Raising the roof
The diverse and innovative array of rooftop gardens that decorate Portland's skyline show just how far the Rose City has come since 1996 when Tom Liptan, a landscape architect with Portland's Bureau of Environmental Services (BES), installed the city's first one on the garage of his home.
Just three years later, the city officially recognized ecoroofs as the stormwater management technique of choice, noting they significantly decrease stormwater runoff, save energy, reduce pollution and erosion, and help preserve fish habitat. Ecoroofs also absorb carbon dioxide, cool urban heat islands, filter air pollutants, increase habitat for birds and insects, and provide more greenspace for people. BES began funding grant programs to install ecoroofs on projects such as the Hamilton West Apartments.
Trent Thelen, an associate partner with ZGF Architects, started working with ecoroofs in the early 2000s, about the time BES began monitoring the Hamilton West Apartments as part of what would become a significant body of research and education about the environmental benefits, financial costs and logistical challenges of maintaining ecoroofs. Around the same time, Portland passed more stringent requirements related to stormwater treatment.
"Europe had been doing them for a long time as a form of insulation, and in the U.S. it started to gain a lot of traction because of pollutants in the stormwater," he said. "Some of the early Pearl District buildings got some of the first green roofs in the city and they were hit or miss."
Ironically, one of the biggest challenges associated with ecoroofs is irrigation. Thelen said that while Portland has a reputation for being a rainy city, the summers present consecutive dry months that other cities like Chicago don't face because they have summer rainstorms. Ecoroofs along the East Coast and the southern portion of the country also thrive for this reason.
"That's the one problem I'm seeing here is that we have to figure out how to keep these watered," he said. "They look great from the fall to spring, but if you let it dry out and die during the summer you lose the heat absorption and insulation benefits and it may not come back in the fall so you've also lost your investment."
As ZGF began designing its headquarters in the mixed-use Indigo@12 West building, the conversation centered around how to make a rooftop garden an amenity where residents would gather while also meeting the city's stormwater treatment requirements and addressing the irrigation issue.
"It really became a point of capturing all of the stormwater on the building and collecting it in cisterns after it had been treated so we weren't releasing it back into the system," Thelan said, adding the captured stormwater is then used to irrigate the roof.
Still, ecoroofs carried big upfront costs and, as the Great Recession ground development to a near halt, the city began exploring how to encourage ecoroof construction in ways that were not cost prohibitive. Brian Martin, a designer with Lango Hansen Landscape Architects, noted that the ecoroof boom took off again in 2008 when BES began offering developers incentives to include them in their projects.
"That was a good way to kickstart it and it got a lot of people thinking about ecoroofs again, whether as a financial incentive or as a way to maximize development space," Martin said.
In the decade or so since he began designing ecoroofs, Martin has not only seen a broader acceptance of them among architects and developers but also greater codification of them by public agencies. In addition, suppliers of ecoroof systems and materials are more prevalent and offer ever-evolving products that make installation and maintenance more efficient.
"There is an increased understanding of what ecoroofs can do and how they can look," he said. "It's OK for them to appear differently in different concepts."
BES discontinued the ecoroof incentives program, but carries on in its efforts to encourage low-cost, low-irrigation systems. Portland's early adoption of the ecoroof movement and its recovery from the recession propelled it to become a national leader, and the city now boasts nearly 25 acres of ecoroofs and an extensive tour of signature projects. Among them, Block 4 of the Brewery Blocks, the Ecotrust Building, the Broadway Building, the Native American Student/Community Center, the Multnomah County Building and Beaverton's Clean Water Services building.
Martin's firm is the landscape architect for the Field Office, a two-building development that features 20,000 square feet of rooftop garden space. "Because of the way the building is, a lot of the ecoroof can be seen by the buildings around it and the deck is an amenity for residents," he said, adding it also serves as a habitat bridge for birds and insects migrating from the Willamette River through the Northwest Industrial District to Forest Park.
Greg Haines, owner of Ecoroofs Everywhere, said the city's recent passage of its Central City 2035 Plan, which highlights the value of ecoroofs, means they will go even more mainstream. While he is impressed with the city's larger, more visible ecoroofs, he fondly recalls the first one he did in 2002.
"My heart still loves the Hawthorne Hostel ecoroof. Every step was new for me, and I returned time and time again to test new plants and soil mixes on it. It still amazes me what plants have survived up there after all these years," Haines said.
Thelen pointed out that Seattle now requires ecoroofs to be included in all new development projects. "It would be great if Portland required that, too, but I think people here are already thinking along those lines."