Boston, Massachusetts: Energy Positive Homes
When then-Mayor Thomas Menino launched the E+ Green Building Demonstration Program in March 2011, it represented another step toward fulfilling Boston’s mission to promote sustainability across the city’s built environment. The demonstration program is intended to advance the next generation of green building design: homes that produce more energy than they consume, while also expanding housing opportunities in areas well served by transit and other amenities.
As part of the program, Boston-based Urbanica developed four energy-positive townhouse units on Highland Street in the city’s Roxbury neighborhood. Each three-story home received a preoccupancy score of less than zero on the Home Energy Rating System (HERS) Index: -7 for the two end units and -9 for the two interior units. Homes with energy-generating capacity that exceeds consumption receive a HERS Index Score below zero. A score of -9 means that the home produces 9 percent more energy than a comparably sized home consumes.
Each of the four townhomes features 38 photovoltaic (PV) panels capable of generating more than 10,000 kilowatt hours of electricity per year. The 8.7-kilowatt array, which adds approximately $50,000 to the cost of each home, should pay for themselves within 6 to 8 years through utility savings and financial incentives from federal and state tax credits, notes Benjamin Cumbie, vice president of Transformations, which designed the project’s PV systems.
Double stud wall construction allows for additional insulation creating a highly efficient building envelope. Image courtesy of Urbanica.
The units also feature a superinsulated envelope to reduce the energy required for space conditioning. Double-stud construction allows for an R-value exceeding 40 in the walls, and the R-value of the ceiling exceeds 60. These features substantially reduce the demand for heating (electric heaters are used). Instead of the 60 percent of a typical home’s energy expenditure, heating the Highland Street homes is expected to be only 25 percent. Because of the advanced building envelope, each unit achieves energy positive status using a smaller heater powered by solar panels.
Sustainable Design Demonstration
Urbanica was one of several teams that responded to the Boston Redevelopment Authority’s (BRA) request for proposals (RFP) at three project sites originally owned by the city’s Department of Neighborhood Development (DND). The RFP called for designs for one- to four-unit buildings that would meet or exceed the requirements for Leadership in Energy and Environmental Design (LEED) for Homes Platinum certification — the rating system’s highest designation — and achieve net-positive energy performance. In addition, at least one of the units available for purchase had to be affordable for a moderate-income household (that is, a household earning between 80 and 100 percent of the area median income). The winning proposals include different housing types for the three sites, including townhouses, duplexes, and single-family detached units.
The competition was an excellent platform for the city to engage developers of smaller residential projects in sustainable building practices. Since 2007, when Boston became the first U.S. city to require developments exceeding 50,000 square feet to be LEED Silver certifiable, the city has focused much of its green building efforts on large residential and commercial projects. “We were very successful in transforming practice at the large building scale . . . so [the demonstration] really did give us a chance to work in a sector that hadn’t had the attention, hadn’t seen the progress that we had seen elsewhere,” notes John Dalzell, senior architect with the Boston Redevelopment Authority.
For Urbanica, the demonstration marked the first time sustainability and energy efficiency were paramount for one of his company’s projects. Dalzell notes that Urbanica was not alone; the competition attracted proposals from developers who do not typically work on small residential projects or who were not familiar with green building. “We were approached by participants who said . . . that the process had changed their perspective and understanding of what was possible [through sustainable design and construction],” says Dalzell.
The four townhouses on Highland Street are the first homes built in Boston’s E+ Green Building Demonstration Program. Image courtesy of Urbanica.
Consumer response to the demonstration has been just as positive as that of the development community. All four of the units sold prior to or shortly after completion; the project’s three market-rate units sold for more than $500,000, and an affordable unit sold for approximately $226,000. The affordable unit received a $60,000 subsidy from BRA and was sold to a moderate-income purchaser, reflecting the demonstration’s goal of providing housing opportunities for buyers earning a range of incomes. According to Dalzell, the response by the local neighborhood group has been positive. “[T]hey wanted to be known as the neighborhood where the most cutting edge and greenest homes are being developed.”
With six energy-positive homes now completed at two demonstration sites and construction to begin soon at the third site, the city is wasting little time in building on this model of green development. The city started its E+ Green Communities Program to scale up the production of energy-positive homes in locations within walking distance of transit service and other amenities. In March 2013, DND issued an RFP for Parker-Terrace Street, a sloping, 57,000 square-foot site spanning the width of a block in the Mission Hill neighborhood. The winning proposal was selected 6 months later and features an inspired design that includes 41 energy-positive rental units (both market rate and affordable), rooftop gardens, and street-level commercial space.
DND and BRA are in discussions to develop another E+ Green Communities site on DND- and BRA-owned parcels near Urbanica’s energy-positive Highland Street townhomes. City officials have been meeting with neighborhood residents over the past two years to explore the potential for additional investments on the city-owned land. Because of these and other efforts to promote sustainability, Boston has earned national recognition. In 2013, the American Council for an Energy Efficient Economy ranked Boston number one in its first City Energy Efficiency Scorecard, which ranks the efforts of the nation’s 34 largest cities to advance energy efficiency.