Today, the Center for Green Buildings and Cities (CGBC) revealed its recently completed headquarters in a former single-family residence in Cambridge, Massachusetts. The roughly 80-year-old, 4,500-square-foot structure, now dubbed HouseZero, has undergone a deep-energy revamp so that the electricity produced by a small rooftop photovoltaic array (15 kW) will far exceed the center’s day-to-day power needs. In addition to covering operations, over the center’s lifespan, the PVs are expected to offset its embodied carbon—those emissions associated with the fabrication and transport of building materials and the construction process. The project’s aim was to create both a prototype for aggressively energy-efficient retrofits and an infrastructure for research, says Ali Malkawi, the founding director of the CGBC, which is part of the Harvard Graduate School of Design.

In order to transform the typical wood-framed house into an energy-sipping workspace for the CGBC’s 25 staff members, Snøhetta, HouseZero’s architect, devised an overhaul that consists of tightly integrated and primarily passive strategies. Without major modifications to the building’s exterior appearance (it is located in an historic district), the project team improved the air-tightness and insulation level of the envelope, removed partitions to open up the interiors, increased the structure’s thermal mass with the addition of radiant slabs, and replaced the existing windows with automated “smart” ones that open and close depending on weather conditions and interior carbon dioxide levels (occupants also can operate the windows manually). The result is an airy office space that Malkawi says will require no electric illumination during daylight hours, will consume almost no energy for heating or cooling, and will operate with only natural ventilation.