Team Austria, competing for the first time in the Solar Decathlon, won first place with its LISI house. As is often the case, the first place winner did not win the People’s Choice Award. Attendees chose UrbanEden, the solar-powered house from The University of North Carolina at Charlotte (Entrants compete in 10 contests, many of which measure how a house functions not just how it looks).
Solar Decathlon winners are those that best blend affordability, consumer appeal, and design excellence with optimal energy production and maximum efficiency. University of Las Vegas Nevada took second place and Czech Technical University took third in the overall competition. All are first-time participants. And it was the closest competition ever with just a three to four points separating top contestants.
Team Austria’s LISI (with the top score of 951.922 points) hides its photovoltaics on the roof. Just a few slits in the floor hint at the home’s HVAC system. Cold water pumped through floor pipes radiantly cools the room. The bathroom makes use of the warm water that normally just goes down the drain. The warm water goes into a heat exchanger in the shower tray so that less energy is needed to heat water.
Exterior patios on the North and South sides of the home double the perceived living space. Automatically controlled shading elements that look like leafy, lacey curtains keep the house from overheating on hot, summer days.
Second-place winner was Team Las Vegas DelSol (947.572 points). Designed to be LEED Platinum, it is “a second-home base-camp for Mojave Desert explorers.” Clad in re-claimed Wyoming snow fence, the home recycles what might otherwise be discarded.
Third-place winner, Czech Technical University, won for its AIR House (945.142 points), a dwelling sheltered by a canopy—a house within a house—to reduce heating and cooling needs. The students focused on designing and building a home for their empty-nester aging parents. Made of renewable wood, the exterior structure not only encloses the living structure but also supports solar panels and shades the terrace.
People’s Choice winner UrbanEden (870.210 points) is a light-filled, passive-solar house that opens to a garden-rimmed, outdoor deck. The garden is a series of planters, Wallgarden, that form a fence and privacy wall, the perfect combination for creating a private garden with flowers and produce. The solar panels that power the house slide over the deck to shade it from hot summer sun. Its people’s choice appeal is clear. The garden is such an inviting and integral part of the home.
One of the home’s engineering wonders that made it a strong engineering competitor (where it took top honors) is its radiant geopolymer pre-cast-panel concrete walls. Geopolymer cements combine aluminum silicate with a chemical activator such as waterglass. Aluminum silicates include a variety of naturally occurring clays as well as industrial by-products such as blast furnace slag and fly ash from coal combustion.
A key benefit of geopolymer cement is that the cements don’t need to be fired as do Portland cements, nor do they give off CO2 during curing, which results in a 90 percent reduction in carbon emissions, according to the students. They believe that their UrbanEden is the first geopolymer concrete used as a building envelope. They are not the first, but they are among the first to use tubes within panels as part of the HVAC system.
To cure panels, students surrounded them in insulation and ran hot water through the tubes to bring to and maintain the panels at the 170-degree cure temperature. On interior panel wythes, the tubes are repurposed as part of the building’s capillary cooling system (that runs cold water through the tubes.
All entrants’ solar energy systems reliably produced more power than houses needed, allowing all the energy-consuming tasks to be completed with energy to spare. In fact, all the teams earned full points in the Energy Balance Contest.