Roxbury E+
2013 / Boston, MA
NET ZERO ENERGY
These competition-winning townhomes were the first built under the City of Boston’s Energy Positive (E+) initiative piloting mixed-income housing designed to produce more energy than it consumes. Certified LEED for Homes Platinum, the homes’ energy monitoring has proven performance over time. The four attached 3-bedroom homes feature robust envelopes and significant photovoltaic solar arrays, consistently performing as designed with HERS ratings between -6 and -9. The design process began with an elemental box that was simple and affordable to construct and predictable in its ability to be tightly air sealed and insulated. The box was transformed through three operations: stepping down the block in response to the local urban context, sloping roofs to maximize solar geometry for photovoltaic panels, and creating a reverse bay window facing the street to provide generous access to natural light and passive cross ventilation.
LOCAL INFLUENCE
Roxbury’s neighborhood fabric includes a rich, stylistically wide-ranging history, with a variety of roof forms and bay window projections adding to the community’s visual texture. The E+ townhome design seeks to echo these playful surface geometries with sloping rooflines and reverse bay windows pushing into the building rather than projecting outwards, both speaking to community context and minimizing exposed perimeter as an energy saving measure.
PARK CONNECTION
The urban location affords connectivity to mass transit as well as green space amenities. Cascading down a significantly sloping hill facing a playground, the buildings express the unique character of the site while allowing for ideal solar orientation. The massing mediates its corner condition by striking a diagonal setback along the main frontage and opening up the side yard to relate to the park across the street.
PROVEN PERFORMANCE
A combination of active and passive energy strategies reduce the buildings’ environmental impact. A thermally robust envelope incorporates double-stud wall construction packed with insulation, air infiltration protection at seams and transitions, and triple-glazed, high-performance windows. The project utilizes HRVs for air exchange and mini split systems to provide efficient heating and cooling. On-site solar photovoltaic electricity production with 38 PV panels and a solar thermal panel for each home provides energy and hot water, with output targeted to exceed demands of the occupants and surplus sold back to the grid.
