The Solar Decathlon, a biennial contest in which 20 teams of US university students build houses that produce as much energy as they consume, was in the ironic position of homelessness in January 2011: the competition had lost its spot on the National Mall in Washington, DC. The news broke during the International Builders’ Show, where teams had met to show off models of their projects. The students were bummed. So they organised themselves and lobbied the government. Team California’s Elisabeth Neigert (left) pleaded their case in The Huffington Post. In the end, the students won. The competition, organised by the US Department of Energy, was due to go ahead in the original venue, with the public able to tour the homes and see students testing brilliant ideas – such as these 22 – in real-world conditions, one watt at a time.

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Teameam California CHIP
CalTech and SCI-Arc’s CHIP (Compact House, Infinite Possibilities) combines engineering and architecture to challenge conventional building practices with concepts such as these:

Solar panel clamps
Rather than penetrating a rooftop with a racking system (which can void roofing warranties and lead to leaks), students combined panel-mounting IronRidge rails with a homemade clamp-and-pipe system that can pinch the panels into place while the vinyl roof membrane remains unbroken.

Power for EV parking
Planning for a vehicle isn’t a competition requirement. But Team California figured out how to use CHIP’s cantilevered upper floor to create an electric-vehicle carport under the bedroom. Beefy wiring connects an exterior outlet to a 20-amp breaker, using the 8,0-kW photovoltaic (PV) system to charge an EV.

Automatic A/C
When asked to name the single best piece of CHIP’s heating and ventilation equipment, CalTech student Fei Yang rattled off a model number: Mitsubishi MXZ- 2B20NA-1. This air conditioner takes infrared measurements of the house; then automated louvres blow cool air to hot areas.

Controls via Kinect
A CalTech modification makes Microsoft’s Kinect system for the Xbox 360 function like a next-gen Clapper. The system, described by designer Cole Hershkowitz as a “gesture- and locationbased home-control interface”, senses specific body motions to turn on lights, fire up the stereo or switch on the TV.

Billboard cladding
The team used vinyl-coated polyester, which could be recycled from billboards, as impervious external wall cladding. The white cladding also wraps the roof.

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Team New Jersey - Enjoy House

Thermal mass
Team New Jersey (Rutgers and the New Jersey Institute of Technology) squeezed 150 mm of expanded polystyrene insulation inside its home’s 30-cmthick precast concrete walls, floor and roof. In winter, the slabs absorb daytime solar heat and release it throughout the night.

U. of Maryland - Water Shed

Solar Pergola
As a backup to a 9,2 kW photovoltaic array on the south slope of its split-butterfly roof, the WaterShed has a solar pergola above its kitchen door. Six 220-watt panels shade a small deck. Microinverters convert DC current to AC current at each panel, eliminating excess wiring.

Team New York - Solar Roof Pod

Modular blocks
The City College of New York’s Solar Roof Pod, designed to perch atop a four- to six-storey structure, includes 2,4 x 1,5 m building blocks that can be used as walls, windows, photovoltaic mounts or glass prisms. Owners can customise the 165 mm-thick blocks’ configuration.

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Appalachian State University - The Solar Homestead

Custom Reflectors
Mirro-rlined troughs beneath an array of solar thermal tubes make each one more efficient at heating a glycol loop, which transfers energy to warm the Homestead’s water. To mould the trough, students pressed flexible mirror film face-down on a length of 325 mmdiameter PVC pipe, clamped it in place with a pair 50 x 100 posts on hinges, then spread fibre and epoxy on the rear to create a firm glass fibre backing. It’s a simple process, but figuring out the exact angle of the trough’s arc and its optimal distance from the tube took engineering physics graduate student Neil Rifkin two full semesters of hardcore number crunching. Parabola? Circle? The sun’s position over Washington, DC, in September? “Once I figured that out, building the reflectors was the easy part,” he says. The resulting 1,8 x 5-metre thermal array is part of a solar skylight above the home’s otherwise windowless mechanical core.

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DIY Solutions
4 Ideas to try at home

Track energy use
The eMonitor system by Intellergy, featured in Middlebury College’s home, displays power consumption as an average or in real time. A top-five list reveals which appliances consume the most juice – info that can curb consumption.

