United States Indoor Environments EPA-402-S-01-001C
Environmental Division (6609J) January 2000
Protection Office of air and Radiation
Agency
Energy Cost and IAQ
Performance of Ventilation
Systems and Controls
Project Report # 3
Assessment of CV and VAV Ventilation
Systems and Outdoor Air control Strategies
for Large Office Buildings
Zonal Distribution of Outdoor Air and Thermal Comfort
Control
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Energy Cost and IAQ Performance of Ventilation Systems
and Controls
Project Report # 3 Assessment of CV and VAV Ventilation Systems and
Outdoor Air Control Strategies for Large Office
Buildings
Zonal Distribution of Outdoor Air and Thermal
Comfort Control
Indoor Environments Division
Office of Radiation and Indoor Air
Office of Air and Radiation
United States Environmental Protection Agency
Washington, D.C, 20460
January 2000
-------
Energy Cost and IAQ Performance of Ventilation Systems and Controls
Project Report # 3; Assessment of CV and VAV Ventilation Systems and Outdoor Air
Control Strategies for Large Office Buildings
Zonal Distribution of Outdoor Air and Thermal Comfort Control
INTRODUCTION
Purpose and Scope of this Report
A companion to this report (see Project Report #2) found that the VAV systems with fixed outdoor
air fraction controls set to deliver 20 cfm of outdoor air per occupant, actually delivered significantly
less during part load conditions. These systems provided no energy advantage over alternative
controls which maintain a minimum of 20 cfm per occupant over the full operating cycle.
This report, a sequel to Project Report #2, examines the performance of the CV and VAV systems
in their delivery of outdoor air to individual zones, and also assesses their control of indoor climate
in those zones. It is designed to assess the extent to which unequal zonal distributions of supply air
affect the outdoor air delivery to occupied spaces. The examination of indoor climate is performed
to see whether, in combination with outdoor airflow characteristics, the inherent design of these
systems is likely to generate situations conducive to sick building syndrome complaints in
situations where air mixing is not significant.
Background
This report is part of a larger modeling project to assess the compatibilities and trade-offs between
energy, indoor air, and thermal comfort objectives in the design and operation of HVAC systems in
commercial buildings, and to shed light on potential strategies which can simultaneously achieve
superior performance on each objective.
This is a modeling study, subject to all the limitations and inadequacies inherent in using models to
reflect real world conditions that are complex and considerably more varied than can be fully
represented in a single study. Nevertheless, it is hoped that this project will make a useful
contribution to understanding the relationships studied, so that together with other information,
including field research results, professionals and practitioners who design and operate ventilation
systems will be better able to save energy without sacrificing thermal comfort or outdoor air flow
performance.
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The methodology used in this project has been to refine and adapt the DOE-2.1E building energy
analysis computer program for the specific needs of this study, and to generate a detailed
database on the energy use, indoor climate, and outdoor airflow rates resulting from various
ventilation systems and control strategies. Constant volume (CV) and variable air volume (VAV)
systems in different buildings, with different outdoor air control strategies, under alternative
climates, provided the basis for parametric variations in the database.
Seven reports, covering the following topics, describe the findings of this project:
• Project Report #1: Project objective and detailed description of the modeling methodology and
database development
• Project Report #2: Assessment of energy and outdoor air flow rates in CV and VAV ventilation
systems for large office buildings;
• Project Report #3: Assessment of the distribution of outdoor air and the control of thermal
comfort in CV and VAV systems for large office buildings
• Project Report #4: Energy impacts of increasing outdoor airflow rates from 5 to 20 cfm per
occupant in large office buildings
• Project Report #5: Peak load impacts of increasing outdoor air flow rates from 5 to 20 cfm per
occupant in large office buildings
• Project Report #6: Potential problems in IAQ and energy performance of HVAC systems when
outdoor airflow rates are increased from 5 to 15 cfm per occupant in
auditoriums, education, and other buildings with very high occupant density
• Project Report #7: The energy cost of protecting indoor environmental quality during energy
efficiency projects for office and education buildings
DESCRIPTION OF THE BUILDING AND VENTILATION SYSTEMS MODELED
A large 12 story office building was modeled in three different climates representing cold
(Minneapolis), temperate (Washington, D.C.), and hot/humid (Miami) climate zones. The building
has an air handler on each floor servicing four perimeter zones corresponding to the four compass
orientations, and a core zone, A dual duct constant volume (CV) system with temperature reset,
and a single duct variable volume (VAV) system with reheat were modeled. Constant volume
systems control the thermal conditions in the space by altering the temperature of a constant
volume of supply air. VAV systems provide control by altering the supply air volume while
maintaining a constant supply air temperature.
Three basic outdoor air control strategies were modeled: fixed outdoor air fraction (FOAF),
constant outdoor air (COA), and air-side economizer (ECON). The FOAF strategy maintained a
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constant outdoor air fraction (percent outdoor air) irrespective of the supply air volume. The FOAF
strategy maintained a constant outdoor air fraction (percent outdoor air) irrespective of the supply
air volume. For VAV systems, the FOAF may be approximated in field applications by an outdoor
damper in a fixed position (Cohen 1994; Janu 1995; and Solberg 1990). but specific field
applications are not addressed in this study. The FOAF strategy was modeled so that the design
outdoor airflow rate is met at the design cooling load, and diminishes in proportion to the supply
flow during part-load. The COA strategy maintains a constant volume of outdoor air irrespective of
the supply air volume. In a CV system, the FOAF and the COA strategies are equivalent, and are
referred to in this report as CV (FOAF). In a VAV system, the COA strategy might be represented
in field applications by a modulating outdoor air damper which opens wider as the supply air
volume is decreased in response to reduced thermal demands. Specific control mechanics which
would achieve a VAV (COA) have been addressed by other authors, (Haines 1986, Levenhagen
1992, Solberg 1990) but are not addressed in this modeling project.
Two air-side economizer strategies are used, one based on temperature (ECONt) and one on
enthalpy (ECONe). The economizer strategies override the outdoor air flow called for by the
prevailing strategy (FOAF or the COA) by bringing in additional quantities of outdoor air to provide
"free cooling" when the outdoor air temperature (or enthalpy) is lower than the return air
temperature (or enthalpy). The quantity of outdoor air is adjusted so that the desired supply air
discharge temperature (or enthalpy) can be achieved with minimum mechanical cooling. Because
outdoor air humidity levels are sometimes high during warm weather, the temperature economizer
in this project is shut off at outdoor temperatures above 65° F.
