A 2,400-square-foot triplex penthouse residence is a world apart from New York’s notoriously cramped housing stock. But even rarefied living quarters have to contend with the city’s tight lots and dense urban fabric, which often eat up light and air. Just ask New York’s Turett Collaborative Architects (TCA), which worked with its client, a Manhattan-based businessman, to craft an inviting two-bedroom, three-bathroom apartment that maximized daylight from its northern and southern exposures, despite being closed in by an adjacent school and apartment tower.

A conventional master bath, isolated from the main living spaces, would obstruct natural light and decrease square footage, explains project manager James Saisakorn. Instead, TCA designed a vitrine-like 122-square-foot washroom, glassed in on three sides and cantilevered over the kitchen below. While TCA aimed to preserve daylight in the space, it needed an elegant solution for a potential privacy problem. With the flip of a switch, users can toggle the bathroom’s glass walls between opaque and transparent by activating a low-level electric current that runs between the panes. “It was an opportunity for us to create this dichotomy between public and private,” says Saisakorn.