The natural ventilation potential uses your project's chosen climate data. It calculates the savings potential by determining the annual number of hours when the outdoor air temperatures are sufficient for cooling (below the thermostat setpoint) when the simulation shows cooling load on the HVAC system. Basically it shows that during these hours you can cool with outside air, and the HVAC cooling can be turned off. Potential energy savings associated with not running the mechanical cooling and ventilation system during this period are projected. And finally, the net hours that cooling is required, even with natural ventilation, are estimated. The calculation assumes that your building form and openings will be designed to allow for stack-effect and/or cross-ventilation that will result in 20 air-changes per hour. The calculations do not take into account your actual design opening placements.
Assumes that up to 20 air changes per hour (ACH) can be brought into the building during hours when the ambient outdoor temperature is conducive to natural ventilation. It takes into account the hourly sensible and latent cooling loads plus the heating loads (ignores any natural ventilation that would result in increased heating energy). It does not take into account actual model geometry, window/opening placement or size when calculating natural ventilation potential, but does take into account windows when calculating the cooling loads. Also, it does not assume a relaxed thermostat setting and does not calculate any cross-ventilation or stack-effect. Hours reported are for hours when at least one space within the building may benefit from natural ventilation.
Note: In GBS, we provide
IDF export, so you can create and run a simulation from Revit, then export the EnergyPlus IDF model input file and open it with an EnergyPlus editor and add natural ventilation features. EnergyPlus provides a number of ways from simple to very complex to model natural ventilation. This however requires some big assumptions and lots of experience and expertise to get valid answers.
Note: While it is not currently connected to GBS, the tool
SimCFD can be used with Revit to model ventilation and airflow with one of the highest quality, industry standard Computational Fluid Dynamics (CFD) modeling tools and some nice features specifically built for architecture.