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.
#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.
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.
#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.”
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.”
#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.
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.”
#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.”
#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.