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Budget HVAC System Types 1-11

This page defines the detailed design specifications for Budget HVAC System Types 1-11 required by ASHRAE 90.1 Performance Rating Method (PRM) Appendix G. These system types specify how to model each baseline HVAC system in EnergyPlus based on building type, cooling/heating requirements, and climate zone.

System Selection Table

Table: Budget HVAC System Types 1-11 (per Table 11.5.2-1)

System No.
System Type
Fan Control
Cooling Type
Heating Type

1

VAV with parallel fan-powered boxes

VAV

Chilled water

Electric resistance

2

VAV with reheat

VAV

Chilled water

Hot-water fossil fuel boiler

3

Packaged VAV with parallel fan-powered boxes

VAV

Direct expansion

Electric resistance

4

Packaged VAV with reheat

VAV

Direct expansion

Hot-water fossil fuel boiler

5

Two-pipe fan coil

Single- or two-speed fan

Chilled water

Electric resistance

6

Water-source heat pump

Single- or two-speed fan

Direct expansion

Electric heat pump and boiler

7

Four-pipe fan-coil

Single- or two-speed fan

Chilled water

Hot-water fossil fuel boiler

8

Packaged terminal heat pump

Single-speed fan

Direct expansion

Electric heat pump

9

Packaged rooftop heat pump

Single- or two-speed fan

Direct expansion

Electric heat pump

10

Packaged terminal air conditioner

Single-speed fan

Direct expansion

Hot-water fossil fuel boiler

11

Packaged rooftop air conditioner

Single- or two-speed fan

Direct expansion

Fossil fuel furnace

Detailed System Descriptions

System 1: VAV with Parallel Fan-Powered Boxes

Component Configuration:

  • Supply Fan: Variable volume fan with VFD (variable frequency drive)

  • Cooling: Chilled water loop (central plant)

  • Zone Heating: Parallel fan-powered boxes with electric resistance heating

  • Parallel Fan Sizing: 50% of zone peak design flow rate

  • Parallel Fan Power: 0.74 W/L/s (baseline specification)

  • Minimum Volume Setpoint: Ventilation requirement per ASHRAE 62.1 Simplified Procedure

  • Supply Air Temperature: Constant at design condition (no reset)

EnergyPlus Objects:

  • AirLoopHVAC (main air distribution)

  • Fan:VariableVolume (supply fan with VFD)

  • Coil:Cooling:Water (chilled water cooling coil)

  • SetpointManager:Scheduled (constant SAT control)

  • OutdoorAir:Mixer (outdoor air intake)

  • AirTerminal:SingleDuct:ParallelPIU:Reheat (parallel fan power box)

  • Fan:OnOff (parallel fan in each box)

  • Coil:Heating:Electric (electric resistance terminal heating)

  • PlantLoop (chilled water loop)

Application:

  • Large buildings with central cooling plant

  • Multiple thermal zones with individual zone heating control

  • Parallel fans maintain circulation during heating

  • Electric resistance heating at zone level

  • Demand-controlled ventilation capable

Climate Zone Application:

  • CZ 0-3A (electric heating with chilled water cooling)

Key Features:

  • Chilled water supply: 6.7°C, return: 13°C (fixed by specification)

  • No supply air temperature reset (constant design SAT)

  • Parallel fan operation at 50% zone flow during heating

  • Central cooling plant with floating condenser water control

System 2: VAV with Reheat

Component Configuration:

  • Supply Fan: Variable volume fan with VFD control

  • Cooling: Chilled water loop (central plant)

  • Zone Heating: Hot water reheat coils in VAV terminal units

  • Central Heating: Fossil fuel boiler (matches proposed design fuel)

  • Supply Air Temperature Reset: +2.8°C above design at minimum cooling load

  • Minimum Volume Setpoint: Larger of ventilation requirement or code minimum

EnergyPlus Objects:

  • AirLoopHVAC (air distribution system)

  • Fan:VariableVolume (supply fan with VFD)

  • Coil:Cooling:Water (chilled water cooling coil)

  • SetpointManager:Warmest (SAT reset control with bounds)

  • OutdoorAir:Mixer (outdoor air intake with economizer)

