The University of Maryland is a veteran Solar Decathlon competitor, with three contests already under its belt — including a second-place win behind Technische Universität Darmstadt in the 2007 competition. But this time out, Team Maryland is pushing beyond the Decathlon’s explicit challenge categories (architecture, market appeal, affordability, engineering, team communications, hot water, appliances, interior comfort, energy balance, and home entertainment) to address ecological issues relevant to the Chesapeake Bay watershed. The area is home to 1.6 million people, with almost 64,000 square miles of cities, small towns, power plants, and farms. The team’s project, called WaterShed, is a 920-sq.-ft. one-bedroom built as two “shed” modules in a staggered, split butterfly configuration. The north module includes public spaces – the kitchen, living room, and dining area – and its roof, which pitches south, is equipped with 480 sq. ft. of WaterShed’s 9.2-kW photovoltaic array and solar thermal collectors. (The balance of the PV system, another 80 sq. ft., is mounted on a pergola on the northwest deck, which extends off the north module.) The south module, which includes a convertible bedroom/office, is topped with a green roof that pitches north. The two independent modules are linked by the bathroom, under which a storm-water catchment basin forms an east-west “water axis” that runs between the two buildings.

Windows and insulation Doors and windows are by Loewen, and Guardian 275 panels, by Major Industries, are used for the translucent clerestory system in the two modules. For the floor framing, the team used 2×10 solid and 9.25-in. engineered wood; floor sheathing is 1-1/8-in. tongue-and-groove by Avantech. Six inches of Demilec Heatlok Soy closed-cell spray foam brings the floor system to R-39. The team has developed a hybrid framing system of standard stick framing and heavy timber framing. The wall framing uses 2×6 studpacks 4 ft. on center in the north module and 3 ft. 4 in. on center in the south module, with two layers of 2-in. extruded polystyrene over the 2×6 tongue-and-groove sheathing and 5.5 in. of Demilec Sealection in the stud bays, bringing the entire wall system to R-44.5. The roofs for both modules also are insulated with 3.5 in. of Demilec Heatlok Soy and 4 in. of polyisocyanurate on the exterior, bringing them to R-57.26. Thermo-treated wood is used for the siding and decking. Bellagio Microline, a three-ply 9/16-in. engineered wood from Oregon Lumber, is used for the interior flooring.

Preserving water’s role in the ecosystem WaterShed’s green roof and water axis, in fact, are designed to function as parts of a mini wetland – a “mirco-scale ecosystem” whose mix of native vegetation, soil, sand, and water can filter rain and graywater for use elsewhere on the property or for eventual release into the Chesapeake Bay watershed. About 200 students and faculty from a range of disciplines, including architecture, engineering, and plant science, have been collaborating on the project, which of course also strives to balance passive and active energy strategies in its design and construction. Appliances will include a supplemental space heating system that draws energy from the solar thermal collectors. The solar thermal collectors are expected to help in another area as well. Like University of Maryland’s LEAFHouse, the second-place winner of the 2007 Solar Decathlon, and Team Florida’s FLeX House, an entry in this year’s Decathlon, WaterShed will be equipped with two liquid desiccant waterfalls (one each in the two main modules) to control humidity. The waterfall liquid – a lithium chloride solution that absorbs moisture from the air as it flows down a vertical wall – is “dried out” in a reservoir heated by the solar thermal system. The Liquid Desiccant Wall, as it is called, is a patent-pending invention of the University of Maryland’s 2007 Solar Decathlon team and is being further developed for the current competition. Other mechanical equipment includes an UltimateAir energy-recovery ventilator, two Mitsubishi minisplit air-source heat pumps, and a NuHeat electric radiant-heat mat in the bathroom. The team will soon be conducting blower-door tests to measure airtightness. The tests will be conducted with the modules fully connected both before and after drywall is installed. Getting from College Park to D.C. Not including decking and landscaping, the project will be divided into five parts for shipping: the two main modules, the bathroom, and both roofs. At the moment, the team is keeping mum on final construction costs, although WaterShed is seeking a buyer – ideally a couple living in the Washington, D.C./Baltimore area with an annual household income of $75,000 to $115,000.