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Rooms and Zones
Zone Result Variables
Zone Result Variables

review the load results for each Zone in the building

Patrick Chopson avatar
Written by Patrick Chopson
Updated over a week ago

A Zone is a group of Rooms which share common internal conditions and external adjacency. In load and energy modeling Zones are used to reflect the intended grouping of rooms on to Variable Air Volume (VAV) boxes, Fan Coil Units (FCU), or other terminal units which will serve the group of rooms. By running simulations with these rooms grouped, the coincident peak is reported for the zone allowing for right sizing of equipment. This article provide a overview of the zone results available after running the simulation

Zone Details

  • Area [ft² (IP) | m² (SI)]: The total area of the zone.

  • Number of People: the total number of occupants in the zone

  • Number of Rooms: the total number of rooms combined into a thermal zone

  • Cooling Setpoint [°F (IP) | °C (SI)]: The temperature setpoint in cooling. This is the internal temperature used to size the air flow.

  • Heating Setpoint [°F (IP) | °C (SI)]: The temperature setpoint in heating. This is the internal temperature used to size the air flow.

  • System Assigned: Air system type, serving the zone

Zone Cooling Peak Load Details

  • Total Cooling Load [Btu/h (IP) | Watts (SI)]: Actual peak cooling load for the zone taking into account the dynamic nature of individual zone loads that make up the total.

  • Sensible Cooling Load[Btu/h (IP) | Watts (SI)]: The component of the total cooling load that is sensible.

  • Latent Cooling Load [Btu/h (IP) | Watts (SI)]: The component of the total cooling load that is latent.

  • Time of Peak: the day and hour of the year when selected zone experience the peak cooling load.

  • Dry Bulb [°F (IP) | °C (SI)]: The dry bulb temperature at the time of peak load.

  • Wet Bulb [°F (IP) | °C (SI)]: The wet bulb temperature at the time of peak load

Zone Cooling Peak Load Breakdown: Cooling peak load is divided into contributing factors to envelope gains and losses as well as internal gains.

Envelope Gains/Losses [Btu/h (IP) | Watts (SI)]: The portion of total cooling load that was gained or lost through building envelope.

  • External Walls: Cooling load gains and losses through external walls.

  • Ground Walls : Cooling load gains and losses through ground contact walls.

  • Roofs: Cooling load gains and losses through the roof.

  • Ground Floor: Cooling load gains and losses through the ground contact floors.

  • Exposed Floor: Cooling load gains and losses through floors exposed to outside air.

  • Glazing Conduction and Solar Radiation: Cooling load gains and losses through glazing conduction and radiation. Typically the heat gains are divided into two components, the Conduction related to the U-value and the Radiation related to the SHGC. Dividing the heat gains in this fashion is helpful because it allows key characteristics of the glazing, U-value and SHGC, to be considered in regard to their impact on cooling loads. More detail on the glazing calculations can be found here.

  • Doors: Cooling load gains and losses through the doors of the zone.

  • Infiltration: Cooling load gains and losses through infiltration between inside and outside of the building

Internal Gains [Btu/h (IP) | Watts (SI)]: The portion of total heating load that was gained through internal loads such as occupant, light, equipment and adjacent spaces.

  • Internal Walls: Internal load gains from the adjacent spaces through internal walls

  • Internal Floors: Internal load gains from the adjacent spaces through internal floors

  • Lights: Internal load gains from lights in the space

  • People: Internal load gains from the occupants

  • Equipment: Internal load gains from the adjacent spaces through electrical equipment

  • Ventilation: Internal load gains through ventilation, note these are only reported when the Ideal Air Load system is used.

Latent Gains/Losses [Btu/h (IP) | Watts (SI)]: The portion of heating load gained or lost representing the amount of energy that is necessary to dehumidify the air in a zone.

  • Infiltration: Latent load gains and losses through infiltration between building and outside environment.

  • People: Latent load gains and losses caused by occupants

  • Equipment: Latent load gains and losses generated by operating equipment.

Simulation Factors [Btu/h (IP) | Watts (SI)]:

  • Breakdown estimate: EnergyPlus calculations peak loads via the Heat Balance method. This method reports a single combined value for all gains and losses at time of peak. In order to report components EnergyPlus runs a secondary method to estimate the gain and losses from each component at that time of peak. The difference between sum of these estimates and the actual peak is reported here.

