Driving energy efficiency is one of the main ways to decarbonize cities, and addressing the operational emissions of buildings is critical. Holcim’s broad range of solutions, from advanced roofing systems and insulation to concrete thermal activation, are making buildings around the world more sustainable in use.
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, Massachusetts, 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.
Holcim contributed to this project by delivering roofing and insulation solutions through its Elevate brand, including Elevate UltraPly TPO SA membrane and next-generation Elevate ISOGARD polyiso insulation, used in the roofing system. 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 Elevate ISOGARD polyiso insulation, HD Composite Board, and 60-mil TPO SA. We installed the Elevate system on multiple levels, including the second, third and 53rd 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 aren’t affected inside the building and business can continue as normal. Even when it’s not specified, we opt to switch to SA as it’s definitely our preferred overall. I think that we’re way more efficient labor-wise utilizing the product.”
The Challenge
Seventy percent of CO2 emissions in the building sector come from building operations, including heating and cooling. This can be brought down by implementing solutions that make buildings more sustainable and energy-efficient in use.
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. Fernández, to create a holistic design strategy for Winthrop Center that would address health and wellness, boost occupant happiness and productivity, and better the environment. Professor 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 Passive House Institute in Darmstadt, Germany was essential in bringing the vision to life.
The Solution
Effectively insulating buildings to improve their energy efficiency is one of the main tools in combating the urban heat island (UHI) effect and reducing carbon footprint. When it comes to ensuring the highest possible energy efficiency, Millennium Partners chose Elevate patented ISOGARD polyiso insulation. ISOGARD has the highest R-value per inch at colder temperatures compared to competitive polyiso products. Installed by Titan Roofing, an Elevate Master Contractor, the insulation board was used in the building’s roof assembly.
Baker noted the ease of working with Elevate products and the team itself. “It starts with the people that we work with on the Elevate side,” he says. “We have a great rep out here and they’re very responsive. When we have a relationship with people like that, we always want to go back to them. The product in and of itself, we’ve had great success with all of the Elevate products. It’s also readily available at multiple vendors locally, which is really helpful.”
Typically, when the temperature drops, the thermal performance of polyiso insulation decreases. ISOGARD, however, is the only polyiso formulation that becomes more effective as the temperature gets colder. ISOGARD polyiso insulation performed up to 40% better in cold temperature 40°F applications according to ASTM C1289 standards than major competitors when tested by an independent third party in September 2022.
According to the company, this performance is due to ISOGARD’s 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. ISOGARD’s patent protected technology was first introduced to the market in 2019 — technology that yields increased R-value as mean temperature decreases.
Elevate UltraPly TPO SA membrane was also installed to provide a protective, waterproof barrier. Designed for easy installation, the product can be recycled at the end of life and has zero volatile organic compounds (VOCs).
The Result
Winthrop Center boasts 812,000 square feet of Class A office space and 510,000 square feet of residential space, and it is a low-carbon and energy-efficient building. A typical Class A building in Boston’s existing stock uses 150% more energy than Winthrop Center’s office space.
In addition to delivering dramatic energy savings through a well-insulated building façade, 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% more fresh air than a standard building of this type. Holcim’s expertise in creating sustainable building solutions played an important role in this project; on average, up to 25% of a typical uninsulated building’s heat loss can be through the roof.
Winthrop Center is unique: It 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: “Buildings like this in Boston, they typically do a wind study. We’re dealing with pretty substantial uplift requirements on a job like this and, working with Elevate, 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.”
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. Innovative solutions such as Holcim’s are integral to creating a more sustainable future through the built environment and we are proud to have partnered with them in the development of Winthrop Center.”
What is a 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. A 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.
TEAM
Architects: Handel Architects, New York, handelarchitects.com; Steven Winters & Associates, New York, swinter.com; SOCOTEC US, New York, socotec.us; Millennium Partners, New York, millenniumptrs.com
Roofing Contractor: Titan Roofing, Springfield, Massachusetts, titanroofing.com
MATERIALS
Membrane: UltraPly TPO SA, Elevate, holcimelevate.com/us-en
Insulation: ISOGARD HD cover board, Elevate
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