While it is recognisd that buildings generate more than 170 million tons of construction waste annually; they account for almost 14 percent of all potable water use; and are responsible for almost 40 percent of carbon dioxide emissions, there is a metric missing from our daily conversations: embodied carbon, says Stacy Smedley* of Skanska USA.
On the operational side of buildings, designers and builders understand how to get to net zero through energy use reductions and renewable energy production. It is not an insurmountable stretch to get to zero emissions by 2050 for building energy consumption.
Embodied carbon, however, encompasses the carbon emissions associated with the manufacture, transport and installation of all of the materials necessary to construct a building or infrastructure project, and how it is the missing piece of the emissions pie chart.
“When you look at the two buckets of building emissions — operational vs. embodied — an interesting story begins to emerge. With such a focus on operational energy over the lifetime of a building, we have failed to give enough attention to the amount of carbon emissions we create in short periods to construct those buildings in the first place,” Stacey says.
“We know there is an imperative of zero carbon by 2050 to keep things on this planet from going haywire, and it’s simply not enough to get to zero on the operational side of the coin if the embodied carbon emissions haven’t also been reduced or offset completely.”
Skanska has moved forward quickly on finding a way to approach embodied carbon similarly to how to tackle operational energy consumption, and understanding the quantitative comparisons of the two.
“We needed to collect any and all building carbon footprints that we could get our hands on and utilize them to set benchmarks for embodied carbon per building type, so there was at least a dart on the dartboard of where to start and what to reduce against,” Stacey explains.
“We helped fund the first phase of research and data gathering for the creation of embodied carbon benchmarks across building types for the University of Washington’s Carbon Leadership Forum. The outcome of this effort is open source and can be found at http://bit.ly/2pz6hFQ.”
The study showed that there were a great deal of variables associated with how embodied carbon calculations are currently being completed. There is a wide spectrum of reasons why teams tackle or don’t tackle this quantification based on understanding, resources or client interest. And there is a glaring need for embodied carbon to be analyzed and benchmarked so it can be better understood and tracked by the building industry. Since the Embodied Carbon Benchmark Study effort, a lot of movement has occurred in a short time, including:
We are also seeing how presenting the data we already have is allowing informed clients to understand their potential embodied carbon and total carbon impact, and begin to set reduction targets that we can then help them work to accomplish. When owners see a metric that their building would need to operate for more than 200 years for the operational energy emissions to equal the embodied emissions of constructing the building in the first place, it’s hard not to want to do something.
We currently have a project in early design that has committed to becoming a zero-carbon building through reductions and offsets, based on the client simply understanding the project’s embodied carbon impact. We expect more to follow.
*Stacy Smedley is sustainability director at Skanska USA, where she provides strategic guidance for local and national projects.