Despite sitting squarely in hurricane territory, the island of Kauai has very few buildings made almost entirely from concrete. But in 2003, when architect Dean Sakamoto was asked to complete Vladimir Ossipoff's original master plan for the National Tropical Botanical Garden (NTBG) by designing the Juliet Rice Wichman Botanical Research Center, concrete was the best option. “The building had to be lean [financially], but had to be a 100-year building, and also needed to withstand hurricanes,” says Sakamoto, describing just a few of the structure's requirements. The final design is a two-level structure cut into a hill above the garden—the building's second level is all that is visible from the street.
It was during the construction process, however, that Sakamoto's team learned at least one of the reasons concrete is used so sparingly in the environment: The island has only one ready-mix plant, and only 10 cement trucks that carry 10 cubic yards apiece, meaning that the 320-cubic-yard pour that had to be completed for the building's second-story floor plate required a carefully choreographed train of trucks going back and forth from the site to the plant, hoping that the traffic gods were with them.
Despite the unconventional pour, the concrete helped meet another requirement for the design: earning LEED Gold certification. Committed as a LEED building from the start, the research center is the first green building on the island and was a learning process for the client, the craftspeople, and the architect himself. “I introduced them to LEED,” says Sakamoto. “I hadn't done a LEED building before, but I was a member of the U.S. Green Building Council.”
To maximize the building's sustainable potential, a photovoltaic (PV) array on the roof contributes to the building's energy load. “PV panels are fused to the roof,” says Sakamoto. “The perimeter of the panels has a fringe that is the same material [as the roofing membrane], so the panels were heat-welded to the roof. This avoids points of penetration, and the panels don't act as sails in high winds.”
The PV panels are part of a larger active roof system that allows light penetration into the building through skylights and collects rainwater. The rainwater collects and moves quickly across the TPO roofing membrane and collects in a 25,000 gallon cistern. “The garden has a real issue,” says Sakamoto. “The existing irrigation system doesn't have enough power to push water up the hill. Now, the spigot can be opened, and gravity takes the water to the garden below.”
On the building interior, the architect kept materials to a minimum, including staining the concrete floor with Lithochrome Chemstain from Scofield Systems instead of installing carpet or hardwood. Wherever possible, glass separates the enclosed spaces so that views are maintained and light can enter. The spaces are open, allowing the NTBG to install shelves to hold the 56,000 plant species that constitute the institution's herbarium. A rare-book room on the lower level holds one of the nation's largest collections of antique botany books, the bequest of which sped up the building's timeline. An HVAC system maintains humidity levels throughout, combatting the moist tropical air. “The building is basically hermetically sealed,” Sakamoto jokes.
Sakamoto credits careful planning for keeping the project on track. And on track it was—the idiosyncrasies of using concrete on an island aside, the building was completed two months ahead of schedule and $500,000 under the $11 million total budget.