Deep Energy Retrofits take hold in US
So, this is my first “blog”, and it doesn’t feel natural yet. I prefer having conversations, giving a lecture to a live audience, and debating ideas about how we can all more effectively make the transition needed to a carbon-neutral society. But for the past two and a half years, OFA has taken a turn in the really challenging, exciting and slightly frightening direction of Deep Energy Retrofits (DERs). For the past 15 years, we have been focused on designing and building Passive House market-rate and affordable housing projects. Our goals were to see if we could demonstrate that PH, Net Zero Energy projects were not only feasible to build from the ground up but can be done, with the right team, with little to no premium. We succeeded and failed throughout the years but in the process, we realized that “how” you build your PH project offers the greatest opportunity for innovation, scale and with it, affordability. This led us to exploring strategies for prefabrication, building our first Passive House project in a modular factory, and later projects with high-performance prefabricated panels. This experience comes in handy if you want to crack the nut on DERs!
Let’s keep something in mind, when we reference the often-quoted metric that 45% of all greenhouse gas emissions come from buildings, that statistic comes from the past, ie, it’s data from existing buildings! So how can we approach DERs the way we approached new-construction Passive House buildings? Well, as many of you know, the Dutch have been hard at work with that challenge over the past 20 years. Their Energiesprong (literally “energy leap”) initiative has inspired many organizations around the world committed to a carbon-free future, including RMI in the US. RMI’s REALIZE program is modeled in many ways after the Energiesprong program. In 2020 OFA was approached by RMI to help them figure out how to actualize such a program in the US. We were asked to help build a team of designers, engineers, manufacturers and builders that would develop a retrofit solution for both combustible, 1-5 story buildings, and non-combustible, above 5 stories, buildings which would allow residents to remain in their homes while an industrialized, panelized and high performance envelope and HVAC system was installed from the outside of the building. Seemed simple enough: wrap ugly, old, leaky energy hogs with an airtight, superinsulated envelope with triple pane windows and doors installed in the factory and somehow include a strategy for HVAC within that same envelope? No worries, all in a day’s work!
Initially, we tried to copy both the financial and technical strategies of Energiesprong. The idea that we could finance the deep energy retrofit of a home based on the utility and maintenance savings afforded the home after the retrofit seemed the most challenging to us. Moreover, the idea that we would be able to create performance-based contracts with high performance panel and HVAC equipment manufacturers, engineers, architects, and builders appeared only possible in the Netherlands because it was backed by a strong national and political will to tackle their nation’s housing and climate crisis collaboratively. These performance-based contracts essentially guarantee the utility consumption of post DER buildings for 30 years. This essential commitment allows lenders to project reliable utility/maintenance savings and amortize that over the 30-year commitment. In fact, OFA was initially asked if we would feel comfortable providing such a commitment, to which we quickly replied NO, but we would be excited about helping to figure out how to actually build out this initiative.
Very quickly it became clear that the fundamental difference between the REALIZE program and Energiesprong was that they were coming at it from opposite directions. Energiesprong approached the challenge from the top down, beginning with the Federal government, which would build a broad coalition of support first in order to tackle their first experiments in industrialized retrofits. They developed a national competition for designers, engineers, manufacturers to come up with cost-effective panelized envelope solutions and new HVAC components that would consolidate and simplify heating, cooling, and hot water for homes that could be installed without relocating tenants. Since we here in the US have a much more fractured and divided political system and Federal government, such initiative and collaboration seemed dubious. In fact, it was clear that REALIZE and OFA would be working from the ground up rather than top down. This didn’t scare us (well maybe a bit) because we were used to having no subsidies, having very little Federal, State or local support in developing our projects over the past 25 years. We knew scrappy, had been perfecting it for years!
With very little structure, OFA agreed to work with RMI as their “solution provider” to build a list of interested panelized manufacturers, engineering teams, general contractors, and a growing pipeline of potential clients being organized by RMI. As we built this team, RMI narrowed in on two affordable housing developers with several buildings in their portfolios in need of significant renovation: Allston Brighton CDC and POAH.
Hano Homes: Allston Brighton CDC
As the team tried to articulate the kind of projects which might be the best for our first attempt at an industrialized retrofit, we landed on “the simpler the geometry and the larger, uglier the building, the better”. Hano Homes was none of these. A very nice collection of ten, two story duplexes in the Allston Brighton neighborhood of Boston, this project houses 20 families, and is, geometrically speaking…complicated. It is also a project that is on a tight urban street, closely aligned with its property lines, and littered with electrical wires and telephone poles at the entrances of the buildings, limiting any ability to use a panelized solution for the envelope. The plan of the buildings in the rear creates common alleyways and challenging detailing between buildings. Not our ideal first project, and yet, as we are currently close to completing our permit set of documents, we now see how valuable this small but challenging project has been for our own education. First, this is a wood building and so we get to develop a “combustible” retrofit solution, and as such why not work with the first wood fiber insulation to be made in North America, TimberHP. We need to first strip the four layers of exterior skins built up over its 100 year history, then place a Zip panel air barrier over the original wall boards, then 5.5” of rigid wood fiber insulation, then a furring strip and Hardie plank rainscreen finish. Full basements allow for two decoupled ventilation and heating, cooling systems. And while our team spent a lot of time developing a ducting strategy to feed units from the outside of the building, eventually a simpler, less expensive interior route was decided on requiring only a one week of relocation for tenants.
In future blogs I will go into more technical detailing decisions for this deep energy retrofit but for now, RMI has put together a terrific summary case study of the project here.
Salem Fairweather: POAH
POAH’s Salem Fairweather project could not be more different than Hano Homes. It is a six story, non-combustible building, with 127 units, gas fired boilers for heating and hot water, and significant water infiltration through the brick façade around windows and doors. Fortuitously, Salem Fairweather sits right next door to Salem Heights, a 281 unit project also owned by POAH, and recently completed its own Deep Energy Retrofit, designed also to meet the Passive House standard. Salem Heights is therefore a perfect comparative model to test our theory that an industrialized, panelized retrofit should be more cost effective than a site built strategy. In Salem Heights, each window was replaced by hand on site. The new superinsulated façade was installed by hand, one board at a time. The new decentralized ventilation, heating, and cooling system chosen at Salem Heights required a new interior closet, lots of interior soffits for ducts, and with it the need to move tenants out of their apartments for at least six months, at a cost to POAH of over $1million (for more info on Salem Heights, RMI has put together a terrific summary case study here).
Salem Fairweather would rethink these strategies. We developed a non-combustible, panelized envelope comprised of a 2x4 metal stud frame with a cementitious wrapped, insulation board which triples as a continuous insulation layer, weather resistant barrier and air barrier. A new metal skin is applied after the panels are installed on site. The panels are approximately 9’-0” high by 20-0” wide and have triple pane windows and doors installed in the factory. This new façade is hovering 7” away from the existing brick façade by way of a bracket and shelf angle. That 7” space between old and new façade gets used to run supply air ducts from roof mounted Energy Recovery Ventilators to each living space, line sets from ground and roof mounted condensers to floor mounted heat pumps within each unit. All gas fired boilers will be removed making it an all-electric building. The project is pre-certified with PHIUS and while the site doesn’t allow for enough solar PV to get the project Net Zero operational Energy, it is designed to use 87% less energy than it currently does. Most importantly, however, the total cost of the Deep Energy Retrofit for Salem Fairweather is coming in at approximately $150,000 per unit compared to Salem Heights at $180,000 per unit. This is a good sign that our goal of reducing the cost of Deep Energy Retrofits through an industrialized and panelized approach seems to be working! Can’t wait to start building!! Again, future blogs will dive deeper into the details but for now, RMI has put together a terrific summary case study of Salem Fairweather here.
