Solar Decathlon proves that solar can be practical

Nov. 8, 2013
The recently concluded Solar Decathlon showed that solar-powered, energy- and water-efficient housing can be beautiful and practical. It was also good to see a renewed interest among the students in solar thermal and radiant heating and cooling systems.

The recently concluded Solar Decathlon showed that solar-powered, energy- and water-efficient housing can be beautiful and practical. It was also good to see a renewed interest among the students in solar thermal and radiant heating and cooling systems.

Collegiate teams from 19 universities from around the world opened their solar-powered houses to the public in early October as the U.S. Department of Energy’s biennial Solar Decathlon kicked off at the Orange County Great Park here. This was the first time that the Solar Decathlon was held here in a terrific location at what used to be the El Toro Marine Air Station. The contest had previously been held at the National Mall in Washington, but the Great Park looks like it’s a superior location — no shortage of space and endless sunshine.

The contest was unaffected by the government shutdown, as it really was too late — the students were in Southern California assembling their houses at the time of the shutdown and the teams from Austria and the Czech Republic had shipped their houses across the Atlantic in July.

In a tight competition, Team Austria, made up of students from the Vienna University of Technology, won top honors overall by designing, building, and operating the most cost-effective, energy-efficient and attractive solar-powered house. University of Nevada Las Vegas took second place, followed by Czech Republic, comprised of students from Czech Technical University, in third place.

The team from California’s Santa Clara University employed a ceiling-mounted radiant heating and cooling system from an Italian company called Messana Air-Ray Conditioning SRL. Why the Italians? They volunteered, said Santa Clara’s spokesman Brian Grau. Offering students products for the houses goes a long way; it seemed like all of the plumbing was from Kohler, except for the Austrians and Czechs, who opted for products from Duravit and Hansgrohe.

The DesertSol house built by the University of Nevada Las Vegas used ground-mounted solar thermal collectors that fed into a 100-gal. Buderus tank that in turn fed an Uponor Quik Trak PEX system in the floor. 

All of the homes contain fire sprinklers and several used Uponor’s PEX-based combination domestic water and fire sprinkler system.

The Austrian team won the competition, although I’m still wondering what those floor-to-ceiling, gas-filled, triple-pane sliding doors really cost them.

The Austrian house used two clever technologies, including a floor grid system that incorporates PEX tubing combined with air channels. Air flowing through the channels picked up heat or coolness from the PEX tubing and exits out slot diffusers in the floor at either side of the house. The arrangement allows both radiant heating and cooling. The Austrians also used a Swiss product from a company called Joulia SA that runs the incoming domestic water through a floor grid in the shower floor. The incoming water picks up heat from the flowing shower, preheating the water going into the water heater. Joulia claims that a family of four can save 1,000 kWh per year with its shower tray, which converts to 3,412,142 Btuh.

You have to love the students from Middlebury College in Middlebury, Vermont. Middlebury is a liberal arts college, and, while the school is strong in environmental studies, there’s no school of architecture or engineering. They finished eighth. That’s right, 11 other schools with engineering and architecture programs scored lower. The Middlebury students figured out that it was more efficient to hold a Bradford-White tank at 110°F and then boost it on demand to 120°F with an Ecosmart tankless unit.

The students do some cool things with their houses to emphasize where they are from. Middlebury, for example, made its flooring from sugar maples and the floorboards had holes in them from where holes had been bored for sap collection.

UNLV had a steel panel for shading that mimicked the shade from a stand of Mesquite. They took a photo of Mesquite grove, converted the picture to black-and-white and fed it into the CAD/CAM system for a laser cutter. The laser used the photo to cut holes in the sheet steel. At first I thought the holes in the panel were random, but when I stood back, yes, indeed, that was a Mesquite grove.

Stanford University’s Start.Home contains a prefabricated 12-ft. x 15-ft. core module that contains all of the wet systems for the kitchen and bath, including a GE heat pump water heater. The bathroom contains a Caroma dual flush toilet and a digital shower control from Kohler. A 25-gal. graywater tank, which was not connected during the contest, would supply drip irrigation to the landscaping.

The plumbing system is a Uponor PEX combination domestic water and fire sprinkler system. As it turns out, however, the house will ultimately be permanently sited in San Mateo County in California, which does not allow PEX for fire sprinklers, so the house will have to be replumbed.

All of the houses were tightly insulated; Stanford’s uses a structural insulated panel, along with a phase change material that fastens onto the USB underneath the roof. Stanford selected 650-sq.ft. of DuPont’s Energain phase change material, which the company says will stabilized temperatures and reduce heating and cooling costs.

Phase change material was big at this year’s Decathlon. Santa Clara filled an old wine barrel with it to store solar heat. Stevens Institute of Technology placed a soy and wax phase change material in their walls. Stevens Institute of Technology, by the way, used a regenerative calcium chloride system to remove humidity, plus the system could also reverse and supply humidity in an arid climate.

The home has 6.5 kW of PV on the roof but no solar thermal.

Heating and cooling is provided by a Mitsubishi Tri-Zone ductless split heat pump. Fresh air is provided by a Fantech heat recovery ventilator and there’s a Panasonic Whisper Fan in the bathroom.

Be sure to check out our photo gallery from the Decathlon at plus our videos from the event on

Also on the solar front, check out an ingeniously simple water heating product that was on display at the Solar Power International Show, the SunBandit Hybrid Solar Water Heating System that you can see here at Photovoltaic panels on the roof generate DC that’s converted to AC by micro-inverters on the back of the panels. The current is fed through Romex to the water heater and heats the water through a “micro-grid resistive element.” In case it’s cloudy or nighttime, the water heater contains regular grid-connected electric resistance elements.

The advantage of the SunBandit, industry luminary Robert “Hot Rod” Rohr pointed out to us, is that because the collectors aren’t connected to anything except the water tank, it circumvents all of the side issues that jack up the cost of a solar system, like permits or a big dollar insurance policy that your electric utility will require.


Finally, the time is running short for you to nominate a contractor for our Contractor of the Year award. You can nominate yourself or any other contractor that you think is deserving. Each year the editors of CONTRACTOR look for a contractor who does something in such an outstanding way — and that could be either a technical or management skill — that other contractors should copy him.  We're looking forward to finding a contracting firm that's so outstanding that we're just blown away.

Submit your nomination at

When we say that our criteria is that the contractor must be doing something that's so good that other contractors should copy it, what do we mean? Past recipient John Smith turned his business around during the recession by remaking himself as the Arizona Green Plumber. Brian Nelson knows the latest in new technology, not just here but all over the globe. John Ward is such an astute businessman that he could probably make a million bucks off a lemonade stand. Bill Erickson became a leader in the green movement and became chairman of the IAPMO Green Technical Committee, which created the IAPMO Green Plumbing & Mechanical Code Supplement. Kevin Tindall, currently president-elect of PHCC-NA, took trailer-load after trailer-load of relief supplies to New Jersey’s Long Beach Island after Hurricane Sandy. The things the first responders appreciated the most were the porta-potties (there were no utilities left after the storm) and dry socks.

Our ultimate winner might be a guy who could sell ice cubes to Inuit or a disciple of Mother Theresa. Either way, it's somebody who should be emulated.

Follow me on Twitter @bobmader

About the Author

Robert Mader Blog | Editor in Chief

Bob Mader is the editor of CONTRACTOR magazine, Green Mechanical Contractor magazine, and Radiant Living magazine. He has been writing about plumbing, mechanical, green building and HVACR topics for more than 25 years.

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