The IAQP (ASHRAE 2007) is a design procedure in which outdoor air intake and other system design parameters are based on an analysis of contaminant sources, and contaminant concentration targets. This is particularly useful for large air distribution systems that serve a number of different zone types with varying occupancy levels. The Controller:MechanicalVentilation object simplifies the procedure for calculating these outdoor air ventilation requirements and resetting them based on varying occupancy levels. The outdoor air ventilation rate can then be reset dynamically as operating conditions change (e.g., variations in occupancy). For using occupancy at every time step, the DCV flag must be set to ‘Yes’. The number of people varies based on the setting of the DCV flag in the Controller:MechanicalVentilation object. The VRP currently requires outdoor air ventilation rates to be determined based on the floor area of each occupied zone plus the number of people in each zone. Determining the outdoor air ventilation rate and introducing this ventilation via the mixed air box are accomplished by the mechanical ventilation and outdoor air controller objects. The inputs for this object are fully described in the EnergyPlus Input Output Reference. The outdoor air system (AirLoopHVAC:OutdoorAirSystem) is a subsystem of an AirLoopHVAC which handles the mixed air portion of the primary air system: the system relief air, the outside air inlet, and any components and controllers associated with the system relief air and outside air streams. DesignSpecification:ZoneAirDistribution to describe air distribution effectiveness and secondary recirculation (for multi-path ventilation systems) for each zone.DesignSpecification:OutdoorAir to describe the outdoor air requirements for each zone.Controller:OutdoorAir to control the outside air flow rate introduced via the mixed air box.Controller:MechanicalVentilation with the DCV flag set to ‘Yes’ to determine the minimum outdoor air flow rate to be provided by the mixed air box.AirLoopHVAC:OutdoorAirSystem to simulate the mixed air box of the air loop.The user must include the following five objects in their input data file in order to model CO 2-based DCV (using VRP or IAQP): The VRP first calculates the breathing-zone outdoor air flow rate based on two components – the zone occupant component and the zone floor area component, then it calculates the zone supply outdoor air flow rate considering the zone air distribution effectiveness and secondary recirculation (for mult-path systems only), and finally calculates the system outdoor air flow rate considering the zone diversity and system ventilation efficiency. Modulating the outdoor ventilation air while maintaining proper indoor air quality has the potential for large energy savings compared to constant rate ventilation systems that are typically designed to provide outdoor ventilation air based on maximum anticipated occupancy.ĮnergyPlus can model CO 2-based DCV by the ventilation rate procedure (VRP) defined in ASHRAE Standard 62.1-2007/2010 for single and multiple path systems, and the indoor air quality procedure (IAQP) defined in Standard 62. CO 2-based demand controlled ventilation (DCV) is being increasingly used to modulate outdoor ventilation air based on real-time occupancy (Emmerich and Persily 1997, Schell et al. Although not a contaminant of concern in most buildings, carbon dioxide (CO 2) levels can be monitored as an indicator of building occupancy and the associated human bioeffluent concentration. ASHRAE Standard 62.1, Ventilation for Acceptable Indoor Air Quality, contains provisions that allow building ventilation systems to vary the amount of outdoor ventilation air delivered to occupied zones based on feedback from sensors that monitor various indoor air contaminants (ASHRAE 2007).
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