Figuring Out Deep Retrofits in Real Time

There’s no getting around the fact that decarbonizing the building sector requires accomplishing large numbers of deep energy retrofits, and as of yet there isn’t a clear pathway toward effectively getting these done at the scale that is needed. A recent research report by the Advanced Building Construction Collaborative estimates that 29.3 million single-family homes and 3.3 million multifamily units are in grave need of deep retrofits—including new windows, air sealing, insulation, ventilation, and swapping out gas appliances for electric ones. Fortunately, some brave souls are undismayed by both the enormity of the task and its inherent difficulties, and instead are plunging ahead, devising and iterating solutions. 

“We're exploring these deep energy retrofits through a couple of different lenses and learning a lot in the in the process,” says Tim McDonald, principal of Onion Flats Architecture (OFA). One of those lenses has been his work with Julie Klump, vice president of design and building performance for the Preservation of Affordable Housing (POAH), which has long been a leader in, well, preserving affordable housing. In 2023 POAH wrapped up a Phius-certified retrofit of Salem Heights, its 281-unit building in Salem, Massachusetts—one of 120 properties POAH owns and manages across 12 states in the Northeast, Midwest, and Mid-Atlantic regions. Despite that project’s challenging aspects—and because of the lessons learned there—Klump hired OFA to make progress on a series of exterior retrofits of similar buildings, starting with the Salem Fairweather. 

POAH owns four Fairweather buildings, all of which are in Massachusetts, were designed by the same architect, built by the same company, and are similar in size. And, they were all built at about the same time, which means they are all due up for refurbishing at the same time. “POAH decided to take on the idea of a deep energy retrofit with exterior prefabricated panels on the Salem Fairweather project, in order to use that as a model for the rest of the buildings,” explains McDonald, who has been tasked with translating that idea into action. 

This model, once it’s successful, promises many benefits, and chief among those is an exterior retrofit minimizes the disruption to the building’s occupants. “What we're trying to do here is save the millions of dollars that would be needed to relocate people if we did all of our work from the inside,” McDonald points out. 

After a year of planning and extensive conversations with many panel manufacturers, in November 2023 the first mock-up panel was installed on Salem Fairweather. Many lessons were learnt on that day. Even more had led up to that day. “We looked at about nine or 10 panel manufacturers, investigated them—got their pricing, availability, and attitude—and it became really clear, really quickly that this is a nascent industry,” McDonald says. There just weren’t a lot of options for a company that was willing to leap into retrofit panel manufacturing at a price that was feasible. Fortunately, OFA found one that fit the bill and is located not far from Salem: facades X. One of the company’s main advantages was its flexibility and willingness to alter its existing offerings to create an assembly that worked for Salem Fairweather, recognizing perhaps that there’s a large pipeline of potential projects for the company that figures out the right product. 

Another lucky stroke for this project was the existing brick wall’s integrity. The OFA team along with the GC for the project, Haycon, had pull-out testing done of the brick at multiple points, and the results showed the wall was still strong enough to handle the added load of these new prefabricated panels. So, instead of having to tie the panels into the structure, they are essentially sitting on shelf angles, which as McDonald points out, is much, much less expensive. 

As with most retrofits, figuring out how to maximize the benefits and the cost-effectiveness of each step is what keeps the project feasible. “I could say the main reason to go with a panelized solution is because we can install the windows in the factory rather than up on a crane one at a time,” explains McDonald, adding, “That relationship between the new window in the panel and the rough opening of the existing window in the wall, that's kind of where the rubber meets the road. We've got to get that right.” To achieve that level of accuracy, a third-party scanning company conducted LIDAR scans of the existing exterior facades and much of the interior of the building as well, converting those scans into a Revit model of the building. Then, OFA and Haycon re-measured many areas on the exterior to verify the dimensions and update the model, which is being used by facades X to fabricate its panels. 

Because the building has six stories, the entire assembly has to meet a two-hour fire rating, which to a large extent determined the panel’s components. The framework is a 2x4 metal stud system with an insulated cementitious panel attached to it. Additional Rockwool insulation will add to the assembly’s R-value, delivering a total additional R-value of 30 to the exterior facade. For airtightness, a fluid-applied air and water vapor barrier will be swabbed onto the existing brick façade, and a secondary air barrier is built into the panel itself. A 4-inch gap between the brick and the new retrofit panel will serve as a chase for ductwork, power lines, and line sets for refrigeration, heating, and cooling. 

Team

• Architect of Record: Onion Flats Architecture

• General Contractor (GC): Haycon

• Panel Manufacturer: facades X + Metalleve

• Facade Consultant: Building Energy Corporation (BEC)

• HVAC Engineer: Seaman Engineering Corporation

• Structural Engineer: TLH Consulting

• Electrical Engineer: John Murphy Electrical

• Code Consultant: JS Consulting