Page 123 - Designing for Zero Carbon-Volume 2_Case Studies of All-Electric Multifamily Residential Buildings

CASA ADELANTE AT 2060 FOLSOM
CASE STUDY NO. 5
Design Analysis: Optimizing Zero-Carbon Design
Design Analysis: Embodied Carbon
In contrast to the previous case study projects in this volume, the design requirements of the 2060 Folsom multifamily residential building motivated the project team to seek embodied car- bon reductions from a normally conventional approach to the structural design and materials selection. One such instance resulted from the design objective of increasing the building height to create the maximum floor area that fits just under the code definition of “high-rise”. This would create a nine-story building design on a site where poor soil conditions already required that a significant amount of concrete to be added at the foundations. The amount of embodied carbon resulting from this large amount of added concrete would be high. Therefore, the project team set a design task to find some low-carbon alternatives for the building materials, including for non-structural components.
Using a Life Cycle Assessment (LCA)17 analysis, the design team found (unsurprisingly) that the large amount of concrete required for the extra foundation work was the main generator of high embodied carbon content. In addition, the analysis showed that the quantity of finished interior walls, typical of large multifamily projects, resulted in an unusually high use of gypsum board finish material, a carbon-intensive material.
The solution adopted for reducing the embodied carbon of the concrete was to optimize the con- crete mixes for structural strength, while reducing the cement content and substituting supple- mentary low-carbon cementitious materials. In the case of the gypsum board and similar finish materials, the designers specified products with lower embodied carbon content and simply left the structure exposed where possible, adopting a “structure-as-finish” design approach.
The result, as shown in the final LCA analysis, was a Global Warming Potential (GWP)18 of 397, compared with the design team’s previous multifamily housing projects of similar size and construction where the GWP numbers were in the range of 500-525. (See the chart of the GWP analysis for this case study project on the next page, with the breakdown by the caregory of ma- terial used in the final construction.)
17 See Sidebar: Embodied Carbon Assessment on the next page for a description of LCA.
18 GWP is a building rating of its total embodied carbon. See Sidebar: Embodied Carbon Assess-
ment for how this rating is determined. Designing for Zero Carbon: Volume 2
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