In 1992, the United Nations called Mexico City "the most polluted city on the planet." With an estimated 35,000 hospitalizations ascribed to dirty air per year, Mexico City had become “Mexsicko City.” Thus the completion of Berlin-based design studio Elegant Embellishments’ sculptural, bad-air-busting façade across the city’s Manuel Gea Gonzalez Hospital next month cannot come fast enough.
As part of a two-decade-long effort to clean up the megacity, the Erwin Hauer-esque screen covers 2,500 square meters (26,900 square feet) and runs 100 meters (328 feet) long. The façade comprises Elegant Embellishments’ white Prosolve 370e tiles—three-dimensional X- and I-shaped modules that attach to a steel substructure. Each lightweight, thermoformed plastic tile is coated with powdered, photocatalytic, air-scrubbing titanium dioxide (TiO2), a nanomaterial patented by Millennium Chem (now Cristal Global) in 2002.
Elegant Embellishments co-directors Allison Dring and Daniel Schwaag ran with Millennium’s innovation to create sculptural tiles that would not only serve as, well, an elegant embellishment, but also maximize surface area, direct natural light into the building, and slow wind flow to generate turbulence that distributes air pollutants better across the tiles' surface. A smart ornament? Take that, Adolf Loos.
The tiles’ irregular and biomimetic pattern derive from a quasicrystalline, or penrose, grid based on sponges and corals. The forms were drawn first in 2D CAD programs and then modeled in Rhino. Despite their visual complexity, they are assembled using standard directional tiling rules and mounted to a vertical grid. The first prints, created in 2006, were stereolithographs (SLAs) that the studio hand-cast in polyurethane.
Today, Prosolve’s hollow modules are made from an ABS-polycarbonate plastic sheet, vacuum-formed over aluminum tools, then cut and coated by a robotic sprayer with layers of TiO2 and primers that adhere to the plastic substrate. The aluminum tools, Dring says, are “cast from a sand mold and then mill-finished by a five-axis CNC machine while being supported by a series of hydraulic copper tubes that heat or cool the surface to maximize performance.”
With help from the New York office of Buro Happold, the two devised Mega Panels, a clustering system for the tiles to connect using CNC-milled plastic plates. For the 509 Mega Panels used on the hospital façade, Elegant Embellishments generated 500 distinct drawings. Each represents a unique configuration of tiles along with connection points and front and back elevations. They then had to train skilled workers to install them. “The nonrepetitive nature of the project carries through from the initial visual randomness of the elevation drawings to the jigsaw-puzzle-like installation process,” Dring says. “There were surprisingly few problems for such complexity.”
Beyond the impressive geometry of the system is its pollutant-reducing capability. When UV rays excite the electrons in 20-nanometer TiO2 particles—just one gram of particles has a whopping surface area of 500 square meters—in the tiles’ coating, the electrons break down nitrogen oxides and VOCs on contact. The byproducts are water and a small amount of calcium nitrate—a common ingredient in fertilizer—that washes away with the first rain. Due to results from third-party testing of TiO2, Elegant Embellishments estimates that the hospital façade, with its voluptuous armature and generous surface area, should eliminate the equivalent amount of NOx produced by 1,000 vehicles on the Mexico City roads per day. The Prosolve modules themselves can be cleaned with a damp cloth and resprayed in situ when its TiO2 coating begins to wear thin—in about the similar lifetime of exterior paint, Dring says.
Today, Mexico City’s air quality levels have improved to become comparable to those of Los Angeles. Meanwhile, Dring and Schwaag are busy researching material maximization. They suggest that the char made from pyrolytic carbon or hydrothermal carbonization (HTC) processes using biomass, or agricultural waste, could be bound with a polymer to form a material suitable for industrial and open-source processes, such as injection molding or used as filament in 3D printing. The result is a material synthesized from carbon dioxide in the atmosphere. Generating more material would mean “that more carbon is scrubbed from the atmosphere, which inverts the current eco-philosophy of leanness, efficiency, and so on,” Dring says. “We are imagining a material-opulent future.”
Note: This article has been updated since first publication to correct the equivalent number of vehicles whose NOx is eliminated by the hospital façade installation.