Team website: www.solar.arch.vt.edu

Coolest features: Eclipsis shutter system made from stainless steel and a translucent polycarbonate panel filled with aerogel; bifacial solar panels so reflected sunlight generates additional electricity.

Technology/Product highlights: Radiant heated concrete floors; embedded Led light in shutters; rainwater collection and greywater recycling; and house management interface.

From Virginia Tech's point of view, the relatively small size of the houses in the 2009 Solar Decathlon doesn't mean they cannot live large. Lumenhaus is an attempt to prove that theory. "We have taken a small space and extended it out," says Andrew McCoy, associate professor of building construction.

Lumenhaus is all about light, so the students designed a pavilion (a la international-style architect Mies van der Rohe) with sliding north and south glass walls that can be opened up to permit sunlight and cross breezes. The wall also helps "expand the footprint of the house onto the decking and outdoor space," the school says. McCoy calls it "responsive architecture" because "the house responds to the outside."

"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 school says.

The large sliding shutters also help extend the house to the outdoors. Made from laser-cut stainless steel and an insulating translucent polycarbonate panel filled with aerogel, the shutters allow the house to respond to the weather and allow the homeowner to adapt the spaces for entertaining or privacy.

Each circular cutout was precisely numbered and cut based on the angle of the sun, the region, and the amount of light penetration desired. "[A]t different times of day and during different weather conditions, the light varies from subtle dancing shadows created by the circular tabs in the Shading Shutter to full sun exposure when the screens and glass doors are completely open," says the school.

More than merely a sun shading device, the shutters collect energy during the day and radiate the energy at night to run the low-energy, LED lighting system built into the insulating panels.

Even the photovoltaic system is well thought out. The students selected a roof-mounted installation that features single-crystal silicon wafers set between transparent glass plates. This is a more efficient system, the school says. "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," it explains.

Inside, the house has a concrete floor that acts as a thermal mass. Embedded with pipes for radiant heat, the slab is heated by the sun and hot water piping (via geothermal heating) during the day and radiates that heat throughout the house at night. Other sustainable or recycled-content materials include zinc cladding, wood decking harvested from fast-growing forests, and concrete floors with recycled fly ash.

"Lumenhaus epitomizes a 'whole building design' construction approach, in which all the home's components and systems have been designed to work together to maximize user comfort with environmental protection," the school says.

Nigel F. Maynard is a senior editor with BUILDER magazine.

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