Designing Winthrop Center, the World's Largest Passive House Commercial Building

Date Published November 06, 2023
Category Sustainable Design, Urban Design
Boston Public Library Reading Room

The distinguishing characteristics of great cities are the civic-scaled spaces that become iconic over time, retaining their essential grandeur and capable of renewing over time with every new generation.

They may be plazas, cathedrals or train stations. They may also be grand rooms, of such shape or quality that they remain lodged in our memories: the Galleria in Milan, the Grand Palais in Paris, or closer to home, the Reading Room of the Boston Public Library, Faneuil Hall, or Trinity Church in Copley Square. They become integral to the image of a city.

The most significant public feature of Winthrop Center is The Connector: a distinctive gathering place active through all seasons and a focal point for activity from morning into the evening.

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It is a new urban room of shape and size, intended to be inherently civic in scale and function.

It is a public connector, a signature space, where an iconic folded ceiling plane visually connects the plaza to the large, multi-function space at the east end. The elemental materials of stone, metal, terrazzo and wood are intended to convey simplicity and a robust permanence, adaptable to different activities inside.

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At either end, as The Connector opens to Winthrop Square and Federal Street, 50 foot tall monumental structural glass walls enhance the continuity of the public realm.

A mezzanine with a bar and restaurant wraps the volume and hanging “meeting pods” above provide overlooks across the space. Similar to great streets, the markets, cafes, restaurants, office lobby, and other programs open directly onto and flank the main spine of the space, further energizing the pedestrian realm.

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The High Rise Skyline

The distinguishing features of Boston’s high-rise skyline have remained relatively unchanged over the past 30 years.

At the western end, the truncated “High Spine” of the Back Bay has been dominated by the Prudential and Hancock Buildings, recognizable fixtures on the skyline. Downtown, the Financial District has been dominated by relatively blocky and undistinguished office buildings, clustered from Beacon Hill to the waterfront. This has begun to change with several impressive projects such as Millennium Tower, whose dramatic form pinpoints Downtown Crossing.

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Winthrop Center gives new definition and vitality to this important urban space.

Nearly 700 feet tall, this building is a synthesis of form: a complex, angular podium base resolving into a taut, symmetrical tower, emerging from within a neighborhood of bulkier office structures and articulated at its crown with a distinctive transition of layered facade geometry. The shape and form creates a new visual pinnacle in the heart of the Financial District and on the city skyline.

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The architectural DNA of the heart of the Financial District around Winthrop and Post Office Square was firmly established in the early 20th century, with a cluster of distinguished Art Deco-era buildings.

It is from this tradition of modernism – with an emphasis on vertical expression coupled with artful detailing – that we drew inspiration for a language of new high-rise expression on this downtown site, harnessed in the service of 21st century high-performance building technology.

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Batterymarch Bldg
Batterymarch Building
Mixed Use Diagram

Building Uses

Winthrop Center is a hybrid mixed-use residential building.

This kind of hybrid building – with its complex and diverse functions – when artfully assembled, has the power to drive significant pedestrian activity on the street through all hours of the day. The public functions of The Connector (retail, restaurants, events) couple with the office spaces, which in turn couple with the residents living in the building, to create a critical mass of activity on the streets and squares in this neighborhood.

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The building is organized as a traditional “tower on a podium.”

The tower, composed of residential apartments, is lozenge-shaped and oriented along the north-south axis. The podium, containing retail, restaurants, and office space, is dramatically punctuated by a major public space linking Federal Street to Winthrop Square, forming The Connector. Straddling The Connector is a mid-rise wing of the office. This eastern tower volume stands apart from the primary tower and establishes the building’s presence on Federal Street.

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Flanking either side of The Connector are retail and a bar, and restaurant uses on the first two levels.

The third level features a set of “floating pod” event rooms that appear to hover within the main volume of The Connector. The office lobby is part of the public realm, accessed through The Connector. The residential lobby is located at the base of the tower at the north corner. Service and parking ramps are discretely situated at the north and south edges of the site.