  • Safety factor represent the added value to the total load to account for the safety factor assigned on the Setting page.

Zone Heating Peak Load Details

  • Total Heating Load [Btu/h (IP) | Watts (SI)]: Actual peak heating load for the zone taking into account the dynamic nature of individual zone loads that make up the total.

  • Sensible Heating Load[Btu/h (IP) | Watts (SI)]: The component of the total heating load that is sensible.

  • Latent Heating Load [Btu/h (IP) | Watts (SI)]: The component of the total heating load that is latent.

  • Time of Peak: the day and hour of the year when selected zone experience the peak heating load.

  • Zone Heating Peak Load Breakdown: Heating peak load is divided into contributing factors to envelope gains and losses as well as internal gains.

Envelope Gains/Losses [Btu/h (IP) | Watts (SI)]: The portion of total cooling load that was gained or lost through building envelope.

  • External Walls: Heating load gains and losses through external walls.

  • Ground Walls : Heating load gains and losses through ground contact walls.

  • Roofs: Heating load gains and losses through the roof

  • Ground Floor: Heating load gains and losses through the ground contact floors.

  • Exposed Floor: Heating load gains and losses through floors exposed to outside air.

  • Glazing Conduction and Solar Radiation: Heating load gains and losses through glazing conduction and radiation. Typically the heat gains are divided into two components, the Conduction related to the U-value and the Radiation related to the SHGC. Dividing the heat gains in this fashion is helpful because it allows key characteristics of the glazing, U-value and SHGC, to be considered in regard to their impact on cooling loads. More detail on the glazing calculations can be found here.

  • Doors: Heating load gains and losses through the doors of the zone.

  • Infiltration: Heating load gains and losses through infiltration between inside and outside of the building

Internal Gains [Btu/h (IP) | Watts (SI)]: The sensible portion of total heating load that was gained through internal loads such as occupant, light, equipment and adjacent spaces.

  • Internal Walls: Internal load gains from the adjacent spaces through internal walls

  • Internal Floors: Internal load gains from the adjacent spaces through internal floors

  • Ventilation: Internal load gains through ventilation, note these are only reported when the Ideal Air Load system is used.

Latent Gains/Losses [Btu/h (IP) | Watts (SI)]: The portion of heating load gained or lost representing the amount of energy that is necessary to dehumidify the air in a zone.

  • Infiltration: Latent load gains and losses through infiltration between building and outside environment.

Simulation Factors [Btu/h (IP) | Watts (SI)]:

  • Breakdown estimate EnergyPlus calculations peak loads via the Heat Balance method. This method reports a single combined value for all gains and losses at time of peak. In order to report components EnergyPlus runs a secondary method to estimate the gain and losses from each component at that time of peak. The difference between sum of these estimates and the actual peak is reported here.

  • Safety factor represent the added value to the total load to account for the safety factor assigned on the Setting page.

Zone Air Flows

  • Supply Air [CFM (IP) | L/S (SI)]: Air volume supplied into the zone during cooling operation

  • Outside Air[CFM (IP) | L/S (SI)]: Air volume of the outside air brought into the zone

  • Return Air [CFM (IP) | L/S (SI)]: Air volume that gets recirculated into the zone

  • Heating Air [CFM (IP) | L/S (SI)]: Air volume supplied into the zone during heating operation

  • Exhaust Air [CFM (IP) | L/S (SI)]: Air volume that gets released into the atmosphere after circulating through the zone

Zone Checks

  • Total Cooling [Btu/h/ft²(IP) | W/m² (SI)]: This check provides the total cooling load per served area for the zone and is calculated by dividing total cooling peak load to the area of the zone.

  • Total Cooling [ft²/ton R (IP)]: Total cooling check reported in ft²/ton of refrigeration.

  • Sensible Cooling [Btu/h/ft²(IP) | W/m² (SI)]:This check provides the sensible cooling load per served area for the zone and is calculated by dividing sensible cooling peak load to the area served by the zone.

  • Sensible Cooling [ft²/ton R (IP)]: Sensible cooling check reported in ft²/ton of refrigeration.

  • Heating [Btu/h/ft²(IP) | W/m² (SI)]: This check provides the heating load value per square foot area of the zone.

