Charlestown’s Bunker Hill Housing Redevelopment project, which broke ground in June 2023 after an eight-year community planning process, promises 21st century comfort, energy efficiency and carbon reducing performance in its new mixed-income residential community. Located in an historic waterfront neighborhood, Boston’s oldest, much of this 1940s-era federal public housing site had fallen into disrepair. Now, in a public-private partnership, the team of Leggat McCall Properties and Joseph J. Corcoran Co., in partnership with the Boston Housing Authority and the Charlestown Resident Alliance, has developed and launched a $1.4 billion plan to replace 42 aging buildings with 15 new residential buildings, plus retail and community space. To strengthen the sense of community, the project features extensive green spaces and improved connections to the surrounding area.

While occupant and neighborhood upgrades loom large, the project also strives to be a shining example of solutions that will successfully deliver on Boston’s 2050 carbon neutral goal. And if all goes as planned Bunker Hill, the largest public housing project north of New York City, will also be among the biggest Passive House projects on the planet. Administered by Passive House Institute US (PHIUS), the Passive House construction concept—which focuses on providing energy efficiency and occupant comfort—seeks heating- and cooling-related energy savings of up to 90% compared to typical building stock, and more than 75% compared with average new builds. Savings strategies incorporate improvements in insulation, windows and ventilation to help keep building occupants cozy year round.

The project team’s Carbon Neutral Building Assessment compares Building M, a design model that seeks to establish a repeatable blueprint for the entire project, with a baseline model. Implementing key strategies from Boston’s 2019 Climate Action Plan, Building M boasts impressive results, setting the structure on a path to accomplish Boston’s 2050 goals early, while providing better comfort, a healthier environment and lower utility costs.

The design for Building M aggressively pursues both energy efficiency and electrification. Building M is pre-registered with PHIUS and the project team is committed to Passive House certification. The project will electrify nearly 70% of its energy loads and is designed for a seamless future transition to full electrification.

“It is exciting to see the leadership that Leggat McCall has demonstrated in setting such truly ambitious green building goals,” said Matt Root, senior project manager for Integrated Eco Strategy, the sustainability consultant providing analysis and documentation for Bunker Hill. “Building M offers a new standard of performance here and for others that follow—and promises to make this project a gem for both residents and Charlestown itself.”   

Thinking beyond operational carbon, the design team also took steps to reduce the project’s embodied carbon (CO2e). Owing to critical design decisions, the project forecasts a 37% reduction in CO2e over the baseline. This impressive result can be heavily credited to the decision to use a mass structure of cross-laminated timber (CLT) and avoiding carbon-intensive concrete and steel.

The use of CLT rather than the standard concrete planks, sequesters more than 1,400 metric tons of CO2e. The project also significantly reduces other harmful impact categories such as acidification (-27%), eutrophication (-42%), ozone depletion (-40%), and smog (-25%).

Stay tuned, as Bunker Hill Housing, part of Boston’s oldest neighborhood, makes regional history again as Boston’s bold step toward a better future.