When we think about carbon emissions, what comes to mind is what is visible, like car exhaust or smog.
However, many carbon sources are less obvious, not seen in our daily lives. One striking example is the carbon footprint of building and construction materials throughout their lifecycles—from manufacturing and transport to use and end of life.
Typically, we focus on addressing operational emissions, like the energy used to heat and cool a building. However, steel, lumber, and most other construction materials are often a significant source of embodied carbon, which factors in emissions from their manufacturing, transportation, installation, maintenance, and disposal. So, although not as noticeable, it is still a significant carbon debt we owe mother nature. Fortunately, there are ways to repay it—and pay it forward for our collective future.
To do so, we must assess the specific impacts of building materials and holistically approach the entire value chain in the built environment.
Assessing the Impact of Building Materials
In our new climate reality, it is important to connect the dots between the outside and the inside. We know that climate change affects our outdoor environment, but those same issues—air quality, extreme temperatures, coastal flooding—also increasingly require us to protect our indoor environments. However, in doing so, we must not worsen carbon emissions but instead focus on new ways to responsibly build and construct the places we live, work, learn, heal, and play.
Step one is to assess the carbon impact of building materials. One of the most meaningful ways is via a Life Cycle Assessment (LCA), which provides insight into the impact of products across their lifespan. They can then be optimized to mitigate the impact of embodied carbon by improving raw material sourcing, energy and water use, and recycling streams.
Once an LCA has been conducted, an Environmental Product Declaration (EPD) can be used to allow architects, consumers, and other stakeholders to compare the environmental impacts of different materials. This transparent communication enables procurement and purchasing functions to make the most sustainable decision for a project.
Additionally, industry groups are beginning to develop enhanced tools that can help materials manufacturers, builders, and designers understand how to best assess the impacts of embodied carbon. For example, the Carbon Leadership Forum (CLF) has developed the Embodied Carbon Calculator for Construction (EC3, the first third-party verified database of EPDs). This tool facilitates easy comparison of embodied carbon emissions from construction materials and products.
A Holistic Approach
To best address embodied carbon, a holistic perspective is needed, considering not just the construction or operational emissions of a building but, critically, assessing the emissions of the whole value chain. This includes the manufacturing process, resources, energy it takes to maintain the structure over its life, and disposal or recycling of materials when the building is demolished.
These can be complex and often frustrating issues, but they are of great importance if the built environment is to reach net zero emissions.
Embodied carbon can be reduced significantly at the planning stage. For example, the most significant way to reduce it is to reuse existing structures instead of constructing new ones. So, architects and designers should ask themselves, “Can an existing structure be repurposed instead of new construction?” This alone can save up to 75% of embodied carbon emissions.
In addition, building renovations can be a significant contributor to embodied carbon emissions, as the structure is only built once. The interior may go through multiple renovations over the lifetime of the building. These cyclical renovations can, over time, contribute more to the embodied carbon emissions of a building than the actual construction process. For example, ceilings and ceiling tiles take up a large portion of a building's interior space. When it comes time to replace them, they can account for significant embodied carbon emissions.
Strategies to reduce embodied carbon include choosing low-carbon interior finishes (like ceilings), limiting carbon-intensive materials in new building or renovation projects, and choosing materials like wood or bamboo, which can sequester carbon over their life. Reusing or salvaging items like wooden beams, bricks, and metals also reduces the energy spent on manufacturing and transporting new products.
We must shift our thinking and take a more all-inclusive approach to assessing the climate impact of the built environment. Doing so will lead to more sustainable buildings, the downstream effects of which will create entire cities and communities that are more sustainable and healthier places to live.