This photograph features the energy-efficient lighting that illuminates the solar-powered Virginia Tech house during the U.S. Department of Energy Solar Decathlon 2009 on the National Mall. The central theme of the Lumenhaus is light. A pavilion design features sliding north and south walls made of glass. These glass walls can be opened up to allow air and light in and expand the footprint of the house onto the decking and outdoor space. Responsive architecture features include the ability to operate the heating, cooling, lighting, insulation, and sunshading with a computer or iPhone, which receives environmental condition data from sensors inside the house and a weather station outside the house.