The goal of this renovation and addition to a residential townhouse in SoHo, New York, was to rethink how a building could actively contribute to a more sustainable urban future. By keeping and converting the existing building with a modest footprint of only 19 x 40 feet, and only adding an extension onto the building we transformed it into an 8-story townhouse for 1 family, wrapped by a spacious lattice envelope that functions as a climatic skin, a “third building”. The spatial and performative properties of the highly recognizable building envelope serve as an adaptable perimeter of the building. Made from lightweight steel frame and folding panels, this climate skin can be opened and closed with ease, thus dramatically extending the building’s volume towards the exterior with an array of variable, semi-enclosed spaces. The innovative, smart folding envelope modulates solar exposure to passively regulate internal temperatures, resulting in a total annual energy savings of up to 45%.