Page 101 - Designing for Zero Carbon - Case Studies of All-Electric Buildings

REDFORD CONSERVANCY AT PITZER COLLEGE CASE STUDY NO. 4
Sidebar: Embodied Carbon Assessment
Embodied carbon in a building refers to the greenhouse gas emissions associated primarily with the extraction and manufacturing of materials used for the construction of the building. It also includes carbon generated by the smaller effects of transportation to the building site, construc- tion processes and disposal of materials at demolition (“end-of-life”).
Operational carbon in a building refers to the greenhouse gas emissions associated with the energy use in the operation of the building in its lifetime. As energy efficiency in buildings increases and renewable energy sources replace fossil fuel sources, the total operational carbon will gradually be minimized and embodied carbon will become the focus of significantly reducing carbon emissions in the building sector.
Embodied carbon reduction is primarily accomplished by choosing the materials and building systems with lowest carbon emission quantities due to raw material extraction, manufacturing and shipping to the building site, while satisfying the particular design requirements of the build- ing. During the design phase, alternative design choices can be compared for embodied carbon quantities.
Units of embodied carbon quantities are typically metric: kg CO2, or kilograms of carbon dioxide. A “metric ton” of embodied carbon is 1000 kg CO2. (Note: for greenhouse gases other than carbon dioxide, the unit of measurement is kg CO2e, where CO2e is “carbon dioxide equivalent”. For example if methane is used to make the product, the number of kilograms is multiplied by 25 to calculate the equivalent to that mass of embodied carbon in the material for its global warming effect.)
The methodology of comparison of design or material alternatives is called Life Cycle Assessment or LCA. This type of software uses built-in datasets of materials and embodied carbon information to evaluate all component parts of a building model. Tally1 is currently most used by design professionals as a plug-in software package for the Revit BIM software. The data inputs for the LCA analysis are obtained directly from the Revit model of the building. EC32 is a similar LCA tool that incorporates individual product specifications.
Another LCA software tool, One Click LCA3, was used to compare the two principal design options for the Redford Conservancy, namely reus- ing the existing 1931 building or building an entirely new building on the site. The embodied carbon of the new building was found to be 380 metric tons compared with 90 metric tons for the renovated building. For the renovation alternative, this even included the solar PV panels that were to be installed sufficient to render the building zero-net-energy (ZNE) operationally.
Embodied Carbon Breakdown - Renovation
Embodied Carbon Comparison Renovation
New Building
1 Tally, Autodesk, https://choosetally.com/overview/
2 EC3, Carbon Leadership Forum, https://carbonleadershipforum.org/what-we-do/initiatives/ec3/. 3 One Click LCA, https://www.oneclicklca.com/
Designing for Zero Carbon: Volume 1
87