believe the growing concentration of greenhouse gases such as carbon dioxide in the atmosphere is responsible for the warming climate scientists have documented over the last century.

The bills have the backing of environmental groups but are opposed by builders and some local officials.

Carolyn Chase, founder of an environmental group called San Diego EarthWorks, suggested that the governor ought to take his own advice and take action to sign the green building bills.

"It's a good time to tell the governor, 'Now's a good time to sign those bills,' " Chase said.

But the building industry argues that it would be better to encourage green building through local incentive programs rather than through mandatory regulations.

"Give us the carrot," said Tommy Thompson, a spokesman for the Riverside County Chapter of the Building Industry Association of Southern California. "Why bust out the stick right away?"

Local builders also have expressed concern about new policies adopted by the California Public Utilities Commission last week.

The regulatory agency said it will require the state's three major electric utilities - including San Diego Gas & Electric Co. and Southern California Edison - to set up new rates to encourage developers to build homes that use renewable energy and don't require new electricity.

Paul Tryon, chief executive officer for the San Diego Building Industry Association, said earlier that he needed to study the policy before taking a position. But he said the policy's 2020 target date for building only homes that require no new electricity was probably unrealistic.

The area's two giant utilities support the new policy.

"The commission's decision is another clear demonstration of its commitment to energy conservation, and we applaud this groundbreaking move," said Anne Smith, senior vice president for customer service for SDG&E.

Southern California Edison officials also praised the move.

"As the nation's leader in energy efficiency program savings, we support the commission's policy desire to make energy efficiency a core part of utility business priorities and create an energy-efficiency policy model for the nation," Edison spokesman Gil Alexander said in a statement.

Chase praised both the new commission policy and the legislation sitting on the governor's desk.

"The technology exists to build more efficient buildings," Chase said. "But you have to sometimes order people to do the right thing, when it comes to increasing the standards."

Dondro, the legislative aide for Laird, said the details of the mandate would have to be spelled out by the state housing department. But the regulations probably would address insulation, design, air conditioning systems and other building practices, aiming to curb electricity consumption and, by extension, carbon emissions.

Thompson of the building association said builders are "opposed to mandates, but we're not opposed to building green."

On the contrary, he said, the Riverside County branch is preparing to ask the Western Riverside Council of Governments later this fall to pass a resolution encouraging member cities to adopt green incentive programs. Thompson said the association would like cities to put projects on a fast track if they include green elements.

Bob Johnson, Temecula's assistant city manager for development, said his city is interested in adopting such a program.

- Contact staff writer Dave Downey at (760) 745-6611, Ext. 2623, or ddowney@nctimes.com.