This group of building descriptors relate to HVAC systems at the zone level. There is not a one-to-one relationship between HVAC components in the proposed design and the standard design since the standard design system is determined from building type, size, and heating source. The applicability of each building descriptor for each of standard design systems is indicated in tables under the building descriptor standard design rules. Additions and alterations should follow the same requirements stated for newly constructed buildings proposed designs and newly constructed buildings standard designs unless otherwise noted in the descriptor.
THERMAL ZONE THERMOSTAT SETPOINT TOLERANCE
Applicability: All thermal zones.
Definition: The number of degrees that the room temperature, when occupied, must be above the cooling setpoint, or below the heating setpoint, for the zone load to be considered ‘unmet’.
Units: Degrees Fahrenheit (°F).
Input Restrictions: The prescribed value is _/-1°F. (This is equivalent to a +/- 1°F temperature tolerance around the heating and cooling setpoint.) No input is needed, and the prescribed value may not be overridden.
Standard Design: Same as the proposed design.
Thermostat Temperature Schedule
Applicability: All thermal zones.
Definition: An hourly schedule of thermostat set points.
Units: Data structure: temperature schedule.
Input Restrictions: Prescribed.
For healthcare facilities, the schedule is the same as the proposed design. For all nonresidential buildings, the schedule is based on the predominant schedule group for the building story or zone. See Chapter 2.3.3 space use classification considerations for details. For multifamily buildings, see Chapter 6 Multifamily Building Descriptors Reference.Standard Design: Schedules in the standard design shall be identical to the proposed design.
Terminal Type
Applicability: All thermal zones.
Definition: A terminal unit includes any device serving a zone (or group of zones collected in a thermal zone) that can vary air flow or reheat or recool or all three in response to the zone thermostat. This includes:
•None or Uncontrolled (applicable for single zone systems only)
•VAV reheat box
•VAV no-reheat box
•Series fan powered VAV box (with reheat)
•Parallel fan powered VAV box (with reheat)
•Dual duct mixing box (constant volume and VAV)
•Active Beam
Units: List (see above).
Input Restrictions: As designed.
Standard Design: Multiple zone systems 5 (packaged VAV) and 6 (built-up VAV) use VAV reheat boxes. See Chapter 5.1.2 HVAC System Map for a summary of the HVAC mapping.
For healthcare facilities, same as the Proposed Design.
Standard Design: Existing Buildings: Same as proposed design for unaltered components; same as newly constructed buildings rules for new secondary systems or terminal units.
This group of building descriptors applies to proposed design systems that have reheat coils at the zone level. The building descriptors are applicable for standard design systems 5 and 6.
Terminal Heat Type
Applicability: Systems that have reheat coils at the zone level.
Definition: The heating source for the terminal unit. This includes:
•Electric resistance
•Gas furnace
•Oil furnace
•Hot water
•Steam
Units: List (see above).
Input Restrictions: As designed.
Standard Design: Hot water for terminal units with reheat coils.
For healthcare facilities, same as the Proposed Design.
Terminal Heat Capacity
Applicability: Systems that have reheat coils at the zone level.
Definition: The heating capacity of the terminal heating source.
Units: Btu/h.
Input Restrictions: As designed.
Standard Design: The compliance software shall automatically size the terminal heating gross capacity to be 25 percent greater than the design loads.
For healthcare facilities, same as the Proposed Design.
Reheat Delta T
(
Applicability: Systems that have reheat coils at the zone level.
Definition: This is an alternate method to enter the terminal heat capacity, which can be calculated as follows:
Where:
•∆Treheat - Heat rise across the terminal unit heating coil F)
•Treheat - Heating air temperature at design (F)
•Tcool_supply - Supply air temperature at the heating coil (F)
•Qcoil - Heating coil load (Btu/h)
•CFM - Airflow (ft3/min)
Units: Degrees Fahrenheit (°F).
Input Restrictions: As designed but may need to be increased if zone unmet load hours are greater than 150.
Standard Design: Method not used for standard design. The temperature difference shall be no more than 40°F. See heat capacity.
For healthcare facilities, same as the Proposed Design.
