A pair of gleaming glass-clad towers, Amazon’s second headquarters are not only reshaping the Arlington skyline, but also generously contributing to the neighborhood with its open-to-the-public ground-floor lobbies and adjacent Metropolitan Park renovation and expansion.
As the world’s largest LEED® Platinum-certified complex, the dog-friendly 22-story Harmon and Merlin towers will house 14,000 Amazonians working in e-commerce, cloud computing, digital streaming and artificial intelligence.
The two crystalline high-rises are clad with Vitro Solarban® 72 Starphire® glass curtainwall, selected for its high performance and clarity. “The low iron makeup makes it extremely clear without the green tint common in high-iron glazing,” explains Brian Earle, AIA, principal, ZGF Architects, Arlington, Virginia.
The curtainwall modules are 13-ft. by 5-ft., with approximately 7 ft., 6-in.-tall vision panel and an approximately 5 ½-ft.-tall spandrel section. “This common chassis was customized into a variety of wall-types that break down the buildings’ perceived mass,” he says.
Between the two buildings, 3,008 custom single-hung operable Solarban® 72 Starphire® glass windows, developed in partnership with Harmon and Wausau, incorporate an integrated bug screen that retracts down into the sill when the window is closed. In addition, a large, 35-ft.-tall picture window with a 2-in.-thick acoustical layup fronts the Large Event Center.
Solarban® 72 Starphire® glass delivers exceptional clarity and superior solar control performance, allowing 68 percent of the visible light to pass through while blocking 72 percent of the sun’s solar rays.
To shade the towers and bounce light deep into the interior from the curtain wall, the building form is sculpted with deep setbacks and perforated copper-colored fins are attached to scalloped light louvres on the west-facing amenity zones. Where site constraints required deeper floorplates on the lower levels, skylights were added.
The podium cladding is charcoal-colored terracotta, referencing the site’s historic use as a brickyard. The Merlin building is decorated with metal fins with a color-shifting pearlescent coating and the Jasper tower features iridescent, dichroic glass that changes colors as the sun rises and sets.
To meet Metropolitan Park’s aggressive performance goals, which included energy savings 24 percent below the ASHRAE baseline, the glazing played a key role.
“The vision panel which spans from 30 in. to 120 in. above the finished floor, is optimized to provide ample daylight throughout the work areas,” says Earle.
At the top 2 in. of the panel is an integral light shelf directing daylighting up to 50 ft. into the building’s interior, providing daylight autonomy for 88% of the occupied areas. Integrated photometric controls adjust the electrical lighting accordingly, driving down lighting loads.
The lighting louvers were engineered with roller shades and sightlines to eliminate glare. “This ensures that even when the shades are drawn for privacy, ample light still makes its way deep into the space,” adds Earle.
For areas of the façade with less exposure to daylighting, spandrels were installed above and below the vision panel. Positioning the spandrel glass over the shadowbox allows for more insulation within the assembly. To minimize the visual impact of and enhance the buildings’ vertical expression, ZGF selected custom gray color which allows the spandrels to blend seamlessly with the vision panels.
With the building sited near the Potomac River, a major bird migratory corridor, the architectural team took this into account with the facade design. Overall, a combination of terracotta, metal and glass fins lend more visibility to the birds. For the building’s lower levels which face the park, an additional frit from Walker Glass was added.
Walker’s AviProtek® E pattern 216 is a bird friendly glass solution with acid-etched visual markers on the exterior surface of the glass and Solarban® 72 solar control, low-e coating by Vitro on surface two. In addition to being visible to passing birds, the acid etch is impervious to UV exposure, wind, dirt and weathering, and lends enhanced durability and maintenance.
The highly sustainable, all electric buildings are powered with 100 percent renewable energy from an off-site solar array, uses 50 percent less water than the code requires and incorporates biophilic design principles to enhance occupant well-being. The towers were designed with 19 rooftop terraces, eight of which can be occupied.
One of these areas, the farm terrace was set up for Amazon employees to grow herbs and vegetables to be donated to community organizations. More than a dozen local, small businesses offer goods and services in 50,000 square feet of retail space and the 2 1/2-acre public park is enjoyed by the public.
Project Credits:
Developer: JBG Smith
Architect: ZGF Architects
Glass Frabricators: Oldcastle BuildingEnvelope® (Wright City, MO) & Cristacurva
Glazing Contractor: Harmon Inc.
General Contractor: Clark Construction Group Inc.
17.06.2024, Vitro Architectural Glass
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