Q: What is meant by “carbon content” in building materials?
A: Carbon content is a phrase used in the design community to compare specific sustainability attributes in building materials. It doesn’t reflect the amount of carbon that is within the material, but actually focuses on the amount of energy required to extract the raw materials, manufacture the product, ship it through distribution and on to the final jobsite location. This carbon content extends beyond the installation of the product. It also includes the life as a product and what occurs in the next phase of the material be it landfill or repurposing. The terms “cradle-to-grave” or “cradle-to-gate” were coined to represent the two different approaches to the “life” of a product. Cradle-to-grave represents where the product is completely discarded, while cradle-to-gate is where the material is either recycled or repurposed for a new application.
The concept of carbon content relates directly to the amount of energy required in each of the steps mentioned above. The intent is to control the amount of greenhouse gases that are produced throughout the life of the product. This energy is derived from the consumption of fossil fuels that emit these greenhouse gases. A corollary phrase is “carbon footprint,” which is related to human activity.
Greenhouse gases are gases that are considered a catalyst for climate change. The U.S. Green Building Council stated in a document, “Buildings and Climate Change,” that “buildings account for 39% of CO2 emissions in the United States.” Carbon dioxide is a prime culprit in greenhouse gas and is therefore a major concern of the design community when considering sustainability. This naturally leads to a discussion of a building material’s carbon content.
To stress the importance of carbon content, the federal government has approved principles that look to reduce the content within building materials. This came from the Green Building Advisory Committee, which advises the U.S. General Services Administration. One of their recommendations was as follows: “A material approach for all projects requiring environmental product declarations for 75% of materials used (by cost or weight), and that their emissions fall in the best-performing 80% of global warming potential among functionally equivalent products.”
This new directive may be the source of what appears to be a recent surge in the interest in and requests for information on carbon content.
Building product manufacturers and their associations are in the best position to provide contractors with information relating to their products’ carbon content. There is a strict protocol in place to establish standardization of the data collection and interpretation. The analysis must follow the requirements established by the International Organization for Standardization. For transparency, the analysis must be undertaken by a recognized third party. The mechanism used to calculate a product’s sustainability attributes is a Life Cycle Assessment. The data found in an LCA can be found and refined in an Environmental Product Declaration. This is typically requested by interested parties, such as architects.
Unfortunately, there is not a heading for carbon content in either the LCA or EPD. The closest one can come is the “Impact category” called “Climate change.” This is tabulated as the global warming potential of the product and is given the units of “kg CO2 – equivalent.” To simplify the process, the Embodied Carbon in Construction Calculator was developed by the Carbon Leadership Forum. Taken from carbonleadershipforum.org, the organization includes “architects, engineers, contractors, material suppliers, building owners and policymakers.” The data contained within the calculator comes from recognized third-party EPDs.
When contractors are asked to provide information on carbon content, they can turn to several sources. The individual building product manufacturers should be able to provide EPDs on their products. Also, the associations that support those products may be able to provide an EPD that is an aggregate of their respective industries. For example, the Gypsum Association website has a downloadable EPD on gypsum panels, and the Steel Framing Industry Association will soon release an EPD on cold-formed steel framing.
The goal of sustainable construction has reached a new level of performance. This is no longer a trend but has become part of the standard design process. The original material properties like combustibility, strength, moisture resistance that influence product selection and specification have been displaced in priority by sustainability properties. Taking the next step in the process, while recycled content was a key driver, carbon content has gotten to be equally important. Contractors who are up-to-date on carbon content will differentiate themselves as sources of sustainability information in the built environment.
Robert Grupe is AWCI’s director of technical services. Send your questions to grupe@awci.org, or call him directly at (703) 538.1611.
