Every few years since 2002, the Solar Decathlon has been staged on the National Mall in Washington, DC, biennially since 2005. Yet the U.S. Department of Energy competition was meant to have impacts well beyond a brief showcase in the nation’s capital. The decathlon ignites whole academic networks, as various college and university teams prepare their entries. And their research moves markets and consumer demand, so that photovoltaics and sustainable building in general becomes more assimilated.
Photo © Ashley Hartzell
Empowerhouse, the first-ranked entry in the affordability contest at the 2011 decathlon, exemplifies the latter intent. Whereas former Solar Decathlon houses are usually sold or used for research and public display, Empowerhouse is the first model in the competition’s history that was designed to permanently house a local family. That team comprised New York’s Parsons The New School for Design and the Milano School of International Affairs, Management, and Urban Policy at The New School, and the Hoboken, New Jersey–based Stevens Institute of Technology. Students and faculty worked with Habitat for Humanity of Washington, D.C., and the D.C. Department of Housing and Community Development to secure a site for the project in Deanwood, a predominantly African-American neighborhood located east of the Anacostia River.
That Empowerhouse was destined for a long life in a residential enclave helps explain its predominant use of engineered wood for framing and sheathing, as well as architectural features like broad porches informed by Deanwood’s vernacular. That the Empowerhouse team engaged the local chapter of Habitat for Humanity reflects students’ desire to achieve an even more widely affordable and replicable model of sustainable housing.
They achieved it by limiting the use of photovoltaics to just a 4.2-kilowatt rooftop array, while making great gains for building efficiency through Passive-House techniques. In addition to optimizing the house for the medium-density site’s solar conditions, the Empowerhouse team framed the building to include a 12-inch cavity filled with cellulose insulation, fitted out the frame with triple-glazed windows and high-performance doors. A sedum green-roof tray enhances insulation overhead.
Inside, daylighting is abundant. When electric lighting is needed, wireless-switch LED and fluorescent lamps are positioned to reflect off interior surfaces; wireless occupancy and daylight sensors manage both. Other micromechanical systems work to use and reuse minimal energy. In one example, the water heater recovers heat from the dryer exhaust, and the cool, dehumidified air that exhausts from it is then redistributed, in order to reduce cooling loads.
Prior to the Solar Decathlon in 2011, a resident was chosen by Habitat for Humanity to live in Empowerhouse with her three sons upon its permanent installation in Deanwood. The 1,000-square-foot demonstration house’s trip from the National Mall to the other side of the Anacostia saw a few other changes—namely, the construction of a two-bedroom, one-bath second story, as well as a mirror-image unit for a second resident. The ribbon was cut on the duo on December 4, 2012, and the homeowners should take occupancy shortly. Although post-occupancy data are not yet available, models suggest that the conjoining of units should improve Empowerhouse’s energy conservation over the single, freestanding prototype.
Habitat for Humanity D.C.’s manager of housing services Orlando Velez worked on Empowerhouse as a Milano student, expands upon the adaptations. Whereas the Solar Decathlon version of Empowerhouse was modular, “The second unit that is attached to the one displayed on the Mall was constructed on-site, stick-build. Habitat primarily works with volunteers, so the team wanted to work with Habitat’s model of construction.”
Besides measuring performance of the completed homes, DC Habitat has promised to continue the Empowerhouse legacy. In addition to making presentations to multiple interested groups, Habitat itself is building another six local homes to Passive House Standards. Potentially notable, Velez reports, “We are also on a team for a response to a RFP put out by D.C. Housing Authority for the redevelopment of a 1,500-unit site in Southeast Washington, 200 of which will be built by D.C. Habitat, and all them based on Empowerhouse—Passive-House, site-net-zero, and using low-impact development systems.” If chosen for the multifamily project, it will be the largest community adhering to Passive House in the United States. The housing authority should make its selection this summer.