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Each office floor includes an outdoor terrace and the capacity for a double-height common space, promoting a healthier and more uplifting workplace.

Both the office tenants and the residents have extensive amenity areas for exercise, relaxation, and socialization, promoting communities of health and wellness

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The high-performance enclosure of the building is conceived as an articulated glass skin dissolving at its crown into a set of deeply etched planes, creating a lively, ever-changing pleated surface of light, shadow and refractions.

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At the podium, this language adapts to express a pattern of solidity made necessary by the insulated Passive House envelope.

In each bay, a fritted, opaque glass panel begins as a sharp density of earth-toned color at the peak which dissolves into a soft transition at the valley. The composition is intended to complement the limestone, light masonry, and warm bronze detailing of the neighboring Art Deco buildings. The glassy, pleated motif is contrasted at the East office wing with a dense pattern of vertically oriented white metal fins. Both the edges of the pleated glass wall system and the vertical fin facade play off the dense angularity and verticality of the neighboring Paul Rudolph masterpiece at 133 Federal Street.

The Pleated Wall

While the fundamental compositional strategy is a tower with podium, the tower, oriented to face east and west, results in a broad surface. Our strategy is then to “break up the box” by fracturing the surfaces. This creates a series of angular planes that wrap the tower and podium and refract the reflections of the sky on the surface, creating an intricate composition of refraction and reflection. This strategy also increases the visual depth of the wall and enhances the presence of the warm colors reflected on the glass.

Not unlike the soft but angular folds of a pleated fabric skirt, the Pleated Wall serves a practical purpose too: bay window spaces inside the office floors orient a large portion of the glazing to the northwest, thereby reducing the solar heat gain while providing ample natural light.

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Urban Connection

Winthrop Center is located in the epicenter of three significant districts of Downtown Boston: the resurgent creative commercial node of Downtown Crossing to the west; the primary transit gateway of South Station; and the vital Financial District to the east. The Connector was designed to become a pedestrian attractor. In this way it is part of urban “tesserae” – or links – that reinforce and add multiple pathways between these major nodes of Downtown.

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Boston is blessed with iconic outdoor urban spaces: The Common, Copley Square, and The Fenway, among others.

Downtown, important intimately-scaled spaces constitute part of the special texture of the Colonial-era city: Post Office Square, Shoppers Park, the plaza dedicated for the Irish Famine Memorial and, between these, Winthrop Square. These are the memorable outdoor urban rooms of this district. In the summer, these spaces are teeming with pedestrians, vendors, tourists, and workers on lunch break enjoying the sun and verdure.

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Boston’s streets were established by cow paths, or so the story goes.

In reality, the Colonial-era pattern was formed by geography: the circumferential pattern east of Beacon Hill traversing the grade around the hill, and the radial pathways connecting the intense commercial activity of the wharves to the upland merchant shops. A distinct pattern of east-west streets are bisected by Washington and Federal Streets, radiating from State Street southwards. Winthrop Center creates new streetscape treatments creating a living street and incorporating the 100 Summer Street Plaza into this network of pedestrian links, connecting Summer Street, the open terrace at 133 Federal, and The Connector. In this way, The Connector becomes part of a larger pattern of mid-block pedestrian open space links.

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The site is bracketed by two 400-foot towers along Devonshire.

Winthrop Center, gracefully inflected on its west face, creates vertical continuity between 100 Summer and 101 Federal. These tower faces roughly trace the contour of Winthrop Square.

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The east side of the site along Federal Street posed a challenge: how to reconstitute the western street wall that has been missing for more than 40 years?

Combined with the “negative space” created by the Bank of America building along half the block on the east side, the shape and character of the Federal Street façade was organized to create some spatial order in an otherwise unresolved block. The design resolves this problem with a detached vertical building form that mediates the height between 150-foot 133 Federal, the 390-foot 101 Federal Street tower, and the 240-foot 75 Federal building at the north end of the block facing on Franklin Street. All the while, natural light is allowed into the existing office windows at 101 Federal. The resultant stepped massing completes the street wall while respecting the inherent morphology of the disparate buildings on the block.

