Baseline HVAC Systems

This page defines the baseline HVAC systems required by ASHRAE 90.1 Performance Rating Method (PRM) Appendix G. The system selection is based on building type, number of floors, floor area, and climate zone.

System Selection Table

ASHRAE 90.1 Baseline HVAC Systems (Systems 1-13)

System No.	System Name	Type	Fan Control	Cooling Type	Heating Type	Application
1	PTAC	Packaged Terminal AC	Constant Volume	Direct Expansion	Hot Water Boiler	Residential; Small buildings
2	PTHP	Packaged Terminal Heat Pump	Constant Volume	Direct Expansion	Electric Heat Pump	Residential with electric heating
3	PSZ-AC	Packaged Single Zone AC	Constant Volume	Direct Expansion	Gas Furnace	Small non-residential; ≤3 floors; <2,300 m²
4	PSZ-HP	Packaged Single Zone Heat Pump	Constant Volume	Heat Pump	Electric Heat Pump	All climates with electric heating
5	PVAV with Reheat	Packaged VAV Reheat	VAV	Direct Expansion	Hot Water Reheat	Mid-size buildings; 4-5 floors; 2,300-14,000 m²
6	PVAV with PFP	Packaged VAV with PFP Boxes	VAV	Direct Expansion	Electric Resistance	Mid-size buildings; electric heating
7	VAV Reheat	VAV with Reheat	VAV	Chilled Water	Hot Water Reheat	Large buildings; >5 floors; >14,000 m²
8	VAV PFP Boxes	VAV with PFP Boxes	VAV	Chilled Water	Electric Resistance	Large buildings; electric heating
9	Gas Furnace	Warm Air Furnace (Gas)	Constant Volume	None	Gas Furnace	Heating and Ventilation Only
10	Electric Furnace	Warm Air Furnace (Electric)	Constant Volume	None	Electric Resistance	Heating and Ventilation Only (Electric)
11	SZ-VAV	Single Zone VAV	VAV	Chilled Water	Variable (Climate Dependent)	Medium buildings; single thermal zone
12	SZ-CV-HW	Single Zone Constant Volume	Constant Volume	Chilled Water	Hot Water Boiler	Medium buildings; constant volume system
13	SZ-CV-ER	Single Zone Constant Volume	Constant Volume	Chilled Water	Electric Resistance	Medium buildings; electric heating

Detailed System Descriptions

System 1: PTAC (Packaged Terminal Air Conditioner)

Component Configuration:

• Supply Fan: Single-speed constant volume fan

• Cooling: Direct expansion (DX) cooling coil

• Heating: Hot water heating coil connected to building hot water loop

• Controls: Thermostat with heating/cooling setpoint

EnergyPlus Objects:

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

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

• Coil:Heating:Water (heating coil)

• ZoneHVAC:PackagedTerminalAirConditioner

Application:

• Residential buildings (apartments, hotels, dormitories)

• Small commercial buildings

• One unit per thermal zone

Climate Zone Application:

• All climate zones with fossil fuel heating (CZ 3B-8)

• Electric heating alternative (PTHP) for CZ 0-3A

System 2: PTHP (Packaged Terminal Heat Pump)

Component Configuration:

• Supply Fan: Single-speed constant volume fan

• Cooling/Heating: Air-source heat pump with DX coil

• Supplemental Heating: Electric resistance coil for heating

EnergyPlus Objects:

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

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

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

• Coil:Heating:Electric (supplemental heating)

• ZoneHVAC:PackagedTerminalHeatPump

Application:

• Residential buildings in mild to warm climates

• Electric heating alternative to PTAC

• One unit per thermal zone

Climate Zone Application:

• CZ 0-3A (mild climates)

System 3: PSZ-AC (Packaged Rooftop Air Conditioner)

Component Configuration:

• Supply Fan: Single-speed constant volume fan

• Cooling: Direct expansion cooling coil

• Heating: Gas-fired furnace

• Controls: Thermostat; economizer for cooling

EnergyPlus Objects:

• Fan:ConstantVolume (supply fan)

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

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

• AirLoopHVAC with outdoor air damper

Application:

• Small non-residential buildings

• 3 floors or fewer

• Floor area < 2,300 m² (24,800 ft²)

• Can serve multiple zones from single rooftop unit

Climate Zone Application:

• CZ 3B-8 (fossil fuel heating)

System 4: PSZ-HP (Packaged Rooftop Heat Pump)

Component Configuration:

• Supply Fan: Single-speed constant volume fan

• Cooling/Heating: Air-source heat pump with DX coil

• Supplemental Heating: Electric resistance coil

EnergyPlus Objects:

• Fan:ConstantVolume (supply fan)

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

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

• Coil:Heating:Electric (supplemental heating)

• AirLoopHVAC with outdoor air damper

Application:

• Small non-residential buildings with electric heating

• Alternative to PSZ-AC in areas without gas availability

Climate Zone Application:

• CZ 0-3A (mild climates with electric heating)

System 5: PVAV with Reheat (Packaged VAV with Reheat)

Component Configuration:

• Supply Fan: Variable volume fan with VFD control

• Cooling: Direct expansion cooling coil

• Zone Heating: Hot water reheat coils in each zone

• Controls: VAV terminal units with heating/cooling logic

EnergyPlus Objects:

• Fan:VariableVolume (supply fan with VFD)

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

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

• Coil:Heating:Water (zone reheat coils)

• PlantLoop (hot water loop)

Application:

• Mid-size non-residential buildings

• 4-5 floors or 5 floors with 2,300-14,000 m² floor area

• Multiple thermal zones served by single air loop

• VAV terminals reduce air volume at part load

Climate Zone Application:

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

Key Features:

• Demand-controlled ventilation capability

• Energy recovery potential

• VFD saves energy at part load

System 6: PVAV with PFP Boxes (Parallel Fan Power Boxes)

Component Configuration:

• Supply Fan: Variable volume fan with VFD control

• Cooling: Direct expansion cooling coil

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

• Controls: VAV terminal units with parallel fan operation

EnergyPlus Objects:

• Fan:VariableVolume (supply fan)

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

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

• Coil:Heating:Electric or Coil:Heating:Water (terminal heating)

Application:

• Mid-size buildings with electric heating preference

• Improves comfort in perimeter zones

• Parallel fan boxes maintain circulation

Climate Zone Application:

• CZ 0-3A (electric heating)

System 7: VAV with Reheat (Central Chilled Water System)

Component Configuration:

• Supply Fan: Variable volume fan with VFD control

• Cooling: Central chiller with chilled water loop

• Zone Heating: Hot water reheat coils in VAV terminals

• Central Heating: Gas or oil-fired boiler

• Condenser Heat Rejection: Cooling tower

EnergyPlus Objects:

• Fan:VariableVolume (supply fan)

• Coil:Cooling:Water (cooling coil on air loop)

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

• Chiller:Electric:EIR (centrifugal or screw chiller)

• Boiler:HotWater (heating boiler)

• CoolingTower:SingleSpeed or CoolingTower:TwoSpeed

• PlantLoop (chilled water and condenser water loops)

Application:

• Large buildings

• 5 floors or >14,000 m² floor area

• Most efficient for large multi-zone buildings

• Serves multiple air handling units

Climate Zone Application:

• CZ 3B-8 (fossil fuel heating)

Key Features:

• Centralized cooling for multiple zones

• Demand-controlled ventilation

• Energy recovery with heat wheel capability

• VFD reduces fan energy at part load

System 8: VAV with PFP Boxes (Central Chilled Water)

Component Configuration:

• Supply Fan: Variable volume fan with VFD control

• Cooling: Central chiller with chilled water loop

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

• Central Heating: Not used (zone heating only)

• Condenser Heat Rejection: Cooling tower

EnergyPlus Objects:

• Fan:VariableVolume (supply fan)

• Coil:Cooling:Water (cooling coil)

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

• Coil:Heating:Electric (electric resistance in terminals)

• Chiller:Electric:EIR (central chiller)

• CoolingTower:SingleSpeed

• PlantLoop (chilled water and condenser water)

Application:

• Large buildings with electric heating

• Provides zone-level heating control

• No central boiler required

Climate Zone Application:

• CZ 0-3A (electric heating)

System 9: Gas Furnace (Heating and Ventilation Only)

Component Configuration:

• Supply Fan: Single-speed constant volume fan

• Heating: Gas-fired furnace (no cooling)

• No mechanical cooling system

• Controls: Thermostat for heating setpoint

EnergyPlus Objects:

• Fan:ConstantVolume (supply fan)

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

• AirLoopHVAC (ventilation and heating only)

Application:

• Buildings with heating only requirements

• Unheated or naturally ventilated spaces

• No summer cooling needed (storage facilities, warehouses)

Climate Zone Application:

• CZ 3B-8 (fossil fuel heating)

System 10: Electric Furnace (Heating and Ventilation Only)

Component Configuration:

• Supply Fan: Single-speed constant volume fan

• Heating: Electric resistance heater

• No mechanical cooling system

EnergyPlus Objects:

• Fan:ConstantVolume (supply fan)

• Coil:Heating:Electric (electric resistance heating)

• AirLoopHVAC (ventilation and heating only)

Application:

• Heated storage spaces

• Ventilation-only with heating backup

• Electric heating alternative to System 9

Climate Zone Application:

• CZ 0-3A (electric heating)

System 11: SZ-VAV (Single Zone VAV System)

Component Configuration:

• Supply Fan: Variable volume fan with VFD control

• Cooling: Chilled water cooling coil (central plant)

• Heating: Climate zone dependent

  • CZ 0-2B: Electric resistance heating

  • CZ 3A and warmer: Hot water reheat or electric resistance

• Controls: Zone thermostat with VAV modulation

EnergyPlus Objects:

• Fan:VariableVolume (supply fan)

• Coil:Cooling:Water (cooling coil)

• Coil:Heating:Water or Coil:Heating:Electric (heating)

• AirLoopHVAC:UnitarySystem or AirLoopHVAC

Application:

• Medium-size buildings with single thermal zone control

• Flexible heating fuel based on climate

Climate Zone Application:

• CZ 0-2B: Electric heating

• CZ 3A+: Hot water or electric heating

System 12: SZ-CV-HW (Single Zone Constant Volume with Hot Water)

Component Configuration:

• Supply Fan: Single-speed constant volume fan

• Cooling: Chilled water cooling coil

• Heating: Hot water heating coil

• Controls: Thermostat with continuous operation

EnergyPlus Objects:

• Fan:ConstantVolume (supply fan)

• Coil:Cooling:Water (cooling coil)

• Coil:Heating:Water (heating coil)

• AirLoopHVAC:UnitarySystem

Application:

• Medium-size buildings

• Simpler control without VAV

• Constant air volume regardless of load

Climate Zone Application:

• All climates with fossil fuel heating availability

System 13: SZ-CV-ER (Single Zone Constant Volume with Electric Resistance)

Component Configuration:

• Supply Fan: Single-speed constant volume fan

• Cooling: Chilled water cooling coil

• Heating: Electric resistance heating coil

• Controls: Thermostat with continuous operation

EnergyPlus Objects:

• Fan:ConstantVolume (supply fan)

• Coil:Cooling:Water (cooling coil)

• Coil:Heating:Electric (electric resistance)

• AirLoopHVAC:UnitarySystem

Application:

• Medium-size buildings with electric heating

• No fossil fuel boiler required

• Simple constant volume control strategy

Climate Zone Application:

• CZ 0-3A (electric heating climates)

System Selection Decision Tree

START: Building Type, Number of Floors, Floor Area, Climate Zone

RESIDENTIAL BUILDINGS
├─ CZ 3B-8 (Fossil Fuel) → System 1 (PTAC)
└─ CZ 0-3A (Electric) → System 2 (PTHP)

PUBLIC ASSEMBLY < 11,000 m²
├─ CZ 3B-8 → System 3 (PSZ-AC)
└─ CZ 0-3A → System 4 (PSZ-HP)

PUBLIC ASSEMBLY ≥ 11,000 m²
├─ CZ 3B-8 → System 12 (SZ-CV-HW)
└─ CZ 0-3A → System 13 (SZ-CV-ER)

HEATED-ONLY STORAGE
├─ CZ 3B-8 → System 9 (Gas Furnace)
└─ CZ 0-3A → System 10 (Electric Furnace)

NON-RESIDENTIAL SMALL (≤3 floors, <2,300 m²)
├─ CZ 3B-8 → System 3 (PSZ-AC)
└─ CZ 0-3A → System 4 (PSZ-HP)

NON-RESIDENTIAL MEDIUM (4-5 floors, <2,300 m² OR 5 floors, 2,300-14,000 m²)
├─ CZ 3B-8 → System 5 (PVAV Reheat)
└─ CZ 0-3A → System 6 (PVAV PFP Boxes)

NON-RESIDENTIAL LARGE (>5 floors OR >14,000 m²)
├─ CZ 3B-8 → System 7 (VAV Reheat)
└─ CZ 0-3A → System 8 (VAV PFP Boxes)

Component Specifications by System

Cooling System Efficiencies

System Type	Component	Baseline Efficiency	EnergyPlus Input
DX Cooling	Packaged Unit	Variable by capacity	EIR from AHRI ratings
Chiller	Centrifugal	0.5-0.6 kW/ton	Chiller:Electric:EIR
Chiller	Screw	0.55-0.65 kW/ton	Chiller:Electric:EIR
Cooling Tower	Single Speed	Approach = 6.7°C	CoolingTower:SingleSpeed

Heating System Efficiencies

System Type	Baseline Efficiency	EnergyPlus Input
Gas Furnace	0.80 (80%)	Coil:Heating:Gas
Gas Boiler	0.85 (85%)	Boiler:HotWater
Electric Resistance	1.0 (100%)	Coil:Heating:Electric
Heat Pump (Heating)	3.0 COP	Coil:Heating:DX:SingleSpeed

Fan Specifications

System Type	Fan Control	Power Per Flow	EnergyPlus Input
Constant Volume	On/Off or Always On	400-600 Pa	Fan:ConstantVolume
Variable Volume	VFD with 0.5-1.0 minimum	400-600 Pa	Fan:VariableVolume

EnergyPlus Simulation Inputs

Air Loop Configuration

AirLoopHVAC
├─ Outdoor Air Intake
├─ Supply Fan
├─ Cooling Coil
├─ Heating Coil
├─ Supply Air Nodes
└─ Thermal Zones

Plant Loop Configuration

PlantLoop (Chilled Water)
├─ Pump
├─ Chiller
├─ Supply Nodes to Air Loops
└─ Return Nodes

PlantLoop (Condenser Water)
├─ Pump
├─ Cooling Tower
└─ Chiller Condenser Connection

PlantLoop (Hot Water)
├─ Pump
├─ Boiler
├─ Supply Nodes to Air Loops and Zones
└─ Return Nodes

Climate Zone Definitions

Climate Zone	Description	Heating	Cooling	Baseline Fuel
0A	Very Hot/Humid	Minimal	Significant	Electricity
0B	Very Hot/Dry	Minimal	Significant	Electricity
1A	Hot/Humid	Low	Significant	Electricity
1B	Hot/Dry	Low	Significant	Electricity
2A	Hot/Humid	Moderate	Significant	Electricity
2B	Hot/Dry	Moderate	Significant	Electricity
3A	Warm/Humid	Moderate	Moderate	Gas
3B	Warm/Dry	Moderate	Moderate	Gas
3C	Warm/Marine	Moderate	Low	Gas
4	Mixed/All	Moderate-High	Moderate	Gas
5	Cool	High	Moderate	Gas
6	Cool	High	Low-Moderate	Gas
7	Very Cool	Very High	Low	Gas
8	Subarctic	Very High	Low	Gas

Key Controls and Setpoints

Thermostat Setpoints (PRM Baseline)

• Heating Setpoint: 21°C (70°F)

• Cooling Setpoint: 24°C (75°F)

• Deadband: Minimum 1.7°C (3°F)

VAV Terminal Minimum Flow

• Default Minimum: 50% of design air flow

• Can be reduced to: 30% with justification

• Based on: Ventilation requirements per ASHRAE 62.1

Supply Air Temperature (SAT) Reset

• Warmest Zone: Increase SAT based on warmest zone heating load

• Outside Air: SAT reset based on outdoor temperature

• Typical Range: 13-21°C (55-70°F)

Economizer Operation

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

• Enthalpy Cutoff: When outdoor air enthalpy exceeds return air

• Integrated Mode: Damper modulation for cooling assistance