If you designed and built a house with all the creature comforts of 21st-century living and powered everything with solar energy, what would it look like?

Judging by the 18 houses entered in the Solar Decathlon, a student competition sponsored by the Energy Department's Office of Energy Efficiency and Renewable Energy and held on the Mall last month, a solar-powered house can be as varied in looks as any other kind of house.

Would I like to live in one? The architecture and engineering student teams, who represented schools in the United States, Canada and Spain, make a strong case for giving solar a chance. A high degree of comfort can be achieved by a judicious mix of high-tech, computer-driven mechanical systems powered by solar electricity and simple passive solar heating and cooling techniques that have used by builders for thousands of years. The systems appeared to be easy to operate and maintain, and the photovoltaic cells on every roof generated enough electricity to run all the appliances used in a typical household.

But to make a sale with me, a solar-powered house must also have enough of the same qualities that I would ask of any house -- a play of light in space, a feeling of spaciousness, a sense of comfort from well-proportioned room sizes and door and window openings, a view to connect the space to its surroundings, great detailing and careful workmanship. In touring each house as a judge for the Dwelling competition, which was one of the 10 Decathlon events, I saw three that would be outstanding by any measure.

All the houses were small. Contest rules stipulated that the house footprint, including shading overhangs and solar-power-generating equipment, could not exceed 800 square feet, a size that is small enough to transport to the Mall but big enough to raise the issues that homeowners who wanted to do this would encounter. Most of the houses had about 550 square feet of livable area, not much for the two people each was to accommodate, but crafty design made a few houses feel twice as big.

The most dramatic entry was Virginia Tech's. The look is futuristic, but, surprisingly, also a nod to the past and a famous Virginia landmark. From either end of this 48-foot-long box, the roof profile appears to be a bird in flight and will remind most observers of the graceful, curving roof of Dulles International Airport's main terminal.

Inside, tastefully executed cabinetry along the north wall houses all the mechanical systems, the single-counter kitchen, and all the appliances. The other three exterior walls were stunning: They are made of white plastic The walls were actually made with two plastic panels and a six-inch air cavity between them, providing wonderful, diffuse lighting and an unusually high level of insulation. Within the cavity are remote-controlled shades, ventilation louvers, and a LED (light-emitting diode), which lights up the walls at night. I didn't see this, but as described to me, occupants can tune the walls to any color of the rainbow and vary the light intensity. A "subdued" setting works for evening reading and casual conversation. "When a task light is on, you hardly notice the walls," noted professor Robert Schubert, a faculty adviser. At more intense levels, the walls bathe the entire room in colored light, which would certainly liven up a party. There is even a strobe feature.

The living room and bedroom are small, but they are designed to create the illusion of spaciousness. In addition to the translucent walls, clerestory windows ring the entire house, bringing even more daylight into the rooms. The ceiling height is unusually high -- 13 feet on one side of the house and 11 feet on the other.

There were a few surprises outside as well. A close look at the cedar decking showed that the boards were carefully fitted between members of a very large steel truss. This truss-and-board combination, which surrounds the entire house, was designed to flip up and encase the house while it is being transported.

Virginia Tech's house is one long box that can be shipped in one piece. The University of Texas at Austin team took a different tack. It designed and built a house that could be disassembled into four sections that fit onto three flatbed trailers. This gave the flexibility to design room shapes like those in most houses.

In the Texas house, the main living area feels like a very comfortable family room. It's actually nicer and bigger than most, and more than adequate for two people. In fact, three or four people could pursue several different activities at the same time -- meal prep at one end, studying at the dining table, reading on the sofa and working on the computer at the built-in work station/entertainment center at the other end.

Again, this space feels bigger than it actually is. This is due to the ceiling height, which is 13 feet at its highest point, a bank of clerestory windows that raises the daylight level and a limited palette that pulls the space together. The room is also enhanced by the extensive use of natural materials -- the ceiling and one long wall are birch-veneered plywood; the flooring is mesquite, a reddish Texas wood; and the shoji-like screens that open onto the bathroom and bedroom have redwood detailing.

New York Institute of Technology's team divided its house into two parts, which the team dubbed the "Green Machine" and the "Blue Box." The degree of flexibility was appealing -- only students used to living in tiny New York apartments could have come up with these solutions -- and it has the potential of broad application.

The Green Machine houses the kitchen, bathroom and most of the mechanical equipment required to run the house on solar power. It was fashioned out of a corrugated metal shipping container, the same kind used for global shipping. It is an inspired example of recycling, though the framing and insulation required to make it habitable produced spaces that are cramped and narrow and make you fee like you're on a boat.

This is an adult consumer's reaction, however. The student designers considered meal prep and bathing to be "transient activities" that didn't require much space. They elected to put most of their square footage into the Blue Box, the living and sleeping area where they imagined the occupants of their house would be spending the most time.

I'm sure I would. The architectural features and the furniture design make it feel huge. The space has a two-story volume, with a sleeping loft and multiple clerestory windows. Even better, there will always be plenty of space for every activity because all the other furniture can be pivoted or otherwise moved out of the way. For example, the office desk can swing out from its corner under the stairs to occupy a large area, while the three-foot diameter cylinder is off to one side. For meals, the desk goes back, the cylinder moves out and the sides pull away to be four dining chairs around a dining table. When someone wants to watch the television from the sofa, the screen swings out from under the stairs. Even more ingenious, the sofa had a small photovoltaic panel on the back, which generated enough power to run an internal fan and cool off anyone sitting in it.

The NYIT team characterized its Green Machine as a "global solution," and it does have that potential. The Green Machine can be shipped to any building site near a port. If it could be mass-produced -- and this is admittedly a big if -- a local home builder could join it to his/her own version of the Blue Box.

For more information on the Solar Decathlon, and more photographs, go to the official Web site, www.eere.energy.gov/solar_decathlon/.

Katherine Salant can be contacted at www.katherinesalant.com.

(c) 2005, Katherine Salant

Distributed by Inman News Features

During the day, the light passing through plastic walls of Virginia Tech's Solar Decathlon is diffuse. New York Institute of Technology's Green Machine on the left is a converted corrugated metal shipping container housing kitchen, bath and solar power equipment. The Blue Box, right, has living and sleeping areas.University of Texas Solar Decathlon team member Chris Gannon relaxes in the team's comfortable and spacious living area.