When the Jean Vollum Natural Capital Center (commonly known as the Ecotrust building) opened in 2001, it quickly became known as a landmark of sustainable design. The brick and stucco warehouse, initially built in 1895 as the McCracken Warehouse, was the first historic redevelopment in the United States to receive a gold-level LEED (Leadership in Energy and Environmental Design) designation from the US Green Building Council.
With a rehab designed by Holst Architecture, Ecotrust also quickly became a center for Portland's sustainable design community, with the city's Office of Sustainable Development headquartered there as well as progressive retailers like Patagonia.
Besides its other sustainable features, Ecotrust also was also pioneering in the use of its green roof, with plantings covering more than half of the building's roof in order to reduce stormwater runoff and provide extra insulation.
But as it happens, Ecotrust's green roof had problems - not more than any other green roof of its generation, but lacking some of the key elements that have come to comprise healthy green roofs since it was originally constructed. "It was installed at a time of burgeoning knowledge but lack of experience," says John Crumrine of Enviroscapes Northwest, the company that created the new green roof. In other words, the Ecotrust roof never malfunctioned, but new technology and understanding of how to make them work means that it was time for it to be replaced.
This of course begs the question: If Ecotrust is a symbol of sustainability, how sustainable is it to re-do a green roof less than a decade after it was put in? But then again, one wants the green roof to function as well as possible, and some lessons have to be learned the hard way, through trial and error.
The main difference between the old green roof and the new one is its built-in drainage and filtration system, but it also has separate layers between rock and soil, something the lack of also caused problems in the old system (seen in accumulated pools of water).
The roof only supports about 14 pounds per square foot and the soil is only a few inches deep, which limits the type of plantings that can go there. Enviroscapes selected a sedum plant with fleshy leaves but, crucially for a green roof, doesn't leave behind any flammable debris. One can actually plant sedum by simply tossing handfuls of it onto the soil - it actually digs its own roots without being embedded in the dirt.
The average cost of a green roof, Crumrine says, is about $11-13 per square foot. The City of Portland provided about $5 per square foot in tax breaks, or about a 40 percent reduction in cost.
As for the benefits of this new roof, like any, Crumrine says the primary one is it will extend the life of the roof membrane by about 2 to 3 times because it's not exposed to UV radiation or extremes of hot and cold. This is also a highly visible roof, on a building associated with advanced thinking in sustainable design and construction, not to mention a popular destination for people to hang out or even have weddings. So it matters that the greenery is sprouting.