The building was designed to the Passive House standard. The certification target shifted during the project, but the performance bar it set never moved, and every system stayed engineered to it. On a tower this slender, holding that standard is harder than it sounds. The hardest system to place was the ERV. An Energy Recovery Ventilation system brings in continuous fresh air while recovering heat and moisture from the exhaust, which makes it central to a high-performance envelope. It needs straight vertical duct chases, and in this building every square inch of floor plan was already spoken for. The apartment layouts also kept moving, with brokers weighing in on the plans well after the mechanical design was underway.