Foundations and Methodology
LCA and embodied carbon
Life Cycle Assessments, or LCAs, measure the environmental impacts (including embodied carbon) of materials we use, including the energy used to extract it to the emissions caused by its demolition.
In a typical code building with a 60 year lifespan, the operational carbon is a larger contributor to carbon emissions. When we look at a high performance project, the embodied carbon starts to be a larger portion of the overall percent of emissions. However, we know that there is a time value to carbon. The Intergovernmental Panel on Climate Change (IPCC) issued a report that states we need to drastically cut carbon emissions by 2030 if we are to meet the Paris Agreement. If we use this 10 year lens from 2020, then embodied carbon emissions far outweigh operational; illustrating the importance that we must consider both the operational carbon and embodied carbon when designing.
We recommend evaluating your facades with this time value of carbon lens (10-year lifespan) in this tool but give you the option of using a typical 60-year lifespan as well.
methodology
This tool compares typical industry building systems in an apples-to-apples manner by using the same module (4’x14’), structure (not included, except if additional steel is needed needed, such as a shelf angle for masonry veneer systems), wall backup from interior drywall to air/vapor barrier, detailing strategy using thermal breaks, and most importantly the same R-value (IBC code minimum R-15.625). The location is set to Boston, but we found that varying the location has minimal impact on the results.
Tally was used to generate the LCA analysis, and THERM was used to verify the R-value of each system.
Multiple lenses are available to view the data. One lens is removing Module D, or the LCA impacts associated with reuse potential outside the system boundary. We suggest removing Module D due to the uncertainty of the end of life of materials, as well as when we take into account the time value of carbon, and view data at only 10 years the product will ideally still be in use. For the 60 year lifespan we give you the choice to include Module D, as it is optional in American ISO LCA standards.
The “All Impacts” graph shows all environmental impacts in one graph using weighting per the impact category’s importance1. While global warming potential is the most crucial to combat climate change, it is important to consider other environmental impacts.
- Global Warming Potential………….. 54%
- Non-Renewable Energy Demand… 18%
- Eutrophication Potential…………….. 11%
- Smog Creation Potential…………….. 7%
- Acidification Potential…………………. 6%
- Ozone Depletion Potential…………… 4%
1 Environmental Impact Importance (%) by Voting Interest and Time Horizon Source: Life Cycle Impact Assessment Weights to Support Environmentally Preferable Purchasing in the United States; Environmental Science and Technology, Gloria, Lippiatt, & Cooper.
Understanding Life Cycle Assessment