Embodied Carbon 101

Embodied carbon is the emission footprint that comes from harvesting, transporting, and manufacturing building materials. Each stage in the process of getting building materials to a construction site causes greenhouse emissions and this carbon footprint from the materials can be very significant. Since the embodied carbon of building is so significant it’s important that we learn how to work with these numbers and come up with accurate figures.

We need to do a basic accounting of how embodied carbon is associated with each material and then how much embodied footprint an entire building will have if we’re going to be able to reduce it. To understand embodied carbon we need data. This data comes from studies called ‘Life Cycle Assessments’ or LCAs which look at all phases of the materials life span and add up all the carbon emissions that happen.

In most scenarios we’re looking at a ‘Cradle to Gate’ emission for a total of all the greenhouse gasses released during harvesting, transportation, and manufacturing of the material. Once we know the ‘Cradle to Gate’ emissions of each material in a building we can add up the sum total of those emissions and get a sense of all the carbon footprint of making one particular building. In the past it’s been difficult to access LCAs which leaves it difficult for anyone to figure out what the carbon footprint of a particular building might be. But now there’s a report called an ‘Environmental Product Declaration’ or EPD in which companies show the life cycle assessments of their products. The embodied carbon is expressed as a ‘Global Warming Potential’ or a GWP factor. For a given amount of a specific material you can then multiply the amount of material you are using by its GWP factor to figure out what the carbon emissions for each material on a building will be. This kind of carbon analysis can give us a really good sense of which materials have a high embodied carbon and which ones we might be able to replace them with a lower embodied carbon. If we make the right choices we can have a dramatic impact on the climate change effects of any given building.