We can easily call this the green era of architecture, but for many, the descriptor owes itself more to a philosophy and less to the color. Living architecture and associations such as Green Roofs for Healthy Cities (GRHC) are changing that by painting our cities with increasingly complex plant ecologies. Although vegetated roofs and walls vary from project to project and city to city, and though they are not one but many things, serving different objectives, meeting dissimilar expectations, and answering varied practical realities—including, simply, what can grow where—as experts and advocates explain, five new trends make the case for a strong and vibrant future.
Trend #1 in Action: Philadelphia Parks Program
Since April 2012, the City of Philadelphia has been in partnership with the EPA
to intercept rainwater at its source, effectively channeling one million gallons of
runoff per acre into the ground by using storm-water bump-out planters, trench trees, porous pavement, wetlands, rain gardens, cisterns, residential rain barrels, and green roofs. The EPA will provide $2 billion to Philly over 25 years—an amount, the city says, that is less than what it would cost to construct traditional “gray” infrastructure. Most of the money will be used to convert select streets, parking lots, schools, and other public spaces into planted landscapes.
New park spaces are geographically distributed to ensure even water absorption. But new parks in all parts of town, some as small as a quarter acre, answer another important need for 200,000 residents who otherwise didn’t have recreational spaces within a 10-minute walk of their homes. The slated 500 acres of new landscaped parks will add jobs, reduce crime, improve human health, and remove 1.5 billion pounds of carbon dioxide over the next 40 years.
#1 Green Beats ‘Gray’
The best thing about traditional storm-water infrastructure is that it’s familiar and everyone knows how to install it, but that’s where the benefits end. People are realizing that green infrastructure, such as bioswales and vegetated roofs, can add more benefit per dollar than a pipe in the ground.
Philadelphia mayor Michael Nutter. Photo: Mitchell Leff
Just ask Philadelphia mayor Michael Nutter. “Philadelphia was the first city in the country to provide safe, clean drinking water to all of its residents in the early 1800s,” he says. “Using green infrastructure on a large scale is an extension of that innovative legacy and makes sense on a number of levels.”
In 2009, Philadelphia, which is the nation’s fifth largest city based on population, declared that it plans to be the greenest city in every respect: municipal energy use (down five percent in 2012 from 2009), recycling rates (tripled), bike lanes (428 miles), and conversion of unused land to parks (100 acres and counting). The parks effort was the beginning of an ambitious plan undertaken by the city’s water department, which entails the conversion of impervious surfaces, such as paved recreation areas and abandoned lots, into neighborhood parks that absorb rain in situ instead of having it run off the flat surfaces and into wastewater treatment.
Regardless of where rain falls, an inch of storm water on a single acre of impervious asphalt, concrete, or rooftop sends 27,000 gallons of water into the city’s aging sewage and storm-water treatment system. With such large storm-water demands in a densely developed city, Nutter says that the water department had two options: it could continue to build new, larger underground infrastructure, or it could promote a mix of green storm-water solutions that would provide a number of benefits for every dollar invested.
Nutter sees his city’s efforts as a public-private endeavor. “Because storm-water management needs to happen on public and private property,” he says, “it makes sense for the city to incentivize residents and business owners to use innovative storm-water management measures like green roofs, storm-water planters, and tree trenches on their own land.” To accomplish this, the city offers a tax credit to private property owners worth 25 percent of green roof installation costs up to $100,000, and actual growing plants must occupy at least 50 percent of the total rooftop to qualify for the incentive. Other major cities that provide green roof incentives via tax reductions, grants, and expedited permitting include Boston, Chicago, Los Angeles, New York, Portland, San Francisco, Seattle, Toronto, Vancouver, and Washington, DC.
But the sustainable benefits for the city don’t end with a reduced load on the water treatment system. “Philadelphia reduces the heat-island effect and becomes a greener city with cleaner air and better water quality,” Nutter says.
Trend #2 in Action: VanDusen Botanical Garden Visitor Centre
If a green roof goes brown, has it failed? The VanDusen Botanical Garden Visitor Centre in Vancouver, British Columbia, endured the record drought of 2012, during which the area received a mere six millimeters of water over five months, and the lush fescues installed in 2011 went into dormancy. “We had to educate maintenance crews and the public that this was the natural course,” says Ken Larsson of Sharp & Diamond, the landscape architect for the 19,000-square-foot structure, which appears from the outside with its undulating roof to be half building and half landscape and is applying for LEED Platinum and Living Building Challenge certification. “Fortunately, all growth returned with vigor by the 2013 growing season,” Larsson notes, proof that superficial aesthetics can be a false measure of green roof success.
