Airflow
These airflows are associated with this room and may be auto sized or user specified.
Room Design Airflow
The following airflows are associated with the room, they simulate the heat and moisture gains and losses from air.
Cooling Flow Rate
Typically Auto Size should be checked to size the design cooling supply airflow for each room. Override this value by un-checking the Auto Size box and specifying the room's supply airflow.
When the design flow rate has been specified here, it may result Sizing Factor Adjustment reported in the load component reports. The Cooling Design airflow can also be set to a relative percentage of the set Room Exhast Flow rate.
Heating Flow Rate
Typically Auto Size should be checked to size the design heating supply airflow for each room. Override this value by un-checking the Auto Size box and specifying the room's supply airflow.
When the design flow rate has been specified here, it may result Sizing Factor Adjustment reported in the load component reports. The Heating Design airflow can also be set to a relative percentage of the set Room Exhast Flow rate.
The main heating supply airflow refers to the hot deck or run-around deck of the following standard system types: Unit Heaters, Two-Fan Double Duct VAV, (Single-Fan) Double Duct VAV, Parallel Fan-Powered VAV, Series Fan-Powered VAV, and Terminal Air Blender.
Warning
For single duct /constant volume System Types (i.e. Variable-Temperature Constant Volume, Water Source Heat Pumps, Packaged Terminal Air Conditioners, Single Zone, etc.), be careful not to enter two different values for the Main Cooling Supply Airflow and the Main Heating Supply Airflow. Since the design cooling airflow must equal the design heating airflow for these types of systems, ensure that the same airflow is entered for both.
Ventilation
Ventilation is outdoor air brought into the building mechanically to meet ventilation requirements. View or modified these values from this tab. By default rooms inherit ventilation from the Airflows Template of the applied Room Type. The program has standard library members that include ventilation rate requirements from several sources. There are two categories for ventilation: ASHRAE 62.1 and 170 and General.
ASHRAE 62.1
People and area based ventilation rates are entered based on the space type selected. These values are determined by table 6-1 of ASHRAE standard 62.1, generally speaking, overrides should not be applied to the people and area based rates. Please note that ASHRAE 62.1 calculations must also be enabled at the system level (see Create Systems>Properties).
When a system has a mix of ASHRAE 62.1 and 170 space types attached, it is appropriate to turn on the 62.1 calculations at the system level. The 170 ventilation values will be viewed as Voz by the 62.1 zone and system level calculations. In this category, the ventilation library member details screen displays the following fields that must be defined:
Type
Space types as defined in standards such as ASHRAE 62.1, California Title 23, etc.
People Based Rate
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Default: Dependent on the space type selected. See Space Type library for more details
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Typical Range: 5 to 20 cfm/ person
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Min Max: 0 to 1000000
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Units: cfm/person; (L/s)/person
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The design outdoor air volume flow rate per person for this zone.
Area Based Rate
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Default: Dependent on the space type selected. See Space Type library for more details
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Typical Range: 0.06 to 0.18 cfm/ ft2
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Min Max: 0 to 1000000
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Units: cfm/ft2 ; (L/s)/m2
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The design outdoor air volume flow rate per floor area. The default rates are from table 6-1 of ASHRAE Standard 62.1- 2010.
Schedule
Schedules define the 24-hour percentage profiles for the variable loads in the room, such as people, lights, miscellaneous equipment, ventilation, infiltration, and more. The % Value entries for each hour in the schedule act as direct multipliers on the corresponding design value
For example, a schedule can be created to define the amount of heat gain due to lighting in a room if the amount of lighting for a room is entered as 250 Watts. This value is considered the design value for that room (i.e., the 100% value). If the schedule selected for the lighting in this room reads 50% for the period between 1 p.m. and 2 p.m., the lighting load in the room during that period is 125 Watts (or 50% of 250 Watts). The percentage of a given load present during time of space and coil peaks depends on the value entered in the associated schedule for that month and hour, as well as the cooling methodology selected. Choose a standard member from the Schedules Library supplied with the program or a custom schedule in the library.
Input Considerations:
Cooing Ez, Heating Ez and Er are defined from the Zone Properties along with Supply and Return Path.
ASHRAE 170
Ventilation rates, supply airflow rates, and in some cases room exhaust rates are entered based on the space type chosen. The values come from table 7-1 of ASHRAE standard 170-2013, Ventilation of Health Care Facilities.
When all the rooms attached to a system use ASHRAE 170 space types, the system level ventilation requirement is simply the sum of the room ventilation requirements. When a system has a mix of ASHRAE 170 and 62.1 space types attached, it is appropriate to turn on the 62.1 calculations at the system level. The 170 ventilation values will be viewed as Voz by the 62.1 zone and system level calculations.