A more detailed description of the building and ventilation system is provided in Report #1.
APPROACH
For this analysis, zone level outdoor air flow and indoor temperature are determined for each hour
of the year and were organized in graphic or tabular formats. Zone level data for relative humidity
was not available, but the relative humidity in the return air duct was organized in the same fashion.
This was done for each HVAC system and OA control strategy. The systems design setting is 20
cfm of outdoor air per occupant, which is the level prescribed by ASHRAE Standard 62-19991.
RESULTS
The presentation of results is designed to shed light on the following questions:
a. How well do alternative outdoor air control strategies for CV and VAV systems deliver
requisite quantities of outdoor air to individual zones?
1 This project was initiated while ASHRAE Standard 1989 was in effect, However, since the outdoor air flow rales for
both the 1989 and 1999 versions are the same, all references to ASHRAE Standard 62 in this report are stated as ASHRAE
Standard 62-1999,
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b. How well do alternative outdoor air control strategies for CV and VAV systems maintain
indoor climate control?
c. Where potential shortfalls in outdoor air or indoor climate control occur in individual
zones, what solutions are appropriate, and what are the energy implications of those
solutions?
Delivery of Outdoor Air to Individual Zones
The quantity of outdoor air delivered to an individual zone in both CV and VAV systems depends
on the supply airflow, the proportion of the supply air which is outdoor air (outdoor air fraction), and
the proportion of the supply air delivered to the zone in question. The interplay of these three
variables is different for CV and VAV systems because of the way in which each system controls
indoor climate.
CV Systems
In CV systems, the supply air quantity is determined by the peak thermal loads of the building, and
each zone, and remains fixed throughout the year. For CV(FOAF) systems, the outdoor air fraction
is determined by the outdoor air requirements of the building (e.g., 20 cfm per occupant) and is
fixed. With CV(ECON) systems, the economizer increases the outdoor air fraction above the
minimum requirement during much of the year. Each zone receives a proportion of the supply air
depending on the peak thermal load of that zone. Thus, perimeter spaces get a larger quantity of
supply air than the core, and the south zone receives a larger quantity of supply air than the north
zone, etc. Since the outdoor air fraction is the same for all zones, the zones with the larger quantity
of supply air will receive a larger quantity of outdoor air and vice versa. This suggests that the core
zone in CV systems may receive an inadequate quantity of outdoor air, even when a sufficient
quantity of outdoor air enters the air handler.
This deficiency of outdoor air in the core zone is shown clearly for the CV(FOAF) system in Exhibit
1, which presents outdoor air flow rates achieved for each zone in this system in the temperate
climate of Washington, D.C. over all outdoor temperature conditions. The core zone was
consistently under-supplied while the perimeter zones were consistently oversupplied with outdoor
air. The results for all climate zones are similar.
Similar plots for the CV(FOAF) system with temperature and enthalpy economizers are presented
in Exhibits 2 and 3. The deficiency of outdoor air flow for systems with economizers only occurred
in the summer season (when the economizer is not operational). The economizer increased the
delivery of outdoor air to all zones, and insured that even the core zone had sufficient outdoor air
during much of the year, depending on the climate.
The results for all three systems in a cold climate (Minneapolis), temperate climate (Washington,
D C.), and a hot/humid climate (Miami) are summarized in Exhibit 4. This Exhibit shows clearly that
the CV(FOAF) system under-supplied the core zone, providing 11-15 cfm of outdoor air per
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occupant rather than 20 cfm/occupant, during all occupied hours in all climates. This resulted solely
from the unequal distribution of supply air to individual zones, based on peak thermal requirements.
The extent to which the economizers make up for the inherent deficiency of outdoor air to the core
zone is dependent on the proportion of the year the temperatures are cool enough for the
economizer to be operational. Economizers are operational approximately 70% of the time in
Minneapolis, 60% of the time in Washington, D.C., and 10% of the time in Miami. Thus,
economizers make up for the core zone deficiency most in cold climates and least in hot/humid
climates. In addition, since the temperature economizer was set to shut off when the temperature
exceed 65°F to avoid potential humidity problems, the enthalpy economizer operates over a slightly
larger portion of the year and therefore had a greater effect on zonal outdoor airflow rates.
VA V Systems
Like the CV(FOAF) system, the VAV(COA) system provide for a minimum outdoor airflow to the
building of 20 cfm per occupant during all operating conditions. VAV systems also distribute the
supply air to individual zones based on their relative thermal loads. However, while the distribution
of air to individual zones in CV systems is based on peak cooling needs and is fixed throughout the
year, VAV systems respond to daily and seasonal changes in thermal loads. Because of this, the
zonal distribution pattern for outdoor air in the VAV(COA) system will be similar, but not identical, to
that of the CV(FOAF) system.
Exhibit 5 shows the flow of outdoor air for the VAV(COA) for each zone over the full range of
outdoor temperatures, where minimum VAV box settings were at 30% of peak supply air flow. The
core zone consistently received less than the perimeter zones at between 15 and 20 cfm per
occupant, except that as the outdoor temperature rose above 65°F, the perimeter zones drew
slightly more air at the expense of the core zone. However, the core zone maintained at least 10
cfm per occupant at all times.
Exhibit 6 summarizes the outdoor air delivery rates for the VAV(COA) system, with and without
economizers, for all climates. For all practical purposes, the VAV(COA) system performed just as
well or slightly better than the CV(FOAF) system in its delivery of outdoor air to individual zones,
though the core zone was consistently under ventilated in both types of systems.
The VAV(FOAF) system provided significantly less outdoor air to all zones than the previous
cases. For VAV(FOAF), the outdoor air fraction at the air handler was established to satisfy the
outdoor air needs of all the zones serviced (20 cfm per occupant) at peak cooling loads, when
supply air quantities are at their maximum. Thus, at part load conditions, the VAV(FOAF) system
reduced the overall quantity of outside air and hence diminished the quantity of outside air to each
zone.
Exhibit 7 shows the zonal distribution pattern for a VAV(FOAF) system without economizer with all
VAV boxes set at a minimum of 30%. This shows that the core zone was consistently provided
with less than 8 cfm per occupant.
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Exhibit 8 summarizes the outdoor air flow rates for the VAV(FOAF) systems in all climates with arid
without economizers. The core zone received less than 10 cfm/occupant during all occupied hours
for Minneapolis and Washington, D.C. climates and for 73% of the occupied hours in Miami, even
though the system design setting was 20 cfm per occupant. Other zones were also under supplied,
but less frequently. The economizers improved the outdoor air performance considerably, but only
when the economizer is operating. The problem of under-supplying individual zones because of
the unequal distribution of air that was experienced with the VAV(COA) and CV(FOAF) system
was thus magnified with VAV(FOAF) system which also under- supplied the building with outdoor
air during part load conditions.
This pattern of unequal zonal distribution need not be a problem where there is significant mixing
between zones, such as in open plan offices that span both the perimeter and the core zones.
However, where air mixing is interrupted, as may be the case with closed offices, this deficiency in
air delivery to the core zones could be a problem. The problem would be partially mitigated by the
fact that both the perimeter and core zones share the same return air stream, but this would is not
likely to be significant especially if the outdoor air delivery to the air handler is also inadequate.
Climate Control with CV and VAV systems
Space Temperatures
The thermostat settings of both the CV and VAV systems were the same, and were designed to
maintain temperature between 70° F and 79° F. Exhibit 9 presents the temperature control
performance of each system in each zone. All systems in all climates in all zones maintained
indoor temperatures within this range. However, the CV system modeled tended to maintain a
lower average temperature than the VAV system. The north and west zones of the CV(FOAF)
system maintained temperatures right at the lower temperature limit of 70° F 2% -12% of the time
in Minneapolis and Washington, D.C, while these zones in the CV system with economizers did so
more often, 12 - 22% of the time. Conversely, the core zone of the VAV(FOAF) remained at 79°F
almost the entire year in Miami and for over half the time in Washington, D C. The addition of the
economizer made no real difference in this performance for Miami and lowered average
temperatures only slightly in Washington, D.C. In addition, the VAV(COA) system with and without
economizers, almost never achieved the high limit temperature in any zone.
If the modeling results are correct, these results suggest that the introduction of outdoor air may
tend, in general, to lower temperatures for both the CV and VAV systems modeled. For the CV
system, adding an economizer tended to exacerbate problems of temperature control in the north
and west zones which may occur in cold and temperate climates. For the VAV systems,
economizers tended to improve temperature control where problems may occur in hot and
temperate climates, but the improvement occurred only when the economizer was operating. The
more consistent gain in temperature control was the VAV(COA) system (compared to the
VAV(FOAF) system) which maintained 20 cfm of outdoor air per occupant during all occupied
hours.
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Relative Humidity
The HVAC systems modeled were riot equipped with specific humidification or dehumidification
equipment. All dehumidification took place through the normal cooling process. Exhibit 10 shows
data on the relative humidity in the return air stream during the year. This data suggests that, for
properly sized systems, interior spaces in office buildings are not likely to experience relative
humidity which is too high. The highest relative humidity were experienced in Miami, but even in this
climate all HVAC systems maintained the relative humidity between 30 - 50%.2
Low relative humidity problems are not simply a function of equipment sizing. The simulations
show that relative humidity below 20% occurred frequently, often over half the time, in the
temperate and cold climate. Because of the low humidity content of cold outside air, as more
outdoor air is drawn into the ventilation system, temperate and cold climates will experience dryer
indoor climate conditions during cold weather. As expected, this occurred more often in cold
climates than in temperate climates, and more often for systems with economizers. Also, while not
shown in the data presented, when these buildings were modeled at 5 cfm rather than 20 cfm of
outdoor air per occupant, the proportion of time that relative humidity dropped below 20%
decreased in all but the economizer systems. No attempt was made to model the energy
implications of humidification.
PROBLEMS AND POTENTIAL SOLUTIONS WITH VAV(FOAF)
VAV controls which approximate the VAV(FOAF) system appear to have a number of inherent
features that argue against their use. First, the VAV(FOAF) almost always provided below design
quantities of outdoor air from the air handler. Second, it provided little if any energy savings over
the VAV(COA) system which provided design quantities all year round3. This problem of
VAV(FOAF) was exacerbated by the tendency of all these systems to under-supply the core zone
and to a lesser extent, the north zone, with outdoor air.
All VAV systems modeled tended to maintain space temperatures at the higher end of the
temperature control deadband. In the core zone, the combination of higher temperatures and lower
quantities of outdoor air could create conditions conducive to sick building complaints in some
buildings. While economizers tend to improve the overall performance of VAV(FOAF) systems in
9
While not presented in this report, none ofthe other office buildings examined in this project presented
relative humidity which ever exceeded 60%, including buildings with low shell efficiencies or high occupant
densities in the hot/humid climate of Miami. This is interpreted to be the result of properly sized equipment.
However, relative humidity in excess of 60% or even 70% can be a problem in very high occupant density
buildings (e.g., schools, auditoriums) without proper controls (see Project Report # 6). Humidity could also
potentially be a problem with temperature controlled economizers (see Project Report # 2). Finally, while DOE-2
calculates a moisture balance, it has very limited capabilities in tracking relative humidity, so modeling results
must be interpreted with caution.
'"See Project Report #2
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the delivery of outdoor air, they do not improve the performance during the summer season, when
temperature conditions may be the warmest.
In Project Report # 2, it was suggested that problems with the VAV(FOAF) type systems may be
worth avoiding. This report reinforces that suggestion. In Project Report #2, operational
modifications to improve the outdoor air performance of FAV(FOAF) systems at the air handler
were explored. These options appeared to offer reasonable improvements in outdoor air flow at
only marginal changes in energy cost.
In this report, potential methods of providing a more even distribution of outdoor air to each zone
are explored, first by operationally altering the VAV box minimum flow settings, then by a system
redesign.
VA V Box Minimum Flow Settings
In previous runs, all the VAV boxes employed a minimum setting of 30%. Altering VAV box
minimum settings can alter both the total supply air delivered from the air handler, and the
distribution of that air to each zone. To better understand this process, the VAV box settings were
systematically changed.
In the VAV(FOAF) system, the VAV box minimum setting for the core zone was changed from 30%
to 75% in an effort to increase the flow of outdoor air to that zone. All other zone VAV boxes
remained set at 30%. The results are shown in Exhibit 11. No change was observed in the
outdoor air flow rates to any zone based on this change. Apparently, the relative constant thermal
demands of the core zone make it insensitive to changes in its VAV box minimum flow setting.
Modeling runs were also made for the VAV(FOAF) system in which all VAV box minimum settings
were changed. In addition to the 30% flow setting, settings of 0%, 45%. and 75% were modeled.
The results of these runs are shown in Exhibits 12 and 13.
From these exhibits two things become apparent. First, lowering or raising all VAV box minimums
settings lowers or increases outdoor airflow from the air handler to all zones. Thus, the deficiency
of the VAV(FOAF) system observed previously in total flow and zonal flow are magnified with
settings below the original 30% minimum flow. Second, as the minimum flow settings are
increased, the VAV system begins to approach the flow behaviors of the CV system. For example,
the zone level flow rates of the VAV(FOAF) system with minimum flow settings of 75% in Exhibit 13
are very similar to those of the CV(FOAF) system in Exhibit 1.
From these exercises, there does not appear to be a reasonable way to alter the VAV box
minimum settings in the VAV(FOAF) system in order to accommodate the outdoor air needs of the
occupants while still maintaining the energy advantages of a VAV system. Even for the VAV(COA)
system, however, the unequal distribution of outdoor air among zones left the core, and sometimes
the north zone under-supplied. This may or may not be a problem depending on the degree of
internal mixing among zones. However, for HVAC engineers who choose to avoid this problem, a
redesign alternative was examined.
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Dual System Design
It is not uncommon for design engineers to service the core zone of a building with a CV system,
and provide a VAV system for the perimeter zones. This makes sense because the thermal
conditions of the core zone remain relatively constant, while the perimeter zones experience daily
and seasonal swings. This option was modeled using a CV for the core zone and alternately
combined with a VAV(FOAF) system and a VAV(COA) system for the perimeter. The outdoor air
flows achieved are compared to the original single system VAV(FOAF) and VAV (COA)
respectively. The outdoor air flow rates for both perimeter and core zones are summarized in
Exhibit 14. The HVAC annual energy costs of these systems is also compared in Exhibit 15.
The dual system design using a CV system for the core zone and a VAV(FOAF) system for the
perimeter zones insures that the core zone always achieves 20 cfm of outdoor air per occupant.
However, in general, the perimeter zones tended to receive less outdoor air than the single
VAV(FOAF) system design, with the north and west zones being particularly under-supplied. For
example, in this dual system, the north zone received less than 10 cfm of outdoor air per occupant
between 38% and 96% of the time, depending on climate.
The dual system design using a VAV(COA) system for the perimeter zones improved the
perimeter outdoor air performance considerably, and appears to be preferable. However, even
this dual system still leaves shortfalls which may be unacceptable in the north and west zones.
Exhibit 15 suggests that the dual system would compare favorably to the single systems in energy
cost (plus or minus $0.01 per square foot) in the cold and temperate climates of Minneapolis and
Washington, D C , but would add about $.04 per square foot (approximately 5%) to the HVAC
energy costs in Miami.
SUMMARY
Whenever an air handler services more than one zone, differences in the thermal requirements
among zones will cause an unequal distribution of supply air, and therefore outdoor air, to individual
zones. The core zone, and to a lesser extent, the north zone, appear to be the most significantly
under-supplied with outdoor air.
The CV systems modeled tended to provide indoor space temperatures close to the lower end of
the temperature deadband, particularly in the north and west zones, while the VAV systems
modeled provided space temperatures close to the high end, particularly in the core zone. Since
the core and north zones were also zones that had the lowest supply of outdoor air, the combination
of extreme temperature and poor outdoor air performance may be conducive to sick building
syndrome complaints, especially where air mixing is limited.
The VAV(FOAF) system experienced the lowest zonal outdoor air flow rates. Attempts to remedy
the problem by raising VAV box minimum settings were unsuccessful. Raising VAV box minimum
setting in the core zone only, showed no change in outdoor air performance. Raising the VAV box
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minimum settings in all zones improved the outdoor air performance, but it did so by raising the
supply air flow rate in the whole system, making the VAV system behave like a CV system, and
removing the inherent energy advantage of the VAV system.
Building professionals might consider providing separate HVAC systems for the perimeter and the
core zones in new building designs. Such a system was modeled using a CV system to service
the core zone, and a VAV(FOAF) or a VAV(COA) system to service the perimeter zones. For
these dual systems, the outdoor airflow rate performance for the core zone was greatly improved,
but the performance of the perimeter zones showed significant shortfalls for the north and west
zones. Dual systems using VAV(COA) provided greater quantities of outdoor air to these zones
than VAV(FOAF), and would appear to be preferable. The energy cost of the dual system was
similar to the single system in the cold and temperate climates, but was about 5% higher in the hot
and humid climate.
The results of this report may be of interest to interior design professionals, and suggests that
whatever the HVAC system design, good airflow communication between zones could be an
important concern. Attention directed to communication from the zones with ample outdoor air
supply to the under-supplied zones might forestall sick building complaints in the under-supplied
zones.
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BIBLIOGRAPHY
Bearg, D, W. 1995. Demand-controlled ventilation. Engineered Systems April 1995:28-32.
Filardo, M. J. 1993. Outdoor air - how much is enough? ASHRAE Journal 35(1); 34-38.
Ke, Y., Mumma, S. A, 1996. A generalized multiple-space equation to accommodate any mix of close off and
fan powered VAV boxes ASHRAE Transactions 102(1): 3950.
Ke, Y. P., Mumma, S. A., Stanke, D.. 1997. Simulation results and analysis of eight ventilation control
strategies in VAV systems. ASHRAE Transactions 103(2); 381-392.
Levenhagen, J. I. 1992. Control systems to comply with ASHRAE Standard 62-1989. ASHRAE Journal
34(9):40-44
Mumma, S A , Bolin. R J. 1995. Real-time, on-line optimization of VAV system control to minimize the energy
consumption rate and to satisfy ASHRAE Standard 62-1989 for all occupied zones. ASHRAE Transactions
101(1): 3753.
Mutammara, AW. and 1 little, D C 1990. Energy effects of various control strategies for variable air volume
systems. ASHRAE Transactions 96(1): 98-102.
Warden, D. 1996. Outdoor air: calculation and delivery. ASHRAE Journal 37(6): 54-61.
Warden, D. 1996. Dual fan, dual duct systems. ASHRAE Journal 38(1): 36-41.
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Building: Office A
Location: Washington, DC
System: CV
OA Control: Fixed Fraction
Design OA Flow: 20 cfm/person
50
45
Exhibit 1
Comparison of Zone Level Outdoor Air
Flow Rates for CV (FOAF) System
o
o
o
E
H—
O
£
o
40
35
o 30
£
25
20
o 15
o
2 10
o
0
10
20
30
40 50 60 70
Outdoor Air Temperature, (deg F)
80
90
100
H— Core
East
North
South —West
Building
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Building: Office A
Location: Washington, DC
System: CV w/ Enthalpy Economizer
OA Control: Fixed Fraction
Design OA Flow: 20 cfm/person
Exhibit 2
Comparison of Zone Level Outdoor Air
Flow Rates for CV (EconT) System
o
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0£
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"D
10
II M I I II I I I I I I I I I I I i I I i I I i I I i ! !
20
30
40 50 60 70 80
Outdoor Air Temperature, (deg F)
90
100
H— Core East
North
West
South
Building
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Building: Office A
Location: Washington, DC
System: CV w/ Enthalpy Economizer
OA Control: Fixed Fraction
Design OA Flow: 20 cfm/person
Exhibit 3
Comparison of Zone Level Outdoor Air
Flow Rates for CV (EconE) System
TO 220
^ 200
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3
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il I I I I II 1
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—gm.
II I I I I I I I I I I I I I I I I M
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30 40 50 60 70 80
Outdoor Air Temperature, (deg F)
—i—Core ~ East North South —West —®— Building
90
100
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Exhibit 4
Occurance of Zone OA Flow Rates for CV Systems
(% of Occupied Hours)
Climate and
CV(FOAF)
CV(FOAF) EconT
CV(FOAF) Ecorip
Zone
OA Flow Rate Achieved (cfm/person)
OA Flow Rate Achieved (cfm/person)
OA Flow Rate Achieved (cfm/person)
<=5 6-10
11-15 16-19 >=20
<=5 6-10 11-15 16-19
>=20
<=5 6-10 11-15 16-19 >=20
Minnea., MN
Core
100.0
40.2 4.6
55.2
29.0 4.6 66.4
East
100.0
100.0
100.0
North
100.0
100.0
100.0
West
100.0
100.0
100.0
South
100.0
100.0
100.0
Wash., DC
Core
100.0
49.9 0.6
49.5
34.5 0.6 64.9
East
100.0
100.0
100.0
North
100.0
100.0
100.0
West
100.0
100.0
100.0
South
100.0
100.0
100.0
Miami, FL
Core
100.0
94.2
5.8
82.2 17.8
East
100.0
100.0
100.0
North
100.0
100.0
100.0
West
100.0
100.0
100.0
South
100.0
100.0
100.0
Energy Cost and IAQ
15
Report# 3
-------
Building: Office A
Location: Washington, DC
System: VAV
VAV Box Min: 30% All Zones
OA Control: Constant Flow
Design OA Flow: 20 cfm/person
Exhibit 5
Comparison of Zone Level Outdoor Air
Flow Rates for VAV (COA) System
a> 30
^ 15
O
o
S 10
3
° 5
0
10
20
30 40 50 60 70
Outdoor Air Temperature, (deg F)
80
90
100
H—Core East North South ~ ~ West
Building
-------
Exhibit 6
Occu ranee of Zone OA Flow Rates for VAV(COA) Systems
(% of Occupied Hours)
Climate and
VAV(COA)
VAV(COA) EconT
VAV(COA) Econp
Zone
OA Flow Rate Achieved (cfm/person)
OA Flow Rate Achieved (cfm/person)
OA Flow Rate Achieved (cfm/person)
<=5 6-10 11-15 16-19
>=20
<=5
6-10 11-15 16-19
>=20
<=5 6-10 11-15 16-19
>=20
Minnea., MN
Core
0.1 48.7 51.2
0.1 29.0 9.5
61.4
0.1 18.5 8.1
73.3
East
100.0
100.0
100.0
North
0.7 22.5
76.8
0.1 2.3
97.7
0.4
99.6
West
0.5
99.5
0.4
99.6
0.1
99.9
South
100.0
100.0
100.0
Wash., DC
Core
0.2 51.5 48.3
39.0 10.4
50.6
27.1 5.0
67.9
East
100.0
100.0
100.0
North
14.4
85.6
4.1
95.9
0.4
99.6
West
100.0
100.0
100.0
South
100.0
100.0
100.0
Miami, FL
Core
80.7 19.3
78.8 15.4
5.8
70.8 12.3
16.9
East
100.0
100.0
100.0
North
5.5 7.5
86.9
CM
CD
LO
92.3
1.1 2.9
96.1
West
2.1
97.9
1.2
98.8
0.7
99.3
South
100.0
100.0
100.0
Energy Cost and IAQ
17
Report# 3
-------
Building: Office A
Location: Minneapolis, MN
System: VAV
VAV Box Min: 30% All Zones
OA Control: Fixed Fraction
Design OA Flow: 20 cfm/person
Exhibit 7
Comparison of Zone Level Outdoor Air
Flow Rates for VAV (FOAF) System
50
45
o 40
O
£ 35
^
-------
Exhibit 8
Occu ranee of Zone OA Flow Rates for VAV(FOAF) Systems
(% of Occupied Hours)
Climate and
VAV(FOAF)
VAV(FOAF) EconT
VAV(FOAF) Econp
Zone
OA Flow Rate Achieved (cfm/person)
OA Flow Rate Achieved (cfm/person)
OA Flow Rate Achieved (cfm/person)
<=5 6-10
11-15
16-19
>=20
<=5
6-10
11-15
16-19
>=20
<=5 6-10
11-15
16-19
>=20
Minnea., MN
Core
3.2 96.8
32.8
1.7
4.0
61.4
19.2
1.7
4.0
75.1
East
68.3
31.7
3.1
8.0
88.9
2.2
3.9
93.9
North
61.8
20.5
16.7
1.0
0.8
18.1
13.7
67.4
0.2
7.0
11.7
81.1
West
68.2
13.1
18.6
6.9
11.2
81.8
2.7
6.8
90.6
South
49.9
9.9
40.2
4.2
5.9
89.9
2.5
3.1
94.4
Wash., DC
Core
0.7 99.3
49.3
0.1
0.1
50.6
28.6
0.1
0.1
71.2
East
46.4
15.3
38.3
6.3
13.5
80.2
1.6
6.2
92.2
North
69.4
24.4
6.2
3.5
19.4
23.8
53.2
6.3
19.6
73.9
West
54.2
15.0
30.8
9.7
14.5
75.7
2.4
8.7
88.9
South
35.2
10.7
54.1
6.1
00
CO
85.1
2.3
5.2
92.5
Miami, FL
Core
73.3
26.7
94.2
5.8
77.9
22.1
East
3.2
9.4
87.4
2.2
10.3
87.5
1.2
6.5
92.3
North
5.8
24.1
43.3
26.7
2.0
28.7
46.0
23.2
0.6
17.2
42.7
39.5
West
11.6
23.3
65.1
8.9
27.1
64.0
4.6
20.9
74.4
South
13.5
86.5
5.4
9.2
85.4
3.4
8.0
88.6
Energy Cost and IAQ
19
Report# 3
-------
Exhibit 9
Percent of Occupied Hours with Specified Indoor Air Temperatures by Zone
System and
Minneapolis, MN
Washington, DC
Miami, FL
Temperature
Core
E
N
W
S
Core
E
N
W
S
Core
E
N
W
S
CV(FOAF)
<=70
0.0
2.2
11.7
3.4
1.7
0.0
0.4
8.9
1.7
0.5
0.0
0.0
0.3
0.0
0.0
71-72
1.6
91.0
88.3
91.0
79.8
0.3
90.0
91.0
93.4
82.5
0.0
72.9
29.3
91.3
88.8
73-74
1.9
4.7
0.0
2.9
9.0
0.7
4.7
0.0
3.0
6.8
0.0
12.0
22.0
4.3
6.6
75-76
9.5
1.8
0.0
1.9
7.1
3.7
3.8
0.0
1.3
7.1
0.0
9.1
28.2
3.2
3.6
77-78
85.9
0.3
0.0
0.8
2.4
90.8
1.1
0.0
0.6
3.1
99.9
5.7
20.1
1.1
1.0
>=79
1.1
0.0
0.0
0.0
0.0
4.5
0.1
0.0
0.0
0.0
0.1
0.3
0.1
0.0
0.0
CV(FOAF)EconT
<=70
0.0
9.7
19.5
12.1
5.8
0.0
4.1
21.7
15.7
6.3
0.0
0.2
0.7
2.4
0.5
71-72
1.6
84.0
80.5
82.4
75.9
0.3
86.4
78.2
79.5
77.1
0.0
72.7
28.9
89.0
88.3
73-74
1.9
4.4
0.0
2.9
9.1
0.7
4.9
0.0
2.9
7.0
0.0
12.0
22.0
4.3
6.6
75-76
9.9
1.6
0.0
1.8
7.1
4.0
3.5
0.0
1.3
6.9
0.0
9.3
28.2
3.2
3.5
77-78
85.6
0.3
0.0
0.8
2.2
90.7
1.0
0.0
0.6
2.7
99.9
5.7
20.1
1.1
1.0
>=79
1.0
0.0
0.0
0.0
0.0
4.4
0.1
0.0
0.0
0.0
0.1
0.3
0.1
0.0
0.0
CV(FOAF)EconE
<=70
0.0
9.7
19.5
12.2
5.8
0.0
4.1
21.7
15.7
6.3
0.0
0.2
0.8
2.4
0.4
71-72
1.6
84.0
80.5
82.4
76.0
0.3
86.6
78.3
79.5
77.2
0.0
72.8
28.9
89.0
88.4
73-74
1.9
4.5
0.0
2.8
9.1
0.7
4.8
0.0
2.9
6.9
0.0
12.0
21.9
4.3
6.6
75-76
9.9
1.5
0.0
1.7
7.0
4.0
3.2
0.0
1.3
7.0
0.0
9.2
28.2
3.2
3.5
77-78
85.6
0.3
0.0
0.8
2.2
91.0
1.1
0.0
0.6
2.7
99.9
5.6
20.1
1.1
1.1
>=79
1.0
0.0
0.0
0.0
0.0
4.0
0.1
0.0
0.0
0.0
0.1
0.3
0.1
0.0
0.0
Energy Cost and IAQ
20
Report# 3
-------
Exhibit 9 (Cont'd)
Percent of Occupied Hours with Specified Indoor Air Temperatures by Zone
System and
Minneapolis, MN
Washington, DC
Miami, FL
Temperature
Core
E
N
W
S
Core
E
N
W
S
Core
E
N
W
S
VAV(FOAF)
<=70
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
71-72
0.0
7.7
23.9
20.1
7.2
0.0
1.2
9.7
5.3
0.5
0.0
0.0
0.1
0.0
0.0
73-74
0.1
46.4
33.9
36.3
31.6
0.0
34.8
37.0
39.4
24.0
0.0
0.9
1.7
4.5
0.8
75-76
5.4
35.4
34.5
30.1
35.5
0.9
44.5
47.5
39.6
45.9
0.0
48.9
13.1
62.6
66.7
77-78
94.2
10.5
7.7
12.9
25.3
35.5
18.8
5.8
15.3
29.2
0.0
46.0
80.8
32.2
31.8
>=79
0.3
0.0
0.0
0.6
0.3
63.7
0.6
0.0
0.4
0.4
100.0
4.2
4.3
0.7
0.7
VAV(FOAF)EconT
<=70
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
71-72
0.0
9.4
25.9
22.5
8.3
0.0
1.4
11.6
6.0
0.6
0.0
0.0
0.1
0.0
0.0
73-74
0.2
46.3
33.7
35.7
32.0
0.0
36.9
36.8
40.4
25.4
0.0
1.1
1.9
5.0
1.0
75-76
8.1
34.6
32.7
29.0
37.5
1.2
43.1
45.8
38.1
47.6
0.0
49.1
13.1
62.2
66.9
77-78
91.5
9.7
7.7
12.3
21.9
47.3
18.1
5.8
15.1
26.0
1.2
45.6
80.5
32.2
31.4
>=79
0.3
0.0
0.0
0.6
0.4
51.5
0.6
0.0
0.4
0.4
98.8
4.2
4.2
0.7
0.7
VAV(FOAF)EconE
<=70
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
71-72
0.0
9.4
25.9
22.6
8.3
0.0
1.5
11.6
6.1
0.6
0.0
0.0
0.1
0.0
0.0
73-74
0.2
46.4
33.7
35.5
32.0
0.0
37.1
37.0
40.6
25.5
0.0
1.1
1.9
5.0
1.0
75-76
8.1
34.7
32.7
29.0
37.8
1.2
43.0
45.6
37.9
47.6
0.0
49.1
13.4
62.2
67.3
77-78
91.5
9.5
7.7
12.2
21.6
48.9
17.9
5.8
14.9
25.9
1.2
45.6
80.3
32.0
31.0
>=79
0.3
0.0
0.0
0.6
0.3
49.9
0.6
0.0
0.4
0.4
98.8
4.1
4.2
0.7
0.7
Energy Cost and IAQ
21
Report# 3
-------
Exhibit 9 (Cont'd)
Percent of Occupied Hours with Specified Indoor Air Temperatures by Zone
System and
Minneapolis, MN
Washington, DC
Miami, FL
Temperature
Core
E
N
W
S
Core
E
