Natural Ventilation: Which spaces are to be considered?

I dont consider non-regularly occupied spaces as needing exhaust or outside air requirements. I havent had problems with reviewers so far. Since a corridor is not an "occupiable space" as per the definition of an occupiable space in ASHRAE 62.1, I ignore the need for outside air. If there are reception areas that "connect" or share the same air as the corridors, then I consider the corridor occupiable. Mixed mode ventilation is a combination of natural and mechanical ventilation. So the toilets are mechanically ventilated. Dont know about the grouping.

Rudolph, I have to disagree with your interpretation of corridors as unoccpiable spaces. Note that ASHRAE and USGBC use different definitions. You refer to "non-regularly occupied spaces" such as what is defined in the LEED reference manual. ASHRAE uses no such terminology. ASHRAE 62.1 Addendum t clarifies the definition of an occupiable space. This definition does not rule out corridors. Furthermore, Table 6-1 includes corridors as spaces that need ventilation. It is true that storage rooms are also included but the differentiating factor between the storage rooms and the corridors is that corridors are utilized for the same purpose in every building and storage rooms vary greatly. That is the reason for the Note B on the storage rooms in the table. The corridor should be ventilated in accordance with the standard. Marco, the doors are considered obstructions. Also, I would calculate the requirement for each room separately and apply it to the system as a whole based on the most demanding percentage.

ASHRAE 62.1-2010 Users manual example 6-E gives some examples. It seems as if this issue should be evaluated on a case by case basis. A school corridor, for example, based on the example 6-E of the users manual, I would not consider occasionally ocupied as a huge number of students occupy the corridor atleast every hour. A corridor on the 10th floor of an office building on the other hand, I would consider occasionally ocupied and not needing outside air.

Rudolph, I agree that there could be times when a corridor is not considered an occupiable space. It may be conservative of me but I only consider a corridor non-occupiable if it only serves spaces that are also non-occupiable. I suppose it is up to the engineer of record to make the determination in each case.