Decarbonize Now!

Laura Karnath, senior associate and senior enclosure technical designer at Walter P Moore and Sophie Pennetier, associate director, special projects at Enclos, address the costs of carbon through the life cycle of buildings, from manufacturing, transportation, use, and less tangible social costs in the Spring 2022 issue of Intelligent Glass Solutions.

In search of natural daylight, views, and enhanced performance, architectural glass has a long history of driving innovation in construction. Today the greatest challenge facing the building industry is the climate crisis. It is well known among building industry professionals that buildings are responsible for approximately 40 percent of global carbon emissions. There are two types of building-related carbon emissions we must consider: operational carbon and embodied carbon.

Operational carbon emissions correspond to the building’s energy use throughout its entire life and represent 28 percent of global carbon emissions, according to the Carbon Leadership Forum. Embodied carbon emissions, representing approximately 11 percent of global carbon emissions, are the emissions associated with building materials and construction: from the extraction and processing of raw materials to manufacturing, transportation, and installation on site. These emissions occur up front, before a building is even occupied. Tackling embodied carbon emissions is crucial to meeting the near-term climate goals set forth in the Paris Agreement. The building industry as a whole and the architectural glazing industry in particular have been markedly successful at reducing operational carbon emissions through improvements in insulated glass units and low-e coatings. There is still much progress to be made, however, on reducing and eventually eliminating embodied carbon emissions associated with the production of facade materials, including glass, aluminum, gaskets, and sealants. We believe supply chain decarbonization is the next frontier of innovation in architectural glass.

Drivers of Embodied Carbon

To understand embodied carbon, we need to understand supply chains and manufacturing processes. Designers should ask themselves: “How and where are the materials I am specifying made?”

The power sources used in manufacturing, including both power purchased from the local grid and on-site fuel combustion, have a substantial impact on embodied carbon of building products. Norsk Hydro and the NSG Group are two manufacturers who are leading the charge in decarbonizing materials used in glazed facades. The NSG Group recently announced they conducted a successful trial of hydrogen power in one of their float lines, which if implemented at scale could dramatically reduce the carbon emissions of glass production. Norsk Hydro currently offers low carbon aluminum with a global warming potential (GWP) of only 4kgCO2eq per kg of aluminum, which they claim is approximately one quarter of the industry average emissions. They achieve carbon reductions through the use of renewable energy at their Norwegian smelters and recycling of postconsumer aluminum, using much less energy than the production of primary aluminum. They aspire to deliver commercial quantities of near-zero carbon aluminum, and to achieve net-zero aluminum by 2030. Sourcing materials from low-carbon manufacturers seems ideal, but is not yet available at scale and might not match the client’s budgets and schedules. Design and construction teams will have to explore other options for carbon reduction while these technologies are scaling up.

Beyond manufacturing, the emissions from transportation, especially in the U.S. market, cannot be ignored. Research by Isabelle Hens in collaboration with Sophie Pennetier and Simon Schleicher, to be published at the next Facade Tectonics 2022 World Congress, shows GWP variations in the range of +/- 5 to 15 percent for the few supply chain options considered. It is important to note that this was a specific benchmark study, and not necessarily representative of systems outside of the context of the study, but it gives us a window into transportation impacts.

Curtain wall supply chains are complex, and design decisions can have unexpected impacts on embodied carbon due to this complexity. Unknown to most designers, choice of location for aluminum extrusion is driven primarily by finish, then length and profile width (die diameter). The location of assembly is driven by a number of factors, such as: economics, labor rates, trucking distances, and more. The same factors apply to the glass supply chain. Glass may be produced in one location, coated in another, fabricated into an IGU in a third, and the IGU installed in a curtain wall unit in a fourth, with each step requiring potentially hundreds of miles of transit between locations. All these steps happen before the glass is even transported to the construction site for installation.