N
W
S
Core
E
N
W
S
VAV(COA)
<=70
0.0
2.2
11.7
3.4
1.7
0.0
0.4
8.9
1.7
0.5
0.0
0.0
0.3
0.0
0.0
71-72
1.6
91.0
88.3
91.0
79.8
0.3
90.0
91.0
93.4
82.5
0.0
72.9
29.3
91.3
88.8
73-74
1.9
4.7
0.0
2.9
9.0
0.7
4.7
0.0
3.0
6.8
0.0
12.0
22.0
4.3
6.6
75-76
9.5
1.8
0.0
1.9
7.1
3.7
3.8
0.0
1.3
7.1
0.0
9.1
28.2
3.2
3.6
77-78
85.9
0.3
0.0
0.8
2.4
90.8
1.1
0.0
0.6
3.1
99.9
5.7
20.1
1.1
1.0
>=79
1.1
0.0
0.0
0.0
0.0
4.5
0.1
0.0
0.0
0.0
0.1
0.3
0.1
0.0
0.0
VAV(COA)EconT
<=70
0.0
9.7
19.5
12.1
5.8
0.0
4.1
21.7
15.7
6.3
0.0
0.2
0.7
2.4
0.5
71-72
1.6
84.0
80.5
82.4
75.9
0.3
86.4
78.2
79.5
77.1
0.0
72.7
28.9
89.0
88.3
73-74
1.9
4.4
0.0
2.9
9.1
0.7
4.9
0.0
2.9
7.0
0.0
12.0
22.0
4.3
6.6
75-76
9.9
1.6
0.0
1.8
7.1
4.0
3.5
0.0
1.3
6.9
0.0
9.3
28.2
3.2
3.5
77-78
85.6
0.3
0.0
0.8
2.2
90.7
1.0
0.0
0.6
2.7
99.9
5.7
20.1
1.1
1.0
>=79
1.0
0.0
0.0
0.0
0.0
4.4
0.1
0.0
0.0
0.0
0.1
0.3
0.1
0.0
0.0
VAV(COA)EconE
<=70
0.0
9.7
19.5
12.2
5.8
0.0
4.1
21.7
15.7
6.3
0.0
0.2
0.8
2.4
0.4
71-72
1.6
84.0
80.5
82.4
76.0
0.3
86.6
78.3
79.5
77.2
0.0
72.8
28.9
89.0
88.4
73-74
1.9
4.5
0.0
2.8
9.1
0.7
4.8
0.0
2.9
6.9
0.0
12.0
21.9
4.3
6.6
75-76
9.9
1.5
0.0
1.7
7.0
4.0
3.2
0.0
1.3
7.0
0.0
9.2
28.2
3.2
3.5
77-78
85.6
0.3
0.0
0.8
2.2
91.0
1.1
0.0
0.6
2.7
99.9
5.6
20.1
1.1
1.1
>=79
1.0
0.0
0.0
0.0
0.0
4.0
0.1
0.0
0.0
0.0
0.1
0.3
0.1
0.0
0.0
Energy Cost and IAQ
22
Report# 3
-------
Exhibit 10
Percent of Occupied Hours with Specified Return Air Relative Humidity
System and
Relative Humidity
Climate
<20%
21-29%
30-50%
51-60%
61-70% >70%
CV(FOAF)
Minneapolis, MN
41.3
16.8
41.9
Washington, DC
26.0
15.4
58.5
0.1
Miami, FL
1.0
1.8
96.2
1.1
CV(FOAF) EconT
Minneapolis, MN
50.4
10.5
38.6
0.5
Washington, DC
31.5
11.9
54.8
1.6
0.1
Miami, FL
1.6
1.4
95.5
1.4
0.1
CV(FOAF) EconE
Minneapolis, MN
48.6
11.4
37.5
2.4
Washington, DC
31.8
12.3
51.3
4.2
0.4
Miami, FL
1.6
1.4
93.0
3.9
0.1
Energy Cast and JAQ
23
Report # 3
-------
Exhibit 10 (Cont'd)
Percent of Occupied Hours with Specified Return Air Relative Humidity
System and
Relative Humidity
Climate
<20%
21-29%
30-50% 51-60% 61-70% >70%
VAV(FOAF)
Minneapolis, MN
37.6
21.6
40.8
Washington, DC
26.1
17.5
56.4
Miami, FL
1.3
2.0
96.7
VAV(FOAF) EconT
Minneapolis, MN
54.3
12.7
33.0
Washington, DC
36.1
11.9
52.0
Miami, FL
2.1
2.1
95.8
VAV(FOAF) Econe
Minneapolis, MN
52.5
15.1
32.3
Washington, DC
37.0
13.8
49.3
Miami, FL
2.3
3.3
94.5
VAV(COA)
Minneapolis, MN
50.8
14.0
35.1
Washington, DC
32.1
14.6
53.3
Miami, FL
1.7
2.0
96.2
VAV(COA) EconT
Minneapolis, MN
54.6
13.3
32.1
Washington, DC
36.3
12.8
50.9
Miami, FL
2.2
2.4
95.4
VAV(COA) EconE
Minneapolis, MN
52,5
15.2
32.2
Washington, DC
37.0
13.9
49.2
Miami, FL
2.3
3.2
94.5
Energy Cost and LAO
24
Report # 3
-------
Building: Office A
Location: Washington, DC
System: VAV
VAV Box Min: 75% Core, 30% Perimeter
OA Control: Fixed Fraction
Design OA Flow: 20 cfm/person
Exhibit 11
Comparison of Zone Level Outdoor Air
Flow Rates for VAV (FOAF) System
a) 30
0
+H-H4+H—H-H-
i i i i n l |-|—h~Hs-f I I I I I I M I I I I I I I
10
20
30 40 50 60 70
Outdoor Air Temperature, (deg F)
80
90
100
H—Core East North South —a— West
Building
-------
Exhibit 12
Building. Office A
Location; Washington, OC
System VAV
VAV Box Win" 0% AH Zones
OA Control: Fixed Fraction
Design OA Flow. 20 cfm/person
Exhibit 12a
Comparison of Zone Level Outdoor Air Flow Rates
for VAV (FOAF) System w/ VAV Boxes at 0%
T»88 '#«
40 50 60 70
Outdoor Air Temperature, (deg F)
100
-East
North
• South
-West
-Supply
Building; Office A
Location: Washington. DC
System; VAV
VAV Box Min1 30% Ail Zones
OA Control; Fixed Fraction
Design OA Row; 20 cfm/person
Exhibit 12b
Comparison of Zone Level Outdoor Air Flow Rates
for VAV (FOAF) System w/ VAV Boxes at 30%
1 0
i i a -I ® |\ / | I 1 1 4 1 t > 1 i » 3 '
nr^
