ASHRAE Journal - October 2024 - 54

2024 ASHRAE TECHNOLOGY AWARDS CASE STUDY
1
ST
shown in Table 1. These values result in the
design conditions to be within the comfort zone
prescribed by Standard 55-2017 calculations.
Exterior spaces use radiators that eliminate cold
conditions or drafts for occupants seated near exterior
walls or windows.
INNOVATION
The school's mechanical system is designed to use
multiple technologies in combination for effi cient
building performance. For cooling there are four
stages of cooling: economizer, ground loop free
cooling, direct evaporative, and indirect evaporative
cooling from a cooling tower. While all four of these
are effi cient means to provide cooling, this allows the
system to modulate and use the most effi cient stages
when the building heat load is lower and ramp up
the cooling capacity as needed. These cooling stages,
combined with the thermal displacement ventilation
system, uses a supply air temperature of 65°F (18.3°C)
design conditions to be within the comfort zone
and requires no mechanical cooling.
The ground loop heat exchanger provides energy
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storage, allowing the heat that is put into the ground
in the summer to provide warmer ground loop
temperatures during part of the heating season,
increasing the water-to-water heat pump effi ciency.
The opposite is true for cooling. The heat taken out of
the ground in the winter allows for signifi cant hours
of free cooling in the spring and summer. Radiators
and hydronic unit heaters were placed in each space
that has an external wall. These heaters are sized to
cover the heat load of each space, providing increased
comfort and allowing the air handlers to remain off
during unoccupied hours during the heating season.
Water to air packaged heat pumps were used to serve
spaces such as data rooms that require 24-hour cooling
and the administration offi ce that will be occupied in
the summer. This was done to allow the air handlers to
remain off any time school was not in session. When the
air handlers are off, the fl ow required on the building
loop for the heat pumps is much lower.
Another innovative application was done to increase
the cost effectiveness of this system through the controls
strategy of the boilers and water-to-water heat pump.
The water-to-water heat pump has a large electrical load
and in turn is responsible for a large electrical demand
charge on the power bill of this building. To limit this,
the building management system (BMS) monitors the
total building electrical demand and limits the stages
of the water-to-water heat pump. This is done to keep
the total building power demand below the owner's
specifi ed limit. The boilers can then supplement the
heat pump as necessary and keep the hot water loop
at the design temperature. This essentially only occurs
during morning warm-up.
OPERATION AND MAINTENANCE
Never a Compromise for Quality or Safety
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information
323.727.9800
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One of the keys to building effi ciency is how the
building is operated. As mentioned above there
are multiple design choices due to the building
occupancy schedule. The owner uses the BMS to
ensure that the building goes into unoccupied mode
whenever school is not in session. This allows the
large air handler fans and multiple pumps to run only
seven to eight hours a day and stay off during summer
break and school holidays.
Maintenance for this system is more involved than
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ASHRAE Journal - October 2024

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