Embodied Carbon Studies Continue

In 2023, C&H intern Molly Neu researched the embodied carbon impact of building renovation projects. Read the full report via link at the bottom.

Executive Summary

Reducing our carbon footprint is critical because it lessens the effects of global climate change, improves public health, and maintains biodiversity. Emissions produced by the built environment account for 40% of global emissions, making reduction of building sector emissions an utmost priority for creating a low carbon future. In recent years, there has been a push towards decreasing the operational carbon of buildings, with the goal of “carbon-neutrality”. However, a building cannot be carbon neutral without considering the emissions associated with construction, material production, maintenance, and demolition. This is where embodied carbon comes in. Embodied carbon is “the greenhouse gas emissions arising from the manufacturing, transportation, installation, maintenance, and disposal of building materials”, as defined by the Carbon Leadership Forum. In order for a building to be carbon neutral or even low-carbon, both operational and embodied carbon must decrease. High embodied carbon has a negative impact on the environment, while the impact of high carbon sequestration is positive.

This project is a carbon study exploring the embodied and operational carbon of Washburn House, an 150-year old dormitory building at Smith College. We calculated the changes over time of the embodied carbon – using the BEAM Tool – as the building went through several renovations, and tracked the operational energy as the college transitioned from coal to oil to methane gas, and soon to a low-temp hot water system powered by electric ground-source heat pumps. Many experts have begun encouraging the renovation of older buildings over demolition, as renovation often releases less total carbon emissions than an entire new build.

Using the CARE Tool, we analyzed two different scenarios, one comparing renovation to a new low-carbon building and another comparing renovation to a typical new building. For the low-carbon building, the renovation produced less emissions for the first 15 years before the new building became slightly lower in emissions due to lower energy consumption. With the typical building comparison, the renovation produced significantly lower emissions for the entire study. Both scenarios supported the notion that renovation is preferable over demolition, as carbon emissions being produced now is of the utmost importance to avoid.

With the ultimate goal of the study being to assess the feasibility of tax credits based on avoided embodied carbon, we then calculated the embodied emissions that would be avoided through renovating instead of demolishing. This included the emissions associated with demolishing Washburn House as well as the embodied carbon of the new build. We chose to complete these calculations for the low-carbon building, meaning the tax credit value would be larger for the typical building.

In order to calculate the value of tax credits, we needed to understand the social cost of carbon, “an estimate of the cost, in dollars, of the damage done by each additional ton of carbon emissions”, as defined by Brookings Institute. Due to technical challenges, such as environmental tipping points and positive-feedback loops fueled by carbon emissions, as well as political disagreements about how to quantify environmental damage, there is still much debate about a precise value for carbon. Although this is the case, many experts still believe carbon is currently greatly undervalued, and considering that as more carbon is added to the environment, the Earth creeps closer to these environmental tipping points, the value of carbon should be ever increasing.

Currently the Biden Administration has set the value at $51/ton, while the EPA suggests raising the number to $190/ton. Even at this increased figure, the value of the carbon tax credits is still too low to have a significant impact on the construction industry and decisions around avoiding demolition to decrease carbon emissions. However, higher figures have been proposed. Specifically, some modeling done by the EPA showing values as high as $340/ton and other modeling completed by the BPEA and Resources for the Future that have shown the value as high as $719/ton. Although these values are currently considered to be outliers, these values must be considered for significant change to occur, as the current and proposed values are far too low to have an impact on construction decisions.

Read the full report here.