When ASHRAE is selected in the room exhaust units field, all air coming into the space will be exhausted as room exhaust. This includes ventilation, infiltration, adjacent room air transfer, and supply airflow. This will cause the room to become negatively pressurized. A consequence of this is that the airflows will no longer balance at the system level, it is the responsibility of the designer to select the correct airflow balance at the system level.
As a reminder, when the airflow units are selected in terms of air changes per hour (ACH) the program views that as a minimum and not a fixed value.
Type
Space type selected from table 7-1 of ASHRAE 170-2013
Outside Air Flow Rate
These ventilation rates for heating and cooling are defined in rates of Air Changes/Hour.
Schedule
Schedules define the 24-hour percentage profiles for the variable loads in the room, such as people, lights, miscellaneous equipment, ventilation, infiltration, and more. The % Value entries for each hour in the schedule act as direct multipliers on the corresponding design value
For example, a schedule can be created to define the amount of heat gain due to lighting in a room if the amount of lighting for a room is entered as 250 Watts. This value is considered the design value for that room (i.e., the 100% value). If the schedule selected for the lighting in this room reads 50% for the period between 1 p.m. and 2 p.m., the lighting load in the room during that period is 125 Watts (or 50% of 250 Watts). The percentage of a given load present during time of space and coil peaks depends on the value entered in the associated schedule for that month and hour, as well as the cooling methodology selected. Choose a standard member from the Schedules Library supplied with the program or a custom schedule in the library.
Input Considerations:
Cooing Ez, Heating Ez and Er are defined from the Zone Properties along with Supply and Return Path.
General
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Default: Per ASHRAE 62.1- 2013 table 2 depending on the Application
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Typical Range: 15 to 60 cfm/person
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Min Max: 0 to 1000000
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Units: cfm/person, cfm/ft2; (L/s)/person, (L/s)/m2
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The standard library members under this category contain ventilation rates obtained from two sources: ASHRAE Standard 62.1-2013 and California Title 24-2010 minimum ventilation rates.
Type
Defines the name of the library member.
Outside Air Flow (rate, units)
The design outdoor air volume flow rate. The rate can be defined as a rate per area (flow/area), per person flow/person), air changes per hour or by the full design volume (flow).
Schedule
Schedules define the 24-hour percentage profiles for the variable loads in the room, such as people, lights, miscellaneous equipment, ventilation, infiltration, and more. The % Value entries for each hour in the schedule act as direct multipliers on the corresponding design value
For example, a schedule can be created to define the amount of heat gain due to lighting in a room if the amount of lighting for a room is entered as 250 Watts. This value is considered the design value for that room (i.e., the 100% value). If the schedule selected for the lighting in this room reads 50% for the period between 1 p.m. and 2 p.m., the lighting load in the room during that period is 125 Watts (or 50% of 250 Watts). The percentage of a given load present during time of space and coil peaks depends on the value entered in the associated schedule for that month and hour, as well as the cooling methodology selected. Choose a standard member from the Schedules Library supplied with the program or a custom schedule in the library.
Infiltration
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Default: NA
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Typical Range: NA
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Min Max: 0 to 1000000
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Units: cfm/ft2 floor, cfm/ft2 wall, cfm/ft2 surface, cfm, ACH; (m3/s)/m2 floor, (m3/s)/m2 wall, (m3/s)/m2 surface, m3/s
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Infiltration is the unintended flow of air from the outdoor environment directly into a room or thermal zone. Infiltration is generally caused by the opening and closing of exterior doors, cracks around windows, and even in very small amounts through building elements.
The basic equation used by EnergyPlus™ to calculate infiltration is:
Infiltration = (Idesign)(Fschedule) [A + B|(Tzone − Todb)| + C (WindSpeed) + D (Windspeed2)]
Where:
A = constant term coefficient
B = Temperature term coefficient
C= Velocity term coefficient
D = Velocity squared term coefficient
The default coefficients (A=1; B, C and D = 0) create a constant airflow infiltration.
The infiltration library member details screen displays the fields that must be defined:
Type
This field is used to select typical infiltration loads from the Internal & Airflow Loads Library. Choose a standard member from the library supplied with the program or create a custom library member.
Override these values directly on the Create Rooms or Airflow Template screens, if desired.
Flow Rate (value, units)
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Default: 0.6 ACH
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Typical Range: NA
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Min Max: 0 to 1000000
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Units: cfm/ft2 floor, cfm/ft2 wall, cfm/ft2 surface, cfm, ACH; (m3/s)/m2 floor, (m3/s)/m2 wall, (m3/s)/m2 surface, m3/s
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The infiltration rate that will be applied to the room. The rate can be defined as a rate per area of floor (cfm/sq. ft. floor), wall (cfm/sq. ft. wall), and air changes per hour or by the full design volume (cfm).
