Heralded as the most energy-efficient building of its kind, Boston’s Winthrop Center features Sotawall’s curtainwall
Soaring 52 stories, Winthrop Center’s new, mixed-use office and residential tower blends health and wellness, sustainability and technology to enhance Boston’s skyline and support the city’s emission-reduction goals. Sotawall customized its THERMO-3 Series unitized curtainwall system to meet the project’s high thermal performance requirements and unique aesthetic. Further contributing to the building’s lasting appearance, Linetec provided fluoropolymer coatings in five colors for four additional architectural aluminum product manufacturers.
In addition to pursuing LEED Platinum through the U.S. Green Building Council and WELL Gold through the International WELL Building Institute, Winthrop Center recently earned a Passive House Trailblazer award. When it opens in 2023, it is expected to be the most energy-efficient, large-scale office building ever constructed in a cold climate to meet Passive House’s rigorous standards.
Applied to commercial projects, the Passive House standard allows for design flexibility while establishing performance criteria for the entire building. These criteria include maximum allowable values for source Energy Use Intensity, heating and cooling demands, and strict requirements for air tightness, ventilation and thermal comfort.
Developed by MP Boston, Winthrop Center was designed by Handel Architects, and is located in the heart of Boston’s financial district on Winthrop Square. The building begins as a singular, angular pedestal curving along the public plaza and rises to form two distinct columns at the top. Enclosed in blue glass, the aluminum-framed façade’s pleated, layered geometry resembles a shimmering prism. Sotawall’s senior project manager, Joseph Dias, called it “a complex, corrugated wall design with an amazing appeal.”
Project architect Handel Architects said, “It is from this tradition of modernism – with an emphasis on vertical expression coupled with artful detailing – that we draw inspiration for a language of new high-rise expression on this downtown site, harnessed in the service of 21st century high-performance building technology.”
At 691 feet tall, Winthrop Square offers 510,000 square feet of residential space and 812,000 square feet of Class A office space. Retailers, restaurants, lobbies and entrance areas are found near the street level. Above it are stationed the tenants’ amenities, such as fitness center, game room, café and lounge, plus meeting pods and co-working spaces. Tenants’ private offices are on the upper levels and the highest floors are reserved for the 317 luxury residences.
Creating 10-foot-high windows with natural light and views, Sotawall provided 10,000 aluminum frames and 1,250 vents totaling 600,000 square feet of material.
“We were able to meet the project’s demanding schedule in spite of COVID-19, material shortages and all that was going in world,” Dias said proudly. “Our THERMO-3 system was modified with deeper mullions, which allowed for the thicker insulation needed to meet spec,” explained Dias.
The curtainwall framing members, and all connections between the exterior wall and the interior structure, are thermally broken to minimize heat loss through thermal bridging. All the panel joints are gasketed and sealed to prevent air leakage. The well-insulated office building façade, air-tight exterior envelope and advanced energy recovery ventilation (ERV) systems work together to reduce heating demand and related energy use.
Handel Architects also shared that the pleated curtainwall design “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.” Exterior fins supplement Winthrop Center’s passive shading, and triple-pane glazing contributes to the building’s overall thermal performance.
According to The Passive House Network, a typical Class A building in Boston’s existing stock uses 150% more energy, and existing LEED Platinum buildings in Boston use 60% more energy than Winthrop Center’s office space is predicted to use, advancing climate change mitigation efforts.
“If the reduction in energy use and greenhouse gas emissions resulting from Winthrop Center’s Passive House design were applied to existing building stock in Boston, the city would save an estimated 3 million metric tons of greenhouse gas emissions. These savings would drive city emissions from 6.4 million tons of CO2 to 3.4 million tons of CO2, a full 10-12 years ahead of the city’s goal,” noted The Passive House Network.
Inside, office tenants have a flexible and adaptable environment where 95% of seating is within 35 feet of a window. Along with heating and cooling efficiencies, daylighting and views, the integrated systems deliver up to 50% more fresh air compared with typical existing office buildings. These thoughtful design strategies and building components are shown to have a positive impact on occupant health, productivity and sense of well-being, which in turn, benefits employees, employers and their community.
“With Class A office space expected to expand by billions of square feet between now and 2050, application of Passive House cannot come soon enough or spread fast enough in this ongoing fight against climate change,” said The Passive House Network’s board chair, Craig Stevenson.
“Winthrop Center is at the forefront of this exciting movement of energy-efficient buildings providing climate change solutions,” said MP Boston’s director of sustainable development, Brad Mahoney. “Passive House plays a market-moving role and the overall success of Winthrop Center will help drive further innovation and change in the industry. We’re already seeing tenants enthusiastically embrace this building standard, eager to walk hand-in-hand with us in this shared vision for a more sustainable future.”
Photos © Greg West Photography