#2 Understanding Performance, Quantifying Value
Green roofs have been trending for a while now, and the question is shifting from, “Should we install one?” to “How well will it perform?” That answer isn’t simple, but Green Roofs for Healthy Cities, a nonprofit industry association, is looking to make that research easier to conduct and find.
David Yocca, a landscape architect and planner and board member at GRHC, has a simple way of describing why green roofs should not be installed on faith alone. “In architecture, we attach metrics to everything,” Yocca says. “We should be able to measure water retention, energy savings, a reduced heat island effect, and a healthier environment overall.”
Spotlight DeVry University Chicago
Vegetal i.D. installed more than 10,000 square feet of its Hydropack green roof system at the new Chicago campus of DeVry University. The green roof is part of how the school hopes to achieve a LEED Silver certification, as it simultaneously complies with Chicago’s mandates to reduce heat island effects from large buildings. Candace Goodwin, campus president, explains that energy management—30 percent use reduction—is an overall goal of the board of directors and the school’s sustainability studies academic leaders. The green roof and surrounding landscape serve as a working model for future bricks-and-mortar campuses of the distributed university system.
Also a principal with Conservation Design Forum in Elmhurst, Illinois, Yocca is heavily involved in the development of the Living Architecture Performance Tool (LAPT), a green-roof certification effort being led by GRHC. Yocca says the program, modeled after the processes used in LEED and SITES, should be fully operational by 2015 and will include measures of environmental benefits and construction and maintenance practices for green roofs, walls, and other living architecture systems.
The LAPT will advance green roofs beyond practical concerns (making a roof that doesn’t leak) and aesthetic ones (it’s prettier than a rubber membrane) and some vague promise of environmental benefits. Performance measures can translate into justifying expenditures and boosting real estate values, Yocca says. The proposed national EPA storm-water rule-making for new and redeveloped buildings and sites might make green roof performance a very meaningful number, and ultimately the LAPT will help stimulate the industry. Yocca says that the tool will bring a “larger percentage of roofs, greater square footage of those roofs, an accelerated pace in the performance characteristics and attributes, and foster more research.”
Yocca also cautions that national standards have to account for regional differences such as rainfall patterns, temperature ranges, and growth zones. “These are living systems, so first we must ensure there is no plant failure,” he says.
Companies like Vegetal i.D. are integral to ensuring that plants thrive and water runoff is reduced. Like its French parent, Le Prieuré, Vegetal’s products include the Hydropack (for roofs) and Vertipack (for walls) that are pre-planted, install-as-is interlocking trays that make it easy for just about anyone to start a green roof or living wall. Although its US product and development manager, Gaelle Berges, cautions that performance varies from building to building, the company has 10 years of rain-runoff data and R-value numbers from past installations to use as a guide.
Echoing Yocca’s comments, Berges notes that in most climates the benefits accrue from heat resistance, thanks to plant evapotranspiration and growing media thermal mass. “Green roofs are so new to the US,” Berges says. “As the market evolves, more data need to be collected.”
Trend #3 in Action: Transbay Transit Center
If there is anything currently under construction that better evokes long-ago images of a faraway future, San Francisco’s Transbay Transit Center is it. A four-level structure with a street running through it, the Transbay Center will be the connecting point of 11 transportation systems from throughout the state of California. Some are calling it the Grand Central Station of the West.
Rana Creek, the center’s environmental planner, worked with building architect Pelli Clark Pelli to crown the bowed-glass structure with a 5.4-acre rooftop park that will provide welcome green space in a densely populated, heavily trafficked section of the city. Perched atop this bustling crossroads will be a new constructed wetland.
“When we began designing this, a lot of the ideas were fairly new,” Rana Creek’s Paul Kephart says. “We wanted an organic, biological system to recycle water and waste while we provided a human environment.” Municipal codes and regulations, however, lacked the vehicle for assessing and approving the design, but the LEED process and amenable agencies have gotten past that hurdle.
