1. ATTIC VENTILATION - 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 and snow. The net free ventilating area shall not be less than 1/150 of the area of the space ventilated. The openings shall be covered with corrosion-resistant metal mesh with mesh openings of 1/4 inch in dimension. 1994 UBC 1505.3 See limited exceptions.