Baseboard Capacity
Applicability: All thermal zones.
Definition: Total heating capacity of the baseboard unit(s).
Units: Btu/h.
Input Restrictions: As designed.
Standard Design: Not applicable.
Baseboard Heat Control
Applicability: All thermal zones with baseboard heating.
Definition: Defines the control scheme of base board heating as controlled by a space thermostat.
Units: List (fixed as By Space Thermostat).
Input Restrictions: Controlled by space thermostat is the only type allowed if baseboard heating is used.
Standard Design: Not applicable.
Baseboard Heat Source
Applicability: All thermal zones with furnaces or baseboard heating at the zone.
Definition: Heating source.
Units: List
•Electric heat
•Gas furnace
•Hot water
Input Restrictions: Electric resistance baseboard shall not be used for healthcare facilities space heating unless it meets one of the exceptions to Section 140.4(g) in the Energy Code.
Standard Design: Not applicable, except for healthcare facilities, same as the Proposed Design.
The following inputs are required when zone systems are connected to a VRF system (condensing unit).
Acceptance Test Required
Applicability: VRF.
Definition: Flag if acceptance test is required.
Units: Boolean.
Input Restrictions: None.
Standard Design: Not applicable.
VRF Zone System Type
Applicability: VRF.
Definition: Type of zone system.
Units: VRF.
Input Restrictions: VRF.
Standard Design: For healthcare facilities, same as the Proposed Design For all other cases, not applicable.
Count
Applicability: VRF.
Definition: The number of duplicate systems represented by the current system. All system attributes must be identical for multiple system assignment.
Units: None.
Input Restrictions: None.
Standard Design: For healthcare facilities, same as the Proposed Design. For all other cases, not applicable.
Indoor Unit Type
Applicability: VRF.
Definition: Ducted or Unducted.
Units: List – Ducted, Unducted.
Input Restrictions: None.
Standard Design: For healthcare facilities, same as the Proposed Design. For all other cases, not applicable.
Design Supply Air Temperature (Cooling)
Applicability: VRF.
Definition: Design SAT in cooling for the zone.
Units: Deg F.
Input Restrictions: As Designed.
Standard Design: For healthcare facilities, same as the Proposed Design. For all other cases, not applicable.
Design Supply Air Temperature (Heating)
Applicability: VRF.
Definition: Design SAT in heating for the zone.
Units: Deg F.
Input Restrictions: As Designed.
Standard Design: For healthcare facilities, same as the Proposed Design. For all other cases, not applicable.
Net Cooling Capacity
Applicability: VRF.
Definition: Net cooling capacity of the zone system (one system if count>1), which includes all cooling to the zone but excludes any fan motor heat.
Units: Btu/h.
Input Restrictions: None.
Standard Design: For healthcare facilities, same as the Proposed Design with adjustment to account for Standard Design fan heat. For all other cases, not applicable.
Net Heating Capacity
Applicability: VRF.
Definition: Net heating capacity of the zone system (one system if count>1), which includes all cooling to the zone but excludes any fan motor heat.
Units: Btu/h.
Input Restrictions: None.
Standard Design: For healthcare facilities, same as the Proposed Design with adjustment to account for Standard Design fan heat. For all other cases, not applicable.
Supply Fan Capacity for Cooling
Applicability: VRF.
Definition: The supply fan flow rate when the zone requires cooling.
Units: cfm (for each mode).
Input Restrictions: Not applicable. The cooling airflow is set to be the same as the system design airflow.
Standard Design: For healthcare facilities, same as the Proposed Design. For all other cases, not applicable.
Supply Fan Capacity for Heating
Applicability: VRF.
Definition: The supply fan flow rate when the zone requires heating.
Units: cfm (for each mode).
Input Restrictions: Not applicable. The heating airflow is set to be the same as the system design airflow.
Standard Design: For healthcare facilities, same as the Proposed Design. For all other cases, not applicable.
Supply Fan Capacity for Deadband
Applicability: VRF.
Definition: Identify the supply fan airflow rate in deadband (floating) mode.
Units: cfm (for each mode).
