ASHRAE Journal - December 2020 - 49

2020 ASHRAE TECHNOLOGY AWARD CASE STUDIES

directly from the 100% outside air lab unit. The outside
air delivery remaining separate of the space-conditioning air in administration spaces and classrooms allows
for effective delivery of outside air to the breathing zone
and precise temperature delivery. If outdoor air was
delivered through a traditional air-handler VAV system,
the air volume would ﬂuctuate and impact the effectiveness of outside air delivery to the breathing zone during
occupancy.
ASHRAE Standard 55-2010 recommended thermal
comfort is maintained with separate thermostatic zoning of all occupied spaces and careful monitoring of
humidity levels. Humidity sensors are provided on all
three ﬂoors, in the return duct of the space-conditioning
air handler and in the exhaust duct of the 100% outside
air lab unit. Humidity sensors are provided on all three
ﬂoors, in the return duct of the space-conditioning air
handler and in the exhaust duct of the 100% outside
air lab unit. These are used to monitor the humidity in
the space and to work in concert with optimized supply air temperature resets and extended unoccupied
setpoints to maintain acceptable indoor environmental
conditions.
Airﬂow measuring stations, controls points totalizing airﬂows from venturi valves, variable-air-volume
boxes, and building pressurization sensors were
employed to allow the user, commissioning agent, and
engineer to ﬁne-tune building pressures and ensure
the air distribution design was executed as intended.
Air devices were selected, examined, and located to
provide appropriate air velocities for optimal occupant
comfort and to address areas with high thermal losses
or gains, such as curtain walls, large glazing, and dense
occupation.
Morning warm-up and morning cool-down modes,
in conjunction with optimal start logic in the controls
system, are used to bring the building temperature back
to occupied thermostatic set points. Activity levels and
clothing were reviewed with the user group to inform
indoor temperature design conditions and establish
allowable temperature ranges in spaces. As an example,
laboratory occupants wear lab coats on a regular basis,
so lower temperatures are allowed in lab spaces.

Innovation
A modular heat-recovery chiller serves the science
building's chilled- and hot-water needs for the heating

and cooling of spaces. The modular heat-recovery chiller
consists of ﬁve modules. Three of the ﬁve modules can
operate in cooling mode, heating mode, or heat recovery mode, while two modules are heating and cooling
only. These modules can all work independently of each
other, and the equipment is automated to decide how
best to assign module operation modes based on chilledand hot-water loads. When implementing this design, it
is essential to understand the simultaneous heating and
cooling requirements to maximize this operation. The
beneﬁt is in the heating aspect, as this approach equates
to a COP of 6.6 instead of traditional, high-efﬁciency
boilers, which are 93% efﬁcient and operate with a COP
of 0.93. To maximize the use of heat recovery operation, a " load dump coil " was implemented to generate a
chilled-water load in the heating-dominant season.
As the science building has very minimal interior
HVAC zones, the design needed to take on the challenge
of how to generate chilled-water loads in the winter,
when most or all spaces are in heating mode. In order to
address this issue, a coil was located in the lab air-handling unit exhaust airstream, where room temperature
air would be taken across a chilled-water coil. The heatrecovery chiller also serves the domestic hot-water heating needs by transferring heat through a domestic hotwater tank with a built-in heat exchanger. These innovative approaches allow the chiller to operate longer in the
heating season, maximizing the system's efﬁciency.

Operation and Maintenance
The design team considered four different options for
the HVAC systems to serve the building: a geothermal
central plant, using a modular heat-recovery chiller
serving air-handler VAV systems in conjunction with
water-source heat pumps for admin spaces; a geothermal central plant, using a modular heat-recovery chiller
serving air-handler VAV systems; a packaged air-source
chiller and boiler system, providing hot and chilled
water to air-handler VAVs; and a modular heat recovery
chiller, using a boiler for heat absorption and a closedcircuit ﬂuid cooler for heat rejection with air-handler
VAVs.
The design team, owner, and user group decided the
fourth option was the best ﬁt for the project. While it
did not achieve the best life-cycle cost, it did ﬁt within
the budget and was a system the owner was accustomed to maintaining, as major equipment was similar
D ECEM BER 2020

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ASHRAE Journal - December 2020

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