Interior always. 3-2" holes with 1/4"hardware cloth, per bay. Google that to verify. Oh-Oh!
I found one site with 1/8" screening. "Ventilation Required. When determined necessary by the building official due to climatic
conditions, enclosed attics and enclosed rafter spaces formed where ceilings are applied
directly to the underside of roof rafters shall have cross ventilation for each separate space
by ventilating openings protected against the entrance of rain or snow. Ventilating openings
shall be provided with corrosion-resistant wire mesh, with the least dimension of 1/8 inch." Be safe, GBAR