The original plan was to receive greywater from surrounding buildings as well as the center, but after testing, the team found it
wasn’t feasible. However, thermal regulation, water recycling, and reduced potable water benefits will be significant, and 50- to 75-foot redwoods, willows, alders, and wetland plants provide habitat for pollinators, dragonflies, migratory birds, peregrine falcons, and, of course, office workers.
#3 Integrating Complex Ecosystems
With more green roofs comes more knowledge of the best ways to make them a part of the building systems required for them to function. Some of the largest green roofs and walls are being built to accomplish extensive goals and concurrently inspire all who have the good fortune to live among, work in, or visit these installations.
Facebook will have a 433,555-square-foot, Frank Gehry-designed addition to its existing headquarters in Menlo Park, California, with what’s described as a rooftop park of intensive landscaping. The Ford truck assembly plant in Dearborn, Michigan, is topped with more than 10 acres of sedum. Chicago outdid its own circa-2001 city hall green roof with Millennium Park, a 24.5-acre intensive green roof that was completed in 2004 and which few visitors know to be a roof at all.
Rana Creek founder Paul Kephart
The living architecture department of Rana Creek, an environmental design firm in Monterey, California, has undertaken numerous large, complex projects in urban and rural environments, including eco-resort Monterey Bay Shores, the Gap Inc. headquarters near San Francisco, Croton Water Treatment Plant in New York City, and the Transbay Transit Center in San Francisco.
What distinguishes many of these projects is their multifunctional nature. “Building rooftop ecologies is a thrilling exploration of how to integrate architecture, engineering, and art,” says Rana Creek founder Paul Kephart, who describes his work as that of an ecologist where water, habitat, and flora function as part of the structure and surrounding environment.
“I see things from a functional and process standpoint, organic in nature,” Kephart says. He began his work on the Transbay Center by looking at the city of San Francisco, pre-building, where creeks historically coursed their way through the city. Informed by that, he and his team designed a rooftop park that minimizes use of potable water in landscaping and attenuates the storm-water runoff from the site, which is complicated in a region characterized by dry summers and wet shoulder seasons. “Architecture has to evolve with seasonality,” Kephart says.
Yet water, plant growth, and animals do not respect property lines, and with birds, trees, skyscrapers (casting shade and reflective light), non-green neighbors, vehicular traffic, and human populations, are complex interactions manageable? “When you break down the parts it becomes simple,” Kephart says. “When you see the relationships it tends to become more efficient. Working with nature can teach us a lot about building.”
Trend #4 in Action: Barclays Center Plaza
The Barclays Center Plaza at Atlantic Yards is the new home of the NBA’s Brooklyn Nets and the NHL’s New York Islanders. Straddled above a major passenger rail hub, the green-roofed arena entrance ushers in visitors by way of a sloping, succulent-covered entry corridor. The facility has no dedicated parking. Instead, city planners want New Yorkers to travel by way of the eleven train lines that lead there.
American Hydrotech was commissioned to install the 11,000 square feet of extensive plant covering on the undulating landscape. “This was a design challenge,” says Nate Griswold. “Given the 53-degree slope in some spots, we had to work closely with the architects and engineers.”
The roof covering was planted in fall 2012, just weeks before Hurricane Sandy blew through. Shockingly, it remained intact. It has since been maintained according to strict specifications provided by Hydrotech to those in charge of building maintenance. On this project, they are assured that an appropriate budget has been allocated to keep the plants thriving, come what may, and they check in occasionally to see for themselves. Photo: Bruce Damonte
#4 Prioritizing Maintenance
It’s easy to install a green roof and then sit back and wait for the benefits, but like all plants, these systems need to be nurtured in order to thrive. “All roofs are microclimates,” explains Dennis Yanez, national marketing manager for American Hydrotech, a Chicago-based waterproofing and roofing products company that has developed an expertise in vegetated roofs. “In urban environments, sun and shade studies reveal what needs to be taken into account in the selection of plants.” Hydrotech has worked on green roofs in Chicago, Boston, Seattle, Denver, Salt Lake City, and San Francisco. Large installations all, each do their best to comply with LEED rules that favor native plants and minimal maintenance.
