Hawaii is known for its commitment to sustainable energy, agriculture, and building practices. So it’s no surprise that this year’s Sustainable Design Award goes to Keauhou Lane, a six-story mixed-use precast concrete building in Honolulu that is home to restaurants, retail, and affordable residential units.
“This project represents the first LEED-certified affordable rental mixed-use project delivered in the state of Hawaii,” says Phil Camp, principal of hi•arch•y llp, the Honolulu-based architect. This project is special because it proves that green buildings can be accomplished with limited resources.
From the start, the project faced serious budget constraints that were exacerbated by rising labor prices in the market, Camp says. His team looked at several material options to meet the budget requirements, and the estimating analysis showed precast concrete delivered a significant savings over other approaches. “Precast was able to offer a stable product that was fairly insulated from the chaotic swings we were seeing in other deliverable structural systems,” he says. “The bulk of the deliverable product could be single-sourced from a reputable supplier who utilized in-house labor and was willing to work with the team to hold budgetary estimates through design until a firm contract was locked down.” Using precast concrete also shaved months off the erection time and allowed rough-in and finishes to commence sooner than any of the other options available.
Despite the many cost-saving benefits of precast concrete, the project faced ongoing financial challenges. Early in the design process, the team went through a round of value engineering where the schematic design was stripped of many key features, and some worried whether the project would ever be completed. However, through close collaborations with GPRM Prestress, Camp’s team was able to gain new efficiencies through the use of repetitive shear panels and by maximizing the use of hollow-core slabs to span three separate units. In doing so, the unit count and the construction efficiency increased, which benefitted the development and reduced construction costs, he says. “Without the savings that were ultimately realized through the design team’s collaboration with the precast team, the project might not have made it beyond design.”
The precaster and designers also worked together to develop a hybrid precast concrete double tee with lowered outwings on the flanges, which could structurally engage the double-loaded corridors while providing increased headroom and space for mechanicals and piping. “We created a brand-new shape to meet the requirements of the project,” says Les Kempers, vice president of GPRM in Kapolei, Hawaii. The new design, dubbed the “low-winged double tee,” allowed utility and waste stack penetrations to occur through the flanges, saving significant time and expense.
To help ease the disappointment over losing many of the architectural attributes due to budget constraints, GPRM created a series of triangular fin walls in critical locations, which allowed the precast concrete interior walls to protrude to the exterior of the building and replicate the aluminum fins that had previously been valued-out of the project. “It was a game-changer from a design standpoint,” Kempers says. “It kept the budget in check while providing a desired design feature, which made the designers and the owners happy.” Precast concrete erection was completed on March 28, 2017, and the grand opening occurred in late November 2017.
While the project team had originally planned to pursue LEED gold certification, thanks to the extensive collaboration between the designer, contractor, and precast concrete producer, they exceeded their sustainability goals and are now pursuing LEED platinum—the highest rating for these structures. “The use of precast concrete for this project, which was all locally sourced and fabricated within a short drive from the jobsite, helped the team to pursue LEED platinum,” Camp says. It will also help the team secure points for innovative design, environmentally preferable products, off-site fabrication, and construction waste reduction.
Camp argues that this is more than just a LEED success story. It is proof that LEED can be done on a budget. “It represents a new standard in being able to deliver a product that is both affordable and sustainable, which is something every community sorely needs."