Recover heat
The Ohio State University’s enCORE house uses an energy-recovery ventilator as part of its heating and ventilation system. The device, which can be retrofitted onto ductwork, passes heat from outgoing indoor air into fresh air as it enters the home. This reduces the load on heating and cooling by capturing energy that would otherwise escape as exhaust.

Go Native
Taking its cue from the Chesapeake Bay lowlands, the University of Maryland built a constructed wetland to manage rainwater and filter greywater. Residents can navigate the native landscaping on rot-resistant cooked-ash decking, which is fired in a kiln and similar to pressure-treated timber.

Amp an awning
Semi-transparent Sanyo solar panels cast diffuse light on Appalachian State’s porch. The partial shade is pleasing and powerful, plus the 42 panels collect UV on both faces to yield about 195 watts apiece.

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Florida International University - Perform[d]ance House

“Hurricane shutters are quite ugly,” FIU project manager Andy Madonna says. His team’s solution: 10 cantilevered, counterbalanced shutters that shade the house and porch. The shutters batten down to weather a storm, or just add privacy, in a quarter of an hour – one-eighth of the time it takes to set up the hurricane shutters sold today. “We’re trying to bring a new product to the market,” Madonna says.

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Team Massachusetts - 4D Home

Hybrid Panels
The Massachusetts College of Art and Design and the University of Massachusetts, Lowell, combined electricityproducing photovoltaic panels and water-heating solar thermal collectors in a single hybrid module. Normal PV panels’ 12 mm silicon sandwich sits in a 32 mm aluminium frame. The 4D Home’s SunDrum solar hybrid system fi ts a 6 mm flat-plate solar thermal collector into the extra space, leveraging it to heat domestic water while making the PV panel cooler and more efficient.

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Parsons Milano Stevens - Empowerhouse

Rain Wrangler
To manage rainwater, the street kerb’s permeable pavers filter storm run-off into the soil. Rainwater that hits the roof feeds into a 4 000-litre underground cistern, accessed for garden use via a spigot. Surplus water feeds a sunken rain garden.

Afterlife
Once the Solar Decathlon ends, many of the contest’s houses end up sitting idle. But the team of Parsons The New School for Design, Milano (The Milano School of International Affairs, Management and Urban Policy at The New School) and the Stevens Institute of Technology identified the DC neighbourhood of Deanwood as the ideal permanent venue for its Empowerhouse. The team plans to show an 80 m2 competition version of the house on the National Mall. After the Decathlon, that home will combine with a second building to create a 250 m2 family dwelling.

Landscape Design
The team chose to surround its house with American hornbeam trees because their slight stature won’t block the sun from reaching a 5 kW solar panel array. Plants such as hydrangeas and switchgrass filter heavy metals, removing them from the garden’s soil.

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Purdue U. - Inhome

Flora Filter
A 1,8 x 5 m vertical wall of plants cleans the INhome’s air as it enters a ventilation and heating return vent. Purdue student Kevin Rodgers designed the garden to grow in a soil-free, porous fabric medium fed by fertiliser-rich drip irrigation. “We use common plants such as golden pothos and heart-leaf philodendron. Pass large amounts of air through the roots, and that’s when you see benefits,” Rodgers says.

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Middlebury - Self-Reliance

Impenetrable Windows
To prevent energy loss through a window wall, architecture co-lead Joseph Baisch specified German Optiwin windows, which use a triple-pane design to resist heat transfer at a stout R-7 rating. The windows, plus R-42 walls and an R-74 roof, take insulation to the extreme.

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Uni. of Tennessee - Living Light

Dual Facçade
Two double-layer windows enclosing a 30 cm air gap cover the home’s north and south walls. “We can maximise transparency, light and view without compromising the thermal envelope,” project manager Amy Howard says. Automated blinds between the glass panels further reduce heating/ventilation system load.

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Team Florida - Flex House

Drizzling dehumidifier
“It’s basically salt water,” Florida State mechanical engineering graduate student Jon Pandolfini says about the calcium chloride blend flowing down a 2,3- metre acrylic sheet. Visible in the house, the sealed chamber doubles as an ventilation system duct. Humid outdoor air enters the duct, then the desiccant collects moisture. Combined with an energy-recovery ventilator, which heats or cools air but doesn’t dry it, the system beats the swamp heat without wasting wattage.

Visit the DOE Solar Decathlon YouTube channel to take virtual tours of the various houses.