30 40 50 60 70
Outdoor Air Temperature, (deg F)
H—Core
•East
North
•South
-West
-Supply
-------
Exhibit 13
Building: Office A
Location: Washington, DC
System1 VAV
VAV Box Mm; 45% All Zones
OA Control: Fixed Fraction
Design OA Flow: 20 cfrrfperscn
Exhibit 13a
Comparison of Zone Level Outdoor Air Flow Rates
for VAV (FOAF) System w/ VAV Boxes at 45%
10 20 30 40 50 60 70
Outdoor Air Temperature, (deg F)
80
90
100
-Core —a—East
North
• South
-West
-Supply
Building. Office A
Location: Washington, DC
vw7oxVMin: 75% aiizones Comparison of Zone Level Outdoor Air Flow Rates
OA Control1 Fixed Fraction
Design OA Fiow. 20 dm/person
Exhibit 13b
for VAV (FOAF) System wI VAV Boxes at 75%
3
o
/\\A Kj-
I | | j [ | | 11 | ; | h+* I I I ! I 1 I I HI I I I 1TI I I I I tTH I I I
10 20 30 40 50 60 70
Outdoor Air Temperature, (deg F)
80
90
100
-Core
•East
North
- South
¦West
-Supply
-------
Exhibit 14
Oceurance of Zone Ootdoor Air Flow Rates for Single and Dual Air Handler Systems
with Fixed Outdoor Air Fraction Control Strategy
(Percent of Occupied Hours)
Climate and Zone
VAV(FOAF)
VAV(FOAF) / Dual AHU
OA Flow Rate Achieved (cfm/person)
OA Flow Rate Achieved (cfm/person)
<=5 6-io
11-15
16-19
>=20
<=5
6-10
11-15
16-19
>=20
Minneapois, MN
Core
3.2 96,8
0.1
0.5
5.8
67.0
26.5
East
68.3
31.7
68.1
21.9
6.2
3.7
North
818
20,5
16.7
1.0
61.0
37.9
1.1
West
68.2
13.1
18.6
81,4
12.6
5.7
0.4
South
49.9
9.9
40.2
60,0
29.7
9.7
0.6
Washington, DC
Core
0,7 99,3
0.3
2.0
97.7
East
46.4
15.3
38.3
64,5
27,4
7.5
0.5
North
69.4
24,4
6.2
96,1
3,9
West
54,2
15,0
30,8
71.1
19,7
7.7
1.5
South
35.2
10.7
54,1
47.8
37,8
13.1
1.4
Miami, FL
Core
73,3
26,7
100.0
East
3.2
9.4
87,4
14.2
50,0
22.7
13.1
North
5.8
24.1
43.3
26.7
5.5
73.2
21,3
West
11.6
23.3
65.1
37.1
51.7
10.5
0.7
South
13.5
86.5
14.3
55,7
22.0
7.9
Energy Cost and JAQ
28
Report # 3
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Exhibit 14 (Cont'd)
Oceurance of Zone Ootdoor Air Flow Rates for Single and Dual Air Handler Systems
with Constant Outdoor Air Control Strategies
(Percent of Occupied Hours)
Climate and Zone
VAV(COA)
VAV(COA) / Dual AHU
OA Flow Rate Achieved (cfm/person)
OA Flow Rate Achieved (cfm/person)
<=5 6-10 11-15 16-19
>=20
<=5 6-10 11-15
16-19
>=20
Minneapolis, MN
Core
0.1 48.7 51.2
100.0
East
100.0
0.2
11.4
88.4
North
0.7 22.5
76.8
1.4 42.3
55.8
0.5
West
0.5
99.5
11.0
23.5
65.5
South
100.0
1.6
7.5
90.9
Washington, DC
Core
0.2 51.5 48.3
100.0
East
100.0
5.1
26.4
68.5
North
14.4
85.6
40.1
58.4
1.4
West
100.0
4.8
29.3
65.9
South
100.0
0.7
10,5
88.8
Miami, FL
Core
80.7 19.3
100.0
East
100.0
12.2
87.8
North
5.5 7.5
86.9
3.9 49.4
46,7
West
2.1
97.9
12.4
38.0
49.6
South
100.0
1.1
14,3
84.8
Energy Cost and JAQ
29
Report # 3
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Exhibit 15
Summary of Annual HVAC Energy Use and Costs
for Single and Dual Air Handler Systems
Location
Annual Energy Use
Annual HVAC Energy Costs
HVAC System
Cooling
(kBTU/sf)
Heating
(kBTU/sf)
Total HVAC
(kBTU/sf)
Cooling
($/sf)
Heating
($/sf)
Total HVAC
($/sf)
Minneapolis, MN
VAV(FOAF)
20.0
20.9
50.6
0.49
0.10
0.79
VAV(FOAF) / Dual AHU
19.8
20.1
49.4
0.50
0.10
0.79
VAV(COA)
18.7
21.2
49.7
0.49
0.10
0.78
VAV(COA) / Dual AHU
19.1
20.3
48.9
0.50
0.10
0.79
Washington, DC
VAV(FOAF)
21.0
9.8
39.5
0.52
0.05
0.74
VAV(FOAF) / Dual AHU
21.1
9.1
39.1
0.53
0.04
0.76
VAV(COA)
20.3
9.9
38.9
0.52
0.05
0.74
VAV(COA) / Dual AHU
20.8
9.2
38.9
0.53
0.05
0.76
Miami, FL
VAV(FOAF)
28.5
0.5
38.3
0.62
0.00
0.81
VAV(FOAF) / Dual AHU
30.1
0.4
40.2
0.66
0.00
0.85
VAV(COA)
29.0
0.5
38.9
0.65
0.00
0.83
VAV(COA) / Dual AHU
30.2
0.4
40.3
0.66
0.00
0.86
Note 1: Total HVAC includes fan, heating, and cooling energy use.
Energy Cost and IAQ
30
Report# 3
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