But is that misguided? “It’s a myth in the industry that a green roof should be able to exist without maintenance, including watering,” says Nate Griswold, senior garden roof technical sales coordinator for Hydrotech. “We should think of it in terms of minimal to maximum care.” Griswold also contributed to GRHC’s “Design Guidelines and Maintenance Manual for Green Roofs in the Semi-Arid and Arid West” and several training programs.
Griswold and Yanez provide examples in which a low- or no-maintenance philosophy does not fit neatly with the realities of living plants in sometimes harsh rooftop environments. They’ve seen situations where the full budget was spent on the installation, but a subsequent plant die-off resulted from a failure to irrigate during the first two years necessary to establish a root system. Or, when construction is completed at the wrong time of year for planting to the leasing agent’s displeasure. Even allowing for a two-year irrigation program, invasive plant species require ongoing removal. And, the species considered native to the region, as specified to earn LEED points, might not necessarily fit the specific wind and sun conditions of a high-rise roof.
Although LEED has been remarkably successful at promoting green building design, materials, and practices, it nonetheless receives criticism on certain points. Among them is failing to account for regional climatic conditions, such as awarding the same points for water conservation in Vermont as it does in Nevada. Such an approach can be severely problematic for green roofs, which are dependent on plant performance to be successful and provide benefits in specific climates. “With the first vegetated roofs we were primarily concerned that there wouldn’t be leaks,” Griswold says. “We’ve now advanced to where we can focus on the specific realities of each project. We investigate more variables and then design the program that best meets the need.”
Trend #5 in Action: Higher Ground Farm
John Stoddard and Courtney Hennessey combined their environmental science educations with passionate interests in food sustainability to found Higher Ground Farm, which grew its first crops in Boston in 2013. They previously worked with CSAs and consulted on community gardening, local and sustainable food-sourcing for restaurants, crop planning, and commercial-scale farming.
When they identified a location and willing landlord at the Boston Design Center for their rooftop farm concept, they decided to go big and source maximum financing. They were able to raise the approximately half-million dollars necessary to establish an extensive growing medium and first-year plantings for the 38,000-square-foot installation. The landlord showed immediate interest. “They saw community and public relations benefits,” Stoddard says. Boston, along with a handful of other cities, incentivizes building owners to install green roofs through various property tax breaks.
Boston’s climate runs a little cooler with temperatures above 70 degrees only in June through September, which illustrates how even a temperate climate can accommodate rooftop farming. The air is a little cleaner up there as well. One researcher studying car exhaust particulates found only a tenth as much exhaust at six stories up than at the street level, where people live and urban gardens are more likely found.
#5 Rooftops Mean Revenue
A building’s rooftop can be covered with a green roof for any number of reasons: provide an outdoor gathering place for building users, mitigate urban heat island effect, publicity—none of which are a direct revenue stream for a building owner. With the abundance of urban food deserts and other “locavore” challenges, developers and others are realizing a profitable solution has existed under (or far above) their noses all along—rooftop farms.
It wasn’t until 2010 that the first large-scale rooftop farm, Brooklyn Grange, was created in Long Island, New York, with a second location in Brooklyn, using a combination of private equity, loans, fundraising, and crowdfunding, such as with a Kickstarter campaign. The entrepreneurial farmers sell produce and organic flowers to New York restaurants and members of their community supported agriculture (CSA) program.
John Stoddard and Courtney Hennessey are building a similar rooftop farm on the Boston Design Center. As with other such programs, these are designed to be profit-making ventures. And why not? Distribution costs are minimized, there is no processing required, and most roofs get the full day’s pass of the sun, free of shade. Building owners who host a rooftop farm are now renting out what was previously just utility space. With sky-high agriculture, owners gain the thermal-regulating qualities of soil and plant material that reduce summer heat by 65 degrees versus a black roof, a roof that lasts 50 to 70 years instead of the typical 20 to 30, and a new stream of rental income.
Buildings that host a roof farm must structurally be able to support between 15 and 84 pounds per square foot, sometimes more for intensive crops that require deep soil, and the rooftop farmers must install several protective layers to ensure protection from root damage to the membrane.
Stoddard explains that the location over the Boston Design Center, which has 87 showrooms catering to the home furniture and furnishings trade, was both a matter of physical appropriateness, and it offers a potential market of CSA customers from building workers. As green roofs in general grow in acceptance, rooftop farms become a positive building amenity that is attractive to prospective tenants.
