“The Triple Decker Challenge, for us, was a really exciting chance to reinvent this iconic typology for Boston and the surrounding areas,” says Elizabeth Whittaker, principal of MERGE Architects, in their submission summary video. Their design solution relies on the construction of a new rear unit, ensuring that existing tenants will experience minimal displacement during the retrofitting process. The additional unit replaces the existing back staircase and porches with a spatially efficient scissor stair connecting the three levels of the rear unit. In their Project Vision & Design Narrative, they write that the retrofit investment “can be done without significant financial penalty through thoughtful balance of trade offs and benefits, energy incentives, and additional rental income.”
The retrofit of the existing building prioritizes a higher performing exterior envelope, as well as upgrades to ventilation, heating and cooling, appliances, and lighting. Passive design strategies and active systems are combined across the retrofit and additional units to maximize energy performance. Cross ventilation ensures that there is an inlet and outlet for natural breezes in each room of the rear unit, balanced daylighting is designed in, and stack ventilation helps the mechanical systems perform better. Ductless ERVs are specified to increase indoor air quality and ductless air-source heat pumps, or ASHPs, to provide full heating and cooling to both the existing and new units. Further, the “design is fully electric, allowing the operating CO2 emissions to be decreased over time as the portfolio of grid sources becomes more renewable.”
MERGE Architects notes in its proposal that many triple decker buildings are located near the coast, making their basements susceptible to flooding and therefore unfit to be used as living space or store other essential equipment. The Back Stack design only utilizes the basement to store the heat pump water heaters.
