When the Seattle Public Library’s new Ballard neighborhood branch opened in 2005, it was just one year after the unveiling of the renowned Central Library designed by architect Rem Koolhaas. Yet it is the more humbly scaled Ballard Branch Library, opened at roughly one-twentieth the total cost of Central, that may better reflect the city’s commitment to sustainability. “It’s probably my favorite building I’ve worked on,” says Robert E. Miller, FAIA, of the Seattle office of Bohlin Cywinski Jackson (BCJ), the library’s architect.

And it couldn’t be more popular with patrons. “The building works as a library and it looks great. It’s very well laid out. It’s the busiest neighborhood branch,” says Glenn Osako, who now manages the Seattle Public Library’s multibranch capital-improvement plan. “Ballard has more than twice the volume of books going in and out of [it compared] to the branch it replaced.”

The building is not LEED certified, but includes a host of features designed to harness natural resources, such as an over-18,000-square-foot green roof and 17 photovoltaic solar panels that generate 4.8 kilowatts of power. It’s also designed as an educational experience. Don’t want to trudge upstairs to see the vegetated roof? You can view it from a periscope downstairs.

“There were a lot of value judgments along the way, like whether we used certified timber. If we were doing LEED, we would have pushed that versus things like the periscope,” Miller says. “But I think this was the right choice. I think a lot of people coming to Seattle have wanted to see Rem’s library, and then they’d get to Ballard and relate to it in a personal way. The number of people has surprised even us, and it’s been steady in the years since we opened. The library now gives weekly tours and the numbers haven’t gone down. Those things have a huge impact.”

The green roof itself has experienced challenges that both architect and client attribute to lessons learned from what was, at the time of construction, a relatively new building technique. Today most roofs like this don’t use grass in plantings, as exists at Ballard. It’s higher maintenance than alternatives such as moss and sedum. They are also now broken up into modules rather than kept as a large whole. “If that roof ever does have a problem, we’re going to be in for a lot of cost to replace it,” Osako says. “But that’s part of the cost of being an early adopter.” Irrigation has also been an issue. Originally, it only reached the majority of the planted area, but not all of it, so the system had to be replaced within a few years.

The library’s 20,000-square-foot roof is also its signature visual element, a swooping wood mass extending over the building to create massive overhangs; its glulams jut out decoratively like the oars of some ancient warship. But these have “weathered beyond just weathering,” Osako adds. “We brought BCJ in two years ago to see what we could do to refinish the rafters. It was about $85,000 redoing a bit of the north and the south. We found a mix of sealers that we think will work. We have something like 80 to 90 tips, so it’s a lot of work. If I saw that design detail again, I’d catch it.”

The building’s photovoltaic panels have performed well. Only the interactive display meter has been problematic to Miller. “Every three panels are connected to a meter so people can see how it’s performing,” he says. “We received the wrong meters so it looks like they’re not producing enough power or not working. If we had monitors at a smaller range, you’d see the panels maximizing on sunny days. We’re hoping replacement of the meters can happen eventually, but the public perception of how that’s portrayed is very important. It can be the same data but the perception is completely different.”

The building has proven to be much more energy efficient than its predecessor, but Miller wishes that there were more data available. “It’s difficult even if we get utility info to determine plug loads and that nature,” he says. “To quantify that would be an interesting next step. I think we were completing this building just before a lot of tools were in place to help us do that.”

And despite his quibbles, Osako believes that the broader context is positive: “Buildings are a team effort. There may be things the architects should have caught, but the building’s been very successful,” he says “It’s a well-designed building: easier to navigate, better lit than what we had before.”