Table of Contents: Engineering Reference

EnergyPlusEngineering Reference
- The Reference to EnergyPlus Calculations(in case you want or need to know)
Overview
Document Overview
General Modeling Overview
Simulation Manager
Warmup Convergence
Integrated Solution Manager
Basis for the Zone and Air System Integration
- Zone Sensible Heat Capacity Multiplier
Summary of Predictor-Corrector Procedure
Air System Control
Moisture Predictor-Corrector
- Moisture Prediction
- Moisture Correction
Carbon Dioxide Predictor-Corrector
- Carbon Dioxide Prediction
- Carbon Dioxide Correction
Generic Contaminant Predictor-Corrector
- Generic Contaminant Prediction
- Generic Contaminant Correction
Summary of Time Marching Solution
- Summary of Timestep Model Formulation
- Zone Update Method
- Variable Timestep
- Simultaneous Solution of Plant/System Water Loop
- References
Surface Heat Balance Manager / Processes
Conduction Through The Walls
- Conduction Transfer Function Module
- Calculation of Conduction Transfer Functions
- Conduction Transfer Function (CTF) Calculations in EnergyPlus
- Conduction Transfer Function (CTF) Calculations Special Case: R-Value Only Layers
- References
Conduction Finite Difference Solution Algorithm
- Basic Finite Difference Solution Approach
- Finite Difference Node Arrangement in Surfaces
- Conduction Finite Difference Variable Thermal Conductivity
- Conduction Finite Difference Source Sink Layers
- References
Combined Heat and Moisture Transfer (HAMT) Model
- Overview
- HAMT Nomenclature
- HAMT Model Description
- References
Effective Moisture Penetration Depth (EMPD) Model
- Overview
- EMPD Model Description
- EMPD Value Determination
- EMPD Nomenclature
  - Greek letters
  - Subscripts and superscripts
- References
Outside Surface Heat Balance
- External Shortwave Radiation
- External Longwave Radiation
- References
- Atmospheric Variation
  - Local Outdoor Air Temperature Calculation
  - Local Wind Speed Calculation
- Outdoor/Exterior Convection
- Exterior/External Conduction
- References
Inside Heat Balance
- Internal Long-Wave Radiation Exchange
- Internal Short-Wave Radiation
- Interior Conduction
- Interior Convection
Adiabatic Boundary Conditions
Infrared Radiation Transfer Material
- Radiation Exchange Basics
- Radiation Transfer Surface Details
  - Specifying an Infrared Transparent (IRT) surface
- Behavior Checks
Transparent Insulation Material (TIM)
- Introduction
- Comparison of Opaque and Transparent Insulation
- Types of Transparent Insulation Materials
- TIM- Basic Mathematical Model
- Sample Test Run Cases: – Comparison
- References
Surface Heat Balance With Moveable Insulation
- Basic Heat Balance Cases
- Heat Balance Cases
- Fortran Algorithm Examples
- Fortran Variable Descriptions
- References
Ground Heat Transfer Calculations using C and F Factor Constructions
- Slab-on-grade and Underground Floors Defined with F-factors
Advanced Surface Concepts
Exterior Naturally Vented Cavity
- Baffle Heat Balance
- Cavity Heat Balance
- Underlying Heat Transfer Surface
- Solar and Shading Calculations
- Local Wind Speed Calculations
- Convection Coefficients
- Radiation Coefficients
- References
Green Roof Model (EcoRoof)
- Overview
- Green Roof Model Description
  - Energy budget in the foliage layer
    - Sensible heat flux in the foliage layer
    - Latent heat flux in the foliage layer
  - Soil Energy budget
    - Sensible heat flux in the soil layer
    - Latent heat flux in the soil layer
- Linearization
- Final Equations
- Green Roof Nomenclature
  - Greek letters
  - Subscripts and superscripts
- References
Climate, Sky and Solar/Shading Calculations
Climate Calculations
- EnergyPlus Design Day Temperature Calculations
- Sky Radiation Modeling
- EnergyPlus Sky Temperature Calculation
- EnergyPlus Design Day Solar Radiation Calculations
- Perez Direct/Diffuse Splitting Model
- Weather File Solar Interpolation
- References
Design Week Specification
Sky Radiance Model
- Sky Diffuse Solar Radiation on a Tilted Surface
- Shadowing of Sky Diffuse Solar Radiation
- Shadowing of Sky Long-Wave Radiation
Shading Module
- Shading and Sunlit Area Calculations
- Solar Position
- Surface Geometry
  - Relative Coordinate Transformation
  - World Coordinates Relative Coordinates
- Shadow Projection
- Homogeneous Coordinates
- Polygon Clipping Algorithms
- Overlapping Shadows
- Solar Gains
- Solar Distribution
- Details of the Interior Solar Distribution Calculation
