Why Should I Care About Embodied Carbon?

From a design perspective, we’ve figured out how achieve “net-zero energy” buildings in almost every climate around the world and building typology. Passive design strategies can reduce the energy required to heat, cool, and light buildings. Some examples include optimizing a building’s orientation to maximize the solar gain in an effort to reduce the demand for heating. Or arranging a building’s form to self-shade itself during the summer to reduce the need for cooling. When applying passive design strategies effectively, the operational energy consumption can be reduced significantly. Coupling passive design strategies with automated controls and efficient equipment and appliances, operational energy consumption approaches zero. Adding rooftop or façade photovoltaics (or another electricity generation system) can move a building’s energy-use intensity to being “net-positive”, producing more energy than it consumes. While “zero-energy” or near “zero-energy” buildings are rare in the context of the global building stock, they can be achieved both in the contexts of retrofitting and new construction.

Yet this idea of “zero-energy” is misleading (why I’ve been putting it in quotes). It does not consider the total lifecycle energy consumption (or emissions) of the building. Let’s think about the typical single-family residence that is commonplace in America. The wood frame structure of this 1000-2000 square foot building uses wood that was grown in the Pacific Northwest and trucked to the jobsite, with fiberglass insulation created from heating silica sand, limestone and soda ash to nearly 2500 degrees Fahrenheit, which sits on a concrete foundation. Each of these materials did not magically appear at a job-site without some sort of energy. Yet, “zero-energy” buildings ignore these energy demands making which is a false-term.

In my experiences talking with designers about their “sustainable” projects, they often boast about the low energy-consumption their buildings have, giving no mention to the materials. Or if they do considering them “locally sourced”, or another green-washed term. Yet, for a low-energy house, the energy and emissions required top manufacture, transport, construction, refurbish, and demolish a building, the “embodied” energy and emissions can be higher than the operational emissions over the building’s lifespan. We need to move away from talking about “zero-energy” buildings and talk about “zero lifecycle-energy” buildings or as I like to call them “absolute zero-energy” buildings.

When we aim to design “absolute zero-energy buildings” we look at both the lifecycle energy consumed, and emissions released – including both the embodied and the operational. This concept is new to building designers, at least in the United States. Going through a 4-year undergraduate degree in one of the top Architectural Engineering programs, I had never heard of the terms “embodied energy” or “embodied carbon”. When working as a structural designer, it wasn’t mentioned once, even though we were working on “sustainable” projects that would become LEED accredited. Over the past couple years, more people are becoming familiar with the embodied environmental impacts of their buildings, which is exciting. Some groups and initiatives that are of note in the United States include Architecture 2030, the Embodied Carbon Network, and Structural Engineers 2050 Challenge.

Here in the United Kingdom, more designers are familiar with the idea of reducing lifecycle emissions. I think it has something to do with the paradigm or a circular economy that many older countries have, and something that the US has yet to need to consider since there’s always more space to expand into and consumption drives economic output.

My research this year focuses upon quantifying the extent to which embodied emissions (specifically carbon) can be reduced in the global building stock. Currently I am working to model the global building stock from a materials perspective (more to come on that). By understanding how materials are used and “flow” through urban environments, we can start to grasp at a large scale (global), the ways in which embodied emissions can be reduced.

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