New heights in sustainability: World’s largest Passive House office building

by tanya_martins | November 8, 2024 2:16 pm

By Jamie Gentoso, P.E.

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Designed by Handel Architects in collaboration with Steven Winters & Associates, SOCOTEC, and WSP to incorporate Passive House design in its office portion, Winthrop Center in Boston is the world’s largest Passive House-certified office building. Passive House principles encompass various aspects of a building, including its walls, roofs, windows, ventilation, and heat exchange systems, all working in harmony to achieve high levels of energy efficiency.

What is Passive House?

Originally focused on single-family homes in Europe during the early 1990s, the “Passive House” concept has now expanded to encompass various project types. The office segment of the Winthrop Center project adheres to the international construction standard established and continuously improved by the Germany-based Passive House Institute (PHI). Passive House is a highly energy-efficient building standard and design approach aimed at reducing a building’s energy consumption for heating and cooling to an extremely low level.

The key principles of a Passive House include:

• High-performance enclosure
• Thermal bridge elimination
• Airtightness
• Balanced ventilation with heat and moisture recovery
• High-performance glazing
• Shading and daylighting

The primary goal of a Passive House is to create a comfortable, healthy, and energy-efficient living environment while drastically reducing energy consumption for heating and cooling.

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Winthrop Center

Winthrop Center boasts 75,437 m² (812,000 sf) of Class A office space and 47,380 m² (510,000 sf) of residential space and is a low-carbon and energy-efficient building. A typical Class A building in Boston’s existing commercial office stock uses 150 percent more energy than Winthrop Center’s office space.

A critical part of the Winthrop Center’s qualification as a Passive House is its roofing system, which supports energy efficiency and watertightness to create a high-performance enclosure. The project uses a self-adhered (SA) roofing membrane and polyisocyanurate (polyiso) insulation. Colby Baker, the project manager of Titan Roofing, the installing contractor, described the task as different than any that he had done before, given the size of the building.

“This job was unique in that it was a high-rise in Boston,” he says. “At 53 stories tall, it was a first for me. This project used polyiso insulation, HD [high-density] composite board, and 60-mil TPO [thermoplastic polyolefin] SA. We installed the roofing system on multiple levels, including the second, third and 53^rd floors, including the penthouse and walls of the penthouses.”

“Since we were working in the winter, using an SA membrane was the best solution since it eliminates the need for applying adhesives, which require inside storage,” Baker notes. “Because it has no VOCs or odors, people are not affected inside the building, and business can continue as normal. Even when it is not specified, we opt to switch to SA as it is our preferred overall. I think that we are more efficient labor-wise utilizing the product.”

In addition to the advanced roofing system, the building’s orientation was carefully planned to minimize solar heat gain, while triple-glazed windows and window shades were incorporated to reduce internal heat loss and maximize natural light. These features helped the building achieve superior energy efficiency and contributed to its Passive House certification.

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The challenge

Seventy percent of CO2 emissions in the building sector come from building operations, including heating and cooling. Implementing solutions that make buildings more sustainable and energy-efficient can reduce this.

Winthrop Center was conceptualized in 2017 by the internationally recognized developer Millennium Partners as an inspirational workplace environment that would set a new global standard for building performance and energy conservation. Millennium Partners partnered with a group of MIT professors led by the director of MIT’s Environmental Solutions Initiative, John E. Fernandez, to create a holistic design strategy for Winthrop Center that would address health and wellness, boost occupant happiness and productivity, and better the environment. Fernandez advised the team on the building’s design and development, especially as it relates to sustainability in the built environment.

Winthrop Center’s office space was a pilot project for Passive House development, representing the first time a developer applied this approach to an office building of this size and scale. Working closely with the specialized designer, Steven Winters & Associates, and experts at the PHI in Darmstadt, Germany, was essential in bringing the vision to life.

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The solution

Effectively insulating buildings to improve their energy efficiency is one of the main tools in combating the urban heat island effect and reducing carbon footprint. To ensure the highest possible energy efficiency, Millennium Partners chose polyiso insulation and Titan Roofing installed the insulation board in the building’s roof assembly.

Typically, when the temperature drops, the thermal performance of polyiso insulation decreases. However, the chosen proprietary product is the only polyiso formulation that becomes more effective as the temperature gets colder. When tested by an independent third party in September 2022, it performed up to 40 percent better in cold temperature 4.44 C (40 F) applications according to ASTM C1289, Standard Specification for Faced Rigid Cellular Polyisocyanurate Thermal Insulation Board.

According to the manufacturer of the insulation system used, this performance is due to its proprietary blend of blowing agents, which directly impacts R-value performance and maximizes the low mean temperature performance of the insulation while maintaining all the other important physical properties.

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The result

In addition to delivering dramatic energy savings through a well-insulated building facade, exterior envelope, and advanced energy recovery ventilation (ERV) system, Winthrop Center’s Passive House office space creates a comfortable, healthy indoor environment for building occupants, bringing in 30–50 percent more fresh air than a standard building of this type.

Winthrop Center is the most energy-efficient large-scale building ever built in a cold climate, where the Passive House approach is critically important to significantly lower the heating demand in the winter and cooling demand in the summer. Baker spoke about what made the project especially suitable for the New England geography:

“For buildings like this in Boston, they typically do a wind study. We are dealing with pretty substantial uplift requirements on a job like this and we were able to put together an assembly that matched the specification they were looking for. As an iconic building that is more sustainable in use than other similarly sized buildings, it stands out as a showcase project for the Passive House industry and sets a high standard for future projects.”

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Passive House certification

The architects involved in the project believe that, in a few years, all buildings will be required to adopt the energy-saving principles and achieve the high level of performance of Passive House. Richard Baumert, partner at Millennium Partners, commented on the implications of this certification for the future of urban construction:

“Architects and developers are increasingly looking to Passive House to curb energy use, and Winthrop Center’s recent achievement in being certified by the Germany-based Passive House Institute as the largest Passive House office building in the world is exciting news for the development community, demonstrating that Passive House and its energy saving principles can be applied to an office building at a size and scale that has never been achieved before.”

Author

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Jamie M. Gentoso, P.E., is the global head of solutions and products at Holcim and president of Holcim Building Envelope. She previously served as CEO of U.S. cement operations for Holcim and is now responsible globally for the solutions and products business unit for Holcim Group. This includes the recently acquired roofing business of Elevate (formerly Firestone Building Products), Malarkey Roofing Products, and most recently Duro-Last. Gentoso sits on the board of directors for Public Service Enterprise Group (PSEG) and has also served on the board of other non-profit organizations. She holds a degree in civil engineering and a master’s degree in business, both from the University of Michigan.

Key Takeaways

Winthrop Center in Boston, designed by Handel Architects and partners, is now the world’s largest Passive House-certified office building. This innovative structure adheres to strict Passive House principles, ensuring high energy efficiency through advanced design features such as airtightness, thermal bridge elimination, and balanced ventilation. With 75,437 m² (812,000 sf) of office space, it dramatically reduces energy consumption compared to typical buildings. The project showcases how large-scale office environments can achieve sustainability, setting a new standard for urban construction and highlighting the importance of energy-efficient design in combating climate change.

Source URL: https://www.constructionspecifier.com/winthrop-center-passive-house-design/

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