- Ground Reflectances
- Ground Reflectances (Snow)
- References
Solar Radiation Reflected from Exterior Surfaces
Diffuse Reflection of Beam Solar and Sky Solar Radiation
- Receiving points
- Rays
- Sky Solar Radiation Diffusely Reflected from Obstructions
- Sky Solar Radiation Diffusely Reflected from the Ground
- Beam Solar Radiation Diffusely Reflected from Obstructions
- Beam Solar Radiation Diffusely Reflected from the Ground
- Beam Solar Radiation Specularly Reflected from Obstructions
Daylighting and Window Calculations
Daylighting Calculations
Daylight Factor Calculation
- Overview
- Interior Illuminance Components
- Daylight Factors
- Sky Luminance Distributions
- Direct Normal Solar Illuminance
- Exterior Horizontal Illuminance
- Direct Component of Interior Daylight Illuminance
  - Unshaded Window
  - Shaded Window
- Internally-Reflected Component of Interior Daylight Illuminance
- Transmitted Flux from Sky and Ground
- Transmitted Flux from Direct Sun
- Luminance of Shaded Window
- Daylight Discomfort Glare
  - Glare Index
Time-Step Daylighting Calculation
- Overview
- Time-Step Sky Luminance
- Interior Illuminance
- Glare Index
  - Glare Control Logic
- Lighting Control System Simulation
- References
DElight Daylighting Calculations
- DElight Daylight Factor Calculation Differences from EnergyPlus Detailed Methods
- DElight Time-Step Interior Daylighting Calculation Differences from EnergyPlus Detailed Methods
- References
Complex Fenestration Daylighting Calculations
- Internal Average Reflected Illuminance From Window
- Luminance from Exterior Elements
- Luminous Flux and Direct Illuminance at Interior Side of the Window
- Handling Exterior Obstructions
Daylighting Devices
- Tubular Daylighting Devices
- Daylighting Shelves
- Window Light Well
  - References
Window Calculation Module
- Optical Properties of Glazing
- Glass Layer Properties
- Glass Optical Properties Conversion
  - Conversion from Glass Optical Properties Specified as Index of Refraction and Transmittance at Normal Incidence
- Simple Window Model
- Glazing System Properties
- Air mass 1.5 terrestrial solar global spectral irradiance values (W/m²-micron) on a 37^o tilted surface. Corresponds to wavelengths in following data block. Based on ISO 9845-1 and ASTM E 892; derived from Optics5 data file ISO-9845GlobalNorm.std, 10-14-99.
- Photopic response function values corresponding to wavelengths in following data block. Based on CIE 1931 observer; ISO/CIE 10527, CIE Standard Calorimetric Observers; derived from Optics5 data file “CIE 1931 Color Match from E308.txt”, which is the same as WINDOW4 file Cie31t.dat.
- Calculation of Angular Properties
- Calculation of Hemispherical Values
- Optical Properties of Window Shading Devices
- Thermochromic Windows
- Screen Properties and Calculations
- Complex Fenestration Calculation Module
  - Complex Fenestration Solar-Optical Calculations
    - Solar radiation calculation outline
  - References
Window Heat Balance Calculation
- The Glazing Heat Balance Equations
  - Absorbed Radiation
- Room-Side Convection
- Solving the Glazing Heat Balance Equations
- Edge-Of-Glass Effects
- Apportioning of Absorbed Short-Wave Radiation in Shading Device Layers
- Window Frame and Divider Calculation
- Beam Solar Reflection from Window Reveal Surfaces
- Shading Device Thermal Model
- Heat Balance Equations for Shading Device and Adjacent Glass
- Solving for Gap Airflow and Temperature
  - Pressure Balance Equation
- Heat Balance Equations for Between-Glass Shading Device
- Airflow Windows
  - Fan Energy
  - Airflow Window with Between-Glass Shading Device
- Evacuated Glazing Unit (EGU)
- Thermal Performance of Deflected Insulated Glazing Unit (IGU)
- Equivalent Layer Fenestration Model
Air Heat Balance Manager / Processes
Convection from Surfaces
Convection from Internal Sources
Infiltration/Ventilation
- Infiltration
- Infiltration Design Flow Rate
- Infiltration by Effective Leakage Area
- Infiltration by Flow Coefficient
  - References:
- Ventilation
- Ventilation Design Flow Rate
- Ventilation by Wind and Stack with Open Area
- Zone Air Balance Outdoor Airflow (ZoneAirBalance:OutdoorAir)
- Reference
Air Exchange
- Temperature Difference Controlled Air Exchange
- Density Difference Controlled Air Exchange
- References
Calculation of Zone Air Temperature
Building System Simulation System Manager / Processes
Air Loops
- Definition of Air Loop
- Simulation Method
- Component Models
