The Smithsonian National Museum of African American History and Culture (NMAAHC), scheduled to open to the public tomorrow, is capping off a nearly decade-long highly publicized planning and construction process. The 400,000-square-foot building is notable for securing the last developable site on the National Mall, and will be the nation’s primary home for exhibiting and celebrating African-American achievements in art, history, and culture. While 60 percent of the structure sits below grade, the remaining 40 percent rises 85 feet above grade and is wrapped in an arresting daylight-filtering screen referred to as a corona. The three-tiered, inverted form merges African and American historical references, drawing from Yoruban caryatids and the Washington Monument. The corona’s pattern was developed by digitizing traditional shapes the team found in historic ornate ironwork from Charleston and New Orleans.
The project is the result of a collaboration among Adjaye Associates, who functioned as the lead designer, Freelon Group (now Perkins+Will), who covered the interior design scope above grade, Davis Brody Bond, who covered the interior design scope below grade, and SmithGroupJJR, who was responsible for the entire enclosure of the building from the foundations to the roof, and from curb to curb.[interstitial]
With four architects and numerous consultant teams on board, the NMAAHC’s design process was fast and highly collaborative. The client and representatives of each of the firms attended workshops and presentations at project milestones. Work on the facade design process proceeded with a smaller team coordinated by Adjaye Associates, who held regular meetings at its New York City office. For federally funded projects, three initial concepts must be presented before narrowing down to one final scheme. Only 14 months was allotted for the time between a final concept submissions to the delivery of bid documents.
Areta Pawlynsky, partner at Heintges & Associates, the consulting firm for facade engineering, said this timeframe was pressing, but ultimately benefitted the project: “This was incredibly demanding, but in a way, easier to keep the momentum going to work through all of these design decisions.” Throughout this process, Pawlynsky said, adhering to the competition-winning design vision was what drove the design development process. “The most challenging part of the project was making sure the facades remained true to the competition.” She continued, “When we look back at the competition entry images and the verbal description, we are very proud the building’s envelope was able to remain true throughout its development. That doesn’t always happen.”
With full height atriums on each of the museum’s four sides, the exterior envelope was conceptualized as an “inside-out” assembly, providing clear spans of glass to the interior. Guy Nordenson & Associates developed the primary structural system—a series of three horizontal trusses that wrap the building, giving the facade its signature tiered form. Construction detailing of the envelope was carried out through a design assist package awarded to a joint venture between Enclos and Northstar, who developed a cost-saving strategy to integrate vertical trusses within the curtain wall assembly. Heintges & Associates then engineered and developed technical options for systems that attached to this structure, including the screen panels and unitized glass panels.
Adjaye Associates’ decorative screen pattern was digitally manipulated—scaling up and down to produce four densities ranging from 65 to 95 percent opacity in response to key views of the surrounding monuments, and to solar orientation. Selective openings in the corona screen provide “lenses” looking outward to key views of the Washington Monument, Lincoln Memorial, Jefferson Memorial, White House, and U.S. Capitol.
The material selection process for the corona screen began with solid cast bronze, which was deemed too heavy with a variation that—over time—would cause undesirable performative and maintenance issues. The design team settled on a cast aluminum due to the material’s track record as a reliable cladding. A unique five-coat application of PVDF produced variation and depth to the bronze coloration of the panels.
The corona screen was assembled on-site from shop-fabricated steel plate carrier frames containing 13 cast aluminum panels each. A staggered paneling running across the facade required selective panels to be installed in the field. These “stitch panels” bridge the gaps between adjacent carrier frames, helping to conceal any visual clues to the pre-fabricated frame assembly.
The design team consulted with Fisher Marantz Stone on a subtle lighting scheme to incorporate backlit panels that bounce light off frit glazed walls to produce a glowing facade at night. These details and lighting effects were scrutinized through numerous design studies and mockups, and by regulatory agencies to ensure the lighting of monuments at night would remain balanced.
Hal Davis, senior vice president at SmithGroupJJR, said the building envelope design was “quite unusual.” Asked if there were any technical challenges associated with designing a curtainwall system with an inside-out weather line, Davis replied, “of course!” He explained that an off-the-shelf-system couldn’t simply be installed backward: “It’s a different approach and it did take quite a bit of effort. We worked with Enclos and Heinges and David Adjaye to get it right and to make sure we were going to maintain the integrity of the design, the tightness and the insulation quality of the system, preventing condensation. For this, we had to develop very subtle heating elements that would eliminate moisture.”
Pawlynsky concluded, “I think the real story of success here is the collaboration, including the contractors, Enclos and Northstar, and CM Clark. There was a strong commitment to executing this facade in the appropriate way, and it extended across the board.”