Solar Decathlon: A Heated Competition

Twenty teams, two years, ten contests and one big old sun--the essential ingredients of the Department of Energy's solar contest on the Mall

Penny Bonda

Interior Design · October 29, 2007

This time the sun cooperated. Unlike the cloud-covered 2005 Solar Decathlon, the twenty teams representing colleges and universities from around the world had plenty of natural power to fuel the solar homes they built on the National Mall this October in Washington, DC. Good thing, because the homes were, for the most part, spectacular.

Here's the challenge: submit an application and win a coveted spot in the competition; spend two years fundraising and securing sponsors; design an 800 square foot house that will run solely on solar power according to very specific criteria; build it so that it can be deconstructed and transported across the country or an ocean; cross your fingers and hope that everything arrives intact; reconstruct and keep it operating for ten days while judges (hopefully) award points and hundreds of thousands spectators wander through. At the end you hope to place in the top three.


The 2007 Solar Decathlon's top honor went to the entry from Germany's Technische Universitat Darmstadt. The house is most notable for the photovoltaics integrated into the oak louvers of the full height doors running the length of the east, south and west elevations. A tracking system automatically tilts the louvers to follow the sun and to provide shading and privacy. PVs are rarely thought of as beautiful but the German team's design of the louvers and the translucent and patterned panels installed on the roof of the south porch is more than just functional. The combination provides dramatic plays of shadow and light and adds a wonderful aesthetic to the home.

Second place: University of Maryland's indoor water wall (photo credit: Amy Gardner)The University of Maryland won second place for its LEAFHouse, inspired by the simple, yet vastly complex leaf. "Just as the leaf changes throughout the year, so can this house, given the mood of the owner," says Jake Zager, student and co-manager of construction. Inside the design does, in fact, mimic a leaf at the ridge of the ceiling where exposed steel supports "branch out" from a wooden spine. The most innovative feature, however, is the indoor water fall designed into the living room's media wall. A liquid desiccant system that's used to control humidity and reduce the load on the air-conditioner works by mixing calcium chloride, a type of salt and a highly absorptive material, into the sculptural design of the water wall where it captures moisture out of the air. As far as the team knows, such a system has never been used for a home.

Third place went to Santa Clara University, located in Silicon Valley, for the design of a house that, not surprisingly given its roots, relies on dynamically smart computer technology to run its systems. The electrochromic windows, for example, darken or lighten with a flip of a switch to help control thermal comfort. There is also a prototype solar thermal unit with absorption chillers used for space conditioning and water heating—a technology more common in large buildings but successfully used here in a small (727 square foot) space.

Third Place: Santa Clara University (photo credit: Kaye Evans-Lutterodt/Solar Decathlon)
About the contests: to compete, the teams must design and build energy-efficient homes that are powered exclusively by the sun. The houses must be attractive with seamlessly integrated energy efficient technologies, and be easy to live in by all including the disabled. They must maintain a comfortable temperature, provide attractive and adequate lighting, power household appliances for cooking and cleaning, power home electronics including televisions and computers, and provide hot water. These houses must also power an electric vehicle to meet household transportation needs.

Whew! This tall order yields plenty of lessons for home designers and builders. Primary among them—household energy efficiency is so much more than the commonly used strategies of changing out light bulbs and turning down the heat. As Amy Gardner, a faculty advisor to the Maryland team states, "LEAFHouse demonstrates that the way forward to a more responsible built environment is through multidisciplinary, integrated, holistic design." That's the message designed into the criteria by DOE and delivered by all twenty houses. The greenest homes use a system of strategies dependant on and reinforcing the others.

There were some very unique features in the houses, such as a sunlight diffusing milk bottle wall in the Penn State house, or the translucent walls made from of polycarbonate sheeting and an aerogel filler used by the Georgia Tech students. At the University of Illinois/Urbana-Champaign house, the heating and cooling is all radiant via ceiling panels that resemble refrigerator coils yet are oddly attractive. By necessity, all the houses are pre-fabricated modular buildings. The University of Colorado/Boulder house, however, used its shipping container decoratively to form the walls and mechanical spines of the central core.

The houses also had many features in common. Because universal design is a requirement, the bathrooms are larger than expected for such small homes and many of the multi-use spaces are defined by sliding walls. In fact, panels on rollers were so ubiquitous it was unusual to see a house without them. Many panels were made of lightweight decorative materials such as 3form. Furniture, often custom designed by the students, served many purposes, such as in the German Darmstadt house where the "lounging pit" and the "sleeping pit" cleverly concealed ample storage.

Lighting strategies almost universally included an LED / fluorescent mixture. However, the MIT team used some incandescent lighting explaining that its house produced more than enough energy to do so. Hmmm? Many of the houses used lighting as a decorative element as well as a functional one. The students from the New York Institute of Technology concealed energy efficient lighting sources behind large stretched fabric frames to good effect.

Kitchens, typically a household energy hog, featured very efficient appliances with almost all teams opting for induction cooktops. Materials selected for their green attributes—recycled content countertops, responsibly forested woods, and locally sourced goods—were common.
But the Solar Decathlon is all about energy—renewable energy. "The earth receives more energy from the sun than the world uses in a whole year. The tools for harnessing that energy are available now," Maryland's Amy Gardner states. "The work of these students has advanced the breadth and depth of all team members' knowledge and abilities, preparing them to bring about a brighter future for all."

Go solar!

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