ASHRAE Journal - December 2022 - 29

FIRST PLACE | 2022 ASHRAE TECHNOLOGY AWARD CASE STUDIES
ILFI's requirements for Net Zero Energy Certifi cation;
residents experience nature and learn about sustainable
design through the building programs and the building
design; and all systems and design components are in
alignment with project costs and long-term, life-cycle
value.
Mechanical System Description and Schematic
A ground source vertical heat exchanger system consisting
of 32 vertical heat exchangers that run 250 ft
(76 m) deep serve as the heat sink for the ground source
heat pump system. Two loops in a reverse-return
arrangement were provided for pumping effi ciency and
redundancy.
A dedicated outdoor air pretreatment system with
an air-to-air total energy recovery wheel is used to
pretreat all mechanically provided outdoor air from
all buildings' general exhaust air systems. The system
modulates based on a CO2 control system and
building pressure control to maintain operational
requirements.
A ground source
water-to-water heat
pump system with multistage
control serves
the hot water radiant
fl oor heating system.
Primary and tertiary/recirculating
systems
with condenser
water decouplers are
used in the ground
source pumping systems,
which allows
loads in rooms they serve to ensure stable operation
and comfort.
Premium-effi cient, ground source water-to-air heat
pumps with multispeed and ECM fans, MERV 14 fi lters
and dehumidifi cation control with variable speed operation
for high density spaces are used for primary space
heating and cooling.
Thermally broken, wood-framed operable windows
are found throughout public spaces and offi ces for
natural ventilation opportunities. Along the main south
circulation corridor, a custom concrete thermal trombe
wall with appropriate exterior shading provides passive
solar heating in winter months. A rooftop solar array
made up of 350 W photovoltaic (PV) panels is integrated
into the slope of the butterfl y roof and is designed to
produce 150,000 kWh AC annually to offset annual
building energy use.
Energy Effi ciency
Figure 1. Simplifi ed system schematic of the building, which has a ground-source vertical heat exchanger
system (A), a dedicated outdoor air system with air-to-air energy recovery wheel (B), a water-to-water
heat pump system (C), optimized pumping (D), radiant fl oor heating and ceiling fans (E) and ground
source water-to-air heat pumps (F).
for optimized pumping. The main ground source
hydronic pumps are operated as little as possible to
maintain ideal condenser water temperature ranges
while tertiary recirculating pumps at each heat
pump-sized for building-loop pressure drop-only
operate when the water-to-air heat pump compressor
is operational.
Main public spaces and staff offi ces feature thermally
massive radiant fl oor heating and operable windows
coupled with ceiling fans to maximize thermal
comfort for energy effi ciency. Radiant fl oor systems
are sized and operated for 85% of perimeter heating
With the assistance of early phase and design refi nement
energy models, the mechanical team guided the
design team and the
owner toward costeffective
and energyeffi
cient choices on
architectural, lighting
and mechanical
systems.
For the mechanical
systems, modeling
indicated that
geothermal/groundsource
heat pump
technology would be
the most effective mechanical heating and cooling system
for the cold winter and warm summers of the upper
Midwest climate. Further design refi nement models
indicated that outdoor air quantities for the multipurpose
rooms and public spaces were a signifi cant driver
of energy use. The use of operable windows and ceiling
fans during milder fall and spring conditions, as well
as an outdoor air pretreatment system, was identifi ed
as the most cost-effective and energy-effi cient strategy.
Furthermore, a radiant fl oor heating system fed by a
ground-source water-to-water heat pump provided
additional winter heating in public spaces.
D E C E M B E R 2 0 2 2 ashrae.o rg ASHRAE JOURNAL
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ASHRAE Journal - December 2022

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