Solar Decathlon 2011
Several teams tackled two other aspects of sustainable design reflected in many of today's "green" homes: indoor air quality and water conservation. In fact, this year's top finishers — the University of Maryland, which took first place, and Purdue University, which came in second — showcased original inventions in the air quality arena.
University of Maryland
Each team of students was tasked with building a home tailored to the climate of its school's geographical region. Maryland's house, dubbed WaterShed, has a "liquid desiccant waterfall" that takes a stylish approach to addressing one of the biggest problems facing energy-conscious builders in the greater Washington, D.C., area: extremely humid summers.
The patent-pending technology builds on a similar system used in LEAFHouse, Maryland's 2007 decathlon entry, which came in second that year. The device uses a high-saline liquid solution to pull moisture out of the air. This lower-energy dehumidification technique reduces the load on the air conditioners both by making the indoor air easier to cool and by helping occupants feel more comfortable.
"Air conditioning is an expensive and energy-intensive way to dehumidify," points out Amy E. Gardner, a faculty adviser to the University of Maryland decathlon team.
While "waterfall" seems like a misnomer for the wall sections comprised of small hollow balls that slow the descent of the liquid solution, the device is so stylish that the student designers opted to backlight it and incorporate it into the interior design.
The house also uses an energy-recovery ventilator to cut down on humidity and transfer the heat from exhaust air into fresh air as it cycles into the house. A couple of ductless mini-split-system heat pumps provided additional heating and cooling. The house is powered by a 9.2-kilowatt photovoltaic array on the roof and a solar thermal system that absorbs sunlight to provide hot water.
With its focus on "the path of a water drop," the team also took on the issue of stormwater runoff — which in the greater D.C. area affects the Chesapeake Bay watershed.
Rainwater flows quickly over impervious surfaces, such as roofs and roads, which can be problematic both because it can disrupt the natural flows in nearby waterways and because it can carry chemical pollutants and sediment that can be detrimental to water quality.
While one half of the WaterShed home's butterfly roof holds solar panels, the other half is topped with plants to retain rainwater, and also help cool the home in summer. The sloping design is also tailored to collect rainwater, which runs through a filtration system that purifies both stormwater and graywater from sinks and shower. T
he rain garden, or "constructed wetlands," that wrap around the house, with pink-tipped wispy native grasses, bushes, and flowering plants, is also designed to absorb stormwater runoff.
With the German team from Technische Universität Darmstadt, which won the 2007 and 2009 decathlons, sitting out this year's contest, Maryland dominated.
It held the number-one spot in the overall rankings throughout the competition, took first place in the architecture contest, and tied for first with other schools in energy balance and hot water production measurements.
The team earned a total of 951 points out of a possible 1,000, finishing 20 points ahead of second-place winner Purdue.
"WaterShed achieves an elegant mix of inspiration, function, and simplicity," says Michelle Kaufmann of Michelle Kaufmann Studio, one of the three jurors for the architecture contest. "It takes our current greatest challenges in the built environment — energy and water — and transforms them into opportunities for spatial beauty and poetry while maintaining livability in every square inch."
In a contest dominated by modern and even futuristic-looking structures, Purdue University's second place-winning INhome was the only house in the competition that approximated the average (non-solar) home. While it has a 9.0-kilowatt rooftop solar array, its ranch-style construction with an attached garage would blend into any number of neighborhoods around the country.
The house took second place in the "comfort zone" contest, but also impressed jurors with innovations such as its self-watering biowall. The vertical garden, tucked away in what could be the space of utility closet, removes chemicals and other impurities from the air — an important consideration in a tightly sealed home such as this one.
The team also attended to air quality in selecting paint free of volatile organic compounds (VOCs).
This year's energy balance contest rewarded teams for balancing energy needs and generation, rather than giving top marks to the house to produce the most solar energy. Teams received full points for producing at least as much energy as their houses needed during the contest week, thus achieving a net energy consumption of zero.
It was no easy balance for many of the teams. While Purdue earned full points, as did Maryland and five other teams, another five teams received no points at all in this category.
Purdue came close to tying for first place in another category as well: the affordability contest, which replaced the lighting contest this year as one of the ten areas of competition. A professional cost estimator began working with teams over a year ago to carefully estimate the construction cost of each abode.
At the decathlon, Purdue was initially awarded full points for keeping estimated costs at or below $250,000, but a few days later officials threw out the original scores after discovering a minor error in the calculations. The INhome fell to second place in this category, with a cost estimated at nearly $258,000.
Only two teams achieved full points: Belgium's E-Cube; and Empowerhouse, from Parsons The New School for Design and Stevens Institute of Technology, which beat the threshold by a generous $20,000.
New Zealand's First Light
Competing in the decathlon for the first time, the New Zealand team, from Victoria University of Wellington, took third place for First Light, a solar home designed as a "kiwi bach," or vacation bungalow. The house was number one in the engineering contest. It ranked second for architecture and third for its market appeal. Jurors praised the team's craftsmanship and "intuitive tree-ring visualization system" for monitoring energy consumption.
Like many of the other entries, the house relies on modular construction for easy transport, heat pumps for maintaining comfortable indoor temperatures, and an energy-recovery ventilation system.
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