What is Deep Energy Retrofitting and why do it instead of Rebuilding?

Retrofitting is a building entail that enhances or alters its existing systems and structures to boost performance, typically emphasizing energy efficiency, sustainability, or structural strength to an existing building.

It’s a question we hear often—why not just tear down and start fresh? The simple answer: retrofitting is one of the most impactful ways to fight climate change. Existing buildings account for nearly 40% of carbon emissions, and rather than sending tons of waste to landfills, deep energy retrofits allow us to extend the life of structures while dramatically improving efficiency. Plus, for the residents of Hano Homes, this means enjoying lower energy bills, better air quality, and improved comfort—without displacement.

Of course, none of this would be possible without the right support. A project of this scale requires collaboration between Allston Brighton CDC, Maloney Properties, Onion Flats Architecture, and an expert team of consultants, all working toward the shared goal of making Passive House-level performance a reality in a multi-unit retrofit.

How is Hano Homes Retrofitted?

Buildings typically consume more energy when they lose heat, a process known as thermal bridging, which occurs through gaps in windows, the U-value of openings, outdated insulation, and inefficient mechanical systems. This project aims to achieve net-zero energy and significantly reduce energy consumption by enhancing the building’s exterior envelope. The upgrades include a highly efficient shell, added insulation and finishes to the roof and walls, and the installation of airtight windows and doors. Additionally, the transition to fully electric mechanical systems will further prevent heat loss and eliminate dependence on fossil fuels. The upgraded building envelope is designed to reach an R-value of R-36.8, a significant improvement from the previous R-10.

The Challenges So Far

With any deep energy retrofit, surprises are part of the package, and Hano Homes has been no exception. One of our first hurdles? Hidden damage. The moment we started peeling back the exterior, we discovered extensive rot in the wood framing—something you don’t fully grasp until the demo phase is underway. Then there were the unexpected plumbing issues, particularly in the basements, where broken pipes and outdated systems needed quick intervention.

Perhaps the biggest logistical challenge has been working with residents still living in the units. Phasing the work while ensuring minimal disruption required a delicate dance of scheduling, temporary relocations, and airtight communication with tenants. From air sealing the basement ceiling to replacing windows and upgrading mechanical systems, each move has had to be meticulously planned. The window replacement process alone, which involved swapping out old double-hung units for high-performance casement windows, was an exercise in precision, taking about a day per unit to install.

Milestones/Achievements:

Hano Homes is on track to become a net-zero energy building, meaning it will produce as much energy as it uses. A large solar array on the flat roof will generate all the power needed for the entire complex. The project is also set to improve indoor air quality and thermal comfort for residents while achieving PHIUS certification for energy efficiency. With a highly insulated building envelope and fully electric systems, the building will significantly reduce energy consumption. According to RMI’s article on Hano homes, these upgrades do not only make the building more sustainable but also save over $40,000 annually in utility costs.

Despite the surprises, we’ve had some major wins. We have moved through the interior work more smoothly than anticipated, wrapping up its two-week tenant move-out period on schedule. The exterior insulation process, a critical component of achieving airtightness, has been progressing efficiently. And speaking of airtightness—our first blower door test revealed some extra air leakage at the compartment walls, but with quick adaptations in the basement, we were able to resolve the issue.

What’s Happening On-Site Right Now?

As of time of writing, we’re deep into the construction phase. The focus is on exterior insulation, mechanical system upgrades, and window replacements. Crews are installing fiber cement Hardie planks over the air-sealed sheathing, ensuring that every detail aligns with Passive House standards. Mechanical work is another huge component—transitioning from gas-powered heating systems to all-electric heat pumps, a shift that will drastically reduce the building’s carbon footprint.

Navigating an active construction site in a residential area requires tight logistics. Material storage is carefully managed in the backyard, where major work has been concentrated. The site office has been set up in the basement, keeping operations running smoothly. Trash removal, initially an every-other-day operation, has now settled into a steady weekly schedule as workflows have become more predictable. And in a move that perfectly encapsulates the spirit of problem-solving in retrofits, we’ve been working within tight spatial constraints, bringing in only enough wood fiber insulation and windows for eight units at a time to ensure efficiency without overcrowding the site.

Looking Ahead

The Hano Homes project is more than a technical challenge; it’s a model for the future of deep energy retrofits in urban settings. The success of this project isn’t just measured in airtightness tests or energy savings—it’s about creating healthier, more comfortable homes while proving that retrofitting affordable housing is both feasible and essential. In a time where cities are grappling with climate change and housing crises, projects like this serve as a critical blueprint for what’s possible.

With the project still underway, there’s plenty more to come. The next few months will see the completion of envelope upgrades, the fine-tuning of mechanical systems, and of course, final air-tightness testing to ensure we’re meeting Passive House standards. Every lesson learned here will help shape future deep energy retrofits, refining the process for the next wave of sustainable renovations.

For now, we’re celebrating the progress, tackling the challenges head-on, and keeping our sights set on the finish line. Stay tuned for more updates as we continue to push the limits of what’s possible in energy-efficient retrofitting!