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This document provides guidance on the Additional fresh air option in Hevacomp Simulator.
Many of the Simulations within Hevacomp Simulator contain an option to incorporate Additional fresh air into your design. The Frequency simulation, for example, features the following:
In Hevacomp v26, this will only affect results if you have chosen the Simple air change rate option, within the Simulator > Design Data > Model menu:
If Multi-zone air flow model is selected on the other hand, results will not be affected by this Additional fresh air. This is because the purpose of the Multi-zone air flow model is to analyse detailed flowpaths such as openable windows, rather than the affect of simple air change figures.
Should you need to specify additional fresh air while using the Multi-zone air flow model, then you can do so by defining the HVAC system that supplies your additional airflow, using Fresh air only, and assign it to the relevant rooms.
This behaviour is a result of a change in functionality with the EnergyPlus Engine that Design Simulation uses.
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a change in functionality with the EnergyPlus Engine that Design Simulation uses.
With V25 (which used V4 of EnergyPlus) whether Multi-Zone or Simple air flow networks were selected, the extra air-change rate would be considered.
With V26 (which uses V8 of EnergyPlus) - extra air change are only considered with Simple air flow networks. For Multi-Zone networks, air changes must be controlled with openings (windows, etc) and HVAC - This is a change within EnergyPlus and is outside of our control.