5 green building trends: Lifecycle carbon assessment takes big step forward

lifecycle assessment tool, EC3, Embodied Carbon in Construction Calculator, Microsoft, Redmond

This is one of five major green building trends we’ve identified for 2019. To explore more of them, see our Five green building trends for 2019 cover story.

The construction industry finally has a plan of attack along its most formidable remaining front in the war against carbon.

So far, architects, engineers and builders have addressed only half the problem. To be sure, they’ve made a lot of progress. New and renovated buildings operate more efficiently than ever before. Energy-use intensity has dropped with each advance in lighting, mechanical systems, insulation, codes and design. Those improvements, alongside leaps forward for solar energy, now make net zero buildings truly viable. If the construction of highly efficient buildings isn’t yet widespread enough, at least it’s headed in the right direction.

It’s all good — right? No. Not really.

“We’ve been focusing hard on the operations side,” says Skanska USA Sustainability Director Stacy Smedley. “[But] we now know that if you look at a building’s lifespan, between now and 2050, half of the carbon will come from operations and half will come from carbon embedded in the materials used in construction.”

In other words, carbon emitted in the process of manufacturing materials, transporting them to the job site and constructing a typical building is equal to the amount that the building will emit during three decades of operations. And it stands to reason that the more efficient building operations get, the larger the share of the problem owned by materials and construction.

Wrapping one’s arms around the issue of embedded carbon has seemed an insurmountable task — replete with starts and stops, transparency issues and a lack of standards.

Until now.

Smedley is part of a team working with the University of Washington Carbon Leadership Forum to develop a standardized system to track carbon embedded in construction materials. They began by collecting data on more than 1,000 buildings, categorizing buildings by type, and digging into the carbon emissions embedded in components of those structures.

One highly efficient Seattle mid-rise demonstrated just how big an elephant in the room materials have become in any discussion of buildings and carbon. The benchmarking exercise found that “it will take 255 years of building operation to equal the amount of embodied carbon produced during manufacturing and construction.”

This isn’t an entirely novel endeavor. Athena Impact Estimator, Tally and One Click LCA are among the tools competing to help project teams measure manage embodied carbon. While LEED offers a credit for lifecycle carbon assessment and the Living Building Challenge sets an “imperative” for embodied carbon, the organizations behind those two certification platforms are developing separate standards for a more systematic “Zero Carbon” certification.

As with the evaluation of toxicity in materials, however, the effort to assess carbon impacts has been stymied by a lack of transparent, systematically collected data.

“It’s at the level of all manufacturers that this information needs to be shared, and there has to be a common understanding of it,” Smedley says. “Everyone needs to come up with their emission data the same way.”

The fruit of all this labor is called the Embodied Carbon in Construction Calculator, or EC3. Although it’s meant to complement existing lifecycle assessment tools, EC3 is an embodied carbon application in its own right. It includes an open-source database on embodied carbon for materials and products, which can be communicated to end users in the form of Environmental Product Declarations.

Microsoft has joined Skanska as a key partner on EC3. Skanska is the general contractor on the software giant’s Redmond, Wash., corporate campus, and the two companies are piloting EC3 on that project.

EC3 is scheduled to become available to the public later this year.

PHOTO AT TOP: A massive renovation of Microsoft’s corporate campus in Redmond, Wash., is serving as the pilot project for EC3. Photo courtesy Microsoft.

The Kendeda Living Building Chronicle reports on regenerative design and construction, which a special focus on the Kendeda Building for Innovative Design and Construction. To explore more of our Five Green Building Trends for 2019, click here.



  1. Some of us have been talking about this issue for a long time. I want to focus on the need to get the terminology and language right. Precision in language is really important and we are muddying this crucial issue by not paying attention to what we are calling our goal. “Zero Carbon” certification, and reducing “embodied carbon” as a goal. This imprecision not only ignores, but unintentionally disadvantages the shift to building materials that have significant physically embodied carbon in them – wood, straw, hemp, and other materials that can sequester carbon in the buildings. So, what we want are high performance buildings with high physical carbon content and low climate impact from their production and use. Using terminology like “zero carbon” buildings as our goal confuses this issue and makes it harder to get people to understand what we’re trying to achieve.

    It is easy to see how this happened by looking back at the history of trying to grapple with the embodied energy versus operating energy issue. For a long time those focused on energy efficiency would dismiss embodied energy concerns as trivial, dwarfed, they would point out, by operating energy over the lifetime of a building. The percentages we heard ranged from roughly 10 to 15 percent of total lifetime energy for buildings. It’s a small number they would say, and I would counter that a huge number (operating energy) made a large number (embodied energy) look small. I would also point out that it’s significance would become more obvious as we created ever more energy efficient buildings, because the embodied energy percentage would increase as the operating energy of these buildings decreased. And, at least as important, because most of the strategies used to reduce operating energy would actually dramatically increase embodied energy – think much more energy- and climate impact-intensive foam insulation (and more insulation overall), higher tech materials, windows, and equipment, and the renewable energy systems used to reach net-zero or net-positive operating energy targets. So, I would ask, when operating energy gets to zero, what percentage of lifetime energy use of a building does embodied energy represent? Not 100% because of repairs, maintenance, refurbishment, etc., but certainly a very high percentage.

    Then, as climate impact finally became the central driving issue, without carefully considering the implications, we just substituted the term “embodied carbon” for “embodied energy.” But the word “embodied” embodies two distinctly different concepts. One is physically embodied carbon, and the other is embodied carbon/climate impact. Though it may seem unimportant to many, this imprecise and inaccurate use of terminology makes communicating the importance of doing both things harder. Something already complex and challenging for many people to grasp is made more difficult.
    And one other aspect of this entire issue, yet to be fully confronted and sorted out is the time value of our actions to reduce the climate impact. When we do all these great things to reduce operating energy to zero, we essentially bring almost all of the impact to the present. Thinking about conventional buildings, we have the embodied impact from the materials and processes that go into making the building, to which, over time is added the operating energy impact. When we focus on getting to net-zero or net-positive energy for these buildings and increase their climate impact in the process, rather than that smaller initial impact with a slowly growing overall impact playing out over the life of the building, we maximize the immediate climate impact just when we need to be focused on reducing our immediate impacts. This is a dilemma that needs much more careful analysis – where is the sweet spot to maximize our effectiveness in reducing near and longer term climate impact. As we look at that issue, we can see that an important part of the strategy is to properly understand, describe, and encourage the use of high embodied carbon materials in our high performance buildings, along with reducing the use of high climate impact materials, systems and designs.

    • Nice summary of a difficult topic, David. In speaking about this issue, I will use the term ‘high sequestered carbon materials’, ie wood, etc., to differentiate these materials from ‘high carbon emitting materials’ ie concrete, etc. I found that ‘sequestration/emitting’ seems to be a better differentiator than ‘embodied’ for the reasons you mention above – the confusion with ‘embodied energy’. Your point about the time value of reducing operating energy later at the expense of high embodied energy materials today is excellent.

  2. My heart is filled with hope when I see such great news! I believe that the big steps will be the future of energy and many technological applications will emerge from the solutions found in the sector!