CHAPTER 4
LIGHT, VENTILATION AND OCCUPANCY LIMITATIONS
About this chapter: Chapter 4 sets forth requirements to establish the minimum environment for occupiable and habitable buildings by establishing the minimum criteria for light and ventilation and identifying occupancy limitations including minimum room width and area, minimum ceiling height and restrictions to prevent overcrowding.
401.1 Scope. The provisions of this chapter shall govern the minimum conditions and standards for light, ventilation and space for occupying a structure.
401.2 Responsibility. The owner of the structure shall provide and maintain light, ventilation and space conditions in compliance with these requirements. A person shall not occupy as owner-occupant, or permit another person to occupy, any premises that do not comply with the requirements of this chapter.
401.3 Alternative devices. In lieu of the means for natural light and ventilation herein prescribed, artificial light or mechanical ventilation complying with the applicable building code shall be permitted.
402.1 Habitable spaces. Every habitable space shall have not less than one window of approved size facing directly to the outdoors or to a court. The minimum total glazed area for every habitable space shall be 8 percent of the floor area of such room. Wherever walls or other portions of a structure face a window of any room and such obstructions are located less than 3 feet (914 mm) from the window and extend to a level above that of the ceiling of the room, such window shall not be deemed to face directly to the outdoors nor to a court and shall not be included as contributing to the required minimum total window area for the room.
Exception: Where natural light for rooms or spaces without exterior glazing areas is provided through an adjoining room, the unobstructed opening to the adjoining room shall be not less than 8 percent of the floor area of the interior room or space, or not less than 25 square feet (2.33 m2), whichever is greater. The exterior glazing area shall be based on the total floor area being served.
402.2 Common halls and stairways. Every common hall and stairway in residential occupancies, other than in one- and two-family dwellings, shall be lighted at all times with not less than a 60-watt standard incandescent light bulb for each 200 square feet (19 m2) of floor area or equivalent illumination, provided that the spacing between lights shall not be greater than 30 feet (9144 mm). In other than residential occupancies, interior and exterior means