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The Virginia Tech Solar Decathlon team has found satisfaction and challenge in seeing a project go from a design on paper to a real-world, working prototype.

Illustration of the Lumenhaus, which is a gray rectangular building. On the near wall are sliding glass walls and translucent photovoltaic panels. Mounted to the flat roof is a tilted PV array. A deck surrounds the exterior and incorporates water pools.

Virginia Tech's Lumenhaus includes glass sliding walls and a PV array configured to generate extra electricity by using both sides of the panels to harvest the sun's energy.

Construction Costs


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Construction Drawings (Zip 14 MB)
Project Manual (Zip 9.3 MB)

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Solar Decathlon 2009

Virginia Tech

Team Web site:

Lumenhaus—Bright Ideas With an International Focus

Architecture student Corey McCalla has never been to Spain, but he and his Virginia Tech teammates will soon be there to participate in Solar Decathlon Europe. Virginia Tech is the only U.S. Solar Decathlon team participating in both competitions.

Virginia Tech team members are excited to compete in both competitions, although they feel some added pressure with double the competition. They are confident that the Lumenhaus will score no matter what happens with the competitions—bringing new ways of living, designing, and working to communities near and far.

The Team

Like many teams, Virginia Tech is discovering that the biggest learning experiences are working with team members from different disciplines and taking a project from the design stage to the real world. Students say that the constant reworking of the design and modifications throughout construction have been eye-opening and sometimes challenging.

The House

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.

The Technology

A concrete floor—rare in Solar Decathlon houses—is part of a strategy to provide passive, radiant heating. The floor functions as thermal mass that is heated by the sun and a radiant hot water system of piping underneath the slab. Water is heated using a geothermal loop coupled with efficient water-to-water and water-to-air heat pumps. The geothermal system consists of a series of pipes in the earth that keep water at a fairly consistent temperature throughout the year—efficiently delivering heated water in the winter and cooled water in the summer. Because it is not possible to drill a 500-ft (152.4-m) well on the National Mall, a simulated geothermal loop system is used during the event.

The Lumenhaus 9-kW photovoltaic (PV) system is also inventive. Single-crystal silicon wafers are mounted between transparent glass plates, so that some sunlight passes through the panel, is reflected off of the roof, and bounces back up to the back side of the wafer to generate additional electricity.

House Highlights

  • A responsive, pavilion design featuring natural light, which incorporates sliding north and south walls of glass and dimmable fluorescent lighting above a translucent ceiling membrane
  • A cement slab floor, heated by an efficient geothermal heat loop and heat pumps, that provides radiant, evenly heated floors
  • A PV system that includes "double hit" PV panels in a large 9-kW array to generate as much as 30% more electricity than the standard approach