In an Ideal Loads Air System, What is the heat gain from ZoneVentilation referring to exactly ?

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I am trying to build a building archetype to try and identify just the heat gains of the building and their component contributions. the climate is 1A according to the ASHRAE classification, so cooling is dominant. I am getting more than 30% of my heat gain introduced to the building coming from ventilation. I understand that that heat gain is linked to the supply temperature of the air to the zone relative to the outdoor temperature. But I want to know whether something else is included under ZoneVentilation and how is the actual cooling energy consumption actually being calculated. I looked in the engineering reference and the InputOutput Reference but the explanations are not detailed enough.