Photo: Mike Kahn/Green Stock Media

The skylights are sometimes supplemented with efficient fluorescent lights.

The building also uses low-energy ­fluorescent bulbs, some of which are hooked up to switched circuits, while ­others are on dimmers. Kaneda wasn’t able to get any good data on which method is more energy efficient, so he plans to collect his own data, which will be invaluable to others embarking on similar projects.

For heating and cooling, Kaneda chose a geothermal heat pump, which takes advantage of the fact that at some point below the surface, the ground remains a constant 10 °C all year round. In Northern California, this point is only about 1.8 meters below ground level; Kaneda installed water pipes that snake throughout the property, an area that will eventually have a landscaped courtyard and a bocce court. When the water flows into the building, it goes through a heat exchanger that collects the heat from the ground in winter and pulls heat out of the building in summer.

Designers of energy-efficient buildings often stop at this point, but for Kaneda, once the first two areas of energy use had been addressed, the amount of energy allocated to computers and other plug-in devices looked huge. All the appliances he purchased for the common room meet the U.S. Department of Energy efficiency goals, and all his employees’ computers will have LCD screens, the lowest-power option. Light and motion sensors will turn on electric lights when daylight gives way to evening and employees are still working, but employees will be able to adjust their personal light levels from their desktop computers. Arming the building security system, which is supposed to happen when the last person leaves for the night, will automatically cut off the power-sucking printers—Kaneda’s own large-format printer, the worst power vampire, draws 40 watts in standby mode.

Kaneda won’t know for sure just how efficient the building will be until he and other tenants—yet to be determined—move in later this fall, but he’s confident he’ll be putting more energy into the grid than he takes out. Though he has yet to set a policy for tenants, he hopes to attract companies that are equally concerned about the environment.

If Kaneda wins the Green Building Council’s approval, his will be among the few Platinum buildings in Northern California (only about 40 exist in the United States as a whole). But whether his will truly be a z-squared building is a matter of debate, since no official definition exists.

Photo: Mike Kahn/Green Stock Media

Meanwhile, water in underground pipes keeps things cool.

Is simply producing more energy than a building consumes enough to call it ­z‑squared? Or does all the energy consumed need to be green energy? If all energy consumed has to be green, how is this guaranteed? Is buying “green power” from the utility company enough? This may mean only that it purchases enough green energy to cover users’ needs but that it doesn’t send that actual energy to them. Or would it be better to buy carbon credits to offset any electricity imported from the grid, based on the utility’s average greenhouse-gas emissions per kilowatt generated? Paul A. Torcellini, a senior engineer with the National Renewable Energy Laboratory in Golden, Colo., notes that in real life some of the electricity you buy is bound to have been generated at the cost of greenhouse-gas emissions.

Torcellini points out that the building stock in the United States is growing faster than builders are deploying energy-efficiency technology. As a result, with buildings accounting for just about 18 percent of the country’s energy consumption, the absolute amount of energy used is increasing one-and-a-half percent per year. So “we either need to save more or build more power plants,” he says.

Kaneda is already developing another z-squared structure, this one for the La Jolla, Calif., research building of the J. Craig Venter Institute, a biotech firm based in Rockville, Md., that is seeking to create artificial life and use genomics to solve a wide array of pressing global problems. With the name of the famed genome pioneer, J. Craig Venter, over the door, that building will get a lot of notice, even if the former San Jose bank remains known only to tech insiders.