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Concrete production, according to some sources, accounts for roughly 8 percent of the world’s carbon emissions each year. That’s a ratio that, if concrete were a country, would give it the third-largest carbon footprint in the world behind China and the United States.

Obviously, for building industry professionals, the amount of concrete used in a project really matters.

鈥淲e can give whole building life-cycle assessment (LCA) in terms of enclosure and structure,鈥� said Baha Sadreddin, a high-performance design specialist with ZGF Architects. 鈥淎nd in around 70 percent or so of a given building the concrete accounts for the carbon; it’s the single biggest impact material.鈥�

Even more important than concrete is the cement it contains. That’s the main source of carbon within concrete. And because it’s part of a larger mixture, the use of cement within concrete can be analyzed 鈥� and changed.

The concrete used today still owes its general makeup to the 19th century process of baking limestone and clay in an oven and then grinding it into powder to form Portland cement 鈥� the key ingredient along with aggregate and sand.

Cement production is very carbon-intensive. But modern researchers have devised new concrete mixes that feature greater use of substitute cementitious material. This practice has expanded in recent years as builders have looked for ways to reduce concrete’s carbon footprint.

Now, Sadreddin and ZGF principal Chris Chatto, also a high-performance design specialist, have devised a new digital tool that analyzes proposed concrete mixtures for their carbon footprint and performs an LCA based on data provided. It can be done in seconds so that results can influence the next pour.

鈥淓verything is moving toward Revit (building information modeling software) integration, and the reality is we have to make decisions way before we have a Revit model,鈥� Chatto said.

Until now, this type of analysis was not done routinely for concrete mixtures until after completion of a project. This seemed backward to Chatto and Sadreddin, so they created their own tool to perform an LCA for any proposed concrete mix based on a simple Excel spreadsheet.

Users enter the desired strength of the mix in pounds per square inch along with the proposed mix of ingredients. The tool then uses an LCA database from Tally, a Revit application that quantifies the environmental impact of numerous building materials, to compare the proposed mix to typical regional practices. By using known baseline mixes for different regions of the country, the tool calculates the impacts of a proposed mix on climate change, energy demand, acidification, eutrophication, ozone depletion and smog formation.

鈥淲e’re using Tally for our data, but our calculator is simple so we could pull different cements in with the right EPDs (Environmental Product Declarations),鈥� Chatto said. 鈥淲e thought about building our own web calculator, but honestly I feel like Excel (is) on everyone’s desktop and it’s easier to save things for a project this way. It takes people five minutes to figure out how to use it.鈥�

The tool thus allows comparison between a proposed concrete mix design and regional baselines without a Revit model and without proprietary EPDs for those mixes.

It’s also a boon for parties seeking Leadership in Energy and Environmental Design certification. The latest iteration of the world’s largest green building certification program assigns valuable points for use of products with EPDs as well as additional points for reaching carbon reduction marks of 5, 10 and 15 percent through the LCA process.

The tool has already proved its worth on several projects ZGF designed for California’s Department of General Services, including the Clifford L. Allenby Building completed in Sacramento this past spring. Use of the tool for that project allowed adjustments to concrete use so that the carbon footprint was reduced by 14.7 percent.

鈥淲e have to go further,鈥� Chatto said, 鈥渂ut this is the first step toward building awareness in the industry. I’ve talked to some of our colleagues at other firms, and some are trying to get involved in LCA, but it’s daunting. But knowing concrete was the worst in terms of carbon footprint, we started there.鈥�

ZGF is now offering its new tool for free to anyone who wants a copy.

鈥淩ight now the focus is to make the tool readily accessible, easy to use 鈥� and we know how high-impact concrete is,鈥� Sadreddin said. 鈥淪o we’re focusing on cement and hopefully we’ll have a lot of people using this.鈥