Metrics of Sustainability: Embodied Carbon vs. Energy Efficiency

Construction workers reviewing embodied carbon and energy efficiency metrics of sustainability on site.

Sustainability is a crucial consideration in the construction industry. There are two main metrics for measuring a building’s sustainability: embodied carbon and energy efficiency. But what’s the difference between them? And which one is more important?

For years, sustainable construction has focused on energy efficiency, but embodied carbon may provide a more accurate reading of the environmental impact of the construction industry.

What is Energy Efficiency?

The discourse about energy efficiency began in the 1970s and was initially just called conservation. This trend was the first major call for builders to consider the environmental impact of their designs.

Energy efficiency is a measure of how much energy a building uses during operation and doesn’t take into account the energy required to create the building. High energy efficiency is the goal of construction trends like net-zero homes and codes and standards such as the 2021 International Energy Conservation Code and American National Standards ANSI/ASHRAE/IES 90.1 and ANSI/ASHRAE/IES 100.

What Is Embodied Carbon?

Embodied carbon is a measure of the carbon dioxide emissions associated with the manufacturing, transportation, and installation of building materials. When these materials are used in construction, they release carbon dioxide emissions, which is the primary greenhouse gas contributing to climate change. The embodied carbon of a building material is typically measured in kilograms of CO2 equivalent per square meter (kgCO2e/m2).

“Embodied energy” and “embodied carbon” as discussion topics have emerged far more recently than “energy efficiency,” as greater strides toward sustainable construction have led both professionals and the public to consider sustainability in a broader context. The goal of analyzing embodied carbon is to increase the energy efficiency of the entire construction industry from beginning to end product, instead of only considering the operational energy costs of the final design.

What is Embodied Energy?

Embodied energy differs from embodied carbon in several ways. Embodied energy takes into account the energy required to extract, process, and transport the raw materials, as well as the energy used in manufacturing, but it doesn’t take into account the source of the energy. Some embodied energy may come from renewable sources that don’t emit greenhouse gases.

“Embodied carbon” is emerging as a more precise term than “embodied energy” to talk about sustainability concerns because embodied carbon measures only the carbon emissions and energy use considered problematic, such as greenhouse gases produced by burning fossil fuels versus hydroelectric power.

Is Embodied Carbon More Important than Energy Efficiency?

Energy efficiency only looks at operational emissions, while embodied carbon only looks at the emissions created during the construction phase. “Operational carbon” has emerged as another measurement of energy efficiency precisely to mirror the measurements of embodied carbon.

Both metrics are important in different ways. Energy efficiency is important for reducing operational emissions once the building is up and running. Embodied carbon is important for reducing the environmental impact of new construction.

Embodied carbon is changing the way we look at sustainable construction. For example, some materials used in energy-efficient homes, such as plastics, allow for lower operational carbon but have a high embodied carbon. Considering the embodied carbon of the home during construction may lead to choosing a different material with lower resulting emissions overall.

What Can be Done to Reduce Embodied Carbon in the Construction Industry?

There are a few things that can be done to reduce embodied carbon, and the building industry can have a significant impact on carbon emissions worldwide. The building sector accounts for roughly 38% of global carbon emissions, so taking steps to reduce emissions at all stages of the process is vital.

Carbon calculators intended for use by industry professionals have been developed to help builders make informed choices on the materials they choose using expected life-cycle assessments (LCAs) and environmental product declarations (EPDs).

Transportation is also a major factor in embodied carbon, so general contractors can assist in lowering emissions by buying locally sourced materials, planning the use of machinery efficiently across the site, and using “no idling” policies already in place in many urban construction sites. Machinery and vehicles that use alternative fuels are also being explored.

Another way to tackle the issue is to focus on resilient construction, creating buildings that will last longer with the same or smaller embodied carbon amount. Because the embodied carbon is finite—the measurement covers a specific phase of construction that ends once the building is constructed—the longer the building lasts, the more efficiently it uses its embodied carbon cost.

Combining Approaches for Best Results

Both embodied carbon and energy efficiency focus on the core challenge of sustainable construction: the carbon emissions generated by the construction and use of buildings. Tackling this challenge effectively requires a multi-pronged approach that considers all aspects of the building process. As the understanding of sustainable construction develops, the industry is creating ever more nuanced approaches to facing climate change.

Contributing Author: Justin Havre, Justin Havre & Associates

Justin Havre is a renowned thought leader in the real estate space and leads the Justin Havre & Associates of RE/MAX First team, the #1 RE/MAX team in Canada.

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