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Green—The New Black
Out of the Dark and into the Green, Everything’s Coming Up Sedums
By Arden Miller, CZM
What do New York City's Rockefeller Center, the Ford Motor Plant in Dearborn, Michigan, and Boston's Four Season's Hotel have in common? While all well-known institutions, their raisons d'etre vary greatly. In Boston, the elegant five-star Four Seasons Hotel is renown for their elaborate high tea service and the rumored celebrity sightings (Mick Jagger! Meryl Streep!), while in the Midwest, the Ford Motor Company's 1,200 acre plant is one of the largest car, truck, and sports utility vehicle manufacturers in the world. And Rockefeller Center is synonymous with New York City's annual internationally broadcast tree lighting ceremony. But despite these vastly different associations, these landmark institutions share one surface area that is the same: green roofs.
Just Add Plants
What are these green roofs, and where did the idea of planting things atop a building spring from? Simply put, a green roof is created when a traditional rooftop is sealed with a protective waterproof membrane, and then a drainage layer, a minimum of two inches of soil, and plants are added, resulting in a rooftop that is covered in—among other things—green. (For specific details, and types of green roofs, see "WOW—That's Intense!".) As for the second part of the question, according to legend, their roots, pardon the pun, go as far back as 600 B.C. with the fabled hanging gardens of Babylon. Considered to be one of the Seven Wonders of the World, the rooftop trees and hanging vines that allegedly graced the famed Mesopotamian palace were created by King Nebuchadrezar to cheer up his foreign-born wife, Amyitis, who missed the greenery of her homeland. These precursors to today's green roofs were made by filling the hollowed out areas on top of terraces with soil and planting trees and vines. Fast forward to more than 2,000 years later and 4,000 miles away where resourceful Icelanders started using sod as insulation for both their roofs and walls in the mid-1800s. To this day, a number of these sod-covered buildings live on (and you thought vinyl siding was long lasting!). Some, such as the still functioning "sod church" in Vidimyri, Iceland, have even become popular tourist attractions.
From Beer Gardens to Roof Gardens
Green roofs have been dotting the European landscape since the late 1960s. But nowhere have green roofs caught on faster—or become more common place—than in Germany. Once upon a time, few vacations to Germany were complete without a trip to one of their world renown beer gardens. But today, roof gardens are a far more common site. In the 10 years between 1989 and 1999, German roofing companies installed nearly 350 million square feet of green roofs. And today, it's estimated that Germans have somewhere between 800 million and one billion square feet of green roofs1-to put it in a New England perspective, that's the equivalent of 3,300-4,250 Fenway Parks (including the stands!).
In Deutschland, they feel so strongly about the benefits of dachbegrunungs—that's green roofs to us—that in some cities, such as Hamburg, more than 90 percent of all commercial and residential rooftops are green, and in other cities, such as Studgarden, all new buildings are required to use green roof technology. A driving force behind these requirements is the demonstrated ability of green roofs to retain stormwater after a rainfall; rather than having countless gallons of water flooding the sewage system, or picking up toxins that get washed into rivers and streams (and, when the geography dictates, can ultimately end up in the ocean), the rain is absorbed on rooftops where, even after an intense storm, only a small portion of it ends up as runoff. To defray the costs of treating water that is not collected by a green roof, and to encourage businesses and individuals to replace traditional black asphalt rooftops with green ones, some German cities levy a "rain tax" on non-greened tops.
Black v. Green
Meanwhile, on this side of the Atlantic, there has been no talk of a rain tax, but green roofs are appealing to more and more people for a variety of reasons. Rick Mattila of Genzyme in Cambridge, Massachusetts, explains their decision to have an extensive green roof installed: "We can see the Charles River right from our building, and we know that 75 percent of the pollution in the Charles comes from stormwater runoff. This is something we can do to help the environment we live in." Mike Maloney of Maloney Morris Associates has been installing green roofs around New England since 1998. "Every year since I've been in the business, more people have become interested—the word is definitely spreading. From an ecological standpoint, they reduce stormwater runoff and also help with the urban heat island effect," Maloney explains. (For an explanation of the urban heat island affect, please see, "It's Getting Hot Out Here!".)
