It's a surprising but true fact: the number one cause of global warming isn't cars, but buildings.
All those office complexes, schools and homes produce about half of all glacier-melting pollution, says CBS News correspondent David Pogue.
But not the 20 houses built for the 2007 Solar Decathlon, a competition for colleges that's run by the U.S. Department of Energy. Not a single one creates any global-warming pollution.
The goal of the competition is to demonstrate what is possible in terms of solar energy.
"These homes, when you look at them, they're not sort of hippy - not something that's sort of out of the mainstream," U.S. Secretary of Energy Samuel Bodman said. "These are homes that are quite attractive places to live."
For the 20 American and European colleges that made the finals, designing and building the solar dream houses was only half the challenge; the other half was getting them to Washington.
"We are here proving that solar energy does work," said the decathlon's director Richard King. "It is esthetic, it's beautiful. You can go in these houses, they're delightful."
King says the contestants are judged on how the homes hold up to regular household activity.
"They have to do tasks, cook dinners, wash dishes, keep TV sets going for six hours a day," King said. "Heat and cool their house between 70 and 78 degrees, 40 and 60 percent humidity. We judge the aesthetics, the architecture, the innovation of these houses - all without being connected to the grid, just [using] solar power."
One reason solar homes haven't caught on yet may be the perception that they're boxy and ugly. But solar homes don't have to be homely. In fact, some of these houses are gorgeous.
It turns out you don't have to sacrifice luxury when you go solar, either. These houses have all the modern comforts: mood lighting, outdoor showers and SubZero refrigerators.
The contest rules put limits on the houses' height and size. And the sun has to power everything - heating, cooling, cooking and even charging an electric cart. Solar panels, or photovoltaic panels, are a major architectural feature.
This year's teams have also focused on using recycled or renewable building materials. One team built a concrete countertop made from 40 percent recycled material from coal-fired power plants.
Many technical breakthroughs are on display at the contest. Some of the terms the contestants use are hard to understand, such as "inductive magnetic field," "hydroponics system," and "evacuated-tube solar water heater." But some of the new ideas are easy to grasp - and easy to get excited about, like an indoor waterfall, which was demonstrated by Nick Venezia from the University of Maryland.
"The moisture comes from the air and it goes down through the bottom of the wall, up through the wall, and the finished product is sent out by this fan system," he said. "About 30 percent of your cooling costs during the summer can be attributed to the moisture in the house. So it's taking the burden away from your air-conditioning system."
Jason Brown showed off Georgia Tech's high-tech house of light. The building's hot water comes from special tube systems, which can heat water as high as 200 degrees.
"It's a bank of 30 long tubes of glass … takes the sun's energy as heat, transfers it into the water, in a hot water tank," Brown said. "With a slight modification, it's like a normal hot water heater."
One home was shipped all the way from Germany by the Technical Institute of Darmstadt. According to team leader Joerg Thoene, it's loaded with energy-saving features.
"The reason why we have three-paned glass is that we need to have a very well-insulated shell to prevent energy from going outside, he said.
Some of its solar panels are hidden on the roof and the rest are in plain view.
"These are solar panels, as well," he said showing off his teams' work. "Wooden louvers with photovoltaics mounted on top of them. We are able to adjust the angle of the louvers according to the angle of the sun, so we always have a maximum amount of gain with them."
But no one has to run around adjusting them; Thoene said computers take care of that. His team also included televisions disguised as mirrors, and beds disguised as floors.
Now, if you ask Secretary Bodman, the U.S. is doing plenty to address the climate crisis.
"This President has always made the statement that this was an important matter. We've clearly learned a lot as time has gone on," he said.
But not everyone agrees that we have done enough.
Greg Kiss has been designing solar buildings for 25 years. He's the chief architecture judge for the Solar Decathlon.
"You know, other countries, Germany, Japan, actually all of Europe these days, have implemented nationwide or even continentwide programs that have a very consistent policy," he said. "Either they pay you extra money for solar electricity that you generate, or they give you a tax break. In this country, the federal government has not been especially supportive on that level."
Finally, the scores from the 10 competition categories were tallied up. After two years of effort and months of sleepless nights, the teams gather to hear the winners announced. The University of Maryland came in second, and the Technical University of Darmstadt from Germany took home the championship trophy.
Although winning the solar decathlon doesn't exactly help these teams recoup the $500,000 to $1 million they've spent on these houses of the future, the contestants say they were not in it for the money, but were hoping to help save the planet.
Copyright 2007 CBS. All rights reserved.