Learn the Language of Carbon
Low-carbon design begins with understanding basic carbon concepts and tools:
Grasp the Terms
Over the years, scientists and advocates have developed a common language for talking about carbon in the built environment. Some terms are widely agreed upon, others can vary in different English-speaking countries:
- Carbon Emissions: Refers to the carbon dioxide emitted into the atmosphere during any process or activity. Sometimes people use just “carbon” as shorthand.
- Carbon & Energy: You might see these terms informally used as though they stand for each other. This is because most carbon emissions occur when we burn fuel for the energy required for a process or activity. While carbon and energy have a direct correlation, some energy sources produce more emissions than others. Renewable energy sources generate no or extremely low carbon emissions.
- Operational Carbon: Refers to the carbon emissions associated with the operation of buildings and interiors—broadly speaking, this is the energy used to “run” the interior. Some of it might be directly reflected in the utility bill, some of it is indirect (for example, the energy required to bring water to your faucet, or the gas that fuels your boilers.)
- Embodied Carbon: Refers to the carbon emissions associated with all the extraction, manufacturing, and transportation of all the materials used in a project, as well as the emissions associated with the construction, maintenance, and demolition of the project—think of it as all the carbon emitted to “make” a building or interiors.
Understand the Documents
In order to assess the carbon footprint of a project, designers have to rely on certain types of documents and information.
- LCA: A Life Cycle Assessment of all the environmental impacts of any project, product, process, or organization. LCAs assess all the impacts from “Cradle to Grave,” which means they cover everything from the origin of materials to the end of its useful life.
- EPD: An Environmental Product Declaration is a third-party certified report created by manufacturers to communicate all the environmental impacts of their product or material offerings, as defined by material-specific Product Category Rules and ISO standards. It translates the information from a product LCA into specific data points (called “indicators”) that designers can use to inform their decisions. EPDs are available as pdf documents on manufacturer websites (look in the sustainability data for any product) or from databases like mindful MATERIALS, the Sustainable Minds Transparency Catalog, or EC3. (Dig deeper with this explanation from the International EPD system or this primer from the Carbon Leadership Forum)
- GWP: Standing for Global Warming Potential, this is the number that represents embodied carbon on an EPD. The GWP is measured in kgCO2e/unit, but it doesn’t represent just carbon dioxide emissions—it actually measures how much energy the emissions of 1 ton of a gas will absorb over 100 years, relative to the emissions of 1 ton of carbon dioxide (CO2). So it takes into account the global warming that could be caused by any greenhouse gases emitted per unit of the product. For some products, a unit might be defined by area (example: one square foot) while in others it might be by volume (example: one cubic foot) or weight. This is why GWP numbers cannot be compared directly across different types of products.
- Baselines: How to tell if the GWP number you are seeing on an EPD is “good” or “bad” for that particular type of product? That’s where baselines come in. Published by the Carbon Leadership Forum annually, these numbers provide a benchmark for GWP for many material categories. The 2021 baselines are available here.
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