For others, going green is an aesthetic or business decision. Matt Carr is a member of the American Society of Landscape Architects, and has worked for Hydrotech, a leading green roof installer in the United States for 15 years and, during that time, has been involved in the scoping of more than 250 green roof projects. "A lot of people are interested in having a green roof because it's a fifth architectural dimension and can give buildings a unique look; it's something special and different. Others just want to know 'When will I see the return on my investment?'" To answer that last question, a series of things need to be taken into account—building size, average outside temperature, type of heating and cooling systems, and internal settings commonly used—and there is no precise answer. (It is estimated that a green roof can cut cooling costs by 20 to 30 percent.) But one thing is clear: having a green roof reduces costs on both the heating and cooling fronts. When it heats up outside, your traditional blacktop roof absorbs the heat, making air conditioner units put in for overtime when temperatures soar. Conversely, having the extra insulation on the outside—not unlike the sod-covered buildings the Icelanders created 200 years ago—helps keep heat in when temperatures dip. "Most buildings will realize a 33 percent savings in heating and cooling costs after a green roof is installed. In energy cost savings alone, they should pay for themselves in six or seven years. If that isn't enough reason to want one, consider this: the average black asphalt roof requires replacing every 10 to 15 years," Carr adds. While green roof technology is still a relatively new concept, the Rockefeller Center's intensive green roof—in place since the mid-1930s—is still holding up, and the German rooftops that have been in place since the 1970s have never needed replacing.
But What About the Cost?
And Do We Have to Hire a Gardner?
Initial expenditures—on average, a green roof will cost anywhere from $10-75 dollars/square foot to install, which is about twice the cost of a traditional blacktop roof—are a prohibitive consideration for some. And then there's the question of maintenance. Who wants to weed and prune the rooftop? It is possible, even preferable from an environmental perspective, to have a rooftop installed that requires very little to no maintenance. The plants most commonly used are sedums, which are in the cactus family and naturally require very little by way of water and nutrients to survive, and can withstand high winds, drought, storms, and intense sun. "Most rooftops require some initial attention; during the first year, as they are growing in, you'll want to make sure that the plants are taking and sprouting where you want them to. And, if there is a drought, of course you have to give them some water," Carr explains.
Still not convinced? There are a number of reasons to embrace the green side. Besides energy cost savings, stormwater runoff reduction, rooftop longevity, and aesthetics, some other reasons to consider the vegetative topping include:
Regardless of motivation, businesses, individuals, and municipalities all over the United States are installing green roofs. City Halls in Atlanta, Chicago, Portland, and Seattle all have green rooftops. (Interesting side note: the rooftop of Chicago's City Hall is planted with 400 different species of plants and flowers, all native to Illinois, and the project won the 2002 American Society of Landscape Architects Professional Merit Award.) Boston's City Hall has undergone a greening too; their 8th and 9th floor terraces are part of a green roof demonstration garden, inspired by the May 2005 Green Roof Conference held in Boston. Across the United States, university campuses—including Harvard, Carnegie-Melon, Massachusetts Institute of Technology, University of Georgia, North Carolina-Chapel Hill, Pennsylvania State, and Michigan State—all have green rooftops on at least one of their buildings. (On some campuses, such as Michigan State and Carnegie Melon, researchers are carefully monitoring plant life and water retention to add to the growing body of research on the topic, and at the University of Pennsylvania, Professor David Beattie, a long-time advocate of green roofs, teaches a course on the topic and has an outdoor area devoted to their study that is affectionately called "Beattieville.") A number of commercial buildings have gone green, too. In Connecticut, Foxwoods Casino—the largest resort casino in the world—has an extensive intensive green roof, while on the West Coast, headquarters for The GAP outside of San Francisco have been teaming with green since 2001. Lincoln Center in New York City, the largest performing arts center in the world, is pushing the green envelope artistically with their plans for a sloping green roof that will be open to the public as part of a multi-million dollar "Avenue of the Arts" renovation project. In Pittsburgh, Pennsylvania, the Heinz 57 Center (yes, the ketchup people!) provide employees with 12,000 square feet of roof meadow and flowering perennials to ponder while thinking up their next condiment campaign. And, closer to home, IKEA, (the Swedish furniture and home accessory giant best known by some as Jerry's furniture store of choice on Seinfeld), supports 37,000 square feet of green atop its environmentally friendly Stoughton store.
LEED By Example
The Deerfield Academy, a college prepatory school in Deerfield, Massachusetts, plans to make the most of their green roof. The project is expected to be complete in spring of 2006, at which time the students will begin monitoring the types of sedum used for school credit. And, while the students are getting credit for their research, the school will be getting credit for having the roof installed. For developers and builders, using energy-saving techniques such as green roofs can qualify them for Leadership in Energy and Environmental Design (LEED) certification, which leads directly to financial savings through tax credits, and has the added cache of being lauded as an environmentally friendly entity.
Everything's Coming Up Roses...
If rooftops imitate life, they'll never be a bed of roses. But beds of colorful sedums, ferns, native plants, and trees are in our foreseeable future. "More and more people are interested in marrying the ecological and technological benefits with the pretty designs," observes Matt Carr. "As we look to ways to conserve our resources and take care of what we have, green roofs are going to become even more popular. And if you don't care about that stuff, well, they just look good." As the seeds spread, be on the lookout for green. It's the new black.
1 Is That a Garden On Your Roof?, Newsweek, August 5, 2005