## Zone Loads ### Internal Gains Internal gains include people, lights, equipment, ventilation, and infiltration. Unlike the Object Info dialog, this dialog does not allow you to view gains in current zones, but only to specify values that will be written to the file. Internal gains are modeled using the input objects 'People', 'Lights', 'ElectricEquipment', 'GasEquipment', 'ZoneVentilation:DesignFlowRate', and 'ZoneInfiltration:DesignFlowRate'. Most fields of these objects are defaulted. Look at the InputOutputReference and Energy+.idd for a full list of all fields. A set of internal gains and schedules for a typical office building have been added for reference only. The schedules are present in the NewTemplate.idf file but will not be available in all existing IDF files. You can reset the internal gains dialog to these values with the "Reset to Default Office" button. No IDF objects will be added for internal gains with values less than or equal to zero. Applying internal gains to selected zones removes these types of objects. Lights objects are required to add Daylighting:Controls to a zone. Remember to remove 'ZoneVentilation:DesignFlowRate' when moving your file to more advanced HVAC systems which provide outdoor air to the space through the system and not at the zone level. Renaming zones after applying internal gains can cause problems. However, you can always fix these by hand in the IDF. You can obtain the last Zone Loads Report in comma separated value (CSV) format to verify the operations that have been performed. You can also save a copy of the IDF before and after the operation and then use a file comparison tool to run a DIFF. ### Ideal Loads Air System For models starting from scratch, HVACTemplate:Zone:IdealLoadsAirSystem gives the quickest path for load calculations using EnergyPlus. The Ideal Loads Air System is used to sum the zone heating and cooling loads without modeling a full HVAC system. It provides a quick and easy way to evaluate the impacts of building envelope perturbations and changes in internal gains. EnergyPlus includes several other HVACTemplate systems such as PTAC, PTHP, and many others which are only slightly more complicated that HVACTemplate:Zone:IdealLoadsAirSystem. These systems must currently be added in the IDF text directly. HVACTemplate systems are expanded to full EnergyPlus input by the ExpandObjects.exe preprocessor before a simulation is run. The expanded IDF file is copied back to the original directory with an 'expidf' extension. EnergyPlus simulations may experience problems if internal gains are present but no system is included to remove energy from zones with internal gains. Adding HVACTemplate:Zone:IdealLoadsAirSystem to selected zones removes existing objects of type HVACTemplate:Zone:IdealLoadsAirSystem. HVACTemplate:Thermostat is referenced by each HVACTemplate:Zone:IdealLoadsAirSystem to specify heating and cooling set points. You can obtain the last Zone Loads Report in comma separated value (CSV) format to verify the operations that have been performed. You can also save a copy of the IDF before and after the operation and then use a file comparison tool to run a DIFF. ### Saved Preferences The initial values for internal gains correspond to a general office building. The initial schedules are those included in NewTemplate.idf when starting a new model from scratch and correspond to a general office building. You can save settings for internal gains that correspond to other space types or variations. You can then reload and apply these settings to model other space types or to generate perturbations on the current model. (Credit: David Goldwasser/NREL)
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