Image courtesy of Millennium Partners

An 11-month installation of the triple-glazed curtain wall is underway at the 1.4 million-square-foot Winthrop Center skyscraper as Millennium Partners develops the world’s largest Passive House-designed office building in Boston’s Financial District.

The 691-foot-tall office-and-residential tower at 115 Federal St. is designed with a tight building envelope expected to reduce energy usage by 65 percent compared with the Boston average and ventilation systems that infuse fresh air to reduce viral transmission rates. Energy recovery units will recirculate fresh air into the building through hospital-grade filtration systems, developers said.

The tower which broke ground in 2019 will contain 812,000 square feet of office space and 321 residences.

Completion of the curtain wall is scheduled for May 2022.

“Delivering building energy performance at this level, and on this scale, has never been done before in the United States,” Handel Architects Partner Blake Middleton said in a statement. The ambitious nature of this project is even more evident when you consider its unique combination of Passive-House energy-performance criteria with a focus on occupant health.”