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The Great Fire of 1872 remade much of this district.

The straightening of several thoroughfares, the creation of Post Office Square, and the new Boston Herald Traveler newspaper building at Winthrop Square gave new shape and a Victorian-architectural veneer to the neighborhood. But the 20th century transformation of the Financial District has been at best indifferent to cogent urban space-making. At Winthrop Square, while the granite One Winthrop Square building still axially organizes the plaza landscape, shear façades of the 400-foot office towers flank the east side with an uneasy counterpoint of 90-foot masonry loft buildings to the west. The office program of Winthrop Center introduces an intermediate scale, gently bending to re-establish the Devonshire Street side of the Square, creating a setback for the tower, and giving definition to the stately One Winthrop Square Building.


New buildings of this scale require a careful balance of respecting and building connections to the existing context while reimagining how the pedestrian realm can create a new and forward-looking environment.

Key to enhancing the pedestrian experience in this location is the repaving of parts of Winthrop Square, Federal Court, and Milton Place. Prioritizing the pedestrian over vehicles can be done successfully in Boston; witness Downtown Crossing at Summer Street or the new Shoppers Park plaza. Our inspiration for this tactic is the plazas and streets in the Netherlands called woonerf, or “shared street.” Vehicles move through the space slowly and purposefully in an environment clearly prioritizing pedestrians. This strategy lets the exterior space and landscape of Winthrop Square extend seamlessly into The Connector and, in similar fashion, the 100 Summer Street Plaza paving reaches northward into Federal Court. This simple paving strategy unifies the block, making the inner portions clearly a pedestrian realm that share in controlled fashion the vehicles moving through it.

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Vehicular Access and Parking

Primary access for residential parking is from Devonshire Street with a drop-off at an internal below-grade lobby.

After the occupant drop-off, vehicles are taken by valets into the lower garage levels. The loading functions for the building occur at an internal dock accessed from Devonshire Street, on the narrower portion of the street south of the plaza.

Primary access for commercial parkers in the property occur off of Federal Street using a separate ramp and the parking spaces located on lower levels. The commercial parking operations are valet-assisted on each level and the garage is outfitted with stackers.

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Sustainability Approach

Winthrop Center incorporates three important sustainability standards: Passive House, WELL, and LEED.

The office program meets Passive House standards, a rigorous performance-based sustainability standard that results in significant energy reduction and healthier interior environments. The office is also WELL Gold Certified, a sustainability standard that focuses on increasing the health, happiness, wellness, and productivity of the users by impacting the building from design through construction, and importantly continues through the long-term maintenance and operation of the building. The office and public spaces will meet LEED Platinum requirements, while the residential will meet LEED Gold. The LEED standard complements Passive House and WELL by prescriptively addressing environmental impacts like water usage, recycling, materials use and sourcing, and building operating procedures.

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To meet the high bar for energy performance, particularly at the office program, the exterior envelope needed to meet rigorous design standards quality control during installation.

Both solar heat gain and internal heat loss had to be minimized, while maximizing the reach of natural light into the office floorplates. As the Passive House envelope, the curtainwall design employs a robust, triple glazed insulated glass window unit coupled with glass spandrel panels to obtain an average R-value of 7.35 Btu/hr.ft².°F. To reduce energy loss, all connections between the exterior wall and the interior structure are thermally broken to minimize heat loss through thermal bridging, and all panel joints are gasketed and sealed to prevent air leakage. The highly insulated spandrel glass panels are designed with a unique fritted pattern that ties aesthetically to the brick and terracotta of neighboring buildings.

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Winthrop Center is now the world's largest Passive House commercial building.

We're are very grateful to our client, Millennium Partners, for trusting in us the design an delivery of such an important project. We could not have done it without the support of so many partners including Suffolk Construction, Steven Winter Associates, Desimone Consulting Engineers, WSP, LAM Partners, Tillotson Design, Socotec, and many others.

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