  • AirTerminal:SingleDuct:VAV:Reheat (VAV terminal with reheat)

  • Coil:Heating:Water (zone reheat coils)

  • PlantLoop (chilled water loop)

  • PlantLoop (hot water boiler loop)

  • Boiler:HotWater (natural draft fossil fuel boiler)

  • Pump:VariableSpeed (hot water and chilled water pumps)

Application:

  • Most common baseline system for large buildings

  • Multiple thermal zones served by single air loop

  • VAV terminals reduce air volume at part load

  • Hot water reheat provides zone-level control

  • Demand-controlled ventilation capable

  • Central chiller with cooling tower

Climate Zone Application:

  • CZ 3B-8 (fossil fuel heating via hot water loop)

Key Features:

  • Supply air temperature reset: +2.8°C at minimum cooling load

  • Variable volume fan with VFD saves energy at part load

  • Chilled water: 6.7°C supply, 13°C return

  • Hot water: 82°C supply, 54°C return

  • Reheat modulation at minimum damper position

  • Economizer integration for cooling assistance

System 3: Packaged VAV with Parallel Fan-Powered Boxes

Component Configuration:

  • Supply Fan: Variable volume fan with VFD control

  • Cooling: Direct expansion (DX) cooling coil (packaged unit)

  • Zone Heating: Parallel fan-powered boxes with electric resistance heating

  • Parallel Fan Sizing: 50% of zone peak design flow rate

  • Minimum Volume Setpoint: Ventilation requirement per ASHRAE 62.1

EnergyPlus Objects:

  • AirLoopHVAC (air distribution system)

  • Fan:VariableVolume (supply fan with VFD)

  • Coil:Cooling:DX:SingleSpeed (DX cooling coil)

  • SetpointManager:Scheduled (constant SAT control)

  • OutdoorAir:Mixer (outdoor air intake)

  • AirTerminal:SingleDuct:ParallelPIU:Reheat (parallel fan power box)

  • Fan:OnOff (parallel fan in each box)

  • Coil:Heating:Electric (electric resistance terminal heating)

Application:

  • Mid-size buildings with packaged rooftop DX unit

  • Multiple zones with parallel fan-powered terminal boxes

  • VAV fan modulation for energy savings

  • Electric resistance zone heating

Climate Zone Application:

  • CZ 0-3A (electric heating with DX cooling)

Key Features:

  • Packaged DX cooling (no central chiller)

  • Parallel fans at 50% zone design flow

  • Constant supply air temperature (no reset)

  • VAV fan with VFD modulation

System 4: Packaged VAV with Reheat

Component Configuration:

  • Supply Fan: Variable volume fan with VFD control

  • Cooling: Direct expansion (DX) cooling coil (packaged unit)

  • Zone Heating: Hot water reheat coils in VAV terminal units

  • Central Heating: Fossil fuel boiler

  • Supply Air Temperature Reset: +2.8°C above design at minimum cooling load

EnergyPlus Objects:

  • AirLoopHVAC (air distribution system)

  • Fan:VariableVolume (supply fan with VFD)

  • Coil:Cooling:DX:SingleSpeed (DX cooling coil)

  • SetpointManager:Warmest (SAT reset control with bounds)

  • OutdoorAir:Mixer (outdoor air intake with economizer)

  • AirTerminal:SingleDuct:VAV:Reheat (VAV terminal with reheat)

  • Coil:Heating:Water (zone reheat coils)

  • PlantLoop (hot water boiler loop)

  • Boiler:HotWater (natural draft fossil fuel boiler)

  • Pump:VariableSpeed (hot water pump)

Application:

  • Standard mid-size baseline system for most buildings

  • Packaged rooftop DX cooling with VAV distribution

  • VAV terminals reduce air volume at part load

  • Hot water reheat provides zone-level control

  • Most common system type in practice

Climate Zone Application:

  • CZ 3B-8 (fossil fuel heating via hot water loop)

Key Features:

  • Packaged DX cooling (no central chiller)

  • Supply air temperature reset: +2.8°C at minimum cooling load

  • Hot water: 82°C supply, 54°C return

  • VAV fan with VFD saves energy

  • Economizer for cooling assistance

System 5: Two-Pipe Fan Coil

Component Configuration:

  • Supply Fan: Single-speed or two-speed fan (within fan coil unit)

  • Cooling: Chilled water loop (central plant)

  • Heating: Electric resistance heating in fan coil unit

  • Fan Control: On/off or two-speed cycling

  • No central heating boiler required

EnergyPlus Objects:

  • PlantLoop (chilled water loop)

  • Pump:VariableSpeed (chilled water pump)

  • Chiller:Electric:EIR (central chiller, per Table 11.5.2-3)

  • CoolingTower:SingleSpeed or TwoSpeed (cooling tower)

  • ZoneHVAC:FourPipeFanCoil or equivalent zone equipment

  • Fan:OnOff (fan coil unit fan)

  • Coil:Cooling:Water (chilled water cooling in fan coil)

  • Coil:Heating:Electric (electric resistance heating in fan coil)

Application:

  • Medium-size buildings with chilled water loop

  • Individual zone fan coil units in each space

  • Two-pipe system (cooling only connection)

  • Electric resistance heating at zone level

Climate Zone Application:

  • CZ 0-3A (electric heating with chilled water cooling)

Key Features:

  • Central chiller with cooling tower

  • Chilled water: 6.7°C supply, 13°C return

  • Electric resistance heating in fan coil

  • On/off or two-speed fan control

  • Floating condenser water control

System 6: Water-Source Heat Pump

Component Configuration:

  • Supply Fan: Single-speed or two-speed fan (within heat pump unit)

  • Primary Heating/Cooling: Water-source heat pumps in each zone

  • Heat Rejection Loop: Water loop maintained at 16-32°C

  • Backup Heating: Boiler for supplemental heating

  • Fluid Cooler: For heat rejection to outdoor air

EnergyPlus Objects:

  • PlantLoop (heat pump water loop at 16-32°C)

  • HeatPump:WaterToWater:EquationFit:Heating (heating heat pumps)

  • HeatPump:WaterToWater:EquationFit:Cooling (cooling heat pumps)

  • Pump:VariableSpeed (heat pump loop pump with shutoff)

  • FluidCooler:TwoSpeed or EvaporativeCooler:IndirectResearch (fluid cooler)

  • Boiler:HotWater (supplemental heating, if included)

  • SetpointManager:Scheduled (loop temperature 16-32°C)

  • ZoneHVAC:WaterToAirHeatPump (zone-level heat pumps)

Application:

  • Buildings with electric heat pump primary heating/cooling

  • Closed-loop water-source heat pump systems

  • Backup heating for peak winter loads

  • Flexible heating and cooling year-round

Climate Zone Application:

  • All climate zones (CZ 0-8)

Key Features:

  • Heat pump loop maintained between 16-32°C continuously

  • Boiler activates when loop temperature drops to 16°C

  • Fluid cooler activates when loop temperature rises to 32°C

  • Individual zone control via water-source heat pumps

  • Pump flow shutoff at each heat pump when compressor OFF

System 7: Four-Pipe Fan-Coil

Component Configuration:

  • Supply Fan: Single-speed or two-speed fan (within fan coil unit)

  • Cooling: Chilled water loop (central plant)

  • Heating: Hot water loop (fossil fuel boiler)

  • Fan Control: On/off or two-speed cycling

  • Both heating and cooling connections available

EnergyPlus Objects:

  • PlantLoop (chilled water loop)

  • PlantLoop (hot water loop)

  • Pump:VariableSpeed (chilled water and hot water pumps)

  • Chiller:Electric:EIR (central chiller)

  • Boiler:HotWater (fossil fuel boiler)

  • CoolingTower:SingleSpeed or TwoSpeed (cooling tower)

  • ZoneHVAC:FourPipeFanCoil (four-pipe fan coil unit)

  • Fan:OnOff (fan coil unit fan)

  • Coil:Cooling:Water (chilled water cooling)

  • Coil:Heating:Water (hot water heating)

Application:

  • Medium to large buildings with dual water loops

  • Individual zone fan coil units in each space

  • Four-pipe system (separate heating and cooling connections)

  • Hot water heating and chilled water cooling

Climate Zone Application:

  • CZ 3B-8 (fossil fuel heating via hot water loop)

