The MIRA residential tower in San Francisco reimagines the classic bay window, a common feature in old city housing, creating a technically advanced, twisted facade that provides abundant daylight and views to each apartment.
Designed by the project architect Studio Gang, with Perry Architects Inc. and Barcelon Jang Architecture as associate architects, the innovative use of bays in the design allows for an efficient exterior, maintaining nearly 180-degree views while meeting stringent energy standards with features such as a variable refrigerant flow (VRF) cooling system, and Leadership in Energy and Environmental Design (LEED) gold certification through graywater harvesting, high-performance glass windows, green roofs, and energy-efficient fixtures.
The tower’s structure includes 10 different bay configurations within an isosceles triangle on the floor plan, each consisting of 4.27 m (14 ft) wide, and 1.83 m (6 ft) and 152.4 mm (6 in) deep, bays, made from 0.12-in-(3-mm)-thick aluminum sheets. These bays rotate every 10 levels and are equipped with balconies on some levels, totaling 1,091 units.
The design incorporates 3D aluminum spandrel panels anchored to the concrete floor slab to cover its edge, with stiffeners to resist wind forces and accommodate different bay configurations.
To address structural challenges, a seismic system with flexible joints was developed in collaboration with Heintges, ensuring the building’s resilience. Windows act as self-supporting elements, and the spandrel panels transfer loads efficiently. A robust central core allows exterior components to move independently during seismic events, enhancing structural stability.
The tower’s unique bay geometries posed a challenge for window cleaning, leading to the creation of a specialized building maintenance unit (BMU) system. This system, developed in partnership with the engineering consultant, C.S. Caulkins Inc., and facade consultant, Sky Rider Equipment Inc., includes a custom platform and intermittent stabilization anchors integrated into the facade panels, facilitating effective window cleaning in the building’s distinctive design.
