Lighting

The Chicago Building Code requires spaces to have a certain amount of natural light, as it is a necessary component of a healthy environment. Windows must have a glazing area (the amount of glass) equal to 8% of floor area, and a minimum illumination equal to six-foot candles placed 30 inches above the floor. For more information on how light intensity is calculated, click here to view Light Search.

If you have a 1,000 square-foot space, you must have 80 square feet of windows for natural light. Artificial light cannot be substituted for natural light in occupied rooms. Outside of natural light for living spaces, there are generally no specific requirements for artificial lighting levels. Requirements change for non-residential spaces, depending on how the property is used and when it was built. In addition, when artificial light is utilized, it must follow the same requirements and standards set for natural light. (See Section 13-196-730 Light and Ventilation of the CBC for further information on light requirements.)

Natural light and ventilation is required for all dwelling units. An exemption to the natural light and vent rule is available, but is only applicable to certain rooms -- called multi-purpose rooms -- in single-family and multi-family dwelling units located in buildings that received their permits before April 1, 1998.

Section 13-172-03: Definitions classifies a multi-purpose room as “a room within a family dwelling unit which may be used as a study, office, multimedia room, or other function normally associated with family dwelling occupancy, and which room is in excess of the essential family needs for living, dining and sleeping outlined in Section 13-172-060 (c). Multi-purpose rooms shall not be used as bedrooms.”

Remember, this exemption does not apply to any new construction, but is intended to encourage the renovation and reuse of existing buildings. With that being said, this exemption applies to dwelling units that meet all of the following requirements:

1. If natural light or ventilation does not exist, then mechanical light or ventilation must be provided, and must meet the current code's requirements.
2. The area of the “multi-purpose room” cannot exceed 15% of the total floor area of the dwelling unit.
3. If the dwelling unit is 1,300 square feet or less, the unit must have at least one bedroom, as well as areas or rooms designated for living and dining, in addition to the exempt multi-purpose room.
4. If the square footage of the dwelling unit is over 1,300, the unit must have at least two bedrooms as well as areas or rooