The 26-story Bronx high-rise, known as 425 Grand Concourse, has received much praise and attention—for good reason. At just over 310,000 ft2, the mixed-use Bronx standout is among the largest buildings to ever obtain Passive House certification (Phius+ 2018). Moreover, it has racked up several major honors, including a Buildings of Excellence award from the New York State Energy Research and Development Authority (NYSERDA) in 2019 and Best Overall Project at the 2022 Phius Passive Projects Design Competition. Most impressive of all, 425 Grand Concourse brings 277 units of new housing to the neighborhood—all of which are affordable.
Completed in the summer of 2022, 425 Grand Concourse is one of the many towers springing up in the South Bronx, redefining a burgeoning skyline that had been static for decades. As of 2017, the portion of Grand Concourse south of East 167th Street had not seen a new residential building completed since the assassination of J.F.K.
While there is often a fear that any new construction will accelerate gentrification, projects like 425 Grand Concourse stand in gleaming contrast to the idea that new or excellently designed and constructed buildings are only for newer members of the community. This project also discourages the cynical notion that development necessarily displaces those who have lived in an area for generations.
Of the 277 units in the building, the majority have been rented to families or individuals making between 30% and 130% of the area median income (AMI). Residents of Bronx Community Board 1, which includes the entire southern tip of the borough, will receive preference for 50% of the total units. An additional 28 units were reserved exclusively for individuals and families who were previously unhoused.
A Welcoming Beacon
Prior to the construction of 425 Grand Concourse, the site had been home to a landmarked public school (P.S. 31) named after journalist and abolitionist William Lloyd Garrison, which had been built in 1899. Constructed in Collegiate Gothic style and known throughout the Bronx as “the Castle on the Concourse” (see Figure 1), a lack of maintenance led to structural problems that ultimately caused the school to close its doors in 1997. Further neglect only made these structural problems worse, particularly following Hurricane Sandy in 2012. Shortly thereafter, it was determined that it would be best to demolish it and build housing on the city-owned property.
By 2015, the New York City Department of Housing Preservation and Development (HPD) was soliciting proposals for the now vacant nearly 30,000-ft2 property. HPD required developers to submit proposals that included deeply affordable units, and the request for proposal (RFP) specified that proposals needed to include ground-floor spaces meant for the surrounding community and required all proposals to achieve certification through the Enterprise Green Communities (2015) Program, a standard for healthy, energy-efficient, and environmentally conscious building.
To meet these requirements, the proposal submitted by developer Trinity Financial, Inc. and their partner, Bronx-based MBD Community Housing Corp., opted not only to meet HPD’s parameters and the number of requirements for the Enterprise Green Communities 2015 certification, but to exceed them. To create a building capable of such a feat, they recruited an all-star team that included Dattner Architects, Steven Winter Associates (sustainability consultants), Dagher Engineering (MEP engineers), GACE Consulting Engineers (structural engineers), and Monadnock Construction (contractors).
From the beginning, the first two floors of 425 Grand Concourse were envisioned as an extension of the community, home to spaces for nearby Hostos Community College, a health clinic with a dental facility, a cultural center, a comfort station for the adjacent playground, and a supermarket—something often lacking in working class areas that may have an abundance of corner stores but few places where one can reliably purchase fresh produce.
To optimize energy efficiency, the team decided early on to let Passive House principles be their guide and to pursue Phius certification, so the building was designed with continuous insulation, high-performance glazing, solar shading devices, and balanced mechanical ventilation. Meanwhile, initiatives like efficient irrigation, offsite waste sorting and materials reclamation, low-flow water fixtures, and a green roof and terrace would further reduce waste. All these factors, in addition to a fitness room, abundant indoor bicycle parking, and easy access to three subways (the 2, 4, and 5) and two bus lines (the Bx1 and Bx19) would improve occupant health.
