Building or retrofitting buildings and housing to make them "green" and energy efficient could have big and relatively fast environmental and economic benefits, according to a report by PennEnvironment.

The 20-page report released in Pittsburgh and nationally today by the environmental advocacy group said adoption and implementation of federal and state policies and codes promoting use of high-efficiency windows and heating and cooling systems will result in significant energy savings for home and building owners and reductions in emissions of greenhouse gases, which contribute to global warming.

"We need policies and commitments from all levels of government to protect the environment from global warming and prevent runaway energy costs," said Erika Staaf, PennEnvironment water advocate. "We are echoing Gov. Ed Rendell's call for a statewide 'green' building code."

Such a code would mandate energy efficient construction techniques, use of recycled and sustainable materials, and efficiencies in heating and cooling systems.

About 40 percent of America's energy, 10 percent of all the energy used in the world, is used to power buildings and homes. The report said much is wasted through poor insulation, leaky windows, and inefficient lighting, heating and cooling systems.