Carboncast Precast Wall Panels Selected For Solar Decathlon House

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Energy-saving performance of walls was critical in choice by UNC Charlotte team, which won “People’s Choice Award.”

Thermally efficient CarbonCast High Performance Insulated Wall Panels ( were selected by a team of students from UNC Charlotte for the exterior of UrbanEden (, the school’s entry into the U.S. Department of Energy Solar Decathalon 2013 (

The CarbonCast panels featured a 4-inch exterior wythe and a 6-inch interior wythe sandwiching 6 inches of continuous EPS insulation. C-GRID carbon fiber grid shear trusses were used to connect the wythes through the insulation. With negligible thermal transfer, the connectors enable continuous insulation and allow the assembly to deliver the full R-value of the insulation, which in this case is about R-24. The thermal mass of the concrete walls also contributed energy savings. The panels were fabricated and donated by Metromont (, a founding member of AltusGroup (, which licenses the CarbonCast technology to precasters nationwide.

According to the UrbanEden website:

In state-of-the-art, high-performance housing it is common to combine high-mass passive solar design with thermal-bridge free, airtight building envelopes. However, the mass component is usually limited to an insulated concrete floor slab. In UrbanEden, the mass has moved to the walls in the form of insulated precast panels. This seemingly simple choice is, in fact, our first major innovation.

It’s the building envelope that makes solar power possible. A high-performance envelope reduces heating and cooling loads, thus allowing the photovoltaic system to be smaller and more affordable. UrbanEden’s envelope was designed to minimize heat and water vapor movement through well-insulated, air-tight construction, while maximizing heat storage capacity by placing considerable mass in the living space.

The UrbanEden project was honored with the People’s Choice Award, which gave the public the opportunity to vote for its favorite house. Overall, the UNC Charlotte team finished 13th out of the 20 universities worldwide chosen to participate in the US Department of Energy Solar Decathlon 2013. The annual event challenges collegiate teams to design, build, and operate solar-powered houses that are cost-effective, energy-efficient, and attractive. The winners of the competition blend affordability, consumer appeal, and design excellence with optimal energy production and maximum efficiency. This year’s Solar Decathlon was held October 3-13 at the Orange County Great Park in Irvine, California.

The UNCC team also replaced the conventional Portland cement in the precast with a fly-ash geo-polymer mixture that resulted in a massive decrease in associated carbon emissions (theoretically up to a 90% reduction) and makes safe use of a waste product of coal production.

The UrbanEden team, which consisted of undergraduate and graduate students in architecture, engineering and business, began the design process in October 2011. Construction of UrbanEden began in March 2013 and was completed in September. The house was dismantled and transported to California to be reassembled at the Great Park.

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