February 9, 2017
The Time Value of Carbon
Making the case for the importance of embodied carbon.
To keep global temperatures from rising above 2°C and avoid catastrophic, irreversible climate change, global emissions need to peak by 2020 and fossil fuels be phased out by 2055[i]. Given those goals, there are two critical components we need to consider when evaluating carbon reduction strategies: first, the amount of potential savings a strategy offers, and second, the time frame of those savings. We need strategies that produce large savings fast.
As an end user of fossil fuels, the built environment accounts for more emissions than any other sector, producing nearly half of total global greenhouse gas (GHG) emissions[ii]. The current gold standard for reducing emissions from buildings is building new, zero net carbon (ZNC) buildings[iii]: super-efficient buildings powered by fossil-fuel free energy sources that have zero net emissions. This is a critical step to realize a carbon neutral built environment, but there is a problem with this strategy: building those new, ZNC buildings will generate substantial emissions.
Two other emission sources may be even more important to address in the short term: embodied carbon (eCO2e) emissions from building materials, products, and construction processes and operating emissions from existing buildings. Architecture 2030 estimates that U.S. eCO2e emissions from building materials and construction are 5.9% of total U.S. emissions[iv]. Since these emissions occur at the beginning of a building lifecycle, the impact on near-term emissions from building becomes more significant than the 5.9% figure implies. Materials matter: designing materially efficient buildings with low carbon materials and products can have a significant impact on near-term carbon emissions.
[i] IPCC. 2014. “Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change.” Geneva, Switzerland: IPCC.
[ii] “U.S. Energy Consumption by Sector”, Architecture 2030, accessed from http://architecture2030.org/buildings_problem_why/ 2016 07 27.
[iii] Architecture 2030, “Zero Net Carbon (ZNC) Building”, Accessed from http://www.architecture2030.org/downloads/znc_building_definition.pdf 2016 07 27.
The Time Value of Carbon Initiative is being led by Larry Strain of Siegel and Strain Architects. He is working to develop a white paper that builds on this topic that will be posted here when complete.