Students From Texas and Germany Team Up for Solar Decathlon 2015

The result is the NexusHaus, which combines the aesthetics of German design and passive design principles into a home for Austin.

Students from UT and TUM help attach a railing to the deck of their design for the U.S. Department of Energy’s Solar Decathlon competition, NexusHaus.

Courtesy Jessica Janzen


Since 2002, the U.S. Department of Energy’s Solar Decathlon competition has been challenging university students to “design, build, and operate solar-powered houses that are cost-effective, energy-efficient, and attractive.” In 2015 the program is in its seventh year. As a team of students from the University of Texas (UT) and the Technische Universität München (TUM), we wanted to tackle more than aesthetics and efficiency. Born from our shared interest in the water-energy nexus, our team NexusHaus, determined that dealing with the issues of water, density, and food were also of particular interest given the ongoing drought, rapidly growing population of Austin, Texas, and  the city’s food deserts, similar to many others throughout the United States.

Our team approached these issues through a series of design interventions. Our combined group met in Germany during the summer of 2014 to begin realizing these interventions, and create designs that “responded to the affordable and sustainable housing needs in Austin,” said Yang Chen, Master of Architecture student at UT. From these designs, we eventually chose three. The three that were chosen “incorporated two modules, a multi-functional green house, and an integrated roof structure which have evolved into the current design,” added Chen. The modules were designed to meet the needs of Austin’s Accessory Dwelling Unit (ADU) housing code which allows for greater density on more than 40,000 single-family lots throughout the city’s center. The units are limited to a maximum 850 square feet, but can be much smaller, based on available lot size. NexusHaus’s two modules (784 square feet total) allow the house to reconfigure or to reduce to approximately 400 square feet based on lot restrictions.

Early design concepts for NexusHaus integrated a greenhouse in the nexus between the night and day module.

Courtesy UT|TUM NexusHaus


As the design evolved, we continued to integrate the aesthetics of German design into a home intended for Austin. This is most apparent in our use of wood, from the cedar rain screen façade to the pine flooring salvaged from a deconstructed Texas barn. “Wood is an incredible resource,” said Simone Salfner, instructor in the Institute of Energy Efficient and Sustainable Design and Building at TUM. “If you are talking about ecological footprint, it is one of the most positive materials because of its carbon sequestration.” Other design decisions are distinctly Texas: the vernacular dogtrot layout promotes cross-ventilation to cool the house and the large covered deck promotes outdoor living—essential to life in Austin—while shading the house from the intense summer sun.

NexusHaus’s passive design is aided by an active system which integrates water into the cooling system. “I had to get involved when I found out the initial concept for the house was the ‘water-energy nexus,’” said Charles Upshaw, Team Captain and UT Mechanical Engineering PhD student. “My research focuses on integrated thermal/water storage and management systems for residential houses, and this project was a perfect opportunity to test my ideas.” Upshaw’s Integrated Thermal Energy and Rainwater Storage (ITHERST) system utilizes the home’s collected rainwater as a thermal storage volume. This shifts home energy use to off-peak, relieving strain to the electric grid.

Collected rainwater is also filtered and used as a potable water source in the house while grey water is collected and used to water NexusHaus’s drought tolerant landscaping. The landscape includes a closed-loop aquaponics system which “demonstrates incredible efficiency in the conversion of both minimal water and energy from sunlight into great amounts of nutritious food,” said UT Master of Architecture student, Alex Krippner. “Even more significantly, it clearly connects the homeowner to the surrounding environment, linking the occupants of the house to greater ecological systems.” In a house competing for a cost-effective, energy-efficient, and aesthetics title, NexusHaus goes beyond to help resolve the issues facing central Texas and the world.

In the current design, the NexusHaus integrates drought tolerant landscaping, an aquaponics system, and thermal storage along the west and south facades. Canopies cover the expansive deck providing opportunities for outdoor living essential to life in Austin while also providing solar shading from the intense summer sun.

Courtesy UT|TUM NexusHaus


NexusHaus’s passive design is aided by an active system which integrates water into the cooling system. “I had to get involved when I found out the initial concept for the house was the ‘water-energy nexus,’” said Charles Upshaw, Team Captain and UT Mechanical Engineering PhD student. “My research focuses on integrated thermal/water storage and management systems for residential houses, and this project was a perfect opportunity to test my ideas.” Upshaw’s Integrated Thermal Energy and Rainwater Storage (ITHERST) system utilizes the home’s collected rainwater as a thermal storage volume. This shifts home energy use to off-peak, relieving strain to the electric grid.

Collected rainwater is also filtered and used as a potable water source in the house while grey water is collected and used to water NexusHaus’s drought tolerant landscaping. The landscape includes a closed-loop aquaponics system which “demonstrates incredible efficiency in the conversion of both minimal water and energy from sunlight into great amounts of nutritious food,” said UT Master of Architecture student, Alex Krippner. “Even more significantly, it clearly connects the homeowner to the surrounding environment, linking the occupants of the house to greater ecological systems.” In a house competing for a cost-effective, energy-efficient, and aesthetics title, NexusHaus goes beyond to help resolve the issues facing central Texas and the world.

Categories: Residential Architecture, Sustainability

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