ASHRAE Journal - June 2024 - 62

2024 ASHRAE TECHNOLOGY AWARDS CASE STUDY
EXEMPLARY
DECARBONIZATION
RECOGNITION
lowering the building's EUI and helped meet
net zero energy goals.
Actual building operation began in September
2020, and the buildings' fi rst-year use showed energy
use on trend with the energy model and showed
a reduction in EUI, with an operational value of
19.2 kBtu/ft2·yr (218 MJ/m 2·yr). While the monthly
data does show a decrease in use in the winter and an
increased use in the summer, the annual operation
evens out to match the trend of annual modeled use.
net zero energy goals.
FIGURE 1 First year monthly energy production and consumption.
140,000
120,000
100,000
80,000
60,000
40,000
20,000
-
Sept. Oct. Nov. Dec. Jan. Feb. March April May June July Aug.
2020/2021
FIGURE 2 Second year energy production and consumption.
140,000
120,000
100,000
80,000
60,000
40,000
20,000
spaces were designed to maintain minimum outdoor
air requirements defi ned by Wisconsin Commercial
Building Code, and aggressive zoning strategies
provided a heat pump for virtually each space. This
zone level control strategy allowed comfort criteria for
each space to be met more easily and keep students
and staff comfortable while minimizing possible cross
contamination between zones.
Minimizing mixing of air between classrooms became
Solar Generation
Modeled
Solar Generation
Actual
Building Load
Modeled
Building Load
Actual
Solar Generation
Modeled
Solar Generation
Actual
Building Load
Modeled
Building Load
Actual
Sept. Oct. Nov. Dec. Jan. Feb. March April May June July Aug.
2021/2022
The actual energy produced by the solar PV system has
been 19.7 kBtu/ft2·yr (223.7 MJ/m 2·yr) compared to the
modeled production of 21.5 kBtu/ft2·yr (244.2 MJ/m 2·yr).
Both the months of January an d February 2021 produced
much less renewable energy than expected as both
months were snowier and colder than projected and
caused snow buildup on the panels.
The school has achieved net zero for the fi rst two full
years of operation and also reached this goal for the
2022 - 2023 school year. The energy consumption and
production profi le of the fi rst two years of operation is
shown in Figures 1 and 2.
Indoor Air Quality and Thermal Comfort
With student health and safety being at the forefront
of the design process, indoor air quality was an
important factor in selecting a ventilation strategy. All
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important as the COVID-19 pandemic raised concern of
virus transmission between rooms. The selected
ventilation strategy allows pretreated outdoor
air to be delivered directly to the space with
return air circulated through a MERV 14 fi lter at
the zone 's heat pump to reduce the spread and
accumulation of microbes in the zone air. At the
height of the COVID pandemic, heat pump fans
were run continuously to increase the amount
of fi ltration in occupied spaces.
The all-electric kitchen design also
removes the possibility of combustion fumes
contaminating adjacent spaces and makes the
breathing zone within the kitchen safer.
Using a DOAS allowed the ventilation air
to be treated at a single location instead of
individual devices in the zones. Since the
DOAS handled all the outdoor air fi ltration
in one location, it was possible to upsize
the fi lters to MERV 13 and provide better
protection against outdoor air contaminants,
such as the recent wildfi re smoke across much of the
U.S.-including Wisconsin.
The DOAS also removes the need for the individual
heat pumps to have active humidity control by
controlling the ventilation latent load centrally.
Since the system is specifi cally designed for humidity
control, it can maintain humidity setpoints without
wasting energy. Using the DOAS system also ensures
adequate ventilation decoupled from the heating and
cooling loads.
High occupancy areas like the gym and cafeteria are
controlled with CO2 sensors per ASHRAE Standard
62 .1 requirements. If there's a CO2 warning, zone
level controls automatically increase supply air with a
modulating damper at the outdoo r air duct connection
to the heat pump air.
Space temperature is maintained by variable fl ow
kwh
kwh
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ASHRAE Journal - June 2024

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