( CNN ) -- Teams from across the globe will soon learn whether their green designs will take top prize at Solar Decathlon Europe 2012 -- a competition that challenges collegiate designers to build houses powered exclusively by the sun . But beyond their use of photovoltaic panels , these sustainable homes of the future will also be judged on overall design , construction quality and the level of innovation . The 19 small houses that run solely on solar power were built over two weeks in September at Villa Solar in Madrid , Spain , and provide an architectural spectacle that the public can tour for free . Read more : Solar Decathlon Europe 2012 . Teams from Europe , China , Japan , Brazil and Egypt , designed these houses to produce minimal waste throughout the structures ' life cycle . The lighting , heating and cooling must be fully functional in each house , as do any household appliances inside them , like televisions and ovens . Plumbing is the only component not set up in these showcase homes . During their final days on display , the houses accumulate points through a series of 10 mini-contests , each measuring specific parameters like architecture , engineering , energy efficiency and market viability . The team with the most points after the final judging wins . With two more contests to go , a French team 's house , `` Canopea , '' is leading the pack , followed by a Spanish team 's `` Patio 2.12 '' and an Italian team 's house , called `` Med in Italy . '' Ecolar , a team from Germany , is in fourth place right now but its team member , Jakob Winter , says just completing the house the way they had conceptualized it is gratifying enough . `` The most rewarding thing is the feedback of the visitors , '' he said . `` So many people have come to me after the tour to say what a wonderful building it is , and the atmosphere inside the house . We 're just very happy because we feel the same inside our house . '' Feedback is important for a team like Ecolar , which is one of the teams that already has concrete plans to take its prototype to the market . `` We already have several inquiries from all around the world of people who would very much like to purchase an Ecolar home , '' Winter said . Ecolar won the award for having the best engineering . It is a prefabricated modular home , meaning that they have designed several structures that can all be pieced together in a broader system . The team enhanced the house 's `` passive '' temperature regulation to save energy , which meant using hemp in its walls , ceiling and floor for better insulation , and installing clay plates on the ceiling to absorb heat . Like several of the other houses , Ecolar uses vertical , semi-transparent solar panels on the house 's faÃ§ade , which lets in natural light while helping to supply energy . Sustainable materials were taken into consideration for most entrants . A team from RWTH Aachen University in Germany , which designed the Counter Entropy House , found several innovative ways to incorporate items normally thought of as unusable : melted CDs were used to build plastic panels for the house 's facade , and salvaged beams and wood from the university 's stadium also served as building material . The house was also designed so that all of its parts can be easily separated for recycling . Amid the boxy structures , one house , designed by the team from the Technical University of Denmark , took an unusual yet striking shape . The house is called Fold , which looks lopsided with slanted walls and a slanted roof . The angles are meant to be adjustable , depending on where the house is built , to maximize the solar panels ' exposure to the sun . Like many other of the entrants , Fold produces more energy than it consumes , which means the excess power can be sent through the grid for other uses . At Villa Solar , the prototype houses ' overall surplus energy powers event spaces . The competition was spun off from the original Solar Decathlon held biannually by the U.S. Department of Energy in Washington , D.C. , and is the result of an agreement between the U.S. and Spain , which is hosting the European edition for the second time .
Solar Decathlon Europe brings together university teams from around the world . The 19 small houses that run solely on solar power were built over two weeks . The public can tour the houses at Villa Solar for free . Many of the teams have plans to sell their houses commercially .