PM-402.1 Habitable spaces: Every habitable space except kitchens shall have at least one window or skylight of approved size facing directly to the outdoors.

PM-402.1.1 Obstructions: 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 and shall not be included as contributing to the required minimum total window area for the room.

PM-402.1.2 Basement habitable spaces: The required window area serving habitable spaces in basements shall have a minimum outside horizontal clear space measured perpendicular to the window, equal to one and one-half times the depth of the window sill below average adjoining grade.

PM-402.1.3 Window area: The minimum total window area of every sleeping room with 100 square feet (9.29 m²) or less of floor area shall be eight percent of the floor area. The minimum total window of every sleeping room with more than 100 square feet (9.29 m²) of floor area shall be eight square feet plus five percent of each square foot of floor area over 100 square feet (9.29 m²). The minimum total window area of every other habitable room for which windows are required shall be seven percent of the floor area.

PM-402.1.4 Adjoining spaces: Where natural light for rooms or spaces without exterior window areas is provided through an adjoining room or enclosed porch, the unobstructed opening to the adjoining room shall be at least eight percent of the floor area of the interior room or space, but not less than twenty-five square feet (2.33 m²). The exterior window area shall be based on the total floor area being served.

PM-402.2 Common halls and stairways:^[73.1] Every common hall, interior stairway and exterior stairway serving residential occupancies shall be provided with artificial light capable of providing a minimum of one footcandle (11 lux) at floors, landings and treads. Continuous operation of the lighting system is required except during those hours when there is sufficient natural light to comply with these requirements.

Exception: Continuous operation is not required for common hall and stairway lighting serving occupancies in Group R-3 which are equipped with light switches located within three feet (914 mm) of the access and entrance doors to such common spaces.

PM-402.3 Other spaces: All other spaces shall be provided with natural or artificial light sufficient to permit the maintenance of sanitary conditions, and the safe occupancy of the space and utilization of the appliances, equipment and fixtures.