Input Restrictions: If a multi-speed or variable speed fan is defined for the VRF fan coil, this will be set to the minimum fan flow. Otherwise, it is set to the design airflow.
Standard Design: For healthcare facilities, same as the Proposed Design. For all other cases, not applicable.
Supply Temp Control
Applicability: VRF.
Definition: The method of controlling the system supply air temperature.
Units: List (Constant, reset by outside air, reset by demand).
Input Restrictions: No Supply Air Temperature Control.
Standard Design: For healthcare facilities, same as the Proposed Design. For all other cases, not applicable.
Auxiliary Power When On
Applicability: VRF.
Definition: The parasitic electrical energy use of the zone terminal unit when either terminal unit coil is operating.
Units: Watts or Btu/h.
Input Restrictions: None.
Standard Design: For healthcare facilities, same as the Proposed Design. For all other cases, not applicable.
Auxiliary Power When Off
Applicability: VRF.
Definition: The parasitic electrical energy use of the zone terminal unit when the terminal unit coils are off.
Units: Watts or Btu/h.
Input Restrictions: None.
Standard Design: Not applicable.
Supply Fan Airflow Capacity Control
Applicability: VRF.
Definition: The supply fan airflow shall be capable of specifying one (constant volume), two or variable speed control and power relationships for each fan unit.
Units: List: Subset of fan capacity control options: constant volume, two speed, and variable speed.
Input Restrictions: As designed. Minimum airflow capacity to be no less than 50% flow.
Standard Design: For healthcare facilities, same as the Proposed Design. For all other cases, not applicable.
Variable Air Volume (VAV) Air Flow
This group of building descriptors applies to proposed systems that vary the volume of air at the zone level.
Design Airflow
Applicability: Systems that vary the volume of air at the zone level.
Definition: The air delivery rate at design conditions.
Units: CFM.
Input Restrictions: As designed.
If the unmet load hours in the proposed design are greater than 150, the user may have to modify the design airflow value manually.
Standard Design: For healthcare facilities, same as the Proposed Design. For systems 5 and 6, the compliance software shall automatically size the terminal airflow to meet both:
The standard design peak cooling load based on a supply-air-to-room-air temperature difference of 20°F for exterior zones or 15°F for interior zones, the required ventilation air from Table 120.1-A of the Energy Code, or makeup air, whichever is greater.
The standard design peak heating load assuming a 95°F supply air temperature.
An exterior zone is a thermal zone that has any exterior walls, and a non-zero amount of vertical exterior fenestration (windows). Any zone that does not meet the definition of an exterior zone is an interior zone.
Terminal Minimum Airflow
Applicability: Systems that vary the volume of air at the zone level
Definition: The minimum airflow that will be delivered by a terminal unit.
Units: Unitless fraction of airflow.
Input Restrictions: Input must be greater than or equal to the outside air ventilation rate
Standard Design: For healthcare facilities, same as the Proposed Design. For systems 5 and 6, packaged VAV units and built-up VAV air handling units, set the minimum airflow to be the maximum of the minimum outside air ventilation rate or 10% of the design airflow..
For laboratories, the minimum airflow fraction shall be fixed at a value equivalent to the greater of the proposed design minimum exhaust requirements or the minimum ventilation rate.
Terminal Heating Control Type
Applicability: VAV boxes with reheat
Definition: The control strategy for the heating mode.
Single Maximum:
In the single maximum control mode, the airflow is set to a minimum constant value in both the deadband and heating mode. This airflow can vary but is typically 30 to 50 percent of maximum. This control mode typically has a higher minimum airflow than the minimum used in the dual maximum below, resulting in more frequent reheat.
Figure 9: Single Maximum VAV Box Control
Source: California Energy Commission
Dual Maximum:
Raises the supply air temperature (SAT) as the first stage of heating and increases the airflow to the zone as the second stage of heating.
The first stage of heating consists of modulating the zone supply air temperature setpoint up to a maximum setpoint no larger than 95°F while the airflow is maintained at the dead band flow rate.
The second stage of heating consists of modulating the airflow rate from the dead band flow rate up to the heating maximum flow rate (50 percent of design flow rate).