- Iteration Scheme
- Determination of Air Mass Flow Rates
Air Loop Simulation
Primary Air System Simulation
- Input data
- Initialization Calculations
- Central air system simulation
Outdoor Air System
- Simulation
Outdoor Air Mixer
- Simulation
Zone Equipment Simulation
- Input data
- Initialization Calculations
- Simulation
Air Path Components
- Overview
- Zone Supply Air Path
- Zone Splitter
- Zone Supply Plenum
- Zone Return Air Path
- Zone Mixer
- Zone Return Plenum
Plant Load Profile
- Calculation Model
Plant/Condenser Loops
- Integration of System and Plant
- Current Primary System Modeling Methodology
- Plant Manager
  - Plant Half-Loop Calling Order
- Plant Flow Resolver
- Summary of Load Distribution Schemes
- Summary of Plant Loop Demand Calculation Schemes
  - Loop Demand Calculation Scheme SingleSetPoint
  - Loop Demand Calculation Scheme DualSetPointDeadband
- Plant and Condenser Equipment Operation Schemes
- Plant Operation Schemes
  - Uncontrolled Loop Operation
  - Cooling Load Range Based Operation or Heating Load Range Based Operation
- Condenser Operation Schemes
- Primary-Secondary Loop Systems
  - Common Pipe
  - Two-Way Common Pipe
- Heat Recovery Loop Systems
- Plant Pressure Drop Simulation
Steam Systems and Component Models
- Steam Loop Assumptions
- Steam To Air Heat Exchanger
- Condensate Pump
  - Description of Pump Model
  - Model Assumptions
- Steam Pipe
  - Description of Model
  - Model Assumptions
Loop, Equipment Sizing and other Design Data
Sizing Manager
Zone Design Loads and Air Flow Rates
- Overview
- Zone Design Data Arrays
- Zone Design Load Calculation
- Updating and Adjusting the Zone Results
System Design Loads and Air Flow Rates
- Overview
- System Design Data Arrays
- System Design Flow Rate and Load Summation and Adjustment
Plant Loop Sizing
- Introduction
- Hot and Chilled Water Loop Sizing
  - Maximum Loop Volumetric Flow Rate
  - Volume of the plant loop
- Condenser Loop Sizing
  - Maximum Loop Volumetric Flow Rate
  - Volume of the plant loop
Component Sizing
- Introduction
- Fan Sizing
  - Max Flow Rate
- Coil:Cooling:Water
  - Design Water Flow Rate (m³/s)
    - System Coils
    - Zone Coils
  - Design Air Flow Rate
    - System Coils
    - Zone Coils
  - Design Inlet Air Temperature
    - System Coils
    - Zone Coils
  - Design Outlet Air Temperature
    - System Coils
    - Zone Coils
  - Design Inlet Air Humidity Ratio
    - System Coils
    - Zone Coils
  - Design Outlet Air Humidity Ratio
    - System Coils
    - Zone Coils
  - Design Inlet Water Temperature
    - System Coils
    - Zone Coils
- Coil:Cooling:Water:DetailedGeometry Sizing
  - Max Water Flow Rate of Coil
  - Number of Tubes per Row
  - Fin Diameter
  - Minimum Air Flow Area
  - Fin Surface Area
  - Total Tube Inside Area
  - Tube Outside Surf Area
  - Coil Depth
- Coil:Cooling:WaterToAirHeatPump:EquationFit Sizing
  - Rated Air Flow Rate
  - Rated Water Flow Rate
  - Rated Total Cooling Capacity
  - Rated Sensible Cooling Capacity
- Coil:Cooling:WaterToAirHeatPump:VariableSpeedEquationFit Sizing
  - Rated Air Flow Rate
  - Rated Water Flow Rate
  - Rated Total Cooling Capacity
- Coil:Heating:WaterToAirHeatPump:EquationFit Sizing
  - Rated Air Flow Rate
  - Rated Water Flow Rate
  - Rated Total Heating Capacity
- Coil:Heating:WaterToAirHeatPump:VariableSpeedEquationFit Sizing
  - Rated Air Flow Rate
  - Rated Water Flow Rate
  - Rated Total Heating Capacity
- Coil:Heating:Water Sizing
  - Max Water Flow Rate of Coil
    - System Coils
    - Zone Coils
  - UA of the Coil
    - System Coils
    - Zone Coils
- Coil:Heating:Steam Sizing
  - Maximum Steam Flow Rate
    - System Coils
    - Zone Coils
- Sizing of Gas and Electric Heating Coils
  - Nominal Capacity of the Coil
    - System Coils
    - Zone Coils
- DX Coil Sizing
  - Rated Air Volume Flow Rate
  - System Coils
  - Zone Coils
  - Rated Total Cooling Capacity
  - System Coils
  - Zone Coils
  - Rated Total Heating Capacity
  - Rated SHR
  - Evaporative Condenser Air Volume Flow Rate
  - Evaporative Condenser Air Volume Flow Rate, Low Speed
  - Evaporative Condenser Pump Rated Power Consumption
  - Evaporative Condenser Pump Rated Power Consumption, Low Speed
  - Rated Air Volume Flow Rate, low speed
  - Rated Total Cooling Capacity, Low Speed
  - Rated SHR, low speed
  - Resistive Defrost Heater Capacity
- DX MultiSpeed Coil Sizing
- Coil:Cooling:DX:VariableSpeed Sizing
- Coil:Heating:DX:VariableSpeed Sizing
