ASHRAE Journal - September 2024 - 64

2024 ASHRAE TECHNOLOGY AWARDS CASE STUDY
1
ST
The modular design allows for improved
effi ciency and load shifting between
heating, cooling and the well fi eld as the heat
sinks. Dedicated server room spaces with redundant
independent water-to-air heat pumps allow
N + 1 redundancy in the event of heat pump failure.
Redundancy is crucial in these portions of the building's
infrastructure because it needs to be online 24 hours
per day, 365 days per year, to support the control center.
Due to the limited length and width of the mechanical
equipment room, the design leveraged the vertical space
by stacking the heat recovery chiller on two levels.
The facility directors also requested mechanical
equipment that would last the life of the building. Fully
custom indoor AHUs with 3 in. (76 mm) triple wall
solid construction were designed with an internal liner
forming a solid cabinet. This construction resulted
in an R-19 with strengthened panels capable of L/240
defl ection or less using a 10 in. (25.4 cm) welded base
rail. Fan arrays using electrically commutated motors
(ECM) with BV-5 balancing certifi cation and discharge
air silencers were provided to reduce vibration and
sound from the penthouse AHUs to the spaces below.
MAINTENANCE & OPERATION
The facility used commissioning services during the
design, construction and post-occupancy phases to
ensure proper systems operation. The systems were
reviewed with the maintenance and operations staff
throughout the design phase and the fi rst several
months post-occupancy to address operational issues.
Systems commissioned include the heat recovery
chiller, heat pumps, circulating pumps, AHUs, kitchen
equipment and terminal equipment.
The building is designed to provide room to maintain
equipment and allow future routes to replace it
without taking additional systems out of service. For
example, exhaust fans are located on the roof with
service from the penthouse level. Equipment located
above accessible ceilings, such as utility service valves,
VAV boxes and heating coils, has been arranged in
easily accessible locations throughout the building.
Equipment located above ceilings has tags on the
ceiling grids, allowing the staff to quickly identify how
to isolate services within the labs without searching
above lay-in tile ceilings to limit impacted areas. Filters
were standardized with a high-quality MERV 13 fi lter,
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ASHRAE JOURNAL ashrae.org S E PTEM B E R 2 0 2 4
so the owner only needs one fi lter type. AHUs were
provided with a spare fan and motor assembly.
COST EFFECTIVENESS
The owner advocated for a geothermal-based
building and provisions to decrease the facility's
overall energy consumption. Two test bore holes were
completed on-site before construction, and the design
team performed independent formation thermal
response testing on the two wells to determine each
well's expected capacity and ensure they could use the
minimum required number of wells in the system. The
mechanical design team worked with the architectural
team to improve the building envelope and examine
how different decisions impacted the overall energy
performance. This was accomplished during the early
predesign and schematic design phases, where the team
looked at three different mechanical systems and the
associated life-cycle costs.
Installation, operational, maintenance and
replacement costs spanning two life cycles for variable
refrigerant fl ow (VRF), distributed heat pumps and a
VAV system were compared. Using energy modeling, the
VRF had the least energy use, and VAV was the highest
with 7.2% more energy use. However, the costs were
compared between systems, and the six-pipe VAV design
was less expensive than the VRF system's life cycle.
Overall, the life-cycle cost for the VAV system was 25.8%
less than the VRF and distributed heat pump systems.
ENVIRONMENTAL IMPACT
The project aimed for Mountrail-Williams Electric
Cooperative to be a leader in electrical energy savings.
The facility's actual energy use and carbon emissions
are 33% less than the Standard 90.1-2010 baseline. The
size of the refrigeration systems was limited with the
integrated six-pipe geothermal heat recovery chiller and
a small quantity of geothermal heat pumps. Based on
a combination of global warming and ozone depletion
potentials, the project's total refrigerant impact is
37.77 per ton, which is below the project's 100 per ton
maximum requirement. Using an integrated design
approach by incorporating a six-pipe heat recovery
chiller, and a geothermal well fi eld for transferring
energy, these features reduced the building's energy and
environmental impact, aiding the building in meeting
and exceeding ASHRAE standards.
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ASHRAE Journal - September 2024

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