Indiana Limestone vs. Cast Stone: Embodied Carbon by the Numbers
Embodied carbon, the greenhouse gas emissions tied to producing, transporting, and installing a material before a building is even occupied, is a growing factor in material selection. Natural stone and cast stone start that calculation from very different places, because one is quarried and the other is manufactured.
Why the Supply Chains Differ
Natural stone’s supply chain is short: quarried, transported to the producer, cut into panels. Cast stone’s runs considerably longer. Minerals are mined and transported, then heated at extremely high temperatures to produce cement. Steel is acquired, transported, and cast into reinforcement rods. Aggregate is mined, crushed, and sorted separately, then all of it, cement, steel, aggregate, fly ash, and other additives, is transported again to the precast manufacturer, combined with water, placed into molds, and cured. A supply-chain comparison published by the Natural Stone Institute maps this out step by step, and the difference in steps is a large part of why the embodied carbon gap exists in the first place.
Loyola Academy Aquatic Center: A Documented EPD Comparison
At the John D. Norcross ’54 Aquatic Center at Loyola Academy in Wilmette, Illinois, a 241 m² cladding scope was evaluated using published Environmental Product Declarations, including Polycor’s own EPD for limestone facades, cladding, and walls. Indiana limestone cladding measured a global warming potential of 21.5 kg CO2e/m². A comparable concrete alternative measured 618.7 kg CO2e/m³. Across the full cladding scope, that worked out to 5.18 metric tons of CO2e for the limestone against 13.74 metric tons for concrete, a 62% reduction in embodied carbon for choosing natural stone on this project.
Freedom Place: Embodied Carbon at Building Scale
Freedom Place at Old Parkland in Dallas offers a second, larger data point, and a genuinely different scenario: the specification was switched from cast stone to Indiana limestone mid-design, so the comparison reflects an actual substitution rather than a hypothetical. Converting the volume of concrete that would have been needed for a precast facade and comparing it to the natural stone panels actually used, the reduction came to 77% less embodied carbon on an industry-wide data basis and 85% less on a company-wide basis using Polycor’s own EPDs. These are two different projects measured on two different bases, industry-wide data at Freedom Place, published third-party EPDs at Loyola, and shouldn’t be quoted as the same figure or averaged together.
ANSI/NSC 373: What to Specify
The Natural Stone Sustainability Standard, ANSI/NSC 373, certifies quarriers and fabricators who demonstrate environmental leadership through sustainable operations. The program has four tiers: Bronze, Silver, and Platinum for quarriers, and Gold for fabricators. Specifying an ANSI/NSC 373 certified quarry supports Corporate Sustainability Report (CSR) documentation and can ease earning LEED credits, giving the sustainability claim independent, third-party verification rather than resting on a manufacturer’s own statement.
When evaluating lifecycle cost, three questions matter beyond embodied carbon alone: what are the upfront material costs, how durable is the product you’re specifying, and what are the long-term maintenance requirements. A lower embodied carbon figure that comes with a shorter service life isn’t automatically the more sustainable choice once the full lifecycle is accounted for.
For material specifications, see the Limestone product page. For more on the material’s history, see Indiana Limestone: America’s Original Building Stone.
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