Super Green Affordable Housing Introduces Passive Design for the Masses
Dwell, May 3, 2015. Image credit: hkarchitects
From the street, there is nothing about the Belfield Avenue Townhomes in North Philadelphia that gives the development away as a subsidized housing project. The modular edifice has a white-and-mint-green facade and solar arrays on the roof, and each of its three town houses features bamboo floors, stainless-steel Bosch appliances, and recessed lighting. But the development, commissioned by the nonprofit Raise of Hope, not only represents an attractive, comfortable housing option for moderate-income families, it’s also a certified Passive House. Built to a strict set of design standards, it is so well insulated and airtight that each unit is expected to consume just a quarter of the energy of a traditional house.
Like most Passive Houses, Belfield Avenue incorporates supercharged wall insulation (in this case, nearly eight inches of densely packed cellulose and Polyiso, a type of rigid foam board), triple-pane windows, and an energy-recovery ventilator, which draws fresh air into the house while expelling kitchen and bathroom exhaust. In the winter, the ventilator transfers heat from the interior exhaust to the fresh air being pulled in from the exterior. (The process is reversed in the summer, with the cooler, drier inside air pretreating the hot, humid air coming in from the outside.) Certified by the Passivhaus Institut in Germany, the complex is also capable of achieving net-zero energy status. As long as the residents don’t excessively use heat, air-conditioning, hot water, or appliances, each unit can produce as much energy as it uses, with help from those rooftop solar panels.
Passive House buildings, while common in Europe, have not caught on as quickly in the United States, where the earliest models have tended to be single-family dwellings commissioned by wealthy clients. In Europe, however, the ultra-energy-efficient standard has been used in public housing for decades—and cities like Antwerp, Belgium, and Cologne and Frankfurt, in Germany, have even made the Passivhaus standards part of their building codes. The pace of this construction is expected to quicken by 2020, when a European Union directive on the energy performance of buildings will allow only “nearly zero-energy” buildings to be built in its member countries.