13-172-070 Natural light.

   (a)   Lighting standards. In the application of the provisions of this chapter, the standard of natural light, unless otherwise specifically required by the building provisions of this Code for special occupancies and uses (described in Section 13-172-060), shall be based on 250 footcandles (2,691 lux) of illumination on the vertical plane adjacent to the exterior of the light- transmitting device in the enclosure wall and shall be adequate to provide an average illumination of at least 6 footcandles (64.58 lux) over the area of the room at a height of 30 inches (762 mm) above the floor level.

   (b)   Minimum glazing area. Every room or space intended for human occupancy shall have an exterior glazing area of not less than 8 percent of the floor area. Natural light shall be provided by glazing areas that open onto courts, yards or public ways which comply with the requirements of Section 13-172-130, or by other approved means.

   (c)   Borrowed light for remote rooms. 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 at least 8 percent of the floor area of the interior room or space, but not less than 25 square feet (2.33m2). The plane of the opening through which light is borrowed for a remote room without windows shall be parallel to the window wall. The exterior glazing area shall be based on the total floor area being served.

(Added Coun. J. 4-29-98, p. 66679, § 1)

13-172-080 Artificial light.

   (a)   General. Artificial light shall be provided that is adequate to provide an average illumination of 10 footcandles (107 lux) over the area of the room at a height of 30 inches above the floor.

   (b)   Stairway Illumination. (i) All stairways within dwelling units and exterior stairways serving a dwelling unit shall have an illumination level on tread runs of 1 footcandle (11 lux). (ii) The control for activation of the required stairway lighting within a dwelling unit shall be operable from the top and bottom of each stairway without traversing any step of the stair. The illumination of an exterior stairway serving a dwelling unit shall be controlled from inside the dwelling unit, unless continuously illuminated or automatically activated.

(Added Coun. J. 4-29-98, p. 66679, § 1; Amend Coun. J. 9-6-17, p. 55278, Art. II, § 45)

13-172-090 Natural ventilation.

   (a)   General. Natural ventilation of an occupied space shall be through windows, doors, louvers or other natural openings to the outdoor air.

   (b)   Ventilation area required. The minimum openable area to the outdoors shall be 4 percent of the floor area being ventilated.

   (c)   Borrowed ventilation for remote rooms. Where rooms and spaces without openings to the outdoors are ventilated through an adjoining room, the opening to the adjoining room shall be unobstructed and shall have an area not less than 8 percent of the floor area of the interior room or space, but not less than 25 square feet (2.3m2). The minimum openable area to the outdoors shall be based on the total floor area being ventilated.

   (d)   Ventilation through area wells. Where openings below grade provide required natural ventilation, the outside horizontal clear space measured perpendicular to the opening shall be at least equal to or larger than the depth of the opening. The depth of the opening shall be measured from the average adjoining ground level to the bottom of the opening.

   (e)   Openings onto yards or courts. Where natural ventilation is to be provided by openings onto yards or courts, such openings shall comply with the requirements of Section 15-8-110 of the Municipal Code of Chicago.

(Added Coun. J. 4-29-98, p. 66679, § 1)

13-172-100 Mechanical ventilation.

   Mechanical ventilation shall conform to the applicable requirements set forth in Chapter 18-13 and Chapter 18-28 of this Code.

(Added Coun. J. 4-29-98, p. 66679, § 1; Amend Coun. J. 9-14-16, p. 31143, § 5; Amend Coun. J. 11-9-16, p. 36266, § 26*)

* Editor's note – The amendment of Coun. J. 11-9-16, p. 36266, § 26 to this section did not take into account the amendment of Coun. J. 9-14-16, p. 31143, § 5, which renders the later amendment unnecessary.

13-172-110 Ventilation of special spaces.

   (a)   Roof spaces.

      (i)   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 ventilation openings. The ventilation openings shall be tested for rain and snow infiltration in a manner representative of the intended installation and shall not permit the entrance of rain and snow when so tested. Ventilation openings shall not be provided in roof areas, or portions thereof, which are subject to snow drift as determined by Section 13-52-280.

      (ii)   The minimum required net free ventilating area shall be 1/150 of the area of the space ventilated. Where ridge or gable vents are utilized, one- half of the ventilation openings shall be provided by ridge or gable vents, with the balance of the ventilation openings provided by eave or cornice vents. The openings shall be covered with corrosion-resistant mesh or other approved materials with openings not more than 1/2 inch (13 mm) in any direction.

      (iii)   The minimum required area is permitted to be reduced to 1/300, provided that a vapor retarder having a permeance not exceeding 1 perm is installed on the warm side of the ceiling; or the ridge or gable ventilation openings are located in the upper third of the space to be ventilated with the balance of the required ventilation provided by eave or cornice vents.

   (b)   Crawl Spaces.

      (i)   Crawl space areas, other than those used as an underfloor plenum, shall be ventilated by an approved mechanical means or by openings in exterior foundation walls. Openings shall be located as close to corners as practicable and shall provide cross ventilation on at least two approximately opposite sides. The openings shall be covered with corrosion-resistant mesh not less than 1/4 inch (6 mm) nor more than 1/2 inch (13 mm) in any direction.

      (ii)   Openings shall have a net area of not less than 1 square foot (0.093 m 2 ) for each 150 square feet (13.95 m 2 ) of foundation space. Where an approved vapor retarder is installed over the ground surface, the required net area of openings shall be reduced to 0.1 square foot (0.093 m 2 ) for each 150 square feet (13.95 m 2 ) and vents shall have manually operable louvers.

   (c)   Alternative mechanical ventilation. Enclosed attic, rafter and crawl spaces which are not ventilated as herein required shall be equipped with a mechanical ventilation system conforming to the applicable requirements set forth in Chapter 18-28 of this Code.

(Added Coun. J. 4-29-98, p. 66679, § 1; Amend Coun. J. 9-14-16, p. 31143, § 6; Amend Coun. J. 11-9-16, p. 36266, § 26*)

* Editor's note – The amendment of Coun. J. 11-9-16, p. 36266, § 26 to this section did not take into account the amendment of Coun. J. 9-14-16, p. 31143, § 6, which renders the later amendment unnecessary.