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Greener Green Roofs by Christian Werthmann The sedum roofs of today symbolize performance-oriented green roof design. Like fine-tuned engines, they run on leaner artificial substrates with almost no organic matter; volcanic rock or expanded shale, baked at 2000 degrees Fahrenheit (1093 degrees Celsius), make the substrates lighter and soil depths as thin as possible. They seem to be race cars in the fleet of green roofs — maximum performance paired with minimum weight. The simple soil mixtures and roof sections of the early days of green roofs developed into multilayered complex systems supporting the homogenous surface of succulents. The unkempt and rough gave way to the groomed and cultivated, reminiscent of the unrelenting beauty of agricultural fields. Grown Up? The modern sedum roofs do not seem to belong to the generation of environmental activists that tried to change the world thirty years ago; they instead belong to a technically savvy society, which cultivates high-tech products like performance fleece, PowerBars and carbon-fiber bicycles. The current technical focus stands in contrast to the 1970s "Back to Nature" mandate that was necessary to spearhead the movement, but had to be overcome for it to enter mainstream architecture. Today, modern green roof technology is far removed from any eco-romance or political ideology. Roofs for Biodiversity The proliferation of sedum carpets is not unanimously approved. Its critics point out that the mandatory implementation of green roofs in Europe has led to low-cost and low-quality sedum roofs with reduced ecological and environmental performance capacities. >>> Discuss this article in the Architecture Forum... This article is excerpted from Green Roof—A Case Study: Michael Van Valkenburgh Associates' Design for the Headquarters of the American Society of Landscape Architects by Christian Werthmann, copyright © 2007, with permission of the publisher, Princeton Architectural Press.
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