Figure 10: Dual Maximum Control Sequence
Source: California Energy Commission
Units: List:
•Single maximum
•Dual maximum
Input Restrictions: Fixed
at single maximum if control system type is not direct digital control
(DDC) control to the zone level
Standard Design: Design: For
healthcare facilities, same as the Proposed Design. For all other cases, dual
maximum.
Fan Powered Boxes
Fan Powered Box Type
Applicability: Thermal zones that have fan powered boxes.
Definition: Defines the type of fan-powered induction box.
Units: List :
•Series
•Parallel
Input Restrictions: As designed.
Standard Design: Not applicable.
For healthcare facilities, same as the proposed design.
Terminal Fan Power
Applicability: Thermal zones that have fan powered boxes.
Definition: Rated power input of the fan in a fan-powered box.
Units: W/cfm.
Input Restrictions: As designed.
Standard Design: Not applicable.
For healthcare facilities, same as the Proposed Design.
Fan Powered Box Induced Air Zone
Applicability: Thermal zones that have fan powered boxes.
Definition: Zone from which a series or parallel fan-powered box draws its air.
Units: List name of thermal zones included in the building model.
Input Restrictions: As designed.
Standard Design: Not applicable.
For healthcare facilities, same as the proposed design.
Parallel Powered Induction Unit (PIU) Induction Ratio
Applicability: Thermal zones that have fan-powered boxes.
Definition: Ratio of induction-side airflow of a fan-powered box at design heating conditions to the primary airflow.
Units: Ratio.
Input Restrictions: As designed.
Standard Design: Not applicable.
For healthcare facilities, same as the proposed design.
Parallel Fan Box Control Method
Applicability: Thermal zones that have parallel fan powered boxes.
Definition: The control scheme used to define when a parallel fan-powered box fans operate.
Units: List: Flow Fraction, Thermostat Offset.
Input Restrictions: None.
Standard Design: Not applicable.
For healthcare facilities, same as the proposed design.
Parallel Fan Box Flow fraction
Applicability: Thermal zones that have parallel fan powered boxes with ‘Flow Fraction’ control method.
Definition: If the primary airflow to the box is above this fraction, the parallel fan is off. If the fraction is set to 0, the fan will only run when there is a call for heating in the zone. Otherwise, the parallel box fan will run according to the system availability schedule, or if activated by night-cycle control.
Units: Ratio.
Input Restrictions: 0 to 1.
Standard Design: Not applicable.
For healthcare facilities, same as the proposed design.
Parallel Fan Box Thermostat Offset
Applicability: Thermal zones that have parallel fan powered boxes with “Thermostat Offset” control method.
Definition: If the zone temperature is equal to or below the heating setpoint plus this offset, the parallel fan will run according to the system availability schedule, or if activated by night-cycle control. Otherwise, the parallel fan is off.
Units: Degrees Fahrenheit (°F).
Input Restrictions: 2°F above the heating setpoint schedule.
Standard Design: Not applicable.
For healthcare facilities, same as the proposed design.
Terminal Ventilation Only Control Schedule
Applicability: Systems that vary the volume of air at the zone level and supply ventilation only air to a space.
Definition: The input shall control the terminal unit to vary airflow to match ventilation requirements only, by means of schedule or link to a space ventilation object which specifies the ventilation airflow requirements.
Units: User selection for ventilation only controls.
Input Restrictions: Yes/No.
Standard Design: Not applicable.
Standard Design: Existing Buildings: Not applicable.
This group of building descriptors describes the rate of exhaust and the schedule or control for this exhaust. An exhaust system can serve one thermal zone or multiple thermal zones. Energy is summed for the exhaust system level, not the thermal zone level.
This chapter also contains unique inputs for kitchen exhaust systems that must meet requirements of §140.9 of the Energy Code.
Kitchen Exhaust Hood Length
Applicability: Exhaust fans in spaces of type kitchen, commercial food preparation.
Definition: The exhaust hood length.
Units: ft.
Input Restrictions: As designed.
Standard Design: Same as the proposed design.
Kitchen Exhaust Hood Style
Applicability: Exhaust fans in spaces of type kitchen, commercial food preparation.
