ASHRAE Journal - August 2024 - 57

2024 ASHRAE TECHNOLOGY AWARDS CASE STUDY
(8230 m2) school sets a national benchmark for state-ofthe-art
educational facilities. Named after John Lewis,
the Georgian congressman and civil rights activist,
the school establishes best practices for educational
spaces while pushing the boundaries of improved
indoor environmental quality and high-performance
design. Despite the school's location in a disadvantaged
area of Washington, D.C., it has seen a 20% increase in
enrollment since opening in August 2021.
This project was able to marry the energy efficiency
goals of a net-zero energy project with the wellness goals
of a WELL Certified Building, which is a combination
that can sometimes be a challenge. For instance,
increased ventilation provides a wellness benefit by
improving indoor air quality (IAQ), but comes with an
energy consumption penalty. Increased daylighting
helps reduce lighting energy consumption and improve
the indoor environment, but when not done well, it
can increase HVAC energy consumption. This project
provides excellent daylighting with a strategy that
reduces HVAC energy consumption and helps reduce
installed HVAC equipment costs. This project also
provides a 30% increase in outdoor air using a control
strategy that improves IAQ while allowing the project to
perform as a net-zero energy facility.
ENERGY EFFICIENCY
The former West Elementary School, which stood on
the site of John Lewis Elementary, was operating at an
EUI of 104 kBtu/ft2 (1181 MJ/m2) per year. Such high
energy consumption, along with the project's zeroenergy/zero-carbon
goals, necessitated an in-depth
evaluation of the new systems to achieve the project's
energy and carbon goals. These included evaluations of
the energy-consuming systems (HVAC, lighting, plug
loads, etc.) as well as the building envelope, cooking
operations and educational programs. Multiple zeroenergy
charrettes occurred during the design phase with
DCPS and diverse DGS stakeholders representing design
and construction, operations, sustainability, faculty,
food service and IT. The purpose of the charrettes was to
introduce energy reduction strategies that would help
drastically reduce the facility's energy consumption
while persuading stakeholders to shift their approach to
building operation and maintenance. Ultimately, these
critical discussions resulted in accepting numerous
energy-saving measures that enabled the building to
meet its zero-energy goal.
First, the geothermal HVAC system with watersource
heat pumps was implemented to provide space
cooling for the project. Ventilation for the building was
provided by a dedicated outdoor air unit, providing
demand-controlled ventilation to help reduce energy
consumption. A low-wattage LED lighting design
was implemented, achieving an overall installed
lighting power density of 0.44 W/ft2 (4.7 W/m2).
The combination of reducing lighting intensity and
extensive daylighting studies to maximize natural light
resulted in a strategy that drastically slashed interior
lighting energy consumption. Next, the owner's food
service team was also receptive to changing the school's
food preparation methods, resulting in all-electric food
service equipment. This approach eliminated on-site
food service combustion and allowed the design team to
implement a Type II hood, reducing cooking equipment
energy consumption and exhaust fan energy. The
kitchen refrigeration systems were also evaluated, and
the cooler/freezer configuration was optimized to reduce
both warm air infiltration and refrigeration load.
Additionally, the design team evaluated the building
massing and site's geographic orientation, performing
multiple energy model iterations to optimize the
building window-to-wall ratios for each building face.
These energy reduction strategies resulted in
John Lewis Elementary becoming DCPS's best
performing elementary school, operating at an EUI
of 22.3 kBtu/ft2·yr (253.3 MJ/m2·yr) after a full year of
operation.
INDOOR AIR QUALITY
Improving the school's IAQ was a top priority at the
outset of design. The previous building experienced
issues with maintaining and controlling proper
ventilation. Instead of providing code-minimum
ventilation air as required by ASHRAE Standard
62.1-2010, the decision was made to increase ventilation
air by 30% in all occupied spaces. To achieve this, the
building's ventilation was provided by a 17,000 cfm
(8023 L/s) dedicated outdoor air unit with energy
recovery located in the lower-level mechanical room. It
provides intake air away from adjacent streets, parking
or other concentrated sources of air pollutants. This unit
serves a demand-controlled ventilation system with
carbon dioxide (CO2) sensors in each space. The sensors
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