Hydraulic systems use biodegradable vegetable oil, the bulk of its cold, rolled steel is from recycled material. Emphasis on smaller elevator cores can save 300 tons of concrete over conventional cores.

"Regenerative drives can actually run the customer's electric meter backwards," says Wayne Valencia, the firm's West region president.

Replenished Materials Green NRDC

The Southern California office of the Natural Resource Defense Council, in Santa Monica, is which opened in 2004, remains the showcase for the latest in sustainable design. It is a Platinum building, the highest of the LEED ratings, one of only six to date in the U.S.

"The N.R.D.C. was a curious as we were to find out exactly what was achievable in terms of sustainability in architecture," says Elizabeth Moule, a principal with Pasadena-based Moule & Polyzoides, the lead architect for the project.

Moule set out to design a building that would use up to 75 percent less energy than a typical commercial building of the same size and consume in both its construction and its operation, only renewable resources. Flooring is made of replenished bamboo and poplar. Floor mats and tiles are from recycled rubber; countertops from recycled glass. Wood is from managed forests.

The roof is partly covered by photovoltaic solar panels that provide about one-fifth of the building's electricity.

Light wells and clerestories bring daylight into first floor offices, reducing the need for artificial lighting, and natural ventilation and operable windows meet most of the cooling and fresh air needs. Energy use is reduced through energy-efficient computers and equipment, dimmable electronic ballasts, occupancy sensors and lighting geared to specific tasks. Moule specified energy-efficient low-mercury lamps to reduce mercury emissions.

When air-conditioning is needed, a high-efficiency system uses displacement ventilation to focus cool air where it is needed. Toilets in the building use water recovered from showers, sinks and rainfall, and are dual-flush systems, permitting a half-flush of about 0.6 gallons or a full flush of 1.2 gallons.

"Every single drop of water that falls on this building is captured and harvested," says Moule.

For the rest of its energy needs, the N.R.D.C. buys renewable energy generation credits (wind certificates).

As a result, 100 percent of its energy is provided by renewable sources.

As efficient as it is, the N.R.D.C model already is being challenged.