This advanced user case study demonstrates how Tally was used on a large architectural project. This case study serves as an example for Tally users on how to successfully apply Tally on their own projects.
By the end of Design Development, the full building Tally report showed that concrete was the most environmentally impactful building material, accounting for approximately 50% of the project’s whole building impacts and 40% of its Global Warming Potential. In response to this finding, the team focused on reducing the percentage of cementitious material in the concrete by increasing the amount of Substitute Cementitious Materials (SCMs). In partnership with the project’s structural engineers, the team identified the building elements where this material substitution could be made without structural consequences. By increasing the SCM content from 25% to 50% in the concrete used for columns, walls, and footings, the team achieved impact reductions across all LEED v4 categories except the Renewable Energy Demand category. These reductions included an approximately 15% reduction in Global Warming Potential, a 19% reduction in Smog Formation Potential, and 20% reductions in Ozone Depletion Potential and Acidification Potential. These material substitutions were significant because concrete was responsible for nearly half of the project’s whole building impacts.
Faced with Seattle’s temperate rainforest climate, the design team decided to include perforated rainscreen panels on several of the buildings’ facades. After designing six different panel options, the team used Tally to perform a design option study comparing each of the panels’ environmental impacts. As a baseline, the team used a solid 1/8-inch steel panel weighing approximately 36.8 kg. The same steel panel with a great maple-inspired radial pattern weighed 27.6 kg, or 75% of the baseline mass, whereas a metal panel with a great maple-inspired tangential perforated pattern weighed 25.7 kg, or 69.8% of the baseline panel’s mass. The mass reductions suggested that the lightest panel, the great maple-inspired tangential pattern, would likely have the least environmental impact. While this preliminary assumption was correct across most of the environmental impact categories, the team was surprised to find that the panel’s fluoropolymer coating contributed disproportionately to its Eutrophication Potential and Ozone Depletion Potential category values. In response to this data, the team went back to the drawing board to design a panel that reduced mass and surface area simultaneously in order to produce the lowest overall environmental impacts.
During Schematic Design, the project team was deciding between a brick or concrete facade on the buildings’ lower levels. As part of their decision making process, the team created a 10-square-foot preliminary wall model in Revit for each envelope assembly and ran a design option comparison in Tally. The results showed the brick option significantly out-performing the concrete option, decreasing the wall’s Eutrophication Potential by almost 20%, its Ozone Depletion Potential by over 40%, its Global Warming Potential by nearly 50%, and its Smog Formation Potential and Acidification Potential by about 65%. These findings led the team to select the brick option, taking advantage of its lower environmental impact.
After deciding on the lower level facade material, the design team compared two different facade options for each of the residence halls’ upper levels: a banded option and a frieze option. The Tally report for this assessment, shown in Figure 6, revealed that the frieze option had lower environmental impacts across all categories required by LEED except for Eutrophication Potential. This is most likely because the frieze option was made predominantly of wood and used metal only as an accent, whereas the banded option predominantly used metal. Based on these Tally results, the team selected the frieze option to reduce environmental impacts in as many categories as possible.
Having conducted LCAs throughout the entire design and construction process, the University of Washington team’s next step was to supply the documentation necessary to earn the LEED v4 Building Life Cycle Impact Reduction Credit, Option 4. To do so, the team once again used Tally to compare a baseline building with the final design. While conducting this comparison, the designers adhered to LEED v4’s scope, which covers cradle-to-grave impacts for a building with a 60 year life expectancy but excludes operational energy. This scope also includes the building’s structure, enclosure, and interior finishes on structural or envelope walls, while excluding non-structural elements of the floors and ceilings, non-structural partitions, MEP systems, and landscape elements.
Using this scope, the team created a baseline building starting from the Revit model created at the end of the Construction Documentation phase. The Tally material definitions in this baseline building were then edited to quickly and efficiently create a model reflecting the alternatives the team had considered during earlier design phases. For example, the buildings’ concrete mixture was returned to the original proposed mixture, solid metal panels were used instead of the decorative rainscreen panels, and the lower facades incorporated concrete instead of brick. This process of editing Tally’s material definitions ensured that the baseline building and final design were equal in function and size as per LEED’s requirements.
After generating the baseline building model, Tally was used to assess the full building environmental impacts of both the baseline and final building designs. Figure 7 demonstrates the significant impact reductions achieved across all impact categories, and was included in the documentation for the LEED v4 Building Life Cycle Impact Reduction Credit, Option 4.