When the Solar Decathlon competition ends later this year in October, most of the student-designed and -built energy-efficient homes will be shipped back to their respective universities, with a notable exception: One home will be modified and become part of a net-zero duplex that could be one of Habitat for Humanity’s most energy efficient homes.
“The house is an extension of the progression that Habitat has made over the last several years,” Kent Adcock, president and CEO of Habitat for Humanity of Washington, D.C., said at the ground-breaking ceremony on June 29. “A number of years ago Habitat built with conventional construction, and then a few years after that we went to Energy Star construction. And then a few years after that we went a little further to EarthCraft certification.” Building to Passive House standards, he added, “is the next sustainable answer for affordable housing.”
Designed and built by a team consisting of students from Parsons The New School for Design, Milano School for International Affairs, Management, and Urban Policy at The New School, and Stevens Institute of Technology, the solar-powered Empowerhouse will start life as a single-family home that will act as an entry into the Solar Decathlon that starts in September. But at the conclusion of the competition, it will be moved to a site in the Deanwood section of Washington and expanded into a two-family home.
The Solar Decathlon is a biennial Department of Energy competition that challenges university teams to design, build, and operate solar-powered houses, but this year the Empowerhouse team was determined to take the endeavour beyond the competition, said Joel Towers, executive dean of Parsons.
“It wouldn’t just be about a demonstration house but about really changing the way people live and about housing,” Towers said at the groundbreaking. “We took that very seriously to the point of doubling our efforts and building two houses for the competition.”
The two Empowerhouses were designed to be net zero and will produce all of their energy needs, says Carly Berger, a third-year architecture grad student at Parsons. Because it’s being built to Passive House standards, the building will have a well-insulated shell and will use natural sunlight and an energy recovery ventilator to help maintain a comfortable inside temperature.
One noticeable change in the construction of the home is in the wall assembly, which will be prefabricated with I-joists instead of conventional studs. “We are using Nordic wood I-joists, which aren’t traditionally used as wall studs, but we are using them in this case because it gives us the depth and it has a thin web that minimizes thermal bridging,” Berger explained at the ground-breaking ceremony.
The walls will be filled with blown-in cellulose; the Zip system sheathing from Huber Engineered Woods will help create a tight shell; and a rainscreen made with fiber-cement siding will complete the envelope, Berger added.
Windows will play a huge role in the home as well, says David J. Lewis, a faculty member at Parsons and a partner in the New York City-based firm LTL Architects. “We’re using the windows to maximize the control of the southern exposure, so that you’re actually using those as an energy generator,” Lewis explained. The team chose R-7 triple-glazed windows from Intus Windows.
“We believe that with this event and [the homes] we’re following up with we will be the test tube that will be used as a laboratory for other Habitats to learn about sustainability,” Adcock said. The home will not be the Habitat’s first net-zero energy house, but it will be its first Passive House and will have implications for the organization. “What we’re talking about is that if we can move in this direction than every future [Habitat] home will be the same in terms of sustainability.”
The Empowerhouse that will be entered into the Solar Decathlon is under construction in New Jersey.
Nigel F. Maynard is a senior editor at Builder.