The central challenge of the Solar Decathlon competition is to design a building powered by the sun. Though the glitzy PV array on the roof is the usual focus of attention, 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.
UrbanEden’s precast concrete walls consist of 6 inches of Styrofoam insulation sandwiched between two layers (or wythes) of geopolymer concrete. Unlike in post and beam or stud systems made of wood or steel, there are no columns in the wall to interrupt the insulation.
Most of the south face of the building is a high-performance triple-pane glazing system from our industry partner Intus windows. In high-performance residential construction, glass is a risk because of its relatively low thermal performance in comparison to insulated wall sections. UrbanEden is an experiment: can we keep the advantages of fully glazed walls and maintain the performance required by a completely solar powered house? UrbanEden’s windows, doors, and window wall have high performance frames that feature warm edge spacers and superior airtightness combined with triple glazing, argon gas fills, and two low-E coatings that deliver center of glass values of R-8. This advanced technology saves energy and also increases comfort through exceptional sound insulation and by keeping glass surface temperatures closer to human body temperature, thereby reducing the radiant heat loss that we often perceive as a “draft” coming from a window.