When we first heard of green roofs, they sounded like a great idea but one that would have a hard time gaining traction.
One of the great successes of green building, there are more than 10,000 green roofs in the US today.
Back in 2003, when there were just 50 green roofs in the US, Ford Motor Company became the host of the largest in the world. Sited on top of its Michigan River Rouge truck factory, it was viewed as a pioneering strategy for brownfield redevelopment, corporate citizenship, and environmental regeneration.
This month marks its 10 year anniversary, and it remains the largest living roof in North America at 10.4 acres.
Designed by preeminent green architects William McDonough + Partners, it is composed of drought resistant species of sedum, known for attracting beneficial insects, birds and butterflies.
"It sustains a dynamic ecosystem of over 35 insect, spider, and bird species and 11 plant species. Within five days of the living roof being installed, local killdeer had nested and laid eggs in the sedum," says Bill McDonough.
Intended to last twice as long as a conventional roof, it's doing far better than that. All the original plant species have survived largely on rainwater, without having to be replaced. Besides supporting a diverse ecosystem, the biomass removes carbon from the atmosphere and reduces energy use at the Ford assembly plant. It also is part of a storm water management system that reduces run-off and costs two-thirds less than a conventional treatment process.
McDonough + Partners describes it this way:
As Ford made plans to expand the manufacturing facility at the Rouge, they were faced with an estimated $50 million to cleanup toxic storm water. It was flowing across a vast area of impervious surfaces into the Rouge River - the EPA demanded it be cleaned up to meet water quality regulations.
Ford hired William McDonough + Partners to develop a master plan that integrated storm water management into the landscape. The result was a 10-acre green roof on top of the 1.1 million square foot truck manufacturing plant. It is the heart of a system of wet meadow gardens, porous paving, hedgerows and bioswales that attenuates, cleanses, and conveys storm water across the site.
Hedgerows lined with swales provide infiltration for rainwater, block the cold winter winds, and frame views of the awe-inspiring coke ovens and blast furnaces, juxtaposing the natural and the industrial and making the presence of these structures more keenly felt from the public areas of the site.
By relying on a landscape-based infrastructure requiring minimum use of pipes, the storm water system cost $15 million, less than a third of conventional practices, catapulting the green roof industry forward. The Green Roof business is growing rapidly, expected to reach a $7 billion market by 2017.
Green roofs are found all over the US today, from the top of the Empire State Building to Walmart stores, at universities and even at airports.