Embodied Decarbonization

Challenge

Increasingly, decarbonization is understood to be the path toward a sustainable future. We know 40% of greenhouse gas emissions are controlled by “operational carbon” or rather by things we do in our households through our active human comfort systems and appliances. However, “embodied carbon” emissions can account for up to 75% of a building’s total emissions over its whole lifespan. Consider all the materials utilized in a home’s construction, from concrete foundations to wood framing, to roof shingles. Embodied carbon is the sum of all the greenhouse gas emissions resulting from the mining, logging, harvesting, and processing of these materials. Plus, the transportation to the job site and the method of construction used. Embodied carbon is all the carbon that is emitted before the building is even occupied. Today, the embodied carbon emissions in constructing a new home are equal to approximately 20 years of operating emissions. And as homes increasingly get more energy efficient, the AIA estimates that 80% of emissions will come from embodied emissions, so lowering embodied carbon emissions is potentially more urgent now than lowering operating emissions.

Opportunity & Response

There are several complimentary approaches to reducing embodied carbon in new home construction. These include:

1) Utilization of low-carbon materials – Architects already use energy modeling software to estimate the energy use (and subsequent carbon emissions) of building operations. But the industry has lacked a standardized system to track the carbon embedded in construction materials. Recently however, the development of open-source tools such as the Athena Impact Estimator, and the Embodied Carbon in Construction Calculator (EC3), are beginning to make it easier. While these tools are currently optimized for commercial building analysis, another approach in residential construction is to utilize “red lists” developed by organizations like HBN. While red lists are focused primarily on health impacts of material specification, research shows that red list materials map closely to high-carbon materials as well.

2) Reducing total materials in the design of the home – simplify systems, reduce redundancy, and insure means and methods during construction to ensure building performance is optimized

3) Design for longevity – consider issues of both durability and resilience in developing building assemblies

4) Repurpose resources – utilize reclaimed and recycled materials, and leverage all “sunk investments” in site development.

Implementation