  • Cooling [CFM/ft²(IP) | L/s/m² (SI)]: This check provides the cooling air volume flowing into the space per square foot area of the zone.

  • Heating [CFM/ft²(IP) | L/s/m² (SI)]: This check provides the heating air volume flowing into the space per square foot area of the zone.

  • Outside Air [CFM/ft²(IP) | L/s/m² (SI)]: This check provides the outside air volume per served area for the zone and is calculated by dividing outside air flow volume to the area of the zone.

Zone Terminal Units

Each Terminal Unit type has specific result variables that capture the details of that device. All Terminal Units sizing is a result of both the peak load calculations, and any assigned Supply Air Flow values for that Zone.

Zone Terminal Unit- CAV with No Reheat

  • Max Air Flow Rate [CFM (IP) | L/S (SI)]: CAV terminal maximum air volume flow rate.

Zone Terminal Unit- CAV with Hydronic Reheat

  • Max Air Flow Rate [CFM (IP) | L/S (SI)]: CAV terminal maximum volume flow rate.

  • Heating Capacity [Btu/h (IP) | Watts (SI)]: This is the maximum capacity of the hydronic reheat coil.

  • Heating Coil Fluid flow [GPM (IP) | L/S (SI)]: Fluid volume passing through the hydronic reheat coil

  • Entering/Leaving Air Temperature [°F (IP) | °C (SI)]: The inlet and outlet air temperature corresponding to the rated reheat coil heating capacity.

Zone Terminal Unit- CAV with Electric Reheat

  • Max Air Flow Rate [CFM (IP) | L/S (SI)]: CAV terminal maximum volume flow rate.

  • Heating Capacity [Btu/h (IP) | Watts (SI)]: This is the maximum capacity of the electric reheat coil.

  • Heating Coil Airflow [CFM (IP) | L/S (SI)]: Air volume passing through the reheat coil

  • Entering/Leaving Air Temperature [°F (IP) | °C (SI)]: The inlet and outlet air temperature corresponding to the rated reheat coil heating capacity.

Zone Terminal Unit- VAV No Reheat

  • Cooling Max Airflow [CFM (IP) | L/S (SI)]:The maximum volumetric airflow rate discharged from the unit

  • Min Airflow [CFM (IP) | L/S (SI)]: The minimum air volume discharged from the unit.

Zone Terminal Unit- VAV with Hydronic Reheat

  • Cooling Max Airflow [CFM (IP) | L/S (SI)]: The maximum volumetric airflow rate discharged from the unit

  • Min Airflow [CFM (IP) | L/S (SI)]: The minimum air volume discharged from the unit

  • Heating Capacity [Btu/h (IP) | Watts (SI)]:This is the maximum heating capacity of the hydronic reheat coil.

  • Heating Coil Airflow [CFM (IP) | L/S (SI)]: The air volume passing through the hydronic reheat coil.

  • Heating Coil Fluid Flow [GPM (IP) | L/S (SI)]: Fluid volume passing through the hydronic reheat coil.

  • Entering/Leaving Air Temperature [°F (IP) | °C (SI)]: The inlet and outlet air temperature corresponding to the rated reheat coil heating capacity.

  • Fluid Temperature [°F (IP) | °C (SI)]: The entering and leaving fluid temperature passing through the hydronic reheat coil.

Zone Terminal Unit- VAV with Electric Reheat

  • Cooling Max Airflow [CFM (IP) | L/S (SI)]: The maximum volumetric airflow rate discharged from the unit

  • Min Airflow [CFM (IP) | L/S (SI)]: The minimum air volume discharged from the unit

  • Heating Capacity [Btu/h (IP) | Watts (SI)]:This is the maximum heating capacity of the hydronic reheat coil.

  • Heating Coil Airflow [CFM (IP) | L/S (SI)]: The air volume passing through the hydronic reheat coil.

  • Entering/Leaving Air Temperature [°F (IP) | °C (SI)]: The inlet and outlet air temperature corresponding to the rated reheat coil heating capacity.

Zone 4-Pipe Active Chilled Beam

Cooling Coil Sizing Results:

  • Sensible Capacity [Btu/h (IP) | Watts (SI)]: This field indicates the Sensible capacity of the cooling coil of the 4-Pipe Active Chilled Beam.

