Overview
Having completed nearly two dozen whole-building LCAs in pursuit of the Building Life-Cycle Impact Reduction credit under LEED version 4, Director of Sustainable Design Dirk Kestner has developed many key takeaways. He and other experts weigh in on the urgency of embodied carbon in the BuildingGreen Spotlight.
“One thing that people … need to start doing is thinking about how they specify their concrete and stop talking about it as ‘percent fly ash,’” said Kestner. “It’s about getting cement content down and using only what you need.”
Reducing cement content can take many forms, he said, including simply using less by specifying higher-quality aggregate or reducing water content. Kestner says successful lower-impact concrete specifications can be performance-based—stating the structural requirements (how much strength is needed when) and environmental requirements (like global warming potential per yard of concrete) rather than specifying a percentage of cement and SCMs. In other words, you might be able to reduce impacts further by asking for exactly what you want. Getting the structural engineer in direct dialogue with the ready-mix supplier is essential to this approach, he said.
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