The 53-story, 1.8-million-sq-ft tower is the world’s largest Passive House office building that also meets WELL Gold and LEED Platinum standards, says the submission. It includes custom energy recovery ventilation, “high performance” doors and windows and “continuous” insulation. Conservation features cut water use by half. A typical Class A building in Boston uses 164% more energy, the team says.

The city’s fourth-tallest building at 691 ft complies with federal height limits with maximized rentable space. Cast-in-place concrete for the primary structure helped boost floor-to-floor heights, adding five more floors than what would have been possible with steel.

Photo courtesy Desimone Consulting Engineering

The building program called for both office and residential floors. To unify incongruous column grids required by this combination, the team engineered a dual-purpose 10,000-ton “sky mat” system—a first in Boston. A steel-framed deck just above a three-story, through-block entry at street level is supported by mega-columns and creates a platform supporting the concrete tower above.

The $1.3-billion project finished at budget and on schedule in more than four years, despite a pause during the COVID-19 pandemic.