ASHRAE Journal - July 2022 - 47

SECOND PLACE | 2022 ASHRAE TECHNOLOGY AWARD CASE STUDIES
PHOTO 1 HVAC airflow system concept.
Total Energy Recovery Coil
EA Out
OA In
High-Momentum Exhaust Fans
Venturi-Type
Control Valve
Active Chilled
Beam (Typ.)
High Performance
Fume Hood
SA Fan
Preheat
Coil
Venturi-Type
Control Valve
General Exhaust Grille
(Typ.)
Active
Chilled
Beam (Typ.)
heat gains. Numerous technologies, strategies and systems
are included in the building to mitigate the energy
impact of these drivers, including:
* Dual-wheel enthalpy and sensible recovery wheels to
deliver neutral air;
* Active chilled beams and perimeter radiators;
* " Airshare " distribution methods and atrium/commons
displacement ventilation;
* District energy from campus chilled water and hightemperature
hot water plants;
* High effi ciency lighting and daylighting with occupancy
sensor controls;
* High performance fume hoods;
* Carbon dioxide level sensors varying airfl ow to teaching
classrooms; and
* High performing envelope and minimal east and
south glazing.
Projected energy use intensity (EUI) for the building
was 174.7 kBtu/ft2·yr (1984 MJ/m2·yr), while actual EUI
was 163.8 kBtu/ft2·yr (1860.2 MJ/m2·yr). The EUI for a
baseline building was 294 kBtu/ft2·yr (3339 MJ/m2·yr).
Energy use savings of 40.6% (35.5% energy cost savings)
were projected compared to ASHRAE Standard
90.1-2007. After the fi rst year of operation, the building's
energy savings were 44% less than the ASHRAE Standard
90.1-2007 baseline , outperforming the energy model's
projected energy performance. The project also complies
with ASHRAE Standard 90.1-2013 as required by
local energy codes.
The project uses a decoupled HVAC system approach.
With a code-compliant variable air volume (VAV) system,
all heating and cooling requirements are provided
from the air-handling unit. A decoupled approach separates
heating, cooling and ventilation air components,
Cooling
Coil
Reheat
Coil
Sensible Energy Recovery Coil
EA In
SA Out (68°F)
eliminating the need for excessive airfl ow rates and
heating/cooling energy required to condition this air.
Dedicated outdoor air systems (DOAS) provide only
the code-required ventilation air at a neutral temperature
(68°F [20°C], dry air). Because ventilation is kept
at 68°F (20°C), reheat coils are not required at supply
terminal units. This drastically reduces the building's
overall cooling (OA dehumidifi cation) and reheat loads.
Chilled beams are provided to meet the space sensible
cooling load requirements. A perimeter heating system
(fi n-tube, radiant panels) meets the envelope heat loads.
Reheat is almost eliminated from the building, and total
airfl ow is reduced by approximately 50% by decoupling
the ventilation air, cooling and heating systems.
Energy wheels optimize the recovery effectiveness in
lieu of other technologies such as energy recovery coil
and glycol runaround loops. Wheel effectiveness can
reach up to 80% for sensible and latent recovery. Energy
coil effectiveness is in the 50% to 55% range for sensible
recovery only. In summer, outdoor air is precooled and
prehumidifi ed with building return air, reducing the air
temperature entering the cooling coil. This reduces the
mechanical cooling energy required from the central
plant.
In heating mode, outdoor air is preheated with building
return air, signifi cantly reducing the heating energy
required. The addition of a sensible energy recovery
coil downstream of the total energy wheel and cooling
coil further increases the effectiveness of the energy
recovery cycle. The sensible wheel also eliminates or
drastically reduces the need for energy-intensive reheat.
In typical HVAC systems, variable air volume (VAV) air
handling units supply 55°F (13°C) air to the building
year-round. Electric or hot water reheat coils on VAV
boxes heat the air to maintain the space temperature.
The sensible wheel in the dual-wheel approach provides
" free " reheat to the building supply air, heating the air to
a neutral temperature (68°F [20°C]).
The building return air leaving the sensible wheel is
reduced in temperature, further increasing the effectiveness
of the total energy wheel, in turn reducing the
cooling coil dehumidifi cation load.
The building includes fume hood-intensive research
spaces. High performance fume hoods are provided to
reduce the exhaust airfl ow requirements through the
hoods. Together with the University Environmental
Safety and Health professionals, the design team was
J U LY 2 0 2 2 ashrae.o rg ASHRAE JOURNAL
47
Enthalpy Wheel
Sensible Wheel
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ASHRAE Journal - July 2022

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