Design Green Design Ford's Giant Green Roof Started Ten Years Ago; How Things Have Changed By Lloyd Alter Design Editor University of Toronto Lloyd Alter is Design Editor for Treehugger and teaches Sustainable Design at Ryerson University in Toronto. our editorial process Facebook Facebook Twitter Twitter Lloyd Alter Updated October 11, 2018 Migrated Image Share Twitter Pinterest Email Design Tiny Homes Architecture Interior Design Green Design Urban Design Image Credit: Green Roofs for Healthy Cities It's ten years since the start of construction of the green roof on top of the big River Rouge plant. Kevin described it in TreeHugger in 2004: "The 10.4 acre sedum roof insulates the building, provides a habitat for birds and insects, produces oxygen to offset the factory's carbon dioxide emissions, and purifies rainwater. "Instead of having a chemical-based storm water treatment plant," Ford says, "this system mimics nature." TreeHugger hero Bill McDonough designed it; it was the largest in the world and entered the Guinness book of Records in 2004. It was a very big deal at the time, and won top prize from the Green Roof industry. Phil Patton writes in the New York Times that it wasn't just about going green, but about economic necessity: Thanks largely to runoff from the factory and its parking lots, the river from which the plant takes its name was highly polluted. Ford was faced with a bill estimated at $50 million to build facilities to clean runoff water to meet Environmental Protection Agency standards. Mr. McDonough's approach was not only greener but cheaper, coming in at $15 million versus more than triple that sum for a comparably scaled conventional water-management system, according to McDonough's firm. The project centered on the 10-acre green roof, but also involved devices to slow runoff and absorb rain, thereby allowing so-called wet meadows and shallow, plant-lined ditches to thrive. The roof was necessarily lightweight; there are fifty foot spans underneath. According to Green roofs for Healthy Cities: The growing medium depth is approximately 1" and consists of 7-9 mm of porous stone, sand, and organic material with a total saturated weight of <10 pounds / square feet. This calculation includes a mineral wool fleece material that absorbs rainwater. Roots penetrate this one inch water retention layer. Ten years later, people are pretty blasé about lightweight sedum green roofs; architects like Lisa Rapoport have to twist and tweak to excite. Landscape architects have a wider range of lightweight plants to chose from, such as in this Prefab, Portable Green Roof Installed In Toronto Renzo Piano's Green Museum in San Francisco Green roofs are no longer just on top of buildings, they have become buildings and changed architecture. What a remarkable transformation in just ten years.