Contextualizing Glass and Carbon Impacts

Addressing Embodied/Operating Carbon with Emerging Glazing Technologies



Climate change goals will require significant improvements in the way buildings are constructed and operated. Building reuse can combat climate change as it minimizes the embodied carbon to create materials and energy required to build a new structure. However, a more holistic and performance-based approach to embodied and operational carbon will be required to achieve the time-based goals of the Paris Agreement and Architecture 2030.

Windows present a significant challenge within building reuse as traditional treatments either require full replacement to achieve reasonable performance or utilize restoration methods with minimal embodied carbon impacts albeit at a lower gain in operational performance. As such, most window upgrades achieve either significant operational carbon reductions or minimal embodied carbon additions, but very few achieve both benefits. More importantly, the operational and embodied carbon impacts aren’t both currently required to be evaluated in project scope. As a result, the project may have untapped potential for climate change impact.

With thoughtful design and emerging glazing technologies, significant step changes can be made using known technologies to shift this embodied carbon/operating carbon paradigm and provide better solutions to the carbon crunch. In existing building stock, significant performance upgrades can be made with emerging technologies such as vacuum insulated glazing (VIG), thin glass, and the thin triple IGU. This allows for step-change improvements in building operations with only a minor increase in embodied carbon. An in-depth analysis of the restoration of the Albert Kahn building in Detroit was completed to showcase a methodology for this process. Evaluating the different potential options and comparing the overall carbon impacts both in terms of embodied and operational carbon offers insight into the real impacts on treatments. This complete analysis is required to understand the full impact of choices and carbon impacts. The report will expand the toolbox of adaptive reuse technologies for overall window design to best minimize carbon impacts in a window project.


Photo of Kayla Natividad, PhD, WELL AP, LEED Green Associate

Kayla Natividad, PhD, WELL AP, LEED Green Associate

Architectural Technical Service Engineer

NSG Group

Photo of Kyle Sword

Kyle Sword

Manager Business Development

NSG Group



The Albert Kahn office building in Detroit, Michigan was completed in 1931 by the renowned architect Albert Kahn. Constructed by the Fisher Brothers and referred to as ‘a building with a purpose’ at inception, this building was originally home to Albert Kahn’s architectural firm as well as a prominent department store and other office suites (McDonald, 2022). Originally named the New Center Building, it went on the National Register of Historic Places in 1980 and was renamed the Albert Kahn Building in 1988.

Lutz Real Estate Investments and Northern Equities Group along with the Kraemer Design group worked to develop this property from an 11-story, 320,000 square-foot office building into mixed-use and mostly residential condo conversions on the upper floors. A significant challenge of the project was what to do with the 700 double-hung bronze windows. Roughly 1.45m x 1.93m (57 x 76”) each and mostly operational, they were poorly sealed and single glazed with 6mm (1/4”) clear glass leading to poor insulation values and high solar transmission. Allen Architectural Metals was contracted as the glazing contractor and worked to create some innovative solutions for the space.

For most historic restoration projects there are 4 glazing alternatives that are typically considered:

  1. Restore existing sash and maintain similar glazing
  2. Restore existing sash with higher-performance glazing
  3. Add secondary glazing (storm windows)
  4. Replace window system with modern replica appearance insulating glazing unit (IGU)

As a historic restoration and National Park Service (NPS) tax credit project, the Kahn had to maintain the original historic look and feel of the building to qualify for tax credits. The original development plan was to clean up the existing windows and add fixed secondary glazing to the inside to improve the energy efficiency. While this would provide some insulation benefits, it also came with some undesirable attributes in aesthetics and fully removed potential for operability of windows. The team was looking for other ways to keep the design truer to the original construction and improve performance function for residential customers. Kate Allen (Vice President of Allen Architectural Metals) reached to Columbia GSAAP (Graduate School of Architecture, Planning, and Preservation) for high-performance glazing options. It was here that vacuum insulating glazing (VIG) was introduced as a potential alternative to re-glaze the existing bronze windows. This would allow the existing simple, double-hung window design to ring true while exceeding the performance expectations they could achieve using secondary glazing. An added benefit to the new VIG approach meant that the windows could now be operable as the fixed secondary glazing would no longer be required. In addition to the basic operational and aesthetic gains from the design, further analysis was pursued to understand the impact on carbon both in terms of operational use and embodied material impacts of each glazing alternative.

Vacuum Insulating Glazing (VIG)

To meet modern energy requirements, most windows installed today are insulating glazing units (IGUs). A standard IGU is comprised of two pieces of 3mm (1/8”) - 6mm (1/4”) glass with

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VIG for the Kahn

In the case of the Kahn, the VIG was a great fit. The use of VIG enabled the restoration of the original bronze sash while updating the glass to modern

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Reference Building Carbon Impacts

To compare embodied carbon vs operational carbon impacts of each window alternative, model building energy analyses were performed using the U.S. Department of Energy (DOE) commercial reference building models and

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The analysis did confirm that a re-glaze of the existing materials will result in the lowest embodied carbon impact of this project. In addition, a re-glaze of the existing conditions

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Future Work

While this project focused on the use of monolithic glass replacement, it highlighted a key point that the most sustainable building is one that already exists. With that in mind

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Kate Allen-Lezak - Allen Architectural Metals

Helen Sanders - Technoform

Rights and Permissions


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