- Pump Sizing
  - Rated Volumetric Flow Rate
  - Rated Power Consumption
- Electric Chiller Sizing
  - Nominal Cooling Capacity
  - Design Evaporator Volumetric Water Flow Rate
  - Design Condenser Volumetric Water Flow Rate
  - Nominal Capacity
  - Design Evaporator Volumetric Water Flow Rate
- Plant Heat Exchanger Sizing
- Humidifier Sizing
  - Rated Power
- Cooling Tower Sizing
  - Design Water Flow Rate
  - Fan Power at Design Air Flow Rate
  - Design Air Flow Rate
  - Tower UA Value at Design Air Flow Rate
  - Air Flow Rate at Low Fan Speed
  - Fan Power at Low Fan Speed
  - Tower UA Value at Low Fan Speed
  - Air Flow Rate in Free Convection Regime
  - Tower UA Value in Free Convection Regime
- Fluid Cooler Sizing
  - Design Water Flow Rate
  - Fan Power at Design Air Flow Rate
  - Elseif ****Performance Input Method = NominalCapacity then**
  - Design Air Flow Rate
  - Fluid cooler UA Value at Design Air Flow Rate
  - Air Flow Rate at Low Fan Speed
  - Fan Power at Low Fan Speed
  - Fluid cooler UA Value at Low Fan Speed
- Evaporative Fluid cooler Sizing
  - Design Water Flow Rate
  - Fan Power at Design Air Flow Rate
  - Else
  - Design Air Flow Rate
  - Fluid cooler UA Value at Design Air Flow Rate
  - Air Flow Rate at Low Fan Speed
  - Fan Power at Low Fan Speed
  - Fluid cooler UA Value at Low Fan Speed
- Fan Coil Unit Sizing
  - Maximum Air Flow Rate
  - Maximum Outside Air Flow Rate
  - Maximum Hot Water Flow
  - Maximum Cold Water Flow
- Window Air Conditioner Sizing
  - Maximum Air Flow Rate
  - Maximum Outside Air Flow Rate
- Unit Ventilator Sizing
  - Maximum Air Flow Rate
  - Maximum Outside Air Flow Rate
  - Minimum Outside Air Flow Rate
- Packaged Terminal Heat Pump Sizing
  - Supply air volumetric flow rate during cooling operation
  - Supply air volumetric flow rate during heating operation
  - Supply air volumetric flow rate when no cooling or heating is needed
  - Outside air volumetric flow rate during cooling operation
  - Outside air volumetric flow rate during heating operation
  - Outside air volumetric flow rate when no cooling or heating is needed
  - Maximum supply air temperature from supplemental heater
- MultiSpeed Heat Pump Sizing
  - Supply air volumetric flow rate during cooling operation at the highest speed
  - Supply air volumetric flow rate during heating operation at the highest speed
  - Supply air volumetric flow rate when no cooling or heating is needed
  - Supply air volumetric flow rate during cooling operation at Speed n (1 to NumberOfSpeed-1)
  - Supply air volumetric flow rate during heating operation at Speed n (1 to NumberOfSpeed-1)
- Single Duct Terminal Units
  - Maximum Air Flow Rate
  - Maximum Heating Air Flow Rate
  - Maximum Primary and Secondary Air Flow Rates
  - Minimum Air Flow Rate
  - Fan On Flow Fraction
  - Max Hot Water Flow
  - Max Chilled Water Flow
- Indirect Evaporative Cooler Sizing
  - Secondary Fan Flow Rate
Zone Outdoor Air Design Data
- Design Outdoor Air Calculation
- References
Demand Limiting
- Algorithm
  - Sequential Priority
    - All Priority
Alternative Modeling Processes
- RoomAir Models
AirflowNetwork Model
- Overview
- Model Description
- Pressure and Airflow Calculations
- Node Temperature Calculations
- Node Humidity Ratio Calculations
- Sensible and Latent Load Calculations
- Impacts of Supply Air Constant Volume Fan Control on Load: Cycling vs. Continuous
- Airflow Calculation Procedure using A Supply Variable Air Volume Fan
- Integration of the AirflowNetwork Model
- Model Output
- References
Simulation Models – Encyclopedic Reference
Air System Distribution Terminals
- Constant Volume Single Duct Uncontrolled Air Terminal
- Constant Volume Single Duct Reheat Air Terminal
- Variable Air Volume Single Duct Reheat and No Reheat Air Terminals
  - Minimum Outdoor Air Control
- Variable Air Volume Heating and Cooling Single Duct Reheat and NoReheat Air Terminal
- Constant Volume Single Duct Four Pipe Induction Air Terminal
- Fan Powered Induction Series and Parallel Single Duct Reheat Air Terminal
- Variable Air Volume Fan Powered Single Duct Air Terminal
- Cooled Beam Unit (AirTerminal:SingleDuct:ConstantVolume:CooledBeam)
- Constant Volume Dual Duct Air Terminal
- Variable Air Volume Dual Duct Air Terminal
- Dual Duct Dedicated Outside Air Terminal with VAV Cooling
Boilers
- Simple Hot Water Boiler
  - Single independent variable:
  - Dual independent variables:
- Steam Boiler
Chillers
- Absorption Chiller