For this to all work, the building would require a floor area ratio (FAR) of 9.46—more than double the 4.0 allowed by the existing zoning. Rather than being opposed to the increasing density, the RFP encouraged respondents to propose rezoning the site to create more housing and acknowledged that a high-density building was required for the stars of affordability and efficiency to properly align. According to John Woelfling, a principal at Dattner, “The denser you can make a project—the more occupants that you can get into a building, the better form factor that you can create—the more energy efficient you can make that building.”
Though rezoning permits are notoriously difficult to obtain (often requiring countless meeting with various groups from the community and years of delays), the team managed to procure one by 2017, largely because of the project’s dedication to affordability, sustainability, energy efficiency, and community renewal. Then-Bronx Borough President Rubén Díaz Jr. even threw his full support behind the project, saying, “425 Grand Concourse will stand out as a welcoming beacon to all who travel along our borough’s most famous boulevard.”
Active Agents and Passive Principles
The decision to certify the project according to Phius standards was not solely due to Trinity’s commitment to developing efficient and sustainable buildings; there was a strong social justice component, too. As Woelfling explains, “One of the things that Trinity decided to do was incorporate Passive House to address environmental inequity. This site is smack-dab in the middle of the Mott Haven section of the Bronx, which has one of the worst childhood asthma rates in the country.”
According to Woelfling, these asthma rates have a multitude of sources. The area is a notorious chokepoint where the Major Deegan and Bruckner expressways converge, funneling commuters and delivery trucks over the Robert F. Kennedy Bridge (also known as the Tri-Borough Bridge) and into either Manhattan or Queens. Additionally, multiple freight and passenger rail lines pass through the area while aircraft coming in and out of the LaGuardia fly overhead, dispersing ultrafine particles on those below. A paper published in Environmental Science & Technology by Shukla and colleagues notes that many buildings in the South Bronx continue to burn No. 4 fuel oil, which is the dirtiest form of heating oil still allowed in New York City. One will find few places in New York City where a thicker and more noxious concoction of chemical exhaust hangs in the air.
Most assume that the damage caused by air pollution is limited to lungs, but research has shown that long-term exposure can have far more wide-ranging effects. Parkinson’s disease has been linked to nitrous oxide, a common pollutant found in car exhaust, while excessive particulate matter exposure is associated with memory deficits and Alzheimer’s disease. Poor air quality is associated with increased rates of long Covid in younger populations and may raise the risk of dementia and depression among older populations.
Similarly, noise pollution can lead to stress-related illnesses that run the gamut from autoimmune disorders like rheumatoid arthritis and inflammatory bowel disease to psychiatric symptoms that include depression and anxiety. As Figures 2 and 3 reveal, noise pollution is common throughout much of New York City but is particularly bad in the South Bronx.
(See the supplemental section, Pollution and Mental Health, below.)
Conversely, these adverse health concerns can be mitigated with passive building. Passive House envelopes are airtight and outfitted with continuous insulation and high-performance windows and doors. Consequently, they shield occupants from excessive noise, effectively allowing even an apartment in the South Bronx to become as quiet as a home in the suburbs. Meanwhile, that same airtightness, combined with mechanical ventilation that’s been outfitted with MERV 13 air filters (rated the same as high-quality face masks), ensures that occupants at 425 Grand Concourse have a steady supply of clean, fresh air, rather than constant exposure to traffic exhaust from the nearby Major Deegan.
For Christoph Stump, Vice President of Design and Construction at Trinity, recognizing the downstream health effects of building to Passive House standards opens your eyes to how much of an impact a developer can have on the health and wellness of future occupants and the surrounding community, particularly within the affordable market. “That makes you think differently about windows and envelope quality,” he says.
Striking The Right Balance
Trinity’s remarkable development is an award-winning high-rise that is affordable, provides tenants with a healthy environment, and was certified by Phius at a cost premium of only a few percentage points. According to Stump, the premium to improve the building envelope was 0.94% of the total cost of development, while the added quality control costs and mechanical costs were 0.60% and 0.63%, respectively. These increases in costs pushed a project that could have cost $186.9 million ($603/ft2) to $191 million ($616.35/ft2)—a difference of $4.15 million ($13.35/ft2). Meanwhile, Stump estimates the difference in annual utility cost between 425 Grand Concourse and a comparable code-built building to be nearly $500,000, indicating a payback period of just over 12 years.
