The ventilation requirement of 1203.2 applies to ENCLOSED attics and ENCLOSED rafter spaces. If the enclosed area is enclosed by roof sheathing on the top, and building ceiling on the bottom, it is enclosed for ventilation purposes. Having the ceiling suspended by furring strips does not change the fact that the attic or rafter spaces are enclosed.
It appears that enclosed attics are required to have ventilation and enclosed rafter spaces formed where ceilings are applied directly to underside of roof framing members require ventilation of each space formed. If the hung ceiling, along with the bracing and insulation, can be detailed to show it does not interfere with the free movement of air than ventilation of every space would not be needed.
While I agree with Mr. Moore that the section applies to "enclosed attics and enclosed rafter spaces" the sentence goes on to define enclosed as "...formed where ceilings are applied directly to the underside of roof framing members..." If the ceiling is not applied directly to the underside of the roof framing members, the section does not apply. However, I would consider a ceiling attached to furring strips that are attached directly to the underside of roof framing members to be creating an enclosed attic space. I suggest the response also note that unvented attics are permitted per Section 1203.3.