  - Steam Loop Calculations
  - Hot Water Loop Calculations
- Indirect Absorption Chiller
  - Steam Loop Calculations
  - Hot Water Loop Calculations
- Combustion Turbine Chiller
  - Chiller Basin Heater
- ChillerHeater:Absorption:DirectFired
- ChillerHeater:Absorption:DoubleEffect
- Constant COP Chiller
  - Chiller Basin Heater
- Hot Water Heat Recovery from Chillers
  - Chiller Basin Heater
- Electric Chiller Model Based on Fluid Temperature Differences
- Electric Chiller Model Based on Condenser Entering Temperature
- Electric Chiller Model Based on Condenser Leaving Temperature
- Engine Driven Chiller
  - Chiller Basin Heater
Ice Thermal Storage
- Simple Ice Storage Model
- Detailed Ice Storage Model
Coils
- Chilled-Water-Based Air Cooling Coil
  - Heat Transfer and Energy Balance
  - Model Description
  - Intermediate calculated U-Factor Times Area Values: The Crux of the Model
  - Design Block Calculations:!!! {:error “Image in Header” :alt “” :img “media/image3097.png”} !!!
  - Variable UA
  - Operating Block Calculations:
  - Effectiveness Equations:
  - Coil Outlet Conditions:
  - Coil Completely Dry Calculations: (operating block)
  - Coil Completely Wet Calculations: (operating block)
  - Coil Part Wet Part Dry Calculations: (operating block)
  - References
- Chilled-Water-Based Detailed Geometry Air Cooling Coil
  - Heat Transfer and Energy Balance
  - Underlying Correlations, Properties, and Assumptions
  - Solution Method of Model
  - Application of Cooling Coil Model to Heating Coils
- Hot-Water-Based Air Heating Coil
  - Overview
  - Model Description
  - References
- Single-Speed Electric DX Air Cooling Coil
  - Overview
  - Model Description
  - Dry Coil Conditions
  - SHR Calculation Using User Specified SHR Modifier Curves
  - Condenser Options: AirCooled vs. EvaporativelyCooled
  - Condenser Inlet Air Temperature
  - Supply Air Fan Control: Cycling vs. Continuous
  - Latent Capacity Degradation
  - Basin Heater For Single-Speed DX Coil
  - Special Calculations for Coil:Cooling:DX:TwoStageWithHumidityControlMode with CoilPerformance:DX:Cooling
  - Standard Rating of Single-Speed DX Cooling Coils
  - Basin Heater For Two-Stage DX Coil
  - References
- Multi-Speed Electric DX Air Cooling Coil
  - Overview
  - Model Inputs
  - Speed 1 Operation
  - Higher Speed Operation
  - Waste heat calculation
  - Basin Heater For Multi-Speed DX Coil
  - Standard Rating of Multi-Speed DX Cooling Coils
  - Standard Rating Cooling Capacity
  - Seasonal Energy Efficiency Ratio (SEER) for Multi-Speed DX Coil
  - References
- Two-Speed Electric DX Air Cooling Coil
  - Overview
  - Inputs and Data
  - Calculation
  - Simulation and Control
  - Basin Heater For Two-Speed DX Coil
  - Standard Ratings
  - References
- Variable Speed DX Cooling Coil
  - Overview
  - Model Description
  - Performance Curves:
  - Lowest Speed Operation:
  - Higher Speed Operation:
  - Evaporatively Cooled Condenser:
- Electric Air Heating Coil
- Gas Air Heating Coil
- Multi-Stage Electric and Gas Air Heating Coil
  - Overview
  - Model Inputs
  - Stage 1 Operation
  - Higher Stage Operation
- Single-Speed Electric Heat Pump DX Air Heating Coil
  - Overview
  - Model Inputs
  - Model Description
  - Frost Adjustment Factors
  - Defrost Operation
  - Heating Operation
  - Condenser Inlet Air Temperature
  - Supply Air Fan Control: Cycling vs. Continuous
  - References
- Single-Speed DX Heating Coil Standard Ratings
  - High Temperature Heating Standard (Net) Rating Capacity
  - Low Temperature Heating Standard (Net) Rating Capacity
  - Heating Seasonal Performance Factor (HSPF)
- Multi-Speed Electric Heat Pump DX Air Heating Coil
  - Overview
  - Model Inputs
  - Speed 1 Operation
  - Higher Speed Operation
  - Waste heat calculation
  - Standard Rating of Multi-Speed DX Heating Coils
  - Standard Ratings Heating Capacity
  - Heating seasonal performance factors (HSPF) for Multi-Speed DX Coil
  - References:
- Variable Speed DX Heating Coil
  - Overview
  - Model Description
  - Performance curves:
  - Lowest Speed Operation:
  - Higher Speed Operation:
  - Defrost Operation:
  - Crankcase Heater Operation:
- Desuperheater-Recovery-Based Air Heating Coil
  - Overview
  - Model Inputs
  - Model Description
  - Load-Based Operation
  - Temperature-Based Operation
  - Parasitic Electric Load
  - References
- Desuperheater-Recovery-Based Water Heating Coil
  - Overview
  - Model Description
  - Float Mode
