Green roofs and walls, firmly planted in geotextiles, are a growing market.
By Frank Edgerton Martin
Jeffrey Bruce, FASLA, recalls that when he first came to Kansas City, Mo., from New Jersey as a young landscape architect, he drove out west into Kansas to see the plains. As the sun was setting, the immensity of this open land spreading out like a giant sheet around him became so compelling that he stopped the car. “I stood on the hood for several hours and just watched the sun set,” he remembers.
Twenty years later, Jeffrey L. Bruce & Company is a pioneer in the engineering and design of green roofs and new applications for geotextiles. Working with soil scientists, architects and manufacturers, Bruce is a uniquely entrepreneurial landscape architect who not only seeks to bring the beauty of prairie flowers into city roofs, but also to invent new soil mixes and applications for existing products that will make green walls and roofs more practical in the building process.
“We hear a lot more about the landscape above the ground than below it,” Bruce says while addressing a group of water engineers in Kansas City. “Yet below the surface is where the majority of organisms live that support plant life…and green roof systems.” By speaking to engineers accustomed to piping runoff water into treatment plants, Bruce directly confronts assumptions about how to manage water in cities. “We can’t build green cities just by using less,” he says to the group. “We need to harness the power of nature to actually restore our rainwater, air and groundwater.” The idea is that landscape architecture can move to the next stage of green design by building environments, roof systems and entire watersheds that heal themselves from the effects of human demands.
The promise of green roofs for urban climates
Considering the fact that roofs cover 30% of the surface of American cities, roof gardens are one practical way to begin this embrace of restorative ecological function. The strategy of planting roofs can significantly reduce stormwater runoff and save billions of dollars in the cost of storm sewers. Facts like these get the engineers’ attention. They also merit further investigation by the industrial fabrics industry whose members can provide new materials and structural systems to support the soil profiles of green roofs and the rapidly emerging field of green walls.
The implication for designers and green industries is to think of cities as opportunities for urban agriculture and a return of cleansing vegetation. Bruce’s message to the engineers and to the well-known architects he consults is that we can never return our cities and suburbs to their fully “natural” structure. But we can learn to think of air and water as connected living systems. They are connected; they are alive.
For example, traditional civil engineering processes isolate and compact soil to build on it, but Bruce promotes a different view of soils as living communities that nourish plant growth and can detain and cleanse water to be reused on-site. Green roof systems are three-dimensional structures in which geotextiles play an essential role in separating functional layers in a “soil profile” or “soil system.” Yet, there are also constraints in the weight and depth that green roof systems add to the top of buildings.
Water is a key to keeping a landscape in hot urban setting alive. But water, if not drained properly, can add significant weight to green roofs and lead to leakage. How water moves through sand and gravel layers is key to detaining and discharging water effectively. Varying sizes of gravel can be used as layers filled with small air pockets that can retain water for slow release to support plant life. Like fine cooking, the solution lies in finding the right mix of ingredients and layers—an area where Bruce’s office carefully collects data and experiments. Geotextiles are key as a soil separator to hold these essential storage layers in place.
“We seek to capture as much rainwater on any given site—whether from roofs, hard surfaces or the soil systems,” explains David Stokes, one of Bruce’s staff landscape architects. “We’re trying to use every drop of water that falls out of the sky without releasing it to the city storm sewer system.” To further reduce environmental impact, “we do a lot of research on fabrics that are recycled or have postconsumer content,” Stokes adds.
Applied research and wholistic thinking
Generally, making a green roof investment can be challenging for builders and owners who are tempted to look first at the short-term bottom line. Yet, retaining water on-site can have significant benefits for reduced irrigation and infrastructure costs, savings that Bruce’s office continues to measure in their projects over time.
Bruce is unusual among landscape architects in that he invests time and money to perform such research. He also partners with manufacturers and soil scientists to develop and test new products. Like a true inventor, he transfers technology and solutions from one market area to another. Indeed, Bruce became a leader in green roof design because he had been working with soil systems for years in professional and collegiate sports—a high-performance design specialty where success requires sophisticated soil engineering.
Bruce’s team applies this 20-year expertise in soil design and drainage to green roofs at such landmarks as Chicago’s new Millennium Park and Soldier Field. Now Bruce’s office is applying its findings from 10 years of green roof work to other harsh city conditions that demand high-performance soils such as improved street tree planting strategies and low-demand irrigation solutions for city parks. Typical of its holistic approach, Bruce’s office doesn’t use the term “irrigation” so much anymore. Rather they speak of “water resource management.” “We hybridize solutions across practice areas,” Bruce says; and in doing so, they find new applications for erosion and water control fabrics.
Technology and products for restorative design
In the near future, Bruce’s design and applied research team is exploring three emerging technologies—nanotechnology, genetic engineering and sustainability—converging in the construction industry to create advanced composite building materials and systems. These materials will not just incorporate living ecologies as surface applications, but the building materials themselves will be restorative for air and water quality in their surroundings. Future building materials will harness and incorporate the self-healing efficiencies of natural systems as already seen in such promising advances as algae colonies that manufacture biodiesel fuels or serve as the basis for self-healing living paints.
One area where the fabric industry can contribute is in developing geotextile wall systems for holding plantings in place against buildings or as stand-alone structures. (See the profile of the green wall at the Vancouver Aquarium in this issue.) Currently, most wall systems involve some type of metal structure and trays for plantings. But given the varieties and durability of existing geotextiles and cabling systems, it’s possible that lighter and less expensive product groups can be developed.
In cities where horizontal space is at a premium, yet vertical walls are everywhere, planting upward can offer significant cooling and aesthetic benefits along sidewalks, near building entries and around transit stops. Bruce’s message for would-be “green builders” and the industrial fabrics industry is simple: landscapes can be more than aesthetic. We can learn from nature to develop green building systems and landscapes that serve as engines for the long-term health of the environment—and our own.