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fe a t u re and the Precast Concrete Institute’s Ascent magazine were continuing to feature UrbanEden’s unique wall system. The U.S. Department of Energy’s Solar Decathlon is a showcase of innovative design and green building practices. Held every two years, the competition challenges academic teams to design, build and operate fully solar-powered homes. UNC Charlotte was one of only 20 teams accepted to participate in the Solar Decathlon 2013, which took place Oct. 3-13 in Irvine, Calif. The two-year process leading up to the rigorous competition is intense, and the 10 days of contests and public tours are grueling. For many teams, all the energy and attention is focused on those 10 days; the decathlon is the end point of a long journey. But for UNC Charlotte, the Solar Decathlon was a key moment in a journey that began well before the team of architecture and engineering faculty and students came together to design and build UrbanEden, and will continue long after the house is reassembled on campus to serve as an educational facility.


Photo by Daniel Coston

FEEDING ONGOING RESEARCH “Past Solar Decathlons have been sort of a dead end for research,” said Thomas Gentry, associate professor of design sciences and sustainable housing. “There’s little carrythrough. We made a conscious decision that this was going to feed into ongoing research.” Led by Assistant Professor of Architecture Mona Azarbayjani, the team of students was “trying to identify a building envelope system that was cutting edge,” said Gentry. He and Brett Tempest, assistant professor of civil and environmental engineering, proposed an integrated wall system that combined elements of their ongoing research and soon became the key innovation of the team’s house. During the next semester, a class of architecture and engineering students, taught by Gentry and Tempest, developed UrbanEden’s revolutionary precast concrete wall system, for which Gentry and Tempest now have a provisional patent. So what’s the revolution? Two things, primarily. Embedded in the walls is a system of tiny plastic tubes, called capillary tubes, through which water can flow to either warm or cool the thick concrete walls.


Assistant professor Brett Tempest (left) and graduate student Clarke Snell visit the precast concrete plant that manufactured UrbanEden’s wall panels.

But perhaps even more significant is the concrete mix itself: a geopolymer mix that, unlike traditional concrete, replaces the portland cement binder with fly ash, a by-product of coal-fired thermoelectric power production. While Tempest and others in his department had been working for years to develop the geopolymer mix, it had “never been used in an architectural precast setting,” Gentry said. “Typically, we’ll make a little test specimen that doesn’t look like anything that you would find out in the world,” Tempest said. “To get something out there as a

demonstration is the big thing. The Solar Decathlon attracted a lot of people to it.” REDUCING CARBON EMISSIONS But what makes geopolymer concrete so special? The process of making the portland cement that is common to traditional concrete produces significant amounts of carbon; in fact, the estimate is that 5 to 7 percent of the world’s greenhouse gases come from concrete. Geopolymer concrete would reduce that emission by up to 90 percent. continued on p. 28 Q114


UNC CHARLOTTE magazine 27

UNC Charlotte Magazine, Q1 2014  

In this edition, you’ll read about proud 49ers who are making Charlotte and the world a better place – two amazing students who have interne...