NAIMA recommends the following widely used ventilation strategies:

• Provide ventilation for each separate space to the outside with ventilating openings protected against the entry of rain and snow.
• The total net free ventilating area shall be no less than 1/150 of the attic floor area if no vapor retarders are used, or 1/300 of the attic floor area when a vapor retarder having a permeance of one perm or less is used.