Construction Management, Environment, Sustainability

A message for those of you working to reduce the carbon impact of our buildings and infrastructure – don’t sleep on embodied carbon. For nearly forty years our answer to the call to address global climate change has been to reduce energy consumption, also known as operational carbon. As one would expect with forty years of focus, we have made great progress – examples include high performance facade design, mechanical system responsiveness and efficiency, LED lighting, the availability of renewables, and robust energy codes. But even if every building achieved operational carbon neutrality, we would still miss our 1.5 degree Celsius target. Why? Embodied carbon. 

Embodied carbon is the greenhouse gas emissions resulting from the manufacturing, transportation, installation, maintenance and eventual disposal of building materials. As I like to say, it’s the carbon that is baked into the cake. Consider this: most of the embodied carbon footprint of a building is front-loaded, meaning that carbon is already in the atmosphere. Whereas operational carbon can be thought of as future carbon, starting at zero on Day 1 and building up from there. With 2030 not far off, embodied carbon offers a tremendous opportunity to make an impact now. An honest accounting of a project’s impact requires a view of the Total Carbon Picture – operational as well as embodied. 

There is a time value to carbon, meaning there are different levels of impact based on when we make reductions. For example, if you have two buildings that reduced carbon by 50 percent over a 10-year timespan, a building that makes those reductions up front via embodied carbon has a significantly lower climate change impact than a building that cuts operational carbon 5 percent a year over 10 years. In a perfect world a project does both, but those unicorns are few and far between. Anybody who has experienced the complete process of planning, design and then construction of a building knows that tradeoffs are unavoidable. What we can do is inform those decisions using the Total Carbon Picture approach so that the tradeoffs made best align with the project mission and its overall carbon performance.

Cities are waking up to this reality. In New York, Mayor Adams recently issued an executive order, EO23 Clean Construction, calling on projects built with city funds to utilize low carbon concrete, develop environmental product declarations, and utilize low emission construction vehicles and equipment. While city-funded projects make up a small percentage of total construction in NYC, the importance of this executive order is its signal to the market that embodied carbon is a priority. Many other cities and states are following suit with either local laws or statewide procurement requirements. Even the federal government is getting into the mix with new guidelines requiring carbon disclosures for vendors over $7.5 million and within the Inflation Reduction Act. While these signals are uncoordinated and generally coastal, there are enough of them to prompt action for those looking at our future market through the lens of competitive advantage or risk management.

At AECOM, our Construction Management business has already begun preparing for this future by measuring embodied carbon on projects whether requested by the client or not. We know, to solve a problem effectively, we must first understand it, but in our case, we must understand it across a variety of project types in a variety of different markets. That means we are measuring the embodied carbon footprint of concrete and steel, from arenas to skyscrapers, from New York to California.

If understanding the problem is step one, doing something about it is an obvious step two. In parallel to our project measurement effort is a large sub-contractor engagement initiative. We recognize that our sub-contractor partners are critical in any effort to decarbonize the construction material supply chain. They have a sensitivity to cost premiums and material lead times that is extremely valuable and through this initiative our relationships are evolving to include discussions around carbon performance that have never happened before. Our goal is to engage with every sub-contractor in the top 50 percent of carbon emissions in our supply chain.

At the other end of the project spectrum, success will require clients to engage builders earlier than in the past. On some projects, we are hired for pre-construction services where we are a voice at the table during design. Traditionally, that role has been focused on cost and schedule, but now we are beginning to roll carbon into the decision-making process. As builders, we are in the unique position to quickly understand the cost and schedule impact of low carbon decisions. Also, through our relationships with sub-contractors, we can bridge any gaps between the low carbon aspirations of the design and what the market is able to deliver.

Solving complex, multivariate problems has been a hallmark of our work for decades and decarbonizing construction will be no exception. Together, we can get it done.

Originally published Apr 27, 2023

Author: Max Driscoll, AIA, LEED-AP