Density was crucial not only to these savings, but also to the building’s performance. As Woelfling noted, “We’re striking the right balance for Passive House performance, and that’s really because we’re able to take advantage of all of those internal heat gains that come from the occupants, that come from the appliances, the lighting loads, and really balance that envelope.” Woelfling continued, “This building is what I think of as much closer to a standard, code building and it really is because of that high density that we were able to leverage.” This lack of disparity is reflected in the building’s relatively standard R-values when compared to code. To comply with New York City’s 2020 energy code, the R-values for the roof, above grade wall, and below grade walls had to be of 30, 13.25, and 10, respectively. To meet Phius standards and to avoid overheating, the same R-values had to be 30, 20, and 10.
Heather McKinstry of Dattner Architects agreed. “We didn’t have to go that much above and beyond for 425 Grand Concourse,” she said. “With a tower like 425 Grand Concourse, we’re also minimizing the roof area to volume and that’s the surface with the greatest potential heat loss,” McKinstry added, and noted that one of Dattner’s other Passive House projects in New York, Vital Brookdale, was only six or seven stories in certain places and had to be equipped with far more roof insulation.
The mechanical system is centralized but split in half. Swegon ERVs for the bottom half of the floors are located on the lower floor containing the terrace, while the ERVs for the top half of the floors are located on the building’s roof. These centralized systems reduce the amount of ductwork necessary and allow there to be more habitable space on each floor.
To counteract the increase in relative humidity and cooling load due to all the occupants, the team is relying on sunshades on the southside of the building for passive cooling measures and an energy-recovery-type variable refrigerant flow (VRF) system created by Mitsubishi to provide heating and cooling. In some units, the team was able to strategically situate floor-mounted VRF units capable of conditioning two rooms rather than just one. When this was not possible, wall-mounted units that service just one room were used.
The placement of the units takes full advantage of a VRF system’s capabilities. Although most of the VRF units are oversized given the dimensions of the rooms, because they are working far below capacity, more units could be connected to the same compressor. “In order to make that work, Mitsubishi had to write custom programming to allow for a greater number of VRF evaporator units to be served simultaneously by one compressor,” McKinstry said. Even more impressive, VRF units that are served by the same branch controller (each floor is serviced by one roof compressor and one branch controller on the apartment floor level) can share heat or cooling without needing to activate the compressor. If one apartment is too hot and another too cold, the system can pull heat from the former unit and transfer it to the latter.
One of the few limitations on high-density buildings is that the opportunities for onsite renewable energy generation are lacking. There simply is not enough space on the roof to generate energy for 277 units. Additionally, some of the non-residential uses could not be included within the Passive House certification. This included the grocery store (which is accessible from the street and via a loading dock), the comfort stations for the adjacent park, and the code-required generators, which each run on fossil fuels. The gas-fired generator provides emergency power for code-required life-safety systems, but is oversized to also provide power to elevators, domestic water pumps, security, and Wi-Fi to provide longer-term resilience to the building. The other generator is a fuel oil generator for the educational facility. “Those generators need huge louver areas to the exterior for venting, so it just wasn’t feasible to have those within our passive envelope,” McKinstry said.
These minimal limitations aside, high-density multifamily building has the potential to address two of the most daunting policy crises today, the affordable housing crisis and the climate crisis. Moreover, 425 Grand Concourse demonstrates that one can do so even while pursing the most rigorous of building standards.
Pollution and Mental Health
According to the Centers for Disease Control and Prevention, constant noise above 70 decibels (dB) can start to damage your hearing if you’re exposed to it for long periods of time. For reference, a humming refrigerator unit may emit 40 dB, a normal conversation is around 60 dB, city traffic from inside a car may reach 85 dB, and an approaching subway train will register 100 dB. However, if you are constantly exposed to noises above 70 dB, it can also produce a stress response that goes far deeper than just being annoyed. (For a deeper dive into decibel levels and hearing health, the National Council on Aging has more.)
