ASHRAE Journal - May 2020 - 52

equipment on the roof as much as possible and installed
spare conduits and panel capacity to facilitate the future
installation of these solar panels.
Each classroom has a "green button" as part of the
lighting controls to minimize energy consumption.
The teachers or students can select this button, which
resets the classroom lighting level from 50 footcandles
to 30 footcandles to reduce the illumination. It also
widens the room temperature dead band by 2°F (1.1°C)
up and 2°F (1.1°C) down. This meets the Kentucky
Department of Education building design guides while
allowing the staff and students to become part of the
energy-saving initiative.
A geothermal water-to-water heat pump produces
domestic hot water. The hot water recirculation pump
is turned off during unoccupied hours to reduce heat
loss through the piping. The kitchen cooler and freezers
do not have conventional air-cooled condensing units
but rather utilize the geothermal well ﬁeld to reject
condenser heat. The cooler/freezer system also has a
dedicated 1/3 hp (0.25 kW) circulating geothermal loop
pump, backed up by emergency generator, to allow the
main centralized 60 hp (45 kW) pump to be shut off
during unoccupied hours and/or summer occupancy.
A domestic water connection was also provided to cycle
water through the compressors should the geothermal
loop need to be drained for maintenance.

Operation and Maintenance
To maintain HVAC equipment, an additional 12 in.
(305 mm) was added to the above-ceiling space after
design development was complete. All service clearances
are shown on the HVAC equipment. During construction, engineers walked through the building with facilities maintenance staff to conﬁrm that service clearances
were maintained. The LED lights installed throughout
the school (along with LED theatrical lighting) not only
save energy but have lamp lives measured in decades
and not hours, so relamping is required rarely, if ever.
The electric panels serving lighting, HVAC, and plug
loads are separately submetered so the owner can monitor and control energy usage.
The design team explored three system types during
design: four-pipe hot/chilled water, water source heat
pumps with a boiler and cooling tower central plant,
and water source heat pumps with a geothermal central plant. With a payback of six years compared to the
52

ASHRAE JOURNAL

ashrae.org

M AY 2020

37.7
WSHP-Geothermal
4-Pipe
WSHP-Boiler/Cooling Tower

33.7
29.7
Cost (In Millions)

2020

ASHRAE TECHNOLOGY AWARD CASE STUDIES

25.7
21.7
17.7
13.7
9.7
5.7
1.7

15
Years
FIGURE 2 Life-cycle cost comparisons-HVAC systems.

four-pipe system, the geothermal central plant was the
preferred option. Compared to the boiler and cooling
tower central plant, the geothermal central plant had a
payback of 9 years (Figure 2).
The school board hired a third-party commissioning
agent as part of the construction progress, but the design
team performed retro-commissioning as a follow-up
to the original agent. The retro-commissioning was
performed using an experimental method, with full
permission of the owner's representative and school
principals. This allowed the design team to try multiple
approaches to energy reduction, and if one was found to
adversely affect the occupants, the design team scaled
back to a previous set point that made the occupants
comfortable. One tried approach was to reduce the differential pressure set point on the main centralized
geothermal loop pump. The design team initially lowered the set point by 5 psi (34 kPa) and found that the
building operated smoothly. An additional decrease of
5 psi (34 kPa) was attempted, but it was quickly found
that the lower set point did not provide adequate ﬂow to
the gymnasium heat pumps.
During the construction process, the building envelope was pressure tested through a series of limited-area
tests. The design team identiﬁed a stairwell in the initial stages of construction that could represent a small
sample of construction methods, with roof, window, and
wall elements. This stairwell failed the initial pressure
test, and the contractor and design team collaborated to
ﬁnd the problem areas and adjust construction methods to meet the leakage requirements. The stairwell
was tested three times before passing the pressure test,
and the lessons learned were applied throughout the

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ASHRAE Journal - May 2020

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