ASHRAE Journal - September 2023 - 53

FIRST PLACE 2023 ASHRAE TECHNOLOGY AWARDS
Due to the success of these projects, BCPS learned
that a collaborative design and construction team can
achieve these audacious goals without the use of grants.
Graceland Park/O'Donnell Heights Elementary Middle
School (Graceland) and Holabird Academy (Holabird)
are prototype sister schools built almost identically
except that they are located on different physical sites
rotated 180 degrees from one another. These two schools
provided an opportunity for the district to reimagine
what energy efficiency could look like in their buildings.
Energy Efficiency
At the time of design, the average BCPS school
had an energy use intensity (EUI) of 70 kBtu/ft2·yr
(795 MJ/m2·yr). The existing Graceland and Holabird
schools had EUIs of 106 kBtu/ft2·yr (1204 MJ/m2·yr) and
70 kBtu/ft2·yr (795 MJ/m2·yr), respectively.
Benchmarking their existing buildings highlighted the
paradigm shifts needed to meet the aspirational goals
of zero energy and zero operational carbon with a target
EUI of 25 kBtu/ft2·yr (283.9 MJ/m2). The design team
led numerous zero energy charrettes focused on drastic
energy reduction and operational maintenance goals
to allow these buildings to succeed in their first year of
operation and long into the future.
Based on historical project data, decentralized
geothermal water-source heat pumps with demandcontrolled
ventilation systems are one of the most energy
efficient system design approaches for K-12 school
buildings. We also knew the integrity of the building
envelope and, in particular, its airtightness are crucial in
reducing energy consumption on day one and over the
building's lifetime. To provide an airtight envelope, and
a well insulated building, the design team designed the
building using insulated concrete form walls.
This system incorporates high mass on the interior
and exterior surfaces of the wall system and the thermal
insulation layer is sandwiched between to eliminate
thermal bridging. The lighting system in the building
was designed with high efficiency LED light fixtures, and
by using a combination of natural and artificial light,
was able to achieve a lighting power density of 0.5 W/ft2
(5.4 W/m2). This was accomplished through reducing
the overall ceiling heights in key spaces and the required
quantity and wattage of light fixtures needed to achieve
CASE STUDY
proper lighting levels for the learning environment. To
provide domestic hot water, a heat pump water heating
system was connected to the central heat pump water
loop system that uses either heat rejected from the
building or the earth's constant heat to heat the water.
The design team worked with BCPS to implement
energy efficiency strategies in the kitchen and food
service equipment systems. After analyzing and
evaluating their current approach to food service and
cooking equipment, we determined they could use a
heat capture Type 2 kitchen hood instead of a Type 1,
requiring significantly less exhaust and makeup air.
The walk-in coolers and freezers were designed to
mitigate problematic heat gain that typically happens
in traditional side-by-side designs in a walk-through
arrangement. To reduce unwanted heat gain to the
walk-in freezers, the walk-in coolers were used as
entry vestibules to the freezers. The cooler and freezer
condenser units are tied to the central heat pump water
system to increase overall efficiency, prolong equipment
life and promote ease of maintenance.
The design followed the ASHRAE Advanced Energy
Design Guide for Zero Energy K-12 School Buildings. The
high-performance design has resulted in the buildings
operating at an EUI of 24 kBtu/ft2·yr (283.9 MJ/m2·yr) for
Graceland and 22 kBtu/ft2·yr (249.8 MJ/m2·yr) for
Holabird, more than a 300% EUI improvement from
their average facilities.
Indoor Air Quality and Thermal Comfort
For both buildings, a centrally located 15,000 cfm
(7079 L/s) variable air volume DOAS provides required
air ventilation to each occupied space. The DOAS has a
FIGURE 1 Building energy performance comparison.
120
100
80
60
40
20
Graceland
Holabird
 Previous  Baseline  Modeled  Actual
Drew Roberts, P.E., is partner/mechanical engineer, Ben Hobbs, P.E., is mechanical engineer, Johnathan Stewart is electrical engineer, and Kevin Mussler is vice president/mechanical engineer at CMTA.
S E PTEM B ER 2023 ashrae.org ASHRAE JOURNAL
53
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