It has long been accepted that there is a positive relationship between psychological stress and risk of hypertension, stroke, and (in the immortal words of Fred Sanford) “the big one”, since psychological stress triggers the release of “stress hormones” like corticotropin-releasing hormone (CHR) and cortisol. In fact, the World Health Organization concluded in a 2011 report that excessive transportation-related noise from cars, trains, and planes is behind an annual loss of 1.6 million years of healthy life just in Western Europe. In 2015, the European Environmental Agency published a report finding that transportation-related noise caused an additional 1.7 million cases of hypertension, an additional 80,000 hospital admissions, and an additional 18,000 premature deaths from coronary heart disease or stroke each year in Europe.
Additionally, constantly elevated levels of these hormones can also interfere with immune function (why you’re more likely to get sick when you’re constantly stressed), disrupt digestion (why you’re likely to experience GI problems or have weight changes when you’re constantly stressed), and lead to tension in muscles throughout the body (why stress may give you a headache or a “pain in the neck”).
However, instead of thinking solely about the symptoms caused by stress, it may be better to think of stress systematically—as a threat to our internal equilibrium (homeostasis) that is triggered by the presence of an adverse agent. Luckily, all organisms are equipped with ways to mitigate stressors via behavioral or physiological responses. Once the stressors have been eliminated, homeostasis is restored. If the stress is constant, however, homeostasis cannot be restored and the behavioral and physiological responses to stress remain constantly engaged. If a person is in an environment that is suffused with pollutants, that person has a higher risk of experiencing the symptoms noted previously.
What is not so apparent is what’s going on at the molecular level. Stress encourages the production of proteins known as proinflammatory cytokines, which are the same proteins released when the body responds to an infection or the presence of a toxin. While these proteins are absolutely necessary for the function of the immune system and help us clear pathogens, they can also damage healthy tissue when they are circulating in the body for extended periods of time. This leads to what is known as chronic inflammation, which can cause insidious forms of tissue damage and perpetuate the inflammation, as the damage leads to an inflammatory response and the recruitment of more cytokines. This cycle makes it difficult to bring the system back into homeostasis.
This same mechanism occurs in the brain—although in this organ it is known as neuroinflammation. In most cases, neuroinflammation is like the inflammatory response described above and is just one of the mechanisms used to bring the central nervous system back into homeostasis (sleep may be another one of these mechanisms, which is a reason why nighttime noise pollution may be particularly problematic). Neural tissue can temporarily be inflamed in response to stressors or pathogens without notice. Problems start to happen when the neuroinflammation is chronic, and it has been linked not only to neurodegenerative diseases like Parkinson’s and Alzheimer’s, but to psychological symptoms like anxiety and depression. Moreover, chronic inflammation in the body and neuroinflammation appear to be intimately connected, providing a common mechanism to explain the high rate of comorbidity between cardiovascular diseases, autoimmune diseases (including asthma), and psychiatric symptoms.
Given the fact that Passive House construction removes noise pollution and air pollution from the indoor environment, its health benefits may be far more extensive than is currently understood.
Thermal Breaks for the Sunshade System
To counteract the increase in relative humidity and cooling load due to all the occupants, the team is relying on sunshades on the south side of the building for passive cooling measures. While these sunshades are a visually striking part of 425 Grand Concourse's design, the potential for thermal bridging was a major concern, as each 100-foot-long sunshade attaches to the interior building slabs via steel brackets. To resolve the issue, the design team specified several hundred Schöck Isokorb® concrete-to-steel thermal breaks that fasten the sunshades and steel entrance canopy to the concrete slab edges. These thermal breaks consist of an insulation block of expanded polystyrene with stainless steel rebar projecting from the interior side of the module that ties into the interior slab reinforcement; they can reduce heat loss by 94%. Less prominent, but still integral to the performance of the project are concrete-to-concrete in-slab thermal breaks, also made by Schöck, that prevent thermal bridging at a small third floor terrace overhang.