Key Features:

  • Central chiller with cooling tower

  • Central boiler for heating

  • Chilled water: 6.7°C supply, 13°C return

  • Hot water: 82°C supply, 54°C return

  • Individual zone control via two-pipe connections

  • On/off or two-speed fan control

System 8: Packaged Terminal Heat Pump

Component Configuration:

  • Supply Fan: Single-speed constant volume fan

  • Heating/Cooling: Air-source heat pump with DX coil (self-contained)

  • Supplemental Heating: Electric resistance coil

  • Thermostat Control: Multistage space thermostat

  • Self-contained unit (one per zone or room)

EnergyPlus Objects:

  • ZoneHVAC:PackagedTerminalHeatPump or AirLoopHVAC:UnitarySystem

  • Fan:OnOff (supply fan)

  • Coil:Heating:DX:SingleSpeed (heat pump heating)

  • Coil:Cooling:DX:SingleSpeed (heat pump cooling)

  • Coil:Heating:Electric (supplemental resistance heating)

  • ZoneControl:Thermostat (multistage thermostat)

Application:

  • Residential and small commercial buildings

  • One unit per thermal zone or room

  • All-electric self-contained systems

  • No central plant required

Climate Zone Application:

  • CZ 0-3A (electric heating climates)

Key Features:

  • Air-source heat pump with integrated cooling/heating

  • Auxiliary heat: Last thermostat stage AND outdoor air <4°C

  • Single-speed constant volume fan

  • Integrated defrost cycle

  • 100% efficient electric resistance auxiliary heating

System 9: Packaged Rooftop Heat Pump

Component Configuration:

  • Supply Fan: Single-speed or two-speed variable speed fan

  • Heating/Cooling: Air-source heat pump with DX coil (packaged unit)

  • Supplemental Heating: Electric resistance coil

  • Economizer: Outdoor air damper (if applicable)

  • Serves multiple zones from single rooftop unit

EnergyPlus Objects:

  • AirLoopHVAC (air loop)

  • Fan:VariableVolume or Fan:OnOff (supply fan)

  • Coil:Heating:DX:SingleSpeed (heat pump heating)

  • Coil:Cooling:DX:SingleSpeed (heat pump cooling)

  • Coil:Heating:Electric (supplemental resistance heating)

  • SetpointManager:Scheduled (heating and cooling setpoints)

  • OutdoorAir:Mixer (outdoor air intake, optional economizer)

Application:

  • Small to medium non-residential buildings

  • Packaged rooftop unit serving multiple zones

  • All-electric system (no fossil fuel)

  • Economizer capability available

Climate Zone Application:

  • CZ 0-3A (electric heating climates)

Key Features:

  • Air-source heat pump with variable speed fan

  • Packaged self-contained unit

  • Auxiliary heat activation: Last stage AND outdoor air <4°C

  • Optional economizer for cooling assistance

  • Multi-zone distribution from single unit

System 10: Packaged Terminal Air Conditioner

Component Configuration:

  • Supply Fan: Single-speed constant volume fan

  • Cooling: Direct expansion (DX) cooling coil (self-contained)

  • Heating: Hot water heating coil connected to building loop

  • No central chiller required

  • One unit per zone or room

EnergyPlus Objects:

  • ZoneHVAC:PackagedTerminalAirConditioner

  • Fan:OnOff (supply fan)

  • Coil:Cooling:DX:SingleSpeed (DX cooling)

  • Coil:Heating:Water (hot water heating from building loop)

  • ZoneControl:Thermostat (zone thermostat)

Application:

  • Residential buildings (apartments, hotels, dormitories)

  • Small commercial buildings

  • One unit per thermal zone

  • Hot water heating from building loop

Climate Zone Application:

  • CZ 3B-8 (fossil fuel heating via building hot water)

Key Features:

  • Packaged DX cooling (no central chiller)

  • Hot water connection to building boiler

  • Single-speed constant volume fan

  • Individual zone control

  • Simple thermostat control

System 11: Packaged Rooftop Air Conditioner

Component Configuration:

  • Supply Fan: Single-speed or two-speed variable speed fan

  • Cooling: Direct expansion (DX) cooling coil (packaged unit)