Schedule
Schedules define the 24-hour percentage profiles for the variable loads in the room, such as people, lights, miscellaneous equipment, ventilation, infiltration, and more. The % Value entries for each hour in the schedule act as direct multipliers on the corresponding design value
For example, a schedule can be created to define the amount of heat gain due to lighting in a room if the amount of lighting for a room is entered as 250 Watts. This value is considered the design value for that room (i.e., the 100% value). If the schedule selected for the lighting in this room reads 50% for the period between 1 p.m. and 2 p.m., the lighting load in the room during that period is 125 Watts (or 50% of 250 Watts). The percentage of a given load present during time of space and coil peaks depends on the value entered in the associated schedule for that month and hour, as well as the cooling methodology selected. Choose a standard member from the Schedules Library supplied with the program or a custom schedule in the library.
Room Exhaust
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Default: Per ASHRAE 62.1- 2013 table 6.5 depending on Occupancy category
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Typical Range: 0.25 to 1.5 cfm; 2.5 to 5 m3/s
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Min Max: 0 to 1000000
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Units: cfm/ft2 floor, cfm/ft2 wall, cfm/ft2 surface, cfm, ACH; (m3/s)/m2 floor, (m3/s)/m2 wall, (m3/s)/m2 surface, m3/s
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Room exhaust is room air that is directly exhausted from the room to the atmosphere. The program has standard library members that include typical zone exhaust rates from ASHRAE Standard 62.1-2013 Table 6.5.
Type
Defines the name of the room exhaust library member.
Flow Rate
Defines the exhaust rate that will be applied to a room. The rate can be defined as a rate per area of floor (cfm/sq. ft. floor), wall (cfm/sq. ft. wall), and air changes per hour or by the full design volume (cfm).
Schedule
Schedules define the 24-hour percentage profiles for the variable loads in the room, such as people, lights, miscellaneous equipment, ventilation, infiltration, and more. The % Value entries for each hour in the schedule act as direct multipliers on the corresponding design value
For example, a schedule can be created to define the amount of heat gain due to lighting in a room if the amount of lighting for a room is entered as 250 Watts. This value is considered the design value for that room (i.e., the 100% value). If the schedule selected for the lighting in this room reads 50% for the period between 1 p.m. and 2 p.m., the lighting load in the room during that period is 125 Watts (or 50% of 250 Watts). The percentage of a given load present during time of space and coil peaks depends on the value entered in the associated schedule for that month and hour, as well as the cooling methodology selected. Choose a standard member from the Schedules Library supplied with the program or a custom schedule in the library.
Room to Room Air Transfer
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Default: 0 cfm
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Typical Range: 2 cfm/bathroom fixture; 0.001 m3/s/bathroom fixture
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Min Max: 0 to 1000000
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Units: cfm/ft2 floor, cfm/ft2 wall, cfm/ft2 surface, cfm, ACH; (m3/s)/m2 floor, (m3/s)/m2 wall, (m3/s)/m2 surface, m3/s
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Room Air Transfer is air that is transferred from one room (source room) to another (receiving room). A receiving room can pull air from multiple source rooms. A receiving room can also be a source for another room. TRACE allows for transfer of more air than is brought into the source room(s). Therefore, care should be taken to ensure airflows balance as unexpected results could otherwise occur.
Source Room
Defines the room(s) that are transferring air into the current room.
Flow Rate
Defines the rate which air will be transferred into a room. The rate can be defined as a rate per area of floor (cfm/sq. ft. floor), per occupant (cfm / person), as a relative percentage of the Room Exhaust Rate, and air changes per hour or by a nominal design volume (cfm).
Schedule
Schedules define the 24-hour percentage profiles for the variable loads in the room, such as people, lights, miscellaneous equipment, ventilation, infiltration, and more. The % Value entries for each hour in the schedule act as direct multipliers on the corresponding design value
For example, a schedule can be created to define the amount of heat gain due to lighting in a room if the amount of lighting for a room is entered as 250 Watts. This value is considered the design value for that room (i.e., the 100% value). If the schedule selected for the lighting in this room reads 50% for the period between 1 p.m. and 2 p.m., the lighting load in the room during that period is 125 Watts (or 50% of 250 Watts). The percentage of a given load present during time of space and coil peaks depends on the value entered in the associated schedule for that month and hour, as well as the cooling methodology selected. Choose a standard member from the Schedules Library supplied with the program or a custom schedule in the library.
The schedule can also be set to match the of the Room Exhaust schedule by selecting the checkbox to the right.
