ASHRAE Journal - July 2024 - 54

2024 ASHRAE TECHNOLOGY AWARDS CASE STUDY
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for space conditioning. This network
of piping allowed other forms of waterof
piping allowed other forms of watercooled
equipment to tie into the heat pump
system, including the kitchen walk-ins, IT variable
refrigerant fl ow risers, the domestic hot water
preheating loop and the heat pump chiller, which
provides dual-temp water to the DOAS units and
kitchen makeup air units. The balance of equipment
adding and removing heat from the same loop
prevents the cooling towers and boilers from having
to supplement with additional loads throughout the
year.
Additionally, each residential space includes Wi-Fi-
programmable thermostats incorporating passive
infrared sensors to detect occupancy. Likewise,
residents can manually enter unoccupied mode as
well, allowing temperature and ventilation setbacks.
Next, the custom rooftop dedicated outdoor air
(DOAS) units use an energy recovery wheel and
energy recovery plate. The wheel recovers energy
from the leaving relief/exhaust airstream, and
the plate reheats the leaving outdoor air to space
neutral at 50% relative humidity. This arrangement
prevents the addition of a heating coil, preventing
simultaneous cooling and heating or the use of an
expensive heat pipe.
The exhaust-driven DOAS unit serving the kitchen
delivers outdoor air directly to the cooking space and
returns from a single location in the dis h cleaning
room. The energy recovery wheel transfers the sensible
and latent energy back to the incoming airstream,
preheating the outdoor air. When the potentially
excessive heat from the dishwasher and dish cleaning
room exceeds the outside air temperature, and the
system is in cooling mode, the outdoor air and exhaust
airstreams bypass the energy recovery wheel and act as
separate makeup air and exhaust fans.
Lastly, the traditional-style residential fl oors
include wet core areas with individual restrooms
off the main corridors. To prevent adding makeup
outdoor air directly to the wet core and unnecessary
airfl ow to the DOAS units, a series of acoustically
lined transfer ducts provide a pathway from the
positively pressurized residential spaces to the wet
cores. These ducts prevent the corridor from acting as
a plenum and reduce capacity of the DOAS units by a
combined 7,200 cfm (3400 L/s).
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ENVIRONMENTAL IMPACT
Further, the renovated design reduces the building's
operational carbon footprint by nearly 35% compared
to the ASHRAE Standard 90.1-2010 baseline. Not
only does this meet the university's carbon goals,
but it also complies with potential future BEPS
carbon taxes. This is an annual savings of around
1,600 metric tons of eCO2, or the amount of carbon
sequestered by 1,900 acres (769 hectares) of forest.
Further, the design team signifi cantly reduced the
building's embodied carbon by reusing most of
the existing concrete structure. Much of the new
embodied carbon was limited to new walls, fi nishes
and other architectural elements.
Similarly, the building requires signifi cantly less
water from baseline use thanks to several watersaving
strategies. The rainwater harvesting system
provides non-potable water for public restrooms in
the dining hall and 100% of the water required for
building irrigation. Indoor water use is reduced by
40% by implementing low-fl ow faucets, showerheads
and water closet slashes. A sidestream sand fi lter
and conductivity meter installed on the condenser
water system maintain a conductivity of 200 µS /cm.
The additional fi ltration maximizes the cooling
tower cycles of concentration, which minimizes the
required domestic makeup water, further aiding in
the building's environmental impact.
COST EFFECTIVENESS
At the project kickoff, the HVAC design was
proposed to be a four-pipe fan coil system per the
owner's preference and matching the pre-renovated
design. This design was carried until midway
through the design process when the potential future
BEPS taxes hit the owner's radar. The design team
compiled 27 energy conservation measures (ECM)
along with the energy and the associated energy and
cost savings. The highest energy-saving ECM was the
conversion to WSHPs.
Initially thought to be an addition to the project,
a budget estimate during the phase indicated the
four-pipe design should be value engineered and
replaced with a heat pump design. Accepting this ECM
and several others resulted in a much more energyeffi
cient design and saved the project over $500,000 on
piping and pipe insulation fi rst cost. 
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