Ventilation.
Municipal Code of Chicago § 14B-12-1202
in effect14B-12-1202 Ventilation.
The provisions of Section 1202 of IBC are adopted by reference with the following modifications:
1. Revise Section 1202.1 to read:
“1202.1 Ventilation required.
Every occupiable space shall be provided with ventilation in accordance with Sections 1202.1.1 through 1202.1.3.
1202.1.1 Mechanical exhaust systems.
A mechanical exhaust system in accordance with the Chicago Mechanical Code shall be provided in toilet rooms and bathrooms.
1202.1.2 Mechanical ventilation.
Mechanical ventilation in accordance with Section 403 of the Chicago Mechanical Code shall be provided in:
1. Ambulatory care facilities.
2. Group I-2 occupancies.
3. Dwelling units and sleeping units complying with or exceeding the new construction building thermal envelope air leakage requirements in the Chicago Energy Conservation Code or Chicago Energy Transformation Code in effect at the time of construction. Dwelling units and sleeping units in buildings and additions constructed in or after 2010 shall be presumed to meet this standard.
4. Rooms or spaces where mechanical ventilation is specifically required by Chapter 4, the Chicago Mechanical Code, the Chicago Energy Transformation Code, or the Chicago Fire Prevention Code.
5. Rooms or spaces required to be provided with cooling and dehumidification equipment in accordance with Section 1203 of this code or Section 803 of the Chicago Minimum Requirements for Existing Buildings.
6. Rooms or spaces not provided with means of natural ventilation in accordance with Section 1202.5.
1202.1.3 Natural ventilation.
Means of natural ventilation in accordance with Section 1202.5 of shall be provided in:
1. Rooms intended for dining, living or sleeping in a dwelling unit or sleeping unit in a Group I-1, R-2, R-3, R-4 or R-5 occupancy.
Exception: Buildings containing 11 or more dwelling units where all dwelling units and sleeping units in the building are provided with mechanical ventilation in accordance with Section 403 of the Chicago Mechanical Code and the building is equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1 or 903.3.1.2.
2. Rooms or spaces not provided with mechanical ventilation in accordance with Section 403 of the Chicago Mechanical Code.”
2. Revise the exceptions to Section 1202.2.1 to read:
"Exception: The net free cross-ventilation area shall be permitted to be reduced to 1/300 provided at least 40 percent and not more than 50 percent of the required venting area is provided by ventilators located in the upper portion of the attic or rafter space. Upper ventilators shall be located not more than 3 feet (914 mm) below the ridge or highest point of the space, measured vertically, with the balance of the ventilation provided by eave or cornice vents. Where the location of wall or roof framing members conflicts with the installation of upper ventilators, installation more than 3 feet (914 mm) below the ridge or highest point of the space shall be permitted."
3. Revise item 4 in Section 1202.3 to read:
"4. Any air-impermeable insulation shall be a Class II vapor retarder or shall have a Class II vapor retarder coating or covering in direct contact with the underside of the insulation."
4. Revise item 5.1.3 in Section 1202.3 to read:
"5.1.3. Where both air-impermeable insulation and air-permeable insulation are provided, the air- impermeable insulation shall be applied in direct contact with the underside of the structural roof sheathing in accordance with Item 5.1.1 and shall be in accordance with the R-values in Table 1202.3 for condensation control. The air-permeable insulation shall be installed directly under the air- impermeable insulation."
5. Delete item 5.1.4 in Section 1202.3.
6. Revise exception 2 to Section 1202.3 to read:
"2. Section 1202.3 does not apply to enclosures that are humidified beyond 35 percent during winter months."
7. Revise Table 1202.3 by deleting all rows except for Climate Zone 5.
8. Revise note a to Table 1202.3 to read:
"a. Contributes to, but does not supersede, thermal resistance requirements for attic and roof assemblies in the Chicago Energy Conservation Code."
9. Revise Section 1202.4 by deleting "1202.4.2."
10. Revise Section 1202.4.1 to read:
"1202.4.1 Ventilation openings.
Ventilation openings through foundation walls shall be provided. The openings shall be placed so as to provide cross-ventilation of the under-floor space. The net area of ventilation openings shall be in accordance with Section 1202.4.1.1 or 1202.4.1.2."
11. Delete Section 1202.4.2.
12. Delete Section 1202.4.4.
13. Revise Section 1202.5 and its subsections to read:
"1202.5 Natural ventilation.
Where required, natural ventilation shall be through windows, doors, louvers or other openings to the outdoors that open upon a public way or a yard or court complying with Section 1205. The operating mechanism for such openings shall be readily controllable by the occupants of the room or space served.
1202.5.1 Ventilation area required.
The net openable area of the openings to the outdoors, without regard for window opening control devices or limiters, shall be at least 4 percent of the floor area being ventilated.
1202.5.1.1 Adjoining spaces.
For the purpose of natural ventilation, any space is permitted to be considered as a portion of an adjoining room where at least one-half of the area of the common wall is open and unobstructed and provides an opening of not less than 10 percent of the floor area of the interior space or 25 square feet (2.32 m2), whichever is greater. The net openable area shall be at least 4 percent of the aggregate floor area.
1202.5.1.2 Remote rooms.
Where rooms and spaces without openings to the outdoors are ventilated through an adjoining room, the opening to the adjoining room shall either:
1. be unobstructed and shall have an area of not less than 8 percent of the floor area of the remote room or space, but not less than 25 square feet (2.3 m2).
2. be equipped with doors, movable panels, or louvers that are operable from within the remote room and that when fully open provide a net open area of not less than 10 percent of the floor area of the remote room or space, but not less than 30 square feet (2.8 m2).
The openable area of the openings to the outdoors shall be based on the total floor area being ventilated.
1202.5.1.3 Residential basements.
Where at least 40 percent of the net floor area of a Group R dwelling unit, not used as congregate living facilities, is located entirely above grade and provided with natural ventilation as required in this section, basement-level occupiable spaces may be provided with mechanical ventilation and exhaust providing at least 0.35 air changes per hour in lieu of natural ventilation openings.
1202.5.1.4 Openings below grade.
Where openings below grade provide required natural ventilation, the outside horizontal clear space measured perpendicular to the opening shall be one and one-half times 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.
1202.5.2 Contaminants exhausted.
Contaminant sources in naturally ventilated spaces shall be removed in accordance with the Chicago Mechanical Code and the Chicago Fire Prevention Code."
14. Delete Section 1202.6.
(Amend Coun. J. 2-19-20, p. 14473, Art. II, § 56; Amend Coun. J. 1-26-22, p. 43756, Art. II, § 14; Amend Coun. J. 6-17-26, p. 45214, Art. IV, § 34)
Source: City of Chicago, Municipal Code of Chicago (American Legal Publishing, codelibrary.amlegal.com)URL: https://codelibrary.amlegal.com/codes/chicago/latest/chicago_il/0-0-0-2665592Fetched: 10/24/2026