How to Measure Embodied Energy in Building Materials

Every building tells many stories, and one of those stories is how it impacts the environment. To understand that story, we can look at the greenhouse gas emissions of all the materials used to erect a building, as well as the energy it took to turn those raw resources into a habitable structure.

Learn how the concept of embodied energy shaped the face of sustainable design, and which materials have the most significant impact on global carbon emissions. We will also look at how architects and construction companies use the idea of embodied energy to build a greener future, and at the newer terms used to refine this idea.

What Is Embodied Energy?

Embodied energy, also known as embodied carbon, refers to the total amount of carbon expended in the front-end creation of buildings. This includes the mining and manufacturing of the building materials, the transportation of the materials to the construction sites, and the construction of the buildings themselves. 

Every material used in construction—including but not limited to concrete, lumber, aluminum, steel, glass and plastic—currently relies on burning fossil fuels during extraction, manufacture, transportation, and construction. Once buildings are erected, they “embody” the carbon expenditures of the resources required to build them. 

However, this embodied energy does not literally reside inside the structures—those emissions have already been released into the atmosphere. That’s why some sustainability experts prefer the term upfront carbon emissions, which more accurately describes the energy expenditures, a term coined by Treehugger's own Lloyd Alter.

Life-Cycle Emissions

Embodied energy is distinct from life-cycle emissions, which include operational emissions of a building (lighting, heating, and cooling, for example), upfront carbon emissions, as well as the eventual disposal of the building materials.

In previous decades, operational emissions far outweighed the embodied energy of buildings. But as operational efficiency has increased, embodied energy or upfront carbon plays a much bigger role in life-cycle emissions. In the most efficient buildings, sometimes as much as 95% of their life-cycle carbon expenditures occur during the initial construction.

How Embodied Energy Is Used in Sustainable Architecture and Design

As architects, construction companies, and designers consider the IPCC’s urgent call to reduce global carbon emissions by 43% by 2030, some sustainable building experts argue that it’s far more “green” to preserve the embodied energy of existing buildings. 

Construction is one of the fastest-growing sources of carbon expenditures and currently accounts for nearly 40% of energy-related carbon emissions worldwide, according to The Institution of Structural Engineers in the UK.

Cement production alone accounts for 5% to 7% of global emissions with one ton of cement production releasing 900 kilograms of carbon into the atmosphere. In 2012, iron and steel accounted for 31% of industrial carbon emissions. A 2022 study conducted in China found that more than 70% of the embodied energy of all building materials resides in cement, steel, and brick.

When a building is demolished to make way for a new one, the totality of its embodied energy is wasted, and a new building with its own upfront carbon demands must be built. Investing both money and carbon expenditures to upgrade existing buildings for better operational efficiency results in those new carbon emissions becoming part of the building’s embodied energy. In preserving and updating existing buildings, the embodied energy of the initial build remains. 

For buildings of historical importance, in particular, embodied energy represents an enormous existing resource that can be preserved and updated to meet contemporary efficiency standards. Construction and architecture professionals depend on research to direct their design choices, but unfortunately, the current rating systems for sustainability don’t reflect the equitable quantification of historic buildings, according to one 2005 study.

Critics of this line of reasoning counter that the “sunk cost”—the carbon already expended to create the existing buildings—shouldn’t dictate future building choices because those emissions are already in the atmosphere. What should be of greater concern, they contend, is future carbon expenditures, either from operational or retrofitting emissions. 

How Is Embodied Energy Measured?

There is no single international standard that clearly defines the embodied energy of any material item, including buildings, making it one of the great challenges sustainable designers face. This is primarily because building materials and their subsequent emissions vary greatly, even within a single country.

Generally speaking, the embodied energy of a building is calculated as the equivalency of carbon emissions in kilograms per volume of material (kgC02e/m3). The materials themselves are measured in kilograms, and the carbon factor for each material is calculated as an equivalency (the e in the equation above) of carbon emissions per kilogram of material.

These measurements, again, are separate from operational emissions, which in the United States are often calculated in terms of pounds of carbon per square foot per year.

Why Embodied Energy Is Important to Sustainability

Sustainable design and architecture experts can use embodied carbon as a design metric when considering both retrofitting and new construction. The earlier in the process that the design team considers these pressing issues, the greater chance that the project has of reaching its greatest level of sustainability. 

This process requires time and dedication as many changes may need to be made after the embodied energy assessment of any given building. This applies to both commercial and residential structures (and residential buildings use the biggest share of energy and natural resources).

For the people paying for energy and water to both residential and commercial buildings, operational efficiency often acts as a cost-savings tool. Heating and cooling costs, for example, are proportionally decreased the better insulated a building is. 

But sometimes the more Earth-friendly solution is more expensive. Take aluminum—the world’s second-most used metal. Aluminum production accounts for 3.5% of global electricity consumption, the majority of which comes from the burning of fossil fuels. A 2020 study found that zero- or low-carbon electricity costs would increase by 26% in order to meet the EU’s target carbon emissions. Unlike plastics, which have next to no recyclability, aluminum is easily recycled and requires less than 5% of the energy required to produce new aluminum.

The future of embodied energy and sustainable architecture lies in the use of recycled or reclaimed materials, raw construction materials that use fewer natural resources to produce (namely less concrete), and better planning for the long-term use of the land and the buildings we place on it.