Award-winning architect Renzo Piano, the Renzo Piano Building Workshop and Chong Partners are adding a new kind of Green to the park: a 500 million dollar renovation of the Academy focused on creating one of America’s most environmentally sound structures. Upon its August 2008 grand reopening, the Academy will showcase innovative sustainable design, from the solar-paneled Living Roof to the polished concrete flooring visitors will walk on to tour amazing earth, ocean, and space-themed exhibits.

With the goal of attaining the U.S. Green Building Council’s coveted Platinum LEED certification, and being the largest public space to earn the honor, the California Academy of Sciences engineers and designers created an unprecedented plan for unifying twelve Academy buildings into one incredibly green restoration. Each material selected for project use was carefully considered for its sustainability and environmental friendliness without sacrificing aesthetic impact. The thirty-person architecture team used materials such as recycled steel, lumber harvested from sustainable forests, blue jean insulation, and 180,000 sq/ft of polished concrete flooring.

"[The architectural] mandate to take the most sustainable route in materials made concrete the right fit for us because it essentially takes away the need to use other materials instead of adding," explains architectural team member Jon McNeal. "Renzo was always saying, ‘the palette of the building must be frugal…a happy factory yet a soft machine’," says Jon regarding the design’s intent. He continues, "It is the idea of taking the frugal, necessary material concrete and treating it enough to make it elegant, clean, durable and beautiful… without painting or covering up."  

The architects considered polished concrete as possible flooring for the Academy after touring the San Francisco Federal Building, a structure replete with an excellent rendering of the application by Tennessee-based contractor Perfect Polish. Dave Padgett, co-owner of Perfect Polish, met with Jon McNeal to discuss polished concrete in the pre-specification stage, which allowed polished concrete to be specified in the architectural plans. "We did several samples of concrete for them," related Padgett about the decision process, "the architects wanted a low finish, not shiny, with a matte look."

Perfect Polish completed mock-ups demonstrating the application and won the bid. The plan was to complete the grind and polish on the chosen top-slabbed concrete in three mobilizations over ten months, working on 5,000 to 10,000 sq/ft at a time.  The specified scope of work outlined a 150-grit metal grind followed by 100-grit resin. A semi-penetrating sealant would then be applied, burnished and buffed out. The sealant was key to the finish, Padgett says, because, "it is breathable but will not break the surface bond, so it provides protection while allowing the floor to breathe."

With a ten-man polishing crew scheduled in two shifts seven days a week for 8-10 weeks at a time, the project was completed in the allotted time period, but was not without its set of challenges. "We had a great team," says Jack Bell, site manager for Perfect Polish, "but there definitely were obstacles to overcome."

Dave Padgett attributes the largest problem, scheduling, to the sheer amount of subcontractors working simultaneously to install multiple construction components. " We were working around 300-400 workmen at all times," elaborates Bell, "and the space we needed just wasn’t available." Padgett emphasizes, "This type of situation can definitely cause bad blood if it isn’t worked out," and Padgett and Bell agree prevention is the best solution to the problem. "Make sure the architects and general contractor understand the importance of open spaces to time and money; for example, bidding a 20,000 sq/ft space vs. a 2,000 sq/ft space causes a significant price difference—the value is in being able to do a lot of open floor space at once," says Padgett, "If you can show the architect and general contractor how scheduling can save time and money before the project begins, the problem can be avoided." Since the Perfect Polish team did not have this luxury, they utilized caution tape around their area to reduce foot traffic. "It was still slow-going," says Bell, "but we finished it."

The second considerable challenge was in the flatwork, which is essential to all exposed concrete finishes. "The end result of the polishing process is determined in large part by how well the slab was laid initially," says Padgett. He further explains that the Academy flatwork required additional grinding steps to achieve the look desired by the architect, so the process was changed to include 80-grit and 50-grit metal grinds before the sealant application.

"An additional grind can add up to 60% more time to the process," says Padgett. By adding the grinding step, Perfect Polish created a very satisfactory result despite the initial difficulty. Though the dips and valleys with many high and low spots created by the initial pour led to a difference in the end appearance, McNeal remarks that the Perfect Polish team did a great job with the challenge and that the architects were happy with the selection of polished concrete.

"The install [of polishing] was tricky, and led to long and difficult discussions with the general contractor," explains Jon McNeal. "The builder’s sub[contractor] poured the floor without knowing the fate of the slab; they didn’t know the sensitivity of the finish. The message just wasn’t conveyed." "The solution is communication," Padgett says, stating that a polisher must "help the general contractor understand the importance of choosing the correct concrete installer: one who will pay close attention to the flatness and the finish of the product." He recommends another way to avoid miscommunication, "Test the flatness of the floor and finish one area so there is not any misunderstanding about how the end result will look." Architect Jon McNeal concurs, saying it is key to, "perform mock-ups and make it absolutely clear how sensitive the finish is to exposing aggregates," to the installer.

Upon completion, the California Academy of Sciences will stand as a testament to environmentally-minded construction and architectural conscientiousness. Its integrative design with the surrounding park landscape makes the Academy a natural fit into the sweeping beauty of Golden Gate Park while the designers’ careful use of resources is sure to inspire some of the thirteen million park-goers expected this year. And, whether they realize it or not, visitors to the natural history museum will be walking on polished concrete flooring, one grey design element that supports the Golden Gate Park’s green goals.