When Charles Rose, AIA, first presented his firm’s design for the John W. Olver Transit Center to local residents, the project drew concern. Greenfield, Mass., contains a wealth of historic architecture, and many worried that a modern building wouldn’t fit in. But Rose’s client, the Franklin Regional Transit Authority, correctly bet that strong design and engineering would ultimately yield a streetscape-enhancing, energy-efficient structure. They ended up with the first net-zero-energy transit center in the country—one that’s popular among both officials and the general public.

Located on a downtown former brownfield site, the center’s dynamic, copper-clad form appears organically created. In reality, it came out of a highly scientific collaboration between Charles Rose Architects and the Cambridge, Mass., office of Arup. As the project’s engineers, Arup built an energy model for the 24,000-square-foot building early in the design process, allowing Rose to fine-tune the massing for maximum solar efficiency and daylighting. “From the beginning, we were already working with Arup, trying to see what forms were going to be the most energy-efficient,” Rose says.

Once the team determined optimum massing, their focus shifted to reducing energy use inside the building. As a transit hub for bus lines and a future rail stop, the Olver Center’s ground floor serves mostly as public space. Its second level, which houses offices for transit authority and other government employees, provided a major opportunity to reduce artificial lighting needs. Using the energy model as a guide, Rose and Arup introduced skylights and chose wall colors to subtly reflect natural light. These efforts to increase daylighting, coupled with strategic task lighting and intelligent controls, allowed them to dramatically lower the building’s lighting load.

Arup’s Julian Astbury describes the team’s HVAC approach as a mix of active and passive strategies. “We have the best possible windows and insulation that we can afford,” Astbury says. “Within this high-performance building envelope, how do we reduce the amount of heating energy we use?” A dark-painted, perforated metal solar wall on the south façade pulls air warmed by the sun into the building. A ground-source heat pump is connected to a system of 22 geothermal wells, and on very cold days a biomass boiler adds extra warmth. The boiler uses about three truck-loads of wood scraps per year from nearby factories; due to the building’s relatively small size, Rose and Arup decided after much research that biomass would qualify as a renewable resource.

A thermal wheel helps retain heating and cooling energy inside the building, and active chilled beams provide an effective circulation system. To push the Olver Center to net-zero, the team added a 98kW photovoltaic array. But even more significant than achieving net-zero status, Astbury says, was the design and engineering team’s holistic process. “In the end, it’s not really about how much renewable energy we can install,” he says. “It’s about creating a high-performance building.”