In E+, DesignSpecification:OutdoorAir defines intentional ventilation outdoor air (calculation methodology and flow rates, optionally defined as ACH). This is usually required for zone load calculations, sizing calculations, HVAC controllers, etc.

In E+, ZoneInfiltration:DesignFlowRate describes unintentional infiltration rates (optionally as ACH). Similarly required for zone load calculations and sizing calculations.

In OpenStudio, both objects are associated to Spaces.