Construction tab in model data under Airtightness header
The infiltration rate (rate of entry of unintentional air from outside through cracks, holes and through the porosity of the fabric) can be set in Air changes per hour (ac/h) and is constant throughout the simulation. The air flow rate in m3/s is calculated from the ac/h data using:
m3/s = ac/h * ZoneVolume / 3600
where ZoneVolume is the total air volume of the space including the volume of floor and ceiling constructions and any raised floor and suspended ceiling voids (if selected in Separate constructions) and including half the volume of partition walls.
Note: this total zone volume value may be different from the value used for calculating air flow rates for natural ventilation and mechanical ventilation which have model options for excluding floor/ceiling constructions.