Charging Ahead with NYC School Electrification
By: Kabi Pandey, PE
Mayor Adams recently announced a $4 billion “Leading the Charge” initiative to electrify New York City’s public school facilities and phase out the use of fossil fuels under the city’s landmark climate-combatting Local Law 97. Under the Mayor’s program, any new school construction directed by the New York City School Construction Authority (SCA) going forward will incorporate all-electric building systems. Work to convert 100 of the existing city schools will begin by 2030, commencing with the first 19 facilities over the next two years. In addition, a ban on the use of Number 4 heating oil will go into effect in 2026, with 200 extant schools currently using the fossil fuel converted to low-sulfur biofuel as a stop-gap measure. The plan aims not only to reduce greenhouse gas (GHG) emissions by as much as 12,000 tons per year, but also to “create healthier learning environments, improve air quality in communities disproportionately burdened by climate change and environmental injustice, and help develop the next generation’s green workforce,” according to the Mayor’s office.
The Institutional engineering team at Lilker were called upon by the SCA to undertake a 7-month study of two promising alternative electrification options for both NYC school retrofits and construction of new facilities. Team members for the study included OLA Engineers, who provided energy modeling services, architectural firm DiDomenico and Partners, and Ellena cost estimators. The SCA’s objectives were to determine the feasibility of electrification in a large high school facility, assess potential energy and carbon emission savings associated with removing the use of fossil fuels from the facility design, and develop cost estimates for the all-electric systems. Studies had been done by SCA on smaller PS/IS sized schools, but this was the first in a larger facility.
Parameters of the study
The prototype high school used for the study was a 130,000-sq.ft. facility with 5 floors above ground and 1 below grade, housing 39 classrooms and serving approximately 975 occupants. Two electrification options were selected from prior studies based on performance as well as the requirement that equipment both be readily available and provided by more than three manufacturers.
Option 1 is primarily a centralized system, with custom heat pump air handling units (AHUs), rooftop units (RTUs) and an electric resistance perimeter heating system servicing the entire facility. The more eclectic Option 2 comprises individual vertical packaged heating cooling ventilating (HCV) units serving the classrooms with custom heat pump AHUs/RTUs serving the interior and public assembly spaces; variable refrigerant flow (VRF) indoor units and dedicated outside air systems (DOAS) serving smaller classrooms, offices and other spaces; and an electric resistance perimeter heating system.
Both electrification options were designed to the 60% Construction Document level of detail and then compared to the base case, defined as SCA’s current standard HVAC system design (natural gas-powered condensing boiler and air-cooled chiller) updated to include 6 energy conservation measures (ECMs) that are part of SCA’s design standards going forward. Among the ECMs are wall thermal and UV glazing upgrades, oversized ductwork and piping, and low flow aerators.
Energy modeling was conducted using Department of Energy (DOE)-developed simulation software that provides detailed, hourly, whole building energy data and simulates multiple HVAC and lighting zones for complex buildings. For every hour of the year, the program adjusts for the many variables including schedules for building occupancy, climate, and HVAC equipment and system performance under actual operating conditions.
Study results and guidance for electrification
In both all-electric options, GHG emissions were reduced versus the base case, by 23 carbon dioxide equivalent units (CO2e) for Option 1 and 13 CO2e for Option 2. Both site energy (building consumption) and source energy (utility and delivery) was reduced as well for both options. And costs for both came in at 3% below the cost to build the current fossil fuel-reliant HVAC systems. The conclusion is that both options are feasible and preferable alternatives to the base case.
Since hot water heating is no longer required in either all-electric option, both designs also eliminate pipe riser shafts at the exterior of the classroom, which increases classroom size and frees up the boiler room in a retrofit for more classroom space.
However, there are some differences between the two options that offer guidance for which system to use and when in the SCA’s electrification roll-out:
- Option 1 requires heavier rooftop equipment, which can be costly in a retrofit, where ductwork roof penetration would be needed to accommodate the new RTUs, as well as ductwork shaft and floor penetration at each level.
- Option 2 on the other hand, is less invasive to an existing building, requiring less ductwork and thereby lower floor-to-floor ceiling height requirements. This is particularly interesting for addition projects with existing low floor-to-floor ceiling heights as it allows the addition floor elevation to be at the same level as the existing floor. Option 2 also provides individual zone control for classrooms and has lower fan power for classroom systems, but this does necessitate small 3 ft. x 4 ft. HCV units in the classroom.
- Option 2 requires exterior intake louvres in every classroom, which has the potential to compromise the building envelope and cannot be implemented in historical buildings or where toxic air or substantial noise pollution is present at or near the building exterior.
In general, Option 2 will be more advantageous for retrofit of existing buildings, but there are extenuating circumstances. For ground up buildings, either option can be utilized, depending on location, building use, air quality at ground level, and noise at ground level of the proposed building.
Each new and existing school project will need to be assessed on a case-by-case basis.
Kabi Pandey, PE is an experienced electrical engineer with a long portfolio of New York City School Construction Authority (SCA) work – including Superstorm Sandy resiliency and COVID ventilation projects. He is currently an active board member on the American Council of Engineering Companies of New York (ACEC NY) Board of Directors. Previously, Kabi served as Chair of the New York City School Construction Authority Committee for ACEC NY.