Jim Tetro
ECO-STRUCTURE recently caught up with Megan Chafin, media spokesperson for Living Light, the University of Tennessee at Knoxville’s entry for the U.S. Department of Energy’s 2011 Solar Decathlon.
How is your solar paneling unique?
Tennessee’s Living Light house solar array makes use of cylindrical thin-film modules. The continuous 360-degree surface of the cylindrical PV film provides stationary sun tracking through its exposure to incoming light from all directions. Our array is capable of producing 10.9kW of electrical power—twice as much power as we anticipate the home requiring. That allows us to showcase options like powering an electric vehicle charger or selling the extra power back to the utility through our state’s buy-back program. The roof-mounted solar array extends past the façades of the house to provide summer shading and sits above a white roof membrane to maximize power generation from reflected light. The array is architecturally integrated to appear as a trellis or sunshade.
What other sustainable features have you incorporated into your design?
The most visually striking features of the Living Light house are its transparent north and south façades, each made of an outer single pane of glass and an inner insulating suspended-film glass unit. Together they sandwich an airspace containing automated horizontal blinds. In the winter, when sun angles are low, outdoor air is brought in through louvers at the base of the south façade and passively preheated before further conditioning by interior mini-split heat pumps. Warm exhaust air from the living space is expelled through the north façade, providing a thermal buffer against the cold. In the summer, the cycle reverses and the overhanging solar array blocks direct gain while cool air is drawn in through the north façade and conditioned by the mini-split heat pumps. Cool exhaust air is expelled through the south façade, providing a buffer against the exterior temperature and preventing heat buildup in the façade. When the home’s sensors detect that humidity is within acceptable levels, it notifies the homeowners that they can naturally ventilate by opening the windows on the inner façade.
A major focus is the intuitive control of the integrated technologies. The team has designed a custom Web-based interface that’s easy to use and accessible from any Web-enabled device. The graphic interface is designed for touch screens and simplifies interaction with the choice of “moods.” Each mood can be configured to control multiple systems at once. For instance, the bedtime mood can draw the blinds, dim the lights, turn down the thermostat, and set the alarm. The interface is also able to show real-time data to enable homeowners to make educated decisions regarding the balance of energy usage and production.
The Living Light house uses a commercially available heat-pump water heater in an innovative way. The water heater is located in the mechanical room to draw waste heat—from the clothes dryer, solar power inverters, and even the condenser coil on the back of the refrigerator—which it then transfers to the stored water, creating a cooler mechanical room and more-efficient water heating.
What was the inspiration for your design, and does it display any regional influences?
The cantilevered barns of East Tennessee and their melding of material, form, and climatic response inspired the Living Light house. The overhang of the barn’s namesake defines a transparent zone of space open to light, views and ventilation. This space is anchored on either end by timber corncribs that act as structure and storage. In our design, the Living Light team appropriated the dual cores to organize the clutter of daily life and reinterpreted the space in between as a multifunctional loft connected to the outdoors through the double façades. Clad in wood, the core elements organize public and private functions. The west core is adjacent to the entry and contains the mechanical room and kitchen appliances. The east core contains the entertainment center, closet, bed, and bathroom.
How has the new affordability criteria affected the design of your house?
Living Light was designed as a response to the ever-increasing size of the American house. We hoped to demonstrate that building smaller, and thus reducing consumption of resources, does not compromise experience or function. We also wanted to incorporate innovative technologies that we’ve developed with our research partners that could have direct application to both residential and commercial construction. The compromise came at a higher price. We both created a small-house experience and showcased technologies scalable to much larger structures. In the end, we chose to bear greater cost in order to further our research goals.
What will happen to the house after the Solar Decathlon?
We decided that the Living Light house would become a traveling exhibit that would tour the region as an education and outreach tool. The house is designed to be transported as the center section of a double drop lowboy highway trailer. It will go on tour staffed with personnel to educate the public, construction industry, and policy makers about energy efficiency and production. At the end of the tour, it will return to campus as a research tool for the university and its research partners to collect data on the performance of its systems.
