Winthrop Center’s passive house office space will recirculate heated air within an unusually tight building envelope for what developers hope will be dramatic energy savings. Image courtesy of Steelblue.

Developer Millennium Partners didn’t anticipate a renewed debate in Congress over carbon taxes as it started designing its $1.35 billion Winthrop Center tower in downtown Boston. 

But the potential to reduce the 691-foot skyscraper’s energy consumption by up to 80 percent compared with a conventionally designed building is starting to look more prescient. 

“We don’t do new buildings very often,” said Joseph Larkin, a principal with Millennium Partners. “We concentrate on one at a time. So, we challenged our team to design a building that’s cutting edge for an extended period of time, hopefully owned by us for generations. How does it stay that way?” 

Enter Handel Architects and consultant John Fernandez, an MIT architecture professor. They recommended a technique that’s gained a cult following in residential projects but has a limited track record in large commercial buildings: passive house design. Pioneered in Germany, passive house calls for tightly sealed building envelopes that moderate fluctuations in temperature. 

Tower Will Dwarf Other ‘Passive’ Projects 

A handful of passive house commercial projects have been built in Europe, and Chicago architects Solomon Cordwell Buenz are working with developer Mark Goodman & Assoc. on what would be the largest yet built in the U.S.: a 268,000-square-foot office building expected to break ground this year in the city’s West Loop. 

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Millennium’s Winthrop Center would dwarf that project, with 750,000 square feet of office space on the lower floors sitting below more than 400 luxury condominiums. 

“We knew coming in that the building had high aspirations,” Fernandez said. “This will be a model of commercial office space in this country and really, globally.” 

Millennium Partners’ Winthrop Center tower will offer office tenants the ability to configure double-height sections within its 38,000-square-foot floor plates. Image courtesy of MP Boston | Steelblue

Millennium Partners says the passive house designs drove up the cost of Winthrop Center by 15 percent. 

Energy recovery ventilators located on a mechanical transfer floor between the office space and condos will recirculate the offices’ interior air, lowering the cost of heat and cooling. 

“When you seal up a building so tightly, you have no choice but to deliver more volume of air into a building,” said Blake Middleton, a partner at Handel Architects. “That preserves a good portion of the heat energy of the building and returns it back. It lowers the cost of heating and cooling the outside fresh air that you’re bringing into this super-insulated volume of space.” 

Winthrop Center’s carbon footprint is expected to be monitored through a proprietary app that will be offered to building tenants, part of a broader effort by the development team to spotlight the property’s sustainability bona fides. It’s also expected to be a selling point to potential office tenants that are eager to trumpet their companies’ commitment to the environment. 

The city sold the 1-acre former parking garage property to Millennium for $102 million last year, with additional payments potentially bringing the total price to $163 million depending upon the final condo sales. 

Uncertain Office Market in Three Years 

As corporate America migrates back to downtown offices in thriving metro areas, tower developers have racked up a series of recent mega-leases in Boston, several of them well ahead of completion. 

Steve Adams

HYM Investment Group is set to begin construction of its 1-million-square-foot One Congress office tower as soon as May, following State Street Corp.’s signing of a 510,000-square-foot lease in January. The deal sets the stage for the simultaneous construction of two towers larger than 1 million square feet in downtown Boston for the first time since the 1970s, according to research by Perry Brokerage Assoc. And three office leases topping 400,000 square feet have been signed in the last five months, a local record according to Perry research. 

But with completion of the Winthrop Center tower still three years away, and the current economic recovery going into extra innings, Millennium executives acknowledge they may need the additional distinction of a groundbreaking design to gain an edge on competitors. 

“We challenged these guys to tell us what we should build,” Larkin said. “Our responsibility is to pay for it, and they turned around and did this work.”