*If you are interested in a free copy of the Concrete LCA Tool, please contact Baha Sadreddin at firstname.lastname@example.org with your request.
Concrete has shaped much of our built environment. It has also contributed significantly to the AEC industry’s carbon footprint, accounting for about 8 percent of global carbon emissions. In fact, if the cement industry was a country, it would rank #3 in emissions only behind China and the U.S.
As a firm deeply committed to designing sustainable and meaningful solutions, we are continuously searching for ways to reduce impact. One of the most significant reductions is through replacing carbon-intensive materials with those that have the lowest possible carbon impact. Recently, ZGF developed a calculator tool to conduct rapid life cycle assessments (LCAs) of a proposed concrete mix. The calculator compares a proposed concrete mix to typical regional practices and estimates environmental impacts related to greenhouse gas emissions and other key sustainability indicators. This LCA considers the concrete’s environmental impact, from the sourcing and refining of the materials; its manufacturing, delivery and construction activities; and its maintenance and final disposal through its useful life.
The LCA tool, powered by Tally, works by analyzing a given concrete mix via six main environmental impact indicators and comparing them to a regional baseline for the specified structural strength (measured in psi). The tool bridges several impediments in current LCA design processes, allowing the comparison between a proposed concrete mix design and the regional baselines without a Revit model and without requiring specific, proprietary Environmental Product Declarations for the mixes. This provides near real-time decision-making at every phase, from concepts to construction, and can drive conversations with contractors and engineers for less carbon intensive mixes. Whether a structure is primarily concrete or if concrete is used in a lesser capacity, the calculator can be used to significantly reduce impact while also maintaining material integrity and safety.
We recently sat down with ZGF high-performance design specialist Baha Sadreddin to learn more about the calculator and why ZGF decided to make the tool available to our AEC industry colleagues.
Q: Let’s start with the basics. Why did ZGF develop this tool?
In many of our projects we were requesting of concrete suppliers and contractors the highest concentration possible of SCMs, or supplementary cementitious materials, to replace a portion of the cement, the material with the highest impact in concrete. We found that depending on the region and the parties involved, the provided mix designs had very different SCM percentages. On one occasion, a supplier increased the amount of SCMs, but didn’t reduce the cement in the mix. At first blush it looked to be a “high SCM” mix, but in reality, its environmental impact was even worse than the initial submittal.
This tool allows us to reduce the cement content of a mix and better understand how a specific mix with or without SCMs would perform. It has realigned our dialogue with contractors and structural engineers around overall environmental impact of a concrete mix design and cement reduction vs. the simple addition of SCMs to a mix. For LEED projects, where we’ve done a conceptual LCA, it has allowed us to predict with accuracy how reducing the concrete impact can affect the project’s overall performance against the Building life-cycle impact reduction credit.
It is furthering the conversation of how to use concrete intelligently and responsibly until less environmentally intensive alternatives become readily available and applicable into mainstream practices.
Q: How does ZGF’s tool differ from other available LCA tools?
This tool offers a few advantages, including speed and minimal additional tools to assess and decide. Specifically:
- This tool enables us to analyze concrete mix designs virtually in real time and make decisions quickly. For instance, in a contractor meeting the day before concrete is poured. Many currently available LCA tools require time-intensive reruns of the whole building LCA.
- It is decoupled from a Revit or Sketchup model.
- The tool doesn’t require Environmental Product Declarations (EPDs). Instead it estimates impact based on mix and LCAs of the supplemental materials for a specific product in a specific region.
- It automates the process of comparing against typical practice baseline.
- It can impact a project at any scale and can be used at every phase—SD, DD, and CD—to ensure the intended environmental impact reductions are maintained throughout design process.
It should be noted that many great LCA tools exist, such as Tally by KieranTimberlake, and more tools, including the much-anticipated EC3, are on the horizon. We’re excited by the amount of choices available to our industry and our goal is for the concrete LCA tool to complement these options.
Q: Tell us more about how the tool works.
Essentially, the calculator is a simple strategy generation tool. It can be utilized throughout the entire design process to lower carbon impact of structural and/or architectural concrete.
The tool analyzes each ingredient of a concrete mix to understand a proposed mix design’s overall carbon impact through six main environmental impact indicators. The user enters the amount of each ingredient in pounds per cubic yard of proposed concrete mix and its structural strength in psi. The tool uses the LCA database contained within Tally to calculate the impacts of each mix on Global Warming, Energy Demand, Acidification, Eutrophication, Ozone Depletion, and Smog Formation, and summarizes how the proposed mix compares to a baseline or standard concrete mix for a given region for the specified psi, as defined by the National Ready Mix Concrete Association.
The resulting data allows project performance specialists, along with project engineers, contractors and concrete suppliers, to specify a concrete mix that has the lowest possible carbon impact while maintaining material integrity and safety.
Q: How has this tool helped reduce carbon footprint of ZGF projects?
We are using the LCA concrete tool on several projects currently in design or construction, including at a corporate tech campus in Redmond, WA, the California Air Resources Board Headquarters in Riverside, CA, the California State Teachers’ Retirement System (CalSTRS) in Sacramento, CA and the Clifford L. Allenby building in Sacramento, CA.
For the Clifford L. Allenby building, we achieved a very significant 26 percent reduction in the amount of carbon-intensive cement used in the project through high utilization of fly ash and slag, two SCMs. We achieved an overall 14.7% reduction in embodied carbon on the project through the concrete mix alone, based on a LEED-compliant analysis that includes the entire structure and envelope. This performance maximizes the available LCA points under LEED v4.0; though the 14.7% reduction is somewhat conservative, as it doesn’t reflect additional and unusual project strategies related to post-tensioned floorplates or the envelope mullion spacing.
Q: Why did ZGF decide to make this tool available to the AEC industry?
The reality is that the built environment is a large contributor to our current climate crisis. We believe we have a responsibility to design buildings that minimize, and ultimately eliminate, this impact. The calculator allows us to use concrete intelligently at every phase of a project and to share that knowledge with the rest of our project teams. We believe that by sharing this knowledge with all our AEC colleagues we can make an even bigger impact in reducing embodied carbon.
Q: What other tools are you working on?
We are developing a similar tool to better understand the impact of insulation material choices in an envelope assembly. The goal is to eventually translate data from the concrete tool, the insulation studies, and our future initiatives into a comprehensive but simple parametric tool that allows designers to compare material selections and envelope assembly choices through a model of one structural bay in a building. This would allow teams to quickly compare alternatives and understand the life cycle impact of each material in relation to the envelope and structure as a whole.
We are also focused on developing parametric tools and methods for daylight, glare and energy studies.
If you are interested in a free copy of the Concrete LCA Tool, please contact Baha Sadreddin at email@example.com with your request.