Definition: The hood style as defined in Table 140.9-C of the Energy Code.
Units: List:
• Wall-mounted canopy
• Single island
• Double island
• Eyebrow
• Backshelf/Passover
Input Restrictions: As designed.
Standard Design: Same as the proposed design.
Kitchen Exhaust Hood Cooking Duty
Applicability: Exhaust fans in spaces of type kitchen, commercial food preparation.
Definition: The hood cooking duty as defined in Table 140.9-C of the Energy Code.
Units: List:
• Light-duty
• Medium-duty
• Heavy-duty
• Extra heavy-duty
Input Restrictions: As designed.
Standard Design: Same as the proposed design.
Exhaust Fan Name
Applicability: All thermal zones.
Definition: A reference to an exhaust fan system that serves the thermal zone.
Units: Text or other unique reference to an exhaust fan system defined in the secondary systems section.
Input Restrictions: As designed.
Standard Design: Same as the proposed design.
Exhaust Air Flow Rate
Applicability: All thermal zones.
Definition: Rate of exhaust from a thermal zone.
Units: Cfm.
Input Restrictions: For nonresidential and hotel/motel spaces, Proposed exhaust air flow rate must meet the minimum exhaust requirements of §120.1(c)4 for applicable spaces in Table 120.1-B.
For laboratory spaces and zones, the design exhaust air flow rate is specified by the user, but a warning shall be posted if less than 1 cfm/ft2.
Standard Design: Same as the proposed design but not above the maximum of the standard design exhaust rates listed in Appendix 5.4A for spaces that do not include covered processes. Exception for buildings with over 5,000 cfm of kitchen exhaust; the standard design is a function of the kitchen exhaust hood length, kitchen exhaust hood style, and kitchen exhaust hood cooking duty, and is determined by Title 24 Energy Code, Table 140.9-A.
For lab exhaust systems, the standard design exhaust flow rate is the same as the proposed.
For healthcare facilities, same as the Proposed Design.
Applicability: All laboratory zones.
Definition: Minimum rate of exhaust from a zone.
Units: cfm/ft2.
Input Restrictions: As designed for non-process zones.
For laboratory zones, the exhaust air flow rate is the maximum of the hood scheduled exhaust air flow rate and the minimum ventilation rate. A warning is posted if the minimum exhaust rate is 2 ACH or less.
Standard Design: For laboratory systems with minimum exhaust flow rates exceeding 10 ACH exhaust, the exhaust minimum air flow rate is equal to the proposed design minimum. For VAV laboratory systems with variable flow and variable speed drive exhaust fan control, the exhaust minimum air flow rate is the proposed design minimum exhaust air flow rate.
Exhaust Fan Schedule
Applicability: All thermal zones.
Definition: Schedule indicating the pattern of use for exhaust air from the thermal zone.
Units: Data structure: schedule, fraction.
Input Restrictions: For healthcare facilities, the schedule is the same as the proposed design. For all nonresidential buildings, the schedule is based on the predominant schedule group for the building story or zone. See Chapter 2.3.3 Space Use Classification Considerations for details. For multifamily buildings, see Chapter 6 Multifamily Building Descriptors Reference.
Exhaust schedules for commercial kitchen exhaust and laboratory processes are prescribed in Appendix 5.4B. For laboratory systems if the exhaust is variable flow, the compliance software shall automatically use either the no sash control or sash control laboratory variable exhaust schedule or a volume-weighted interpolated average of the two schedules if only a fraction of the exhaust hoods have sash control.
Standard Design: Same as the proposed design for non-covered process spaces.
Exhaust schedules for kitchen exhaust hoods are prescribed and specified in Appendix 5.4B.
For laboratory spaces, the standard design is constant volume if the proposed exhaust system is constant volume and has a minimum exhaust air flow rate greater than 10 ACH. Otherwise, the standard design is variable volume. If the standard design is variable volume and the proposed laboratory space is fume hood intense (as defined in Standards Table 140.9-C of the Energy Code) then the standard design will use a modified VAV schedule for hoods with sash controls, volume-weighted by the fraction of exhaust that is served by exhaust hoods with vertical-only sashes. If the standard design is variable volume and the proposed space is not fume hood intense then the standard design shall use the VAV exhaust schedule for non-controlled sashes.
For healthcare facilities, same as the proposed design.
Exhaust Fan Fraction Sash Control
Applicability: Zones with laboratory exhaust hoods with vertical sashes.
Definition: The airflow-weighted fraction of exhaust hoods with vertical sashes that have automatic sash controls. This input is needed to appropriately model cases where only a fraction of the exhaust hoods that have automatic sash controls.
Units: Fraction.
Input Restrictions: As Designed (between 0 and 1).
Standard Design: 1 if sash controls are required for the laboratory space (per Table 140.9-D of the Energy Code).
For healthcare facilities, same as the Proposed Design.
Standard Design: Existing Buildings: As Designed (between 0 and 1).
Ventilation Source
Applicability: All thermal zones.
Definition: The source of ventilation for a thermal zone. The choices are:
• None (ventilation not provided directly to the zone)
• Natural (by operable openings)
• Forced (by fan)
Units: List: None, Natural, or Forced.
Input Restrictions: For hotel/motel guest rooms, can be ‘Natural’ or ‘Forced’.
For all other occupancies, must be ‘Forced’.
Standard Design:
For hotel/motel guest rooms, same as the proposed.
For other occupancies, Forced if the proposed design is also ‘Forced’, otherwise ‘None’.
Applicability: Thermal zones with special ventilation requirements, such as a process space, which have no defined requirements in Title 24.
Definition: Minimum ventilation rates for:
• Title 24 (default)
• Other
Units: List: See above.
Input Restrictions: None.
User should be prepared to show justification for not using Title 24 ventilation source. If ‘Other’ is used, the user must enter a description of which standard applies, such as OSHPD3, Animal Shelter, etc.
Standard Design: Same as proposed.
Standard Design: Existing Buildings: Same as proposed.
Design Ventilation Rate
Applicability: All thermal zones.
Definition: The quantity of ventilation air that is provided to the space for the specified thermal zone at the design condition.
Units: CFM.
Input Restrictions:
To accommodate transfer air requirements for makeup air for exhaust from other zones, the design ventilation rate may be between 95 percent and 110 percent of code required ventilation rates for on a building story without penalty.
Ventilation rates below 95% of the code required ventilation rate for a building story are not allowed.
If the ventilation source is natural for hotel/motel guestroom spaces, then the proposed design ventilation will be modeled as infiltration.
Standard Design: For labs and healthcare facilities, same as the Proposed Design.
If the total exhaust airflow requirement on the building floor does not exceed the total ventilation requirement, then the standard design outside air ventilation rate shall be the same as the proposed. The standard design ventilation rate is the same as the proposed but is constrained to be between 95% and 110% of the code ventilation requirement. If the proposed ventilation rate exceeds the limits above, the standard design ventilation rate for each space shall be the proposed rate uniformly reduced such that the total ventilation air delivered to the building story is equal to the maximum allowed ventilation air rate:
Design Ventilation Ratestd = Design Ventilation Rateprop x ( BFVentstd / BFVentprop )
Where:
BFVentstd is 110% of building floor design minimum required ventilation flow, as specified by the Energy Code, and
BFVentprop is the building floor design ventilation flow for the proposed design.
Standard Design: Existing Buildings: Same as the proposed, if unaltered. If space type is altered such that different ventilation rate requirements apply, the outside air ventilation rate should follow the same rules as for newly constructed buildings.
Building Floor Ventilation Requirement
Applicability: Internal variable, calculated for each building story (floor).
Definition: The total outside air ventilation airflow requirement for all spaces on a building story or floor.
This is calculated by summing the ventilation levels for each space and comparing it to the minimum required ventilation rate and the design exhaust air flow requirements.
Units: cfm (ft3/min).
Input Restrictions: Not a user input; derived by summing the ventilation and exhaust air flows from all spaces on the building floor.
Standard Design: For labs and healthcare facilities, same as the Proposed Design.
For all other spaces:
This is calculated by the following procedure:
Ø Calculate the proposed ventilation for the building story as the sum of design ventilation flow for each space included on a building story, including all conditioned spaces except space designated as lab space.
Ø Calculate the proposed exhaust for the building story as the sum of design exhaust flow for each space on the building story, including all conditioned spaces except spaces designated as lab space.
Ø Calculate the code minimum ventilation requirement as the sum of all minimum required ventilation airflows, as defined by Appendix 5.4A, for all spaces in the building story.
Ø If the proposed exhaust is greater than the code minimum ventilation rate, then:
o Total standard design building story ventilation requirement shall be: Standard ventilation = Min (proposed ventilation, code minimum exhaust x 1.2)
Otherwise:
Ø Standard ventilation = Min (code minimum ventilation, proposed ventilation)
Minimum Ventilation Rate
Applicability: All thermal zones that have variable ventilation control.
Definition: The minimum quantity of ventilation air that must be provided to the space when it is occupied.
Units: cfm (ft3/min).
Input Restrictions: As designed but not lower than code minimum (default value).
The default value shall be the larger of 15 cfm times the design occupancy times the occupancy fraction or the conditioned floor area times the applicable ventilation rate from Appendix 5.4A.
For spaces where demand control ventilation is installed, the minimum ventilation rate is specified by the greater of the rate in Table 120.1-A or 15 cfm times the scheduled occupancy for that hour.
For hotel/motel guestroom spaces where the proposed design ventilation source is natural ventilation, the minimum ventilation rate will be modeled as infiltration.
Standard Design: For labs and healthcare facilities, same as the Proposed Design.
For spaces where demand control ventilation is required, the minimum ventilation rate is specified by the greater of the rate in Appendix 5.4A or 15 cfm times the scheduled occupancy for that hour.
Ventilation Control Method
Applicability: All thermal zones
Definition: The method used to determine outside air ventilation needed for each hour in the simulation.
This information is reported to the system serving the zone. The method of controlling outside air at the system level in response to this information is discussed under secondary systems. Options at the zone level are:
• CO2 sensors in the space: The outside air is varied to maintain a maximum CO2 concentration in the space. This shall be approximated by multiplying the ventilation rate per occupant times the number of occupants for that hour. (When turnstile counts are used to automatically adjust ventilation levels based on occupancy, this method may also be used.)
• Fixed ventilation rate: Outside air is delivered to the zone at a constant rate and is equal to the design ventilation rate (see above).
Units: List (see above)
Input Restrictions: As designed
If the space includes a design occupant density greater than or equal to 25 persons per 1,000 ft2, and the system includes an airside economizer, or if the design airflow rate for the system exceeds 3,000 cfm, the input is restricted to CO2 sensors in the space.
Note: a classroom space greater than 750 ft2must have an occupancy sensor for ventilation control and setback to meet the mandatory Title 24 Standards requirements of §120.2(e)3. This requirement should be indicated on the appropriate compliance form submittal.
Standard Design: For healthcare facilities, same as the Proposed Design.
If the default occupancy for the specified space function from Appendix 5.4B is greater than or equal to 25 persons per 1,000 ft² and the system includes an airside economizer, set control method to CO2 sensors in the space. Otherwise, set to fixed ventilation rate.
Demand Control Ventilation (DCV) Minimum Ventilation Schedule
Applicability: All projects.
Definition: The DCV minimum schedule modifies the ventilation airflow rate for a given space based on the controllability of a ventilation system and the allowance of the energy standard for the space to modulate outdoor air. The schedule is dependent on the occupancy schedule for a space type and shall include a lower limit to airflow based on spaces where minimum ventilation air has a lower limit greater than 0.
Units: Data Structure: schedule, fractional.
Input Restrictions: The DCV minimum ventilation schedule is prescribed for California compliance based on a space type.
Standard Design: DCV minimum ventilation schedules shall be used in all spaces where DCV is a mandatory requirement. DCV minimum ventilation schedules can be different between the proposed and standard design buildings based on a proposed building adopting DCV control in spaces the energy standard does not require.
Standard Design: Existing Buildings: Same as proposed.