The living roof

California Academy of Sciences Living RoofThe California Academy of Sciences took nearly 10 years to build and cost 500 million dollars. A masterpiece in sustainable architecture, the new Academy blends seamlessly into the park’s natural setting, is filled with hundreds of innovative exhibits and thousands of extraordinary plants and animals.

The California Academy of Sciences is now the largest public Platinum-rated building in the world, and also the world’s greenest museum.

The Academy earned the platinum rating (highest rating possible) for Leadership in Energy and Environmental Design (LEED). This commitment to sustainability extends to all facets of the facility – from the bike racks and rechargeable vehicle stations outside the building to the radiant sub-floor heating inside the building to the energy-generating solar panels on top of the building!

From the basement to the roof, the choices behind each element of construction reflect a commitment to energy efficiency, reducing the carbon footprint and preserving the natural world.

Sustainable initiatives applied in construction include the use of soil as insulation. The six inches of soil substrate on the roof act as natural insulation as well as preventing large amounts of rainwater becoming stormwater. The steep slopes of the roof also act as a natural ventilation system, funnelling cool air into the open air plaza on sunny days. The skylights automatically open to vent hot air from the building.

Solar panels will generate approximately 213,000 kilowatt-hours of energy per year and provide up to 10% of the Academy’s electricity need.

The Academy is installing a radiant heating system in the museum’s floors. Tubes embedded in the concrete floor will carry hot water that warms the floor. The proximity of the heat to the people who need it will reduce the building’s energy need by an estimated 10% annually.

Insulation also keeps buildings warm. The Academy, rather than using typical fiberglass or foam-based insulation, chose to use a type of thick cotton batting made from recycled blue jeans. This material provides an organic alternative to formaldehyde-laden insulation materials. Recycled denim insulation holds more heat and absorbs sound better than spun fiberglass insulation. It is also safer to handle. Even when denim insulation is treated with fire retardants and fungicides to prevent mildew, it is still easier to work with and doesn’t require installers to wear protective clothing or respirators

Some interesting facts:

  • 90% of all demolition materials were recycled
  • 32,000 tons of sand from foundation excavation applied to dune restoration projects in San Francisco
  • 95% of all steel from recycled sources
  • 15% fly ash (a recycled coal by-product), 35% slag in concrete
  • 50% of lumber harvested from sustainable-yield forests
  • 68% of insulation comes from recycled blue jeans
  • 90% of office space will have natural light and ventilation
  • 60,000 photovoltaic cells; 213,000 kilowatt-hours
  • 30% less energy consumption than federal code requirement

By any measure, Renzo Piano stands among the world’s greatest architects. As the jury awarding him the 1998 Pritzker Prize wrote, “Piano achieves a rare melding of art, architecture, and engineering in a truly remarkable synthesis. He celebrates structure in a perfect union of technology and art.”

“I try to get at the fundamental emotion of a site,” says the architect. The roof design “is like lifting up a piece of the park and putting a building under it.”

The Living Roof´s 1.7 million native plants were specially chosen to flourish in Golden Gate Park´s climate. After experimenting with thirty native species, the finalists were all able to self-propagate. These nine species, located inside and outside of the special exhibit, will thrive with little water, resist the salt spray from ocean air, and tolerate wind.

The roof will provide habitat for a wide variety of wildlife. A future project will seek to introduce the endangered San Bruno elfin butterfly and the Bay checkerspot butterfly to this new habitat.

Assembling a 197,000-square-foot rooftop to accommodate a living tapestry of native plant species is challenging enough. Add to that the technical problems posed by the roof’s extreme dips and slopes. How to keep the plants and soil from sliding off? Rana Creek, who worked with Piano to design the roof, developed and patented a solution called the BioTray®. They used 50,000 porous, biodegradable trays made from tree sap and coconut husks as containers for the vegetation. These trays line the rooftop like tile, yet enable the roots to grow and interlock, binding the trays together like patchwork.

The more typical black tar-and-asphalt building rooftop leads to a phenomenon called the “Urban Heat Island” effect. The endless swath of black rooftops and pavement trap heat, causing cities to be 6 to 10 degrees warmer than outlying greenbelt areas. One-sixth of all electricity consumed in the U.S. goes to cool buildings. The Academy’s green rooftop keeps the building’s interior an average of 10 degrees cooler than a standard roof would. The plants also transform carbon dioxide into oxygen, capture rainwater, and reduce energy needs for heating and cooling.

An open-air observation terrace enables visitors to get a close-up look at the roof’s lush canopy of plants. The view encompasses the densest concentration of native wildflowers in San Francisco. The expansive vista is also an ideal location for watching Northern California’s birds, butterflies and insects. Skylights above the larger domes open and close throughout the day, enabling sunlight to reach the exhibits below. The steep slopes of the rooftop’s hills draw cool air into the open piazza at the center of the building. Weather stations on the roof monitor wind, rain, and changes in temperature to help inform the automated passive ventilation systems.

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