ASHRAE Journal - May 2023 - 56

TECHNICAL FEATURE
FIGURE 2 CO2 levels of all rooms in Phase 2 of the project, plotted versus ach.
Carbon Dioxide vs Air Changes Per Hour (Phase 2/All Rooms)
1,400
1,200
1,000
800
600
400
200
Action Level = 1,000 ppm
High Limit = 1,200 ppm
to Phase 2, total fan energy decreased 34%. A 30% annual
reduction in chilled water energy and a 22% annual
reduction in boiler energy was measured. (Associated
pumping energy was reduced by 46%; however, the
magnitude of that savings was much lower.)
A weather bin analysis, based on 15 years of historical
weather, was used to extrapolate energy savings for the
whole year from the Phase 2 data. Savings were applied
to chilled water and boiler energy, based on the reduction
of air. Cost savings were calculated using $0.16/kWh
and $0.52/therm. The resultant savings were a 17%
decrease in overall building energy consumption, with a
cost savings of more than $375,000.
2
4
6
ach
FIGURE 3 Particulate contamination levels (PN1+) all rooms in Phase 2 of the
project, plotted versus ach.
Particles vs Air Changes Per Hour (Phase 2/All Rooms)
1,000
900
800
700
600
500
400
300
200
100
Action Level = 864 #/L
8
10
12
Phase 3 Energy Data and Savings
In Phase 3, the energy savings is a result of the
reduced ventilation levels for the zones on the first
and second floor. Since this was a small change to the
facility relative to the entire tower energy baseline, the
data was extrapolated to determine the full Phase 3
savings potential. The calculations show that if Phase
3 minimum ventilation setpoints were applied to
every eligible administrative room, the average cfm
could be reduced an additional 9.3%. Phase 3 energy
consumption and savings were also calculated from the
temperature bin analysis above. From the baseline, this
calculation yielded fan energy savings of 50%, chilled
water energy savings of 36% and boiler energy savings of
29% (Figure 4).
2
4
6
ach
The random occurrence and magnitude of the spikes
suggest episodic contamination rather than steadystate
or continuous contamination. Aside from the
spikes, the overall average TVOC level was 76 ppb, well
below action level.
Ozone: Indoor ozone levels were consistently less than
outdoor and below action levels. Zone data indicates that
indoor ozone is a diluted fraction of outdoor ozone, with
no relationship to zone ventilation rate.
Phase 2 Energy Savings
In Phase 2, the terminal units were converted from
CAV to VAV. This change directly reduced the overall airflow
to and from the building. From the baseline period
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ASHRAE JOURNAL ashrae.o rg M AY 2023
8
10
12
Energy Savings for the Project Site
The overall projected savings from the project is nearly
95,000 therms, or 29% of the boiler energy and 21% of
the total natural gas consumption of the tower. The project
is also projected to save over 2.8 million kWh of electricity,
or 25% of the total electricity consumption of the
tower. These projections show an annual cost savings of
nearly $460,000 per year and a carbon emissions reduction
of over 2,460 metric tons of CO2 equivalent. That is
the equivalent of removing 539 passenger cars from the
road each year.
COVID-19's Effect on Project Changes
In early 2020, during the COVID-19 patient surge,
the hospital reset the VAV minimums, reverting to CAV
systems at full flow. In June of 2021, after most of the
patient surges passed, the hospital reestablished the
Particles (N/L)
C02 (ppm)
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