  • Primary Airflow [CFM (IP) | L/S (SI)]: Air flow rate from the central air handler into the zone. Note that this does not include any of the secondary airflow that is induced by the convector and nozzle action.

  • Fluid Flow [GPM (IP) | L/S (SI)]: This field indicates the fluid flow rate for the cooling coil of the zone component.

Heating Coil Sizing Results

  • Sensible Capacity [Btu/h (IP) | Watts (SI)]: This field indicates the Sensible capacity of the heating coil of the 4-Pipe Active Chilled Beam.

  • Fluid Flow [GPM (IP) | L/S (SI)]: This field indicates the fluid flow rate for the heating coil of the zone component.

  • Estimated Length of Beams Required [ft (IP) | m (SI)]: This field indicates the length of beams required for the 4-pipe active chilled beam system.

Zone 2-Pipe Chilled Beam

  • Sensible Capacity [Btu/h (IP) | Watts (SI)]: This field indicates the Sensible capacity of the 2-pipe chilled beam.

  • Primary Airflow [CFM (IP) | L/S (SI)]: Air flow rate from the central air handler into the zone.

  • Fluid Flow [GPM (IP) | L/S (SI)]: This field indicates the fluid flow rate for the cooling coil of the zone component.

  • Estimated Length of Beams Required [ft (IP) | m (SI)]: This field indicates the length of beams required for the 2-pipe chilled beam system.

Zone 4-Pipe Induction Unit

  • Heating Capacity [Btu/h (IP) | Watts (SI)]: This field indicates the total heating capacity of the 4-pipe induction unit.

  • Total Cooling Capacity [Btu/h (IP) | Watts (SI)]: This field indicates the total cooling capacity of the 4-pipe induction unit.

  • Heating Airflow [CFM (IP) | L/S (SI)]: Total airflow rate for heating of the 4-pipe induction unit.

  • Cooling Airflow [CFM (IP) | L/S (SI)]: Total airflow rate for cooling of the 4-pipe induction unit.

  • Heating Fluid Flow [GPM (IP) | L/S (SI)]: Total fluid flow rate for heating of the 4-pipe induction unit.

  • Cooling Fluid Flow [GPM (IP) | L/S (SI)]: Total fluid flow rate for cooling of the 4-pipe induction unit.

Heating Coil Temperatures

  • Entering Air Temperature Dry Bulb [°F (IP) | °C (SI)]: Dry bulb temperature of the entering air

  • Entering Air Temperature Wet Bulb [°F (IP) | °C (SI)]: Wet bulb temperature of the entering air

  • Leaving Air Temperature Dry Bulb [°F (IP) | °C (SI)]: Dry bulb temperature of the leaving air

  • Leaving Air Temperature Wet Bulb [°F (IP) | °C (SI)]: Wet bulb temperature of the leaving air

  • Entering Fluid Temperature [°F (IP) | °C (SI)]: Value of the entering temperature of the fluid

  • Leaving Fluid Temperature [°F (IP) | °C (SI)]: Value of the leaving temperature of the fluid

Cooling Coil Temperatures

  • Entering Air Temperature Dry Bulb [°F (IP) | °C (SI)]: Dry bulb temperature of the entering air

  • Entering Air Temperature Wet Bulb [°F (IP) | °C (SI)]: Wet bulb temperature of the entering air

  • Leaving Air Temperature Dry Bulb [°F (IP) | °C (SI)]: Dry bulb temperature of the leaving air

  • Leaving Air Temperature Wet Bulb [°F (IP) | °C (SI)]: Wet bulb temperature of the leaving air

  • Entering Fluid Temperature [°F (IP) | °C (SI)]: Value of the entering temperature of the fluid

  • Leaving Fluid Temperature [°F (IP) | °C (SI)]: Value of the leaving temperature of the fluid

Zone Series Fan Powered Box - Electric

  • Total Capacity [Btu/h (IP) | Watts (SI)]: This field indicates the total capacity of the series fan powered box.

  • Primary Airflow [CFM (IP) | L/S (SI)]: Air flow rate from the central air handler to the series fan powered box for the zone.

  • Reheat Airflow [CFM (IP) | L/S (SI)]: Air flow rate for the reheat purposes of the series fan powered box.

  • Min. Primary Air Fraction: This field indicates the minimum fraction for the primary air for the series fan powered box.

