This prerequisite establishes a baseline for providing a minimum amount of outdoor air to buildings in order to maintain good indoor air quality and keep occupants comfortable and healthy. This prerequisite references ASHRAE 62.1-2004 (with errata but without addenda) and is often more stringent than local building codes, although it is not likely to entail any added costs.

Two cases, both may be needed

The compliance paths for mechanically ventilated and naturally ventilated spaces, are somewhat different and you may need to follow both paths for the same building. Naturally ventilated spaces must follow the distinct methodology for natural ventilation defined by ASHRAE 62.1, paragraph 5.1, even if other spaces in the same building are mechanically ventilated and are following the methodology defined by ASHRAE 62.1, section 4 through 7 (for spaces with both mechanical and natural ventilation, or just mechanical ventilation). 

New construction additions will need to confirm that any ventilation systems serving the project meet the ventilation rates required by ASHRAE 62.1-2004, even if the ventilation system design itself is outside the scope of the project. If base building systems do not meet the standard’s requirements, you will need to either modify the base building system or provide detailed analysis documenting the constraints and explaining why the base building systems cannot be upgraded.