Construction tab in model data under Airtightness header
When Calculated natural ventilation is active, the Airtightness is defined by a position on a five point scale:
The five settings correspond to the five Crack templates.
You can switch off calculated infiltration off by unchecking the Model infiltration checkbox. This may be useful if you are carrying out a summertime simulation of a large building to reduce the number of cracks in the model and so speed simulations.
Note: if you do switch off infiltration when calculated natural ventilation is active, you should make sure that Natural ventilation (HVAC tab) is switched on to ensure that sufficient flow paths exist. Otherwise EnergyPlus may crash.