A bespoke aluminum building skin transforms an abandoned war bunker into a high-performing boutique hotel.Restoration hotelier Unlisted Collection recently acquired a historically listed, vacant municipal building in London’s East End that served as a set favorite for film luminaries like David Lynch. The 1910 Edwardian fore building and its utilitarian 1937 addition had served as the town hall of Bethnal Green before World War II. In order to convert the complex into a boutique hotel, Unlisted hired London-based architecture practice Rare and tasked the firm with designing an addition to the existing buildings to add space for more guest rooms and amenities, while unifying the three disparate elements into a single entity. Rare directors and founders Nathalie Rozencwajg and Michel da Costa Gonçalves answered this last charge with an ornamental screen facade that visually ties together the historic and modern buildings while also improving user comfort and environmental performance. “The yellow brick facade of the 1937 building wasn’t finished due to the outbreak of the Second World War, when it was repurposed as a bunker,” Rozencwajg recently told AN. Since the building had suffered no major damage during the war, the designers had to move forward while abiding by the English heritage guidelines for preserving historical structures, including the decorative Eduardian facade along the street front. To expand square footage and enable the building’s function as a hotel, the team designed a fourth-level add-on for additional guest rooms. The addition is enclosed in a double-glazed curtain wall that is screened by a parametrically designed ornamental skin. Working in a custom-scripted plugin for Rhino, the team designed a pattern for the screen wall derived from an old ventilation grill that they found in the 1937 extension. In developing the pattern, the designers divided the project into three major zones. The uppermost level functions as a brise soleil with a tightly defined pattern that blocks most of the southern sunlight that impacts this part of the building. Toward the center, the pattern is varied, more open in some places and more closed in others to accommodate interior programming—guest rooms feature smaller apertures for greater privacy while the public spaces are clad in a more open screen. At the bottom level, apertures are kept small to provide privacy from street-level passersby. Approximately 980 feet of the building’s surface is wrapped in this screen, fabricated from laser-cut, 4-mm-thick aluminum sheets. Eight 7-by-4-foot panels in varying pattern densities are bolted into a frame that hangs from the curtain wall. At the roof level, the panels were designed to conceal the building’s elevator towers, plenum, and pitched roof profiles. Rozencwajg estimated that unique panel shapes make up 30 percent of the screen system. Each panel was numbered for efficient installation and bolts in each of the panels’ four corners prevent damage from wind and other environmental factors. The modularity of the panel system also provides for future design flexibility. “If you rearrange the space internally and want to reconfigure the facade, you can change out the panels for more or less opacity,” said Rozencwajg. The panels are finished with a metallic powdercoat that changes hue based on the sun’s angle. Since the historical listing prohibited the architects from altering the existing building—including the old sash windows—the new curtain wall had to improve overall building performance. The south elevation features double glazing to minimize heat gain and natural ventilation is enhanced with trickle vents and energy-efficient windows on the new level. The combined efforts resulted in a BREAM rating of Very Good.