In 2008, Rana Creek Living Architecture won GRHC’s Extensive Institutional Awards of Excellence for the incredible 2.5 acre green roof on top of Renzo Piano’s masterpiece, the LEED Platinum California Academy of Sciences in San Francisco. The undulating roof mimics the four hills of San Francisco, and the gabion basket walkways are like the roads that cross this landscape, oblivious to the steep grades as anyone who has visited San Francisco knows. The green roof growing media is six inches deep and designed to hold more than 70% of the rainwater that falls upon it. The remaining runoff is collected in cisterns and reused later for roof irrigation. The roof cools the ambient air temperature, allowing refreshed air to fall into the building through one of the many circular skylights on the hills and down by the glass ceiling in the middle section.
Nine species of native plants were initially planted, which provided impressive displays of color during the early years. The green roof used biodegradable, coconut coir manufactured trays, impregnated with microrrhizal fungi to facilitate their break down over time. The green roof is part of the living laboratory which is the Academy, with tens of thousands of visitors riding the elevator up to have an intimate view of the roof. So how is the roof performing, more than ten years into its life span?I had the unique opportunity to visit it alongside its designer, Paul Kephart and a number of students who were taking the GRP training course in the fall of 2016.
Paul shares with me his initial frustration over the limited plant pallette, “We tested dozens of species and the decision was made to severally limit them”, he said. “I was quite upset until Renzo took me aside and told me not to worry, because the roof was like a canvass that the Academy would be painting for some time.” The first thing I notice when we arrive on the roof is the diversity of plants. As predicted, the Academy has actively been introducing a wide variety of species of plants to the roof, which now number more than 75 native species, including some rare and/or endangered species such as the California Pipe Vine which supports the California Pipe Vine Swallowtail butterfly. The Academy is hoping to providing a breeding grounds for the Pipe Vine swallowtail. Many of these plants have come to the roof from natural processes like seed dispersal wind and birds. A full plant species list is available from the Academy Web site: https://goo.gl/CKk5o4