Materials for Sustainable Sites

By Meg Calkins
John Wiley & Sons, 2008, 464 pp., $80 hardcover

Finding effective materials that are also environmentally benign is becoming an important task for designers, builders, and developers. This hefty new book by an adviser to the LEED (Leadership in Energy and Environmental Design) program should help make selection of the right substances easier.
In 464 densely packed pages of text, charts, tables, photos, and drawings, Meg Calkins of the College of Architecture and Planning at Ball State University explains how to evaluate the materials and methods available to today’s construction industry. She looks at the performance, efficiency, and environmental and human health effects of concrete, brick, asphalt, stone, aggregates, wood, metals, plastics, rubber, earthen, and biobased materials.
The range of subjects covered in the book is enormous, but I’ll focus this review mainly on a topic that’s recently attracted considerable interest among new urbanists: permeable pavement. Calkins reports that conventional paving — the concrete and asphalt that municipalities and developers have used for decades — generates approximately two-thirds of the storm water runoff that urban areas have to cope with. This runoff routinely overburdens sewer systems, which in turn sends pollution into lakes, streams, and harbors. Porous pavement is substantially better for the environment. It can be obtained in either concrete or asphalt.
The key to porous concrete is that it contains a uniform size of aggregate, which creates spaces large enough for water to flow through. Despite these spaces, the pavement is strong; it can support loads of 2,000 pounds per square inch — or even more if the slab and subbase are thickened. In porous asphalt, the aggregate in a 2- to 7-inch-thick surface course is made up 14 to 18 percent of air voids that water can pass through. The base or “reservoir” course also contains aggregates of a consistent size to let the water gradually seep into the ground and to prevent this lower layer from becoming clogged. A filter fabric layer beneath the reservoir course further prevents clogging.

Technical but clear
Much of the technology discussed in this book is complicated, as you might expect, but Calkins makes complex matters understandable even for nonexperts. In each section that I sampled, I came away pleased by how much Calkins was able to convey, and how clearly. She put the cost of porous asphalt into perspective by noting that the material can cost about the same as, or less than, standard asphalt paving if the cost evaluation includes the “entire system.” In other words, the paving may cost extra, but the premium can be offset by savings on storm water management facilities. (This being so, perhaps sewer and pollution control authorities should offer developers financial incentives to use permeable pavement.) Permeable asphalt offers other benefits as well: It reduces the “heat island” effect. Infiltration of water through the pavement fosters healthier trees in urban settings and minimizes ice formation.
    It’s encouraging to see that some of the sustainable methods evaluated by Calkins are being incorporated into new urbanist developments. The New Columbia HOPE VI project in Portland, Oregon, for example, has “skinny streets” — their driving lanes separated by a strip of porous unit pavers. The High Point HOPE VI project in Seattle contains Washington’s first porous concrete street; the reservoir beneath six inches of concrete lets water make its way to an adjacent bioswale.
Many topics of interest to environmentally conscious people as well as to members of the building and development industry are addressed here. Among them: the overall efficiency of brick masonry and concrete. “Sixty years ago there were thousands of brick manufacturers with nearly 3,000 brick plants in operation,” she notes. “Now there are 83 manufacturers operating 204 plants.” Today’s bricks consequently travel farther — not good for the environment — but consolidation of the industry into larger, better-capitalized companies has, Calkins says, spurred “energy-efficient production processes and pollution controls.”
Calkins says that according to some sources, exposed exterior concrete structures and pavement typically last for only half the 30- to 40-year design life they’re projected to have. She examines the reasons for concrete’s failures, and points out how designers can maximize the material’s environmental performance.
    Materials for Sustainable Sites is an instructive and frequently enlightening book. It deserves a place on the new urbanist bookshelf right next to Doug Farr’s Sustainable Urbanism, issued in 2007 by the same publisher.