  • Heating: Gas-fired furnace (integral to rooftop unit)

  • Economizer: Outdoor air damper for cooling assistance

  • Serves multiple zones from single rooftop unit

EnergyPlus Objects:

  • AirLoopHVAC (air loop)

  • Fan:ConstantVolume or Fan:VariableVolume (supply fan)

  • Coil:Cooling:DX:SingleSpeed (DX cooling coil)

  • Coil:Heating:Gas or Coil:Heating:Fuel (gas furnace)

  • SetpointManager:Scheduled (heating and cooling setpoints)

  • OutdoorAir:Mixer (outdoor air intake with economizer)

Application:

  • Small to medium non-residential buildings

  • Packaged rooftop unit serving multiple zones

  • Gas furnace for heating (fossil fuel)

  • Economizer for cooling assistance

Climate Zone Application:

  • CZ 3B-8 (fossil fuel heating)

Key Features:

  • Packaged DX cooling with integral gas furnace

  • Economizer integration for cooling load reduction

  • Single or variable speed fan available

  • Multi-zone distribution from single rooftop unit

  • Outdoor air damper control

Component Specifications by System

Cooling System Efficiencies

Systems 3, 4, 6, 8, 9, 10, 11 (Direct Expansion):

  • Baseline COP: 3.0-3.5 typical for packaged AC

  • EIR = 1 / COP

  • Performance curves required for part-load modeling

Systems 1, 2, 5, 7 (Chilled Water):

  • Scroll chiller (≤352 kW individual): COP 3.2-3.8

  • Screw chiller (352-1055 kW individual): COP 3.5-4.0

  • Centrifugal chiller (≥1055 kW individual): COP 4.0-5.0

  • EIR = 1 / COP at rated conditions

Heating System Efficiencies

Systems 1, 3, 5, 8, 9 (Electric Heating):

  • Electric resistance: 100% efficiency (1.0)

  • Supplemental heat pump: 2.0-2.5 COP typical

Systems 2, 4, 7, 10, 11 (Fossil Fuel Heating):

  • Natural draft boiler: 80% AFUE typical (per ASHRAE 90.1 baseline)

  • Hot water: 82°C supply, 54°C return

  • Furnace: 78-80% efficiency typical

System 6 (Heat Pump):

  • Primary heat pump: 2.0-3.0 COP typical (varies by outdoor temperature)

  • Boiler backup: 80% AFUE typical

  • Boiler activation: When loop temperature <16°C

Fan Specifications

Systems 1, 2 (VAV with Central Chiller):

  • Type: Fan:VariableVolume with VFD

  • Power: 0.74 W/L/s (baseline specification)

  • Minimum flow: Per ventilation requirement

  • Modulation: VFD control for duct static pressure

Systems 3, 4 (Packaged VAV with DX):

  • Type: Fan:VariableVolume with VFD

  • Power: Per proposed design if specified

  • Minimum flow: 30% typical

  • Modulation: VFD for SAT setpoint or duct pressure

Systems 5, 7 (Four-Pipe and Two-Pipe Fan Coil):

  • Type: Fan:OnOff or two-speed fan

  • Speed: Single or two-speed operation

  • Control: Thermostat cycling control

  • Power: Per fan coil unit design

System 6 (Water-Source Heat Pump):

  • Type: Fan:OnOff or two-speed fan

  • Location: Within each zone heat pump unit

  • Control: Cycling with heat pump compressor

  • Power: Per unit design

Systems 8, 10 (Packaged Terminal Units):

  • Type: Fan:OnOff (single-speed)

  • Speed: Single-speed constant volume

  • Control: On/off cycling with thermostat

  • Power: Per unit design

Systems 9, 11 (Packaged Rooftop Units):

  • Type: Fan:ConstantVolume or Fan:VariableVolume

  • Speed: Single or variable with VFD

  • Control: Thermostat or economizer control

  • Power: Per rooftop unit design

EnergyPlus Simulation Inputs

Air Loop Configuration

AirLoopHVAC (Systems 2, 3, 4, 9, 11):

  • Outdoor Air Intake (with economizer damper if applicable)

  • Supply Fan (constant or variable volume)

  • Cooling Coil (DX or water-based)

  • Heating Coil (water-based or electric, if applicable)

  • Supply Air Nodes and Setpoint Managers

  • Thermal Zone Connections

Plant Loop Configuration

PlantLoop (Chilled Water, Systems 1, 2, 5, 7):

  • Pump (variable-speed)

  • Chiller(s) (count and type per Tables 11.5.2-2 and 11.5.2-3)

  • Supply nodes to air loops or fan coil units

  • Return nodes from zones

  • Floating condenser water control per Table 11.5.2-5

PlantLoop (Hot Water, Systems 2, 4, 6, 7, 10):

  • Pump (variable-speed)

  • Boiler (fossil fuel or electric)

  • Supply nodes to air loops, reheat coils, or fan coils

  • Return nodes

  • Temperature setpoint and reset control

PlantLoop (Heat Pump Loop, System 6):

  • Pump (variable-speed with shutoff)

  • Heat pumps (water-source type)

  • Fluid cooler for heat rejection

  • Boiler for supplemental heating (if included)

  • Loop temperature control 16-32°C

Climate Zone Definitions

CZ 0-3A: Electric Heating Zones

  • Mild to warm climates with minimal heating demand

  • Systems: 1, 3, 5, 6, 8, 9

  • Examples: Hawaii, Miami, Los Angeles, Phoenix, San Diego

CZ 3B-8: Fossil Fuel Heating Zones

  • Temperate to cold climates with heating demand

  • Systems: 2, 4, 7, 10, 11

  • Examples: Chicago, New York, Denver, Minneapolis, Seattle, Boston

Key Controls and Setpoints

Thermostat Setpoints (Budget Baseline):

  • Heating Setpoint: 21°C (70°F)

  • Cooling Setpoint: 24°C (75°F)

  • Deadband: Minimum 1.7°C (3°F)

Supply Air Temperature (SAT) Reset:

  • Systems 1, 3, 5, 6, 8, 9: Constant design temperature (no reset)

  • Systems 2, 4: Design + 2.8°C at minimum cooling load

  • Systems 7, 10, 11: Per unit control

System 2 and 4 SAT Reset Detail:

  • Base SAT: Design temperature (typically 13°C for chilled water, varies for DX)

  • Maximum SAT: Design + 2.8°C (typically 15.8°C)

  • Reset logic: Linear or staged based on cooling load

  • Control: SetpointManager:Warmest with bounds

Hot Water Temperature Reset (Systems 2, 4, 7, 10, 11):

  • Design: 82°C at peak heating

  • Reset: Outdoor air reset recommended

  • Example: 82°C at -15°C outdoor, 55°C at +15°C outdoor

  • Control: SetpointManager:OutdoorAirReset

Chilled Water Temperature (Systems 1, 2, 5, 7):

  • Design supply: 6.7°C (fixed by specification)

  • Design return: 13°C (fixed by specification)

  • No temperature reset (maintain constant 6.7°C)

  • Control: SetpointManager:Scheduled

Condenser Water Temperature (Systems 1, 2, 5, 7):

  • Floating control per Table 11.5.2-5

  • Design approach: 10.02 – (0.24 × WB)

  • Design temperature rise: 5.6°C (fixed)

  • Control: SetpointManager:OutdoorAirReset or scheduled

Economizer Operation (Systems 3, 4, 9, 11):

  • Dry Bulb Cutoff: 21°C outdoor (varies by climate per Table 6.5.1.1.3)

  • Enthalpy Cutoff: When outdoor air enthalpy exceeds return air

  • Integrated Mode: Damper modulation for cooling assistance

  • Type: Air (dry bulb) or Fluid (enthalpy) per climate zone

VAV Terminal Minimum Flow (Systems 1, 2, 3, 4):

  • Default Minimum: 50% of design air flow (can be reduced to 30% with justification)

  • Based on: Ventilation requirements per ASHRAE 62.1 Simplified Procedure

  • Calculation: MAX(ASHRAE 62.1 ventilation requirement, applicable code minimum)

  • Range: Typically 15-50% depending on zone requirements

Document Status: Complete Last Updated: November 2025 Covers: Budget HVAC System Types 1-11 (Table 11.5.2-1) Design Specifications for EnergyPlus

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