  • Entering Temperature Dry Bulb [°F (IP) | °C (SI)]: Dry bulb temperature of the entering air

  • Entering Temperature Wet Bulb [°F (IP) | °C (SI)]: Wet bulb temperature of the entering air

  • Leaving Temperature Dry Bulb [°F (IP) | °C (SI)]: Dry bulb temperature of the leaving air

  • Leaving Temperature Wet Bulb [°F (IP) | °C (SI)]: Wet bulb temperature of the leaving air

Zone Series Fan Powered Box - Hydronic

  • Total Capacity [Btu/h (IP) | Watts (SI)]: This field indicates the total capacity of the series fan powered box.

  • Primary Airflow [CFM (IP) | L/S (SI)]: Air flow rate from the central air handler to the series fan powered box for the zone.

  • Reheat Airflow [CFM (IP) | L/S (SI)]: Air flow rate for the reheat purposes of the series fan powered box.

  • Min. Primary Air Fraction: This field indicates the minimum fraction for the primary air for the series fan powered box.

  • Entering Air Temperature Dry Bulb [°F (IP) | °C (SI)]: Dry bulb temperature of the entering air

  • Entering Air Temperature Wet Bulb [°F (IP) | °C (SI)]: Wet bulb temperature of the entering air

  • Leaving Air Temperature Dry Bulb [°F (IP) | °C (SI)]: Dry bulb temperature of the leaving air

  • Leaving Air Temperature Wet Bulb [°F (IP) | °C (SI)]: Wet bulb temperature of the leaving air

  • Entering Fluid Temperature [°F (IP) | °C (SI)]: Value of the entering temperature of the fluid

  • Leaving Fluid Temperature [°F (IP) | °C (SI)]: Value of the leaving temperature of the fluid

Zone Parallel Fan Powered Box - Electric

  • Total Capacity [Btu/h (IP) | Watts (SI)]: This field indicates the total capacity of the parallel fan powered box.

  • Primary Airflow [CFM (IP) | L/S (SI)]: Air flow rate from the central air handler to the parallel fan powered box for the zone.

  • Reheat Airflow [CFM (IP) | L/S (SI)]: Air flow rate for the reheat purposes of the parallel fan powered box.

  • Min. Primary Air Fraction: This field indicates the minimum fraction for the primary air for the parallel fan powered box.

  • Entering Temperature Dry Bulb [°F (IP) | °C (SI)]: Dry bulb temperature of the entering air

  • Entering Temperature Wet Bulb [°F (IP) | °C (SI)]: Wet bulb temperature of the entering air

  • Leaving Temperature Dry Bulb [°F (IP) | °C (SI)]: Dry bulb temperature of the leaving air

  • Leaving Temperature Wet Bulb [°F (IP) | °C (SI)]: Wet bulb temperature of the leaving air

Zone Parallel Fan Powered Box - Hydronic

  • Total Capacity [Btu/h (IP) | Watts (SI)]: This field indicates the total capacity of the parallel fan powered box.

  • Primary Airflow [CFM (IP) | L/S (SI)]: Air flow rate from the central air handler to the parallel fan powered box for the zone.

  • Reheat Airflow [CFM (IP) | L/S (SI)]: Air flow rate for the reheat purposes of the parallel fan powered box.

  • Min. Primary Air Fraction: This field indicates the minimum fraction for the primary air for the parallel fan powered box.

  • Entering Air Temperature Dry Bulb [°F (IP) | °C (SI)]: Dry bulb temperature of the entering air

  • Entering Air Temperature Wet Bulb [°F (IP) | °C (SI)]: Wet bulb temperature of the entering air

  • Leaving Air Temperature Dry Bulb [°F (IP) | °C (SI)]: Dry bulb temperature of the leaving air

  • Leaving Air Temperature Wet Bulb [°F (IP) | °C (SI)]: Wet bulb temperature of the leaving air

  • Entering Fluid Temperature [°F (IP) | °C (SI)]: Value of the entering temperature of the fluid

  • Leaving Fluid Temperature [°F (IP) | °C (SI)]: Value of the leaving temperature of the fluid.

Rooms in Zone

Shows the room(s) connected to the respective thermal zone. Clicking any of these rooms will bring up that Rooms details on the right most panel.

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