Embodied Carbon

May 19, 2021

Have you ever wondered where the material in your building really comes from, how much energy it takes to get it to the construction site, and how the use of that material impacts the environment?

Embodied carbon (EC) is a way to define these effects. The EC of a building represents the total greenhouse gas emissions associated with the construction of the building, starting with the extraction of the raw building elements. Materials have an EC history before they even reach the construction site. Documenting that history is critical to gaining a full understanding of the environmental impacts of a building.

As structural engineers, we are used to thinking about the load path through a structure. In a way, tracking EC follows a similar logic. We are following the load path of greenhouse gases into the environment over the course of the building’s life cycle, from raw material extraction through disposal or reuse, with greenhouse gas emissions accumulating along the way. Missing a stage in the process provides an incomplete picture of the system behavior.

One of the challenges with quantifying EC is having access to accurate and complete data for different materials. Wood, steel, and concrete are heavy in embodied carbon at different stages in their life cycle, so a comparison between the three can be misleading if there is not sufficient data to capture each stage. Furthermore, EC is measured as kilograms of CO2 equivalent per kilogram of material, so comparing the embodied carbon of one material to another is misleading without a full building analysis.

Starting from a 3D structural model in Revit, it is possible to approximate the EC of a project. By linking a life cycle assessment tool, such as Tally, to the structural model we can calculate the EC based on industry averages for the greenhouse gas emissions associated with each material.

Once this information has been gathered it is much easier to see where effective changes can be made in order to construct a more sustainable building.

This month’s blog is by Lydia Moog.

For additional information on mass timber and embodied carbon, please read our June 2020 blog post.

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