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(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)
(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)
(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)
(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.
(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.
All courts and yards required to serve rooms for natural light or natural ventilation purposes shall comply with the requirements of this section.
(a) Minimum width. (i) Every such court or yard shall have a minimum width of 3 feet (1,005 mm) up to a height of 36 feet above grade and thereafter an additional 2 inches (76 mm) for each 1 foot (305 mm) of height or fraction thereof up to a maximum width of 15 feet (7,620 mm). Above required width values shall apply to outer courts and twice these values shall apply for inner courts. (ii) In the case of irregular or gore- shaped courts or yards, as these are defined in Section 13-172-030, the average width shall not be less than the required width of a court in accordance with subsection (a) (i) of this section, but shall not be less than 5 feet (1,524 mm) at any point.
(b) Access to court. A door or other means of access shall be provided at the bottom of every court that is not otherwise provided with convenient access for purposes of cleaning.
(c) Air intakes. Every court which serves one or more habitable rooms and which does not open for its full height on one or more sides to a street or legal yard, shall be connected at or near the bottom with a street or yard by a horizontal intake or passage of fire-resistance rated construction, as provided in Section 15-8-660. Such intake or passage shall have a cross-sectional area of not less than 21 square feet (1.95m2) and shall remain fully open at both ends and unobstructed for its full size and length, except that grilles of noncombustible construction are permitted at the ends of the intake.
(Added Coun. J. 4-29-98, p. 66679, § 1)
(a) Permissible projections. Every required court and yard shall remain unobstructed for its required area and full height, except for the projections permitted in subsections (b) through (f) of this section.
(b) Maximum encroachment. A part of any building or structure shall not extend into side courts, inner courts or yards required for light and ventilation of habitable and occupiable rooms unless permitted by the Chicago Zoning Ordinance. The encroachment shall not exceed 20 percent of the legal area of the yard or court which is required for light and ventilation purposes.
(c) Accessories. In Class A (residential) and Class B (institutional) occupancies, clothes poles, arbors, garden trellises and other such accessories shall not be prohibited in the open spaces at ground level.
(d) Steps and architectural features. Steps, window sills, belt courses and similar architectural features, as well as rain leaders and chimneys, shall not project more than 2 feet (610 mm) beyond the face of the wall.
(e) Exterior stairways and fire escapes. Outside stairways, smokeproof tower balconies, fire escapes or other required elements of a means of egress shall not project more than 4 feet (1,219 mm) beyond the face of the wall.
(f) Motor vehicle parking. Where approved, required court and yard areas for automobile parking spaces or private garages not exceeding one story in height where accessory to and only for the occupants of a Class A (residential) occupancy are permitted, provided that required windows for light and ventilation are not obstructed thereby.
(Added Coun. J. 4-29-98, p. 66679, § 1; Amend Coun. J. 4-15-15, p. 106130, § 12; Amend Coun. J. 9-14-16, p. 31143, § 7)