The designers of Seattle's Bullitt Center set out to prove that a six-story office building could generate all its own energy. And, after one year of operation, they have surpassed this ambitious goal: the 52,000-square-foot building is sending a sizable surplus to the grid.
According to data released in April by its owner, the Bullitt Foundation, the building's energy appetite is far lower than expected. The project's architects, the Miller Hull Partnership, and its m/e/p engineers, PAE, projected consumption of 16kBtu/sf—half the energy-use intensity (EUI) of Seattle's best-performing office building. Instead, consumption during its first year was just 10kBtu/sf. Factoring in the excess energy generated by the 242kW solar array on the cantilevered roof, the site's net EUI is an amazing -6kBtu/sf.
PAE president Paul Schwer estimates that consumption will rise slightly when the last unoccupied floor is leased, for a final building EUI of 12kBtu/sf and net site EUI of -4kBtu/sf. At that level, the energy flowing from the array—sized to just offset projected energy consumption—will also offset electricity use for about a dozen houses. These energy numbers, says Schwer, demonstrate that net zero office buildings are viable even in overcast Seattle, at least at six stories.
Its exemplary performance should help the Bullitt achieve Living Building designation—a status bestowed by the International Living Future Institute (ILFI) through a rigorous process that entails satisfying 20 "imperatives" addressing a building's site, its water consumption, and the well-being of its occupants, among other factors. The Bullitt can't apply for Living Building certification just yet, however. It must first demonstrate net zero energy operation (or better) for a full year with at least 85 percent of the building occupied. Denis Hayes, the foundation's president, says the Bullitt hit that level in December, so he expects to file for certification next January.
Hayes credits the project team for the Bullitt's success. The designers integrated a suite of energy-saving strategies, including passive climate controls, radiant floors, and 14-foot floor-to-floor heights with correspondingly tall triple-glazed windows. "We've figured out a way to dramatically reduce energy consumption without any sacrifices of comfort or lighting," he says.
The designers insist that the tenants, including the foundation and ILFI, have also played a critical role. Schwer and Miller Hull principal Brian Court emphasize that lower-than-expected plug loads account for most of the surplus. Before its own move to the Bullitt, PAE replaced IT equipment, slashing workstation power use by 80 percent. An incentive scheme should keep occupants engaged: each tenant has an energy allowance and only pays when consumption exceeds its budget.
While the foundation gathers more energy data, it is also working out a final kink in the project's bid to achieve net zero water use. The building is designed to capture rain and treat it to achieve potable standards. However, it got caught in a catch-22: regulators insisted on chlorination of the water, which violates Living Building sustainable materials requirements. Although Hayes worked hard to overturn the order, arguing that filtration and ozone-based purification were sufficient, the authorities didn't budge. Ultimately, ILFI accepted chlorination with the addition of charcoal filters.
Hayes now awaits the final approval required to start serving up the rainwater: certification of the Bullitt Center as an independent water district, which is expected by the end of this summer.