Natural Ventilation model Option

Natural ventilation can either be 'Scheduled' or 'Calculated'

Scheduled - the ventilation rates are predefined using a maximum air change rate modified by operation schedules.

Calculated - the ventilation rates are calculated using wind and buoyancy-driven pressure, opening sizes and operation, crack sizes etc.

You should generally use the 'Scheduled' natural ventilation model option because it is quicker and easier to enter the related model data and also because the simulations run more quickly. However if you need to calculate natural ventilation rates which can be achieved with a particular configuration then you should use the 'Calculated' option.