In a former industrial city 30 miles north of Boston, this innovative adaptive reuse project has transformed a nearly 200-year-old mill building into one of the region’s most energy-efficient all-electric apartment communities – remarkably meeting both ambitious energy code requirements and strict historic preservation guidelines and setting a new precedent for historic conversions.

Called Stone Mill Lofts and now comprising 86 mixed-income rental apartments, the 149,220-square-foot building was first constructed in the 1840s, helping to power the Industrial Revolution as a manufacturing hub supplying parts to other mills and factories across New England. Yet like many historic industrial complexes, it sat empty and derelict for years by the time its transformation began in 2021.

In reviving this landmark for residential use, the project team preserved the unique historic characteristics that make older buildings so compelling as new homes – restoring the beautiful field stone façade, and replacing the deteriorated slate roof. Inside, common spaces and apartments benefit from high ceilings, large window openings and thoughtful integration of existing elements such as exposed, original wood beam ceilings and shiplap and historic wood trim. The resident experience is fully up-to-date, with shared lounge and work-from-home spaces, a children’s playroom, indoor bicycle parking, secure package room, and landscaped outdoor areas.

These elements exist within an airtight, ultra-efficient new building envelope whose performance is competitive with a modern Passive House development. In a rare occurrence for a historic mill conversion of this size, Stone Mill Lofts is completely fossil fuel-free and uses highly efficient heat pumps to provide heating, cooling, and hot water. It’s a case study in how the building industry can accomplish several crucial goals at once, by prioritizing sustainability and decarbonization — both embodied and operational — while preserving landmark buildings and cultural heritage, enhancing housing affordability, and providing comfortable, attractive and inspiring homes.