  - Heating Mode
  - Model Outputs
- Heat Exchanger Assisted Air Cooling Coil Systems
  - References
- Single-Speed Electric Heat Pump DX Water Heating Coil
  - Overview
  - Model Description
  - Model Outputs
- Water Source Electric DX Air Cooling Coil
- Water Source Electric Heat Pump DX Air Heating Coil
- Steam-Based Air Heating Coil
- Variable Refrigerant Flow Cooling Coil
  - Overview
  - Model Description
  - Dry Coil Conditions
  - Condenser Options: Air Cooled vs. Evaporative Cooled
  - Condenser Inlet Air Temperature
  - Supply Air Fan Control: Cycling vs. Continuous
  - Average Air Flow Calculations
- Variable Refrigerant Flow Heating Coil
- Variable Speed Water to Air Heat Pump (Heating & Cooling)
  - Coil:Heating:WaterToAirHeatPump:VariableSpeedEquationFit
  - Overview
  - Model Description
  - Coil:Cooling:WaterToAirHeatPump:VariableSpeedEquationFit
  - Overview
  - Model Description
  - References
- Packaged Thermal Storage Cooling Coil
HVAC Controllers
- Control Valve for Water-Based Air System Coils
  - Model Description
- Outdoor Air Damper Controller for Air Systems
- Outdoor Air Damper Controller for Zone Energy Recovery Ventilator
  - Controller Logic
Baseboard Heaters
- Hot Water Baseboard Heater with Only Convection
- Electric Baseboard Heater with Only Convection
- Hot Water Baseboard Heater with Radiation and Convection
Electric Baseboard Heater with Radiation and Convection
- Overview
- Model Description
- Steam Baseboard Heater with Radiation and Convection
Cooling Towers and Evaporative Fluid Coolers
- One, Two, and Variable Speed Cooling Towers and Evaporative Fluid Coolers
- Variable Speed Cooling Towers Empirical Models
- Cooling Towers with Multiple Cells
- Cooling Tower Makeup Water Usage
  - References
- One and Two Speed Fluid Coolers
Demand Controlled Ventilation
- Ventilation Rate Procedure
  - Calculation of zone minimum outdoor air flow
  - Calculation of system minimum outdoor air flow
- Indoor Air Quality Procedure
- Proportional Control
- References
Evaporative Coolers
- Direct Evaporative Cooler
  - Saturation Efficiency
  - Curve Fitting Evaporative Media
- Dry Coil Indirect Evaporative Cooler
- Wet Coil Indirect Evaporative Cooler
  - Efficiencies of the Indirect Stage
- Two Stage Direct/Indirect Evaporative Cooler
- Indirect Evaporative Cooler Special Research Model
  - Water Consumption
- Direct Evaporative Cooler Special Research Model
  - Water Consumption
Air System Fans
- Overview
- Model
- References
Air System Compound Component Groups
- Unitary Systems
- Forced-Air Furnace and Central Air Conditioning
- Unitary Systems
- Unitary System with Changeover-Bypass-Variable Air Volume
- Unitary Air-To-Air Heat Pump
- Unitary Multi-Speed Air-To-Air Heat Pump
- DX Cooling Package
  - Overview
  - Controls
- DX Heating Package
  - Overview
  - Controls
- Desiccant Dehumidifier Package
- Unitary Water-To-Air Heat Pump
- Water To Water Heat Pumps
- Equation Fit Water To Water Heat Pump Model
  - Coefficient estimation procedure:
- Parameter Estimation Water-To-Water Heat Pump Model
Variable Refrigerant Flow Heat Pumps
- Variable Refrigerant Flow Heat Pump Model
- Zone Terminal Unit List
Heat Exchangers
- Air System Air-To-Air Sensible and Latent Effectiveness Heat Exchanger
- Air System Air-To-Air Flat Plate Heat Exchanger
- Air System Air-To-Air Balanced Flow Desiccant Heat Exchanger
- Plant Loop Deep-Ground-To-Water Vertical U-Tube Field Heat Exchanger
- Plant Loop Pond-To-Water Heat Exchanger
- Plant Loop Surface-Ground-To-Water Heat Exchanger
- Plant Loop Fluid-to-Fluid Heat Exchanger
- References
Air System Humidifiers
- Overview
- Electric Steam Humidifier
  - Model
  - Controller
  - Component
  - References
Zone Internal Gains
- Sources and Types of Gains
- Heat Gain from Lights
- Heat Gain from People
- Heat Gain from Baseboard Heat
- Distribution of Radiant Gains
- References
Pipes
- Heat Transfer Pipes (Objects: Pipe:Indoor & Pipe:Outdoor)
  - Heat Loss and Time Delay in Pipes
  - References
- Underground Pipe (Object: Pipe:Underground)
- PipingSystem:Underground Simulation
Pumps
- Summary of Pump Rules
- Dynamic Pump Pressure Head
- Variable Speed Pump
- Pressure-based Flow for Variable Speed Pumps
- Constant Speed Pump
- Pressure-based Flow for Constant Speed Pumps
- Pump Heat Addition to the Loop
- Pump Heat Addition to Surrounding Zone
- Headered Pumps
- Condensate Pumps
Ideal Loads Air System
- Overview
- Model
  - Inputs and Data
  - All input data for the ZoneHVAC:IdealLoadsAirSystem is stored in the array PurchAir. The model and data are encapsulated in the module PurchasedAirManager.Calculation
- References
District Cooling
District Heating
CentralHeatPumpSystem
- Overview
- Model Description
ChillerHeaterPerformance:Electric:EIR
- Overview
- Model Description
  - Cooling-only mode
  - Heating-only mode and Simultaneous cooling-heating mode
- References
Plant Temperature Source Component
- References
Radiant System Models
- Low Temperature Radiant System Model
- High Temperature Radiant Heater Model
  - References
Refrigeration Equipment
- Overview
- Refrigeration Compressor Racks
  - Compressor Energy Use
  - Condenser Heat Rejection, Energy Use, and Water Use
- Refrigerated Cases
- Walk-In Coolers and Freezers
- Air Chillers and Air Chiller Sets
- Detailed Refrigeration Systems
- Secondary Refrigeration Systems
- Transcritical CO₂ Refrigeration System
- References
Setpoint Managers
- Overview
- Scheduled
- Outdoor Air Reset
- Single Zone Reheat Heating and Cooling
- Single Zone Heating Only
- Single Zone Cooling Only
- Single Zone Minimum Humidity
- Single Zone Maximum Humidity
  - Model Description
- Mixed Air
- Outdoor Air Pretreat
- Warmest Zone Supply Air Reset
- Coldest Zone Supply Air Reset
- Return Air Bypass Flow
- Warmest Temp Flow
- Multizone Heating Average
- Multizone Cooling Average
- Multizone Minimum Humidity Average
- Multizone Maximum Humidity Average
- MultiZone Minimum Humidity Supply Air Reset
- MultiZone Maximum Humidity Supply Air Reset
- Follow Outdoor Air Temperature
- Follow System Node Temperature
- Follow Ground Temperature
- Condenser Entering Water Temperature Reset
- Ideal Condenser Entering Water Temperature Reset
Solar Collectors
- Flat-Plate Solar Collectors
- Integral-collector-storage (ICS) Solar Collector
- References:
- Photovoltaic Thermal Flat-Plate Solar Collectors
  - Simple PVT Thermal Model
  - References
- Unglazed Transpired Solar Collectors
System Availability Managers
- Overview
- Scheduled
- Scheduled On
- Scheduled Off
- Night Cycle
- Night Ventilation
- Differential Thermostat
- High Temperature Turn Off
- High Temperature Turn On
- Low Temperature Turn Off
- Low Temperature Turn On
- Hybrid Ventilation Control
- Optimum Start Controls
Occupant Thermal Comfort
- Background on Thermal Comfort Models
- Mathematical Models for Predicting Thermal Comfort
- Fanger Comfort Model
  - Fanger Model Nomenclature List
  - Description of the model and algorithm
- Pierce Two-Node Model
  - Pierce Two-Node Model Nomenclature List
  - Description of the model and algorithm
- KSU Two-Node Model
  - KSU Two Node Model Nomenclature List
  - Description of the model and algorithm
- Adaptive Comfort Model Based on European Standard EN15251-2007
- Dynamic Clothing Model
  - References
- Mean Radiant Temperature Calculation
  - Description of the model and algorithm
- References
Trombe Walls
- Passive Trombe Wall
- Active Trombe Wall
  - Input File
  - Results
Water Thermal Tanks (includes Water Heaters)
- Mixed Water Thermal Tank
- Heat Pump Water Heater
- Stratified Water Thermal Tank
- Water Heating Sizing
Water Systems
- Water Mains Temperatures
  - References
- Water Use Equipment and Connections
- Unconnected Water Use Equipment
- Zone Heat Gain from Water Use Equipment
- Connected Water Use Equipment
- Water Use Equipment Calculations
- Drainwater Heat Recovery
  - Calculate Connections Heat Recovery
Zone Controls
- Thermostatic Zone Control
- Zone Thermostats
- Operative Temperature Control
- Temperature And Humidity Control
  - The input object ZoneControl:Thermostat:TemperatureAndHumidity is used to modify the behavior of ZoneControl:Thermostat objects (control types ThermostatSetpoint:SingleCooling and ThermostatSetpoint:DualSetpoint only) based on zone air humidity conditions. Specifically, this TemperatureAndHumidity zone control resets the ZoneControl:Thermostat’s cooling setpoint temperature downward when the zone air relative humidity exceeds the Dehumidifying Relative Humidity Setpoint defined in this object. The reduced cooling setpoint temperature typically results in longer cooling coil runtimes and additional dehumidification. While additional dehumidification (lower absolute humidity level in the zone air) may be achieved, the resulting dry-bulb temperature and absolute humidity of the zone air will determine if the zone air relative humidity is reduced.
    - The rate at which the cooling setpoint temperature is reduced is dictated by the user-specified Overcool Control Ratio. The maximum reduction in cooling setpoint temperature is defined by the user-entered Overcool Range, although the Overcool Range may be reduced from the user-defined value when this TemperatureAndHumidity control is used in tandem with a dual setpoint thermostat (see discussion below). Note that occupants are sensitive to overcooling and can experience discomfort if the overcool range is too large.
- Humidistat
- Thermal Comfort Zone Control
  - Zone Control Based on Fanger Thermal Comfort
Zone Equipment and Zone Forced Air Units
- Air Distribution Terminal Unit
  - Overview
  - Model
  - Inputs and Data
  - Calculation
  - Simulation and Control
  - References
- Inlet Side Mixer Air Terminal Unit
  - Overview
  - Model
  - Inputs and Data
  - Calculation
  - Simulation and Control
  - References
- Supply Side Mixer Air Terminal Unit
  - Overview
  - Model
  - Inputs and Data
  - Calculation
  - Simulation and Control
  - References
- Simple Duct Leakage Model
  - Overview
  - Principles and Description
  - Inputs and Data
  - Implementation
  - References
- Fan Coil Unit
- Window Air Conditioner
- Packaged Terminal Air Conditioner
- Packaged Terminal Heat Pump
- Zone Single Speed Water-To-Air Heat Pump
  - Overview
  - Single Speed Equation-Fit Model:
  - Coefficient estimation procedure:
- Zone Air DX Dehumidifier
  - Overview
  - Model Description
- Energy Recovery Ventilator
  - Model Description
- Zone Evaporative Cooler Unit
  - Controls
- Unit Heater
  - Controls
- Unit Ventilator
  - Controls and Outdoor Air
- Variable Refrigerant Flow Terminal Unit
  - Overview
  - Model Description
  - Average Air Flow Calculations
  - Calculation of Outlet Air Conditions
  - Calculation of Zone Heating and Cooling Rates
- Ventilated Slab
  - Model Overview
  - Connections to the Heat Balances
- CoolTower
  - Overview
  - Model Description
  - Simulation and Control
- Earthtube
  - References
- Thermal Chimney Model
  - References
- Zone Outdoor Air Unit
- Controls
- Zone Exhaust Fan
On-Site Generation
Electric Load Center Distribution Manager
- Overview
- Electric Load Center Generators
- Inverters
- Electrical Storage
- Electrical Storage – Kinetic Battery Model
  - References
- Electric Load Center Transformers
  - References:
Photovoltaic Arrays
- Simple Model
  - Mathematical Description
- Equivalent One-Diode Model
  - Mathematical Description
  - References
- Sandia Photovoltaic Performance Model
  - Mathematical Description
  - References
Generators
- Internal Cumbustion Engine
- Turbine Generator
- Microturbine Generator
- Micro-Cogenerator
  - References
- Fuel Cell Cogenerator
  - References
- Custom Fuel Supply for Generators
  - References
- Wind Turbine
Performance Curves and Lookup Tables
Performance Curves
- Curves based on a single independent variable
- Curves based on two independent variables
- Curves based on three independent variables
  - TriQuadratic Curves
- Pressure drop curve
  - Functional Pressure Drop Curve
Performance Tables
- Tables based on a single independent variable
- Tables based on two independent variables
Economics Calculations
Component Costs
- Line Item Costs
- Adjustments
- Comparisons
Tariff Computation
- Conceptual Framework – Variables and Hierarchy
- Default Order of Computation
- Computation Steps
Life-Cycle Cost Computations
- ExpressAsCashFlows
- ComputePresentValue
- ComputeTaxAndDepreciation
Special Modules/Reporting
Environmental Impacts
- Types of Pollutants
- Carbon Equivalent
- Fossil Fuel Emissions Factors
- Off-Site Electricity Generation Emissions
- Other Energy-Related Pollutants and Sources of Other Information
- References
Zone Component Loads Summary
- Estimated Component Load Details

Table of Contents: Engineering Reference — EnergyPlus 8.1