Race to the Sun
For the walls, the Colorado students used biobased structural insulated panels made of strong but lightweight recycled cellulose and a lightweight foam insulation made of soybean oil. They also implemented a radiant solar thermal system for space and water heating.
They installed photovoltaic cells on the roof and awnings to provide shade as well as electricity. The PV system is made of 32 200-watt panels with about 16 percent efficiency. After the Solar Decathlon, it was expected that the house would be returned to Colorado, reassembled, and connected to a utility grid as part of the university's education and outreach.
The Colorado team also received highest marks in the categories of "documentation" (thoroughness of process drawings and of energy performance analysis), "communication" (success in representing the teams' vision through Web sites and public tours), and "getting around" (how far their electric car could go on excess energy generated by the house).
Second in the overall ratings was a multidisciplinary team of architecture and engineering students from Cornell University. They too looked beyond the immediate competition requirements and created a modular house that could be mass-produced.
The Cornell house features a custom-designed energy recovery ventilator (ERV) that effectively ventilates enough to maintain healthy indoor air quality without wasting the energy embodied in warmed air in the winter or cooled and dehumidified air in the summer.
The key component of Cornell's ERV is a rotary wheel composed of silica gel. In the summer, it absorbs humidity from the fresh air intake before it reaches the air handler. The gel is then wheeled around to be regenerated, transferring the humidity to the exhaust along with extracted heat. This preconditioning can dramatically reduce the amount of fuel required by the heating and cooling system.
The Cornell team received highest marks in the categories of "comfort zone" (ability to control temperature and humidity) and "hot water" (ability to deliver 15 gallons of hot water in 10 minutes or less, using an innovative system).
California Polytechnic State University
Third in rank was the team from CalPoly, San Luis Obispo, California. Their goal was simplicity, and they differed from other teams in making the house interactive rather than automated.
As a result, their house is "switch-rich," fitted with operable windows, shading devices, and user-friendly controls. The students say this will allow occupants to "sail" the house, adjusting the "trim" according to conditions of sun, wind, and temperature. Appropriate to the California climate, the Cal Poly house includes a large south-side opening that adjoins a substantial deck for year-round outdoor living.
The CalPoly team received highest marks in the areas of "lighting" (functional and aesthetic excellence in integrated electric and natural light) and "appliances" (further enhancing the energy efficiency of off-the-shelf efficient equipment).
Virginia Polytechnic Institute and State University
Although fourth in overall rankings, Virginia Tech ranked high in the very important categories of "architecture" and "dwelling." Architecture was defined in the language of Vitruvius as "firmness" (structural integrity), "commodity" (function and comfort), and "delight" (aesthetic appeal). The dwelling dimension looked at "livability" and "buildability."
The Virginia Tech team wanted to be able to transport their house to Washington intact so they could spend more time fine-tuning and testing it, rather than reconstructing it, as the other teams did. The result is a unique synthesis of manufactured housing principles and innovative transportation solutions.
The structure has supporting trusses on either side used during transportation that fold down to become supports for the outside deck. The north wall is made of ThermalSteel structural insulated panels and houses the electrical and mechanical systems and the kitchen appliances.
The south, east, and west walls are constructed of two panels of very thin translucent polycarbonate material, each filled with aerogel insulation. Motorized shades adjust temperature in the wall cavity during the day and provide visual privacy at night. Movable dampers in the walls allow fresh air inside the wall cavity to be brought into the building or to be exhausted outside. At night, LED lights at the base of the walls illuminate the entire surface.
Clerestories between the walls and the roof bring daylight into the interior. The roof, structured like a folded plate with a stressed skin, curves upward. Its underside reflects daylight into the house during the day and distributes the house's fluorescent light at night.
Already, twenty teams have been selected to compete in the 2007 Solar Decathlon.
The primary sponsor of the Solar Decathlon is the U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy, with its National Renewable Energy Laboratory and private-sector sponsors: the American Institute of Architects, the National Association of Home Builders, BP, the DIY Network, and Sprint.
Discuss this article in the Architecture Forum...