Embodied carbon refers to the greenhouse gas (GHG) emissions produced throughout the lifecycle of a building material, including raw material extraction, processing, transportation, and disposal. It is measured from the material's origin to its final use, often referred to as "cradle-to-gate" or "cradle-to-site." As buildings become more energy-efficient, the focus has shifted toward reducing embodied carbon emissions. Key strategies include using low-carbon, carbon-neutral, or carbon-storing materials like wood, hemp, or bamboo, as well as incorporating recycled materials to minimize emissions associated with new production.

To calculate embodied carbon and assess its environmental impact, a Life Cycle Assessment (LCA) is used. These results are often shared through Environmental Product Declarations (EPDs), which act like "nutrition labels" for materials. EPDs detail a product’s global warming potential, smog formation, and ozone depletion impact, enabling informed decisions about material selection.

The Urgency of Addressing Embodied Carbon

The world’s building stock is projected to double by 2060, equating to the addition of an entire New York City to the planet every month for the next 40 years. While this growth is promising for concrete producers, it presents a significant challenge for climate change. Cement, the key ingredient in concrete, is one of the largest contributors to CO2 emissions in the built environment. Cement production alone accounts for ~7% of global CO2 emissions, making it the single largest contributor to embodied carbon in construction.

Globally, the built environment contributes 42% of annual CO2 emissions. Within this, 27% comes from building operations, such as energy use for heating and cooling, while 15% is attributed to the embodied carbon of four critical materials: cement, iron, steel, and aluminum. Without substantial changes in how these materials are produced and used, the built environment will continue to exacerbate global emissions.

Why Reducing Embodied Carbon Matters

Addressing embodied carbon is vital for meeting global climate goals. Federal and state-level initiatives are already taking steps to tackle this challenge. For instance, California’s Buy Clean legislation sets strict limits on the GHG emissions of construction materials, with other states following suit. At the federal level, frameworks to encourage or require reductions in embodied carbon are under evaluation.

Reducing embodied carbon by just 10–20% can make a significant difference, cutting millions of metric tons of emissions annually and advancing decarbonization efforts. This can be achieved through innovations in material production, widespread adoption of low-GWP alternatives, and improved collaboration between designers, manufacturers, and policymakers.

Balancing Specifications with Real-World Constraints

Structural engineers play a pivotal role in reducing the carbon footprint of construction projects by conducting detailed embodied carbon analyses. These analyses identify low-GWP (Global Warming Potential) materials, such as specialized concrete mixtures and building enclosures, as well as options that incorporate recycled content into the superstructure. These recycled materials, including aggregates and industrial byproducts like fly ash or slag in concrete, can significantly reduce emissions by minimizing the reliance on virgin materials. However, the real challenge lies in the hands of general contractors (GCs), who must turn these design goals into practical realities.

One of the primary obstacles is the availability and cost of these materials. Low-carbon concrete mixes or recycled-content materials may not always be locally available, and when they are, they often come at a higher cost than conventional alternatives. Additionally, many material suppliers lack the capacity or expertise to meet the stringent low-carbon and recycled-content requirements within tight project timelines, further complicating the process.

The importance of effective time management cannot be overstated when it comes to implementing embodied carbon strategies. Embodied carbon analysis must be integrated into the early stages of a project, ideally during pre-construction. Delays in finalizing specifications for low-GWP or recycled-content materials can result in teams defaulting to traditional, high-carbon options due to scheduling pressures. To address this, early collaboration among structural engineers, suppliers, and GCs is crucial. This ensures that all stakeholders are aligned with the project’s embodied carbon goals from the outset. Furthermore, the extended production or testing times often required for specialized or recycled-content materials must be factored into the project schedule to prevent rushed decisions. Establishing quality assurance protocols to test and verify the low-carbon and recycled specifications of delivered materials is equally essential to avoid costly delays or rework on-site.

Even with the right materials in hand, GCs face additional challenges during construction. Workforce training is critical, as crews need proper guidance on handling, pouring, and curing concrete mixes that include recycled content or installing unfamiliar enclosure systems. Specialized or recycled-content materials may also extend certain phases of construction, requiring meticulous scheduling and coordination to maintain the overall project timeline. Successfully addressing these challenges demands a proactive approach, combining early planning, collaboration, and ongoing communication to align design intentions with the practical realities of construction. By doing so, GCs can effectively implement embodied carbon strategies and maximize the use of recycled content, contributing to a more sustainable and resilient built environment.

Looking Ahead

Successfully implementing embodied carbon strategies demands collaboration, foresight, and adaptability from all parties. By prioritizing early embodied carbon analysis and integrating procurement planning into the critical path of the project, GCs can ensure sustainable material choices don’t conflict with schedule or budget constraints. In an era where building codes and sustainability targets are tightening, proactive approaches to embodied carbon reduction will enable contractors to stay competitive, comply with evolving regulations, and make a meaningful contribution to global decarbonization efforts.