The building industry is unique in that its end-product, i.e., the building itself, contributes to society and often serves a greater good. Have you ever been involved in the construction of a hospital? How about a university building? Or even an apartment complex? Then you have contributed to society by improving health care facilities, educational centers, or even housing! This is a satisfying reward for a job that can often be taxing; you get a tangible product that will stand as proof of your hard work. Beyond being a symbol of your accomplishments, new buildings can be a symbol of what the future holds for the community in which it’s built. Over time, people will actually interact with it, utilize its features, and learn to live around and within it. Designers, architects, engineers, and constructors have the special opportunity to shape the future with each new construction project. But as they say, with great power comes great responsibility, and contributing to society means more than just providing a functioning building. It also means ensuring that the building is sustainable for the community and environment in which it’s built.
Sustainability is a term that is often used, and sometimes scoffed at in our industry. It is frequently referenced in a universal sense, and the typical individual is not properly educated on how their individualproject could make a difference toward contributing to a more sustainable future. They may recognize that building sustainably is generally a good thing, but do they understand the impact of each building on the environment? Therefore, the goal of this paper is to give some credibility behind the need for sustainable design and construction by educating industry professionals on embodied carbon and its role in the building industry. I’ll define sustainability and embodied carbon, the effect of concrete on a building’s carbon footprint, and look at some alternative building products that could benefit the environment. From there, one should have a higher ability to recognize environmental impacts on their projects and how each project can make a difference.
What do we mean by “sustainability”?
Building designers and engineers are tasked with an extremely difficult equation: how does one design a building that serves its function, fits the community, and is built with an environmentally friendly approach? This is inherently what we mean by sustainability. Figure 1 illustrates the “triple bottom line” of sustainability which are: social benefits, environmental effects, and economic viability. Achieve all three, and you have yourself a sustainable building.
This means finding products that allow structures to be built with the end-users in mind first, at cost-effective prices, while minimizing environmental impact. It’s therefore important to remember that it is not just building operation that causes an environmental impact through energy consumption, but also the materials and energyconsumed in the actual construction of the building. Architecture 2030 explains that buildings generate nearly 40% of annual global CO2 emissions, with building operations responsible for 28%, and building materials and construction (typically referred to as embodied carbon) responsible for an additional 11%1. A prime contributor is cement. “Cement is responsible for 7% of global greenhouse gas emissions, and is predicted to grow with increasing development,” write Jane Anderson and Alice Moncaster (2020). Cement is used in concrete, and as I write this, no material is used more frequently in buildings worldwide than concrete2; further, the embodied carbon content of concrete is significant.
What do we mean by “embodied carbon”?
Simply put, embodied carbon refers to the amount of greenhouse gas emissions (like CO2) that stem from the production, transportation, installation, and removal of a material.3 As a result, each building that is constructed inherently comes with a baseline carbon footprint that is unchangeable simply based off the materials that are used in its construction. Designers can be creative in the types of systems that operate the building to reduce CO2 emissions over the life cycle of the building, but this doesn’t change the amount of greenhouse gas emissions it took just for the building to be exist in the first place. Leadership in environmental design of building materials (and how they get to the job site and installed on the building) is therefore paramount.
Can you provide an example?
The manufacturing of a cubic yard of concrete is equivalent to releasing about 400 pounds of CO2, which is about the same as the average tank of gas in a car4. Assuming a ten-story building with approximately 24,000 cubic yards of concrete, this translates to 9,600,000 pounds of CO2, or 7,200,000 miles driven by a car (which is like driving back and forth from Los Angeles to New York 2,942 times). And that is just for one ten-story building! So, the environmental cost of concrete is obviously significant when extrapolated across projects all over the world.
What is being done about it?
While there is a long list of measures that industry leaders, like the US Green Building Council (USGBC), are taking to reduce the carbon footprint of buildings through LEED and other initiatives, one that is especially exciting is the use of mass-timber in lieu of typical steel and concrete structures on high rise buildings. Cross-laminated timber (CLT) is growing in popularity in “heavy” applications and will continue to do so. Figure 2 shows the makeup of CLT, which is layers of timber laminated in alternating directions to provide rigid wood “panels” that can be used for floor slabs, beams, or columns. Its use has been popular in Europe over the last decade, but it has taken some time to gain traction in the United States. The 2015 International Building Code allows its use in certain situations, but the 2021 International Building Code will have expanded allowances and new building types for mass timber structures to encourage more mass timber construction5. It’s worth noting that using wood products obviously results in cutting down trees, which are fantastic carbon sinks (where CO2 is taken out of the environment rather than put into it). Therefore, to optimize its environmental impact, CLT must be harvested from a sustainably managed forest. If done correctly, mass timber can have a much lower embodied carbon value than concrete.
As a proof of concept in the United States, the 80 M Street Project in Washington D.C. is scheduled to be complete in 2022, and is the first office building in D.C. to utilize mass timber construction (see the end of this post for renderings of this project).
Façade products with a focus on embodied carbon
My background and career are in exterior façade systems, which are installed well after a building’s structure is in place. However, I recognize that exterior building components can also have a significant effect on the embodied carbon of a construction project and am in the fortunate position of being exposed to a variety of wall cladding materials. There are many manufacturers that are attempting to optimize sustainability, cost, and overall building performance, but a few are clearly leading the way. In doing research, one product, the Kingspan Quadcore Panel, caught my eye specifically. In 2020, Kingspan released a study on “Reducing the Embodied Carbon of Walls in Industrial Buildings”, which I found fascinating because it applied so directly to this topic, but also because I had no idea that this report existed! I’m sure there are designers and engineers that are aware of it, but again I believe this proves my point that the typical industry professional isn’t aware that embodied carbon is a problem that each of us must assist in resolving. The report (2020) establishes that Kingspan’s “Quadcore” panel’s Global Warming Potential is 28% lower than insulated concrete and tilt-up concrete panels, which have significantly higher levels of embodied carbon6. This is illustrated by Figure 3 below. Again, finding alternates to concrete building materials is an important step towards improving the built environment in our structures and façades alike.
In conclusion, sustainability and embodied carbon need to continue to grow as topics of discussion amongst the common building industry professional. It’s important that manufacturers continue to take initiative on reducing embodied carbon, but there is also an onus on us to educate ourselves as well. Each project can make a difference.
27 October 2021
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1Why the building sector? Architecture 2030. (n.d.). Retrieved October 27, 2021, from https://2030dev-architecture-2030.pantheonsite.io/why-the-building-sector/.
2Anderson, J., & Moncaster, A. (2020). Embodied carbon of concrete in buildings, Part 1: analysis of published EPD. Buildings and Cities, 1(1), 198–217. DOI: http://doi.org/10.5334/bc.59
3 1 – Embodied Carbon 101. Carbon Leadership Forum. (2021, June 27). Retrieved October 27, 2021, from https://carbonleadershipforum.org/embodied-carbon-101/.
4Carbon foot print – portland cement association. (n.d.). Retrieved October 28, 2021, from https://www.cement.org/docs/default-source/th-paving-pdfs/sustainability/carbon-foot-print.pdf.
5Cross-laminated timber info sheets – tallwoodinstitute.org. (2019). Retrieved October 28, 2021, from http://tallwoodinstitute.org/sites/twi/files/Info%20Sheets_Final_200616.pdf.
6Reducing embodied carbon. Kingspan. (2020, June 7). Retrieved October 28, 2021, from https://www.kingspan.com/us/en-us/about-kingspan/kingspan-insulated-panels/reducing-embodied-carbon.
80 M Street; Renderings courtesy of Hickock Cole