Article Designing with Carbon in Mind

Every product requires energy to produce, and this is referred to as embodied energy. When all of the embodied energy required in a building or city is considered, it becomes a large impact. One of the most common environmental impact measurements directly linked with energy is the embodied carbon, which is becoming a greater focus for architects and designers. There are growing initiatives to identify and reduce embodied carbon associated with the design process.ng at when considering commercial flooring needs.

What is Embodied Carbon?

Carbon is a chemical element, and carbon-based molecules are the basic building blocks of all living things. Carbon can be found in the ocean, plants, animals, air, rocks, and soil, as well as in fossil fuels, like gasoline, coal, oil, and natural gas. When a fossil fuel is burned, carbon is released in the form of carbon dioxide (CO₂) gas. The following table shows pounds of CO₂ emitted per million British thermal units (Btu) of energy for various energy types:

Source: https://www.eia.gov

Different types of fossil fuels release differing amounts of carbon dioxide when burned. Embodied carbon — or carbon footprint as it is commonly called — measures greenhouse gases released from a product over its lifecycle, including during manufacturing. So a product made with renewable energy like solar or wind would have less embodied carbon than a product produced from energy derived from coal. Embodied carbon includes the energy used to make the raw materials, so even if a product is produced with solar energy, the raw materials may still be produced from fossil fuels.

In studying climate change, scientists use greenhouse gas equivalents; for example, 1 kg of methane, a greenhouse gas, is equivalent to 25 kg of carbon dioxide. Because of these conversion factors, scientists are able to provide a carbon dioxide equivalent (CO₂e) or global warming potential for products. A CO₂e value expresses the potential global warming impacts of all greenhouse gases released during a product’s life cycle in CO₂ equivalents. This process allows greenhouse gases to be “bundled” in such a way that the impact of potential greenhouse gases can be compared.

What is Operational Carbon?

In addition to embodied carbon, a building also has operational carbon impacts. Operational carbon measures the emissions of carbon dioxide during the operational or in-use phase of a building. Together, embodied carbon and operational carbon make up the total carbon impact of a building. Recently, attention has been focused on understanding and reducing operational carbon in buildings. As efforts to reduce operational carbon succeed, focus is shifting to the importance of embodied carbon.

Now that we’ve set a foundation for carbon and how it is discussed, let’s look at action steps for designing with carbon in mind.

Growing Urban Populations

One hundred years ago, about 20% of the global population was urban, while today that numbers sits at 55% — and it’s expected to increase to 68% by 2050, which is adding 2.5 billion new urban residents (United

Nations, World Urbanization Prospects). The increasing concentration of population results in a need for more buildings, which involves both operational and embodied carbon at increasing rates.

Due to a growing need for places to live and work, global building square footage is projected to double between now and 2050 (IEA, Energy Technology Perspectives, 2017). Planning and designing with these facts in mind will continue to rise in importance. Operational carbon often gets a lot of the attention, but as population densities continue to shift, designing with embodied carbon in mind — alongside operational carbon — will improve life cycle emissions in building.

Lowering the Carbon Footprint in Building

Architects and designers are in a position to take a more holistic look at carbon as they work toward net-zero operational energy. Net-zero is achieved when renewable energy supply (including off-site generation or procurement) equals total energy demand. Favorable pricing trends of renewable energy means “closing the gap” will be achieved primarily through increasing renewable supply, instead of lowering demand beyond code requirements.

As we continue to move toward net-zero energy performance, the carbon impact of products, materials and construction will continue to grow as a percentage of overall impact. When looking at the energy consumption footprint from 2015 through 2050, building materials are expected to contribute 90% of energy consumption while building operations consume just 10% (2030, Inc. & EIA (2011), Richard Stein, CBECS, McKinsey Global Institute).

In light of the impact of embodied carbon on energy consumption compared to operational carbon, designers can focus efforts on high-volume, high-impact materials such as steel and concrete, and understanding that the manufacturing locations of building materials can have major impacts on total embodied carbon.

Identifying Carbon in Products

A product’s carbon impact is shown in Environmental Product Declarations (EPDs), which have been gaining fast recognition as the gold standard of product disclosures. EPDs help designers understand the environmental impacts of a product, what causes them, and where they occur in the life cycle. This provides opportunities to reduce a project’s carbon footprint. When dealing with a manufacturer who provides EPDs, there’s a good chance you can be confident that they are credible and environmentally responsible, because manufacturers use these documents as a roadmap to improve their products and reduce carbon footprints.

Life Cycle Assessment (LCA) is a method to systematically measure the environmental impacts, including the carbon footprint, associated with each stage of a product system or building’s life cycle. LCAs can be found in EPDs, and can help designers consider durability and recyclability when selecting products, choose lower-carbon alternatives, and consider reusing materials or high-recycled content materials for projects.

For more information and tools on designing with carbon in mind, consider these resources:

• NIST Building for Environmental and Economic Sustainability (BEES) Tool
• Embodied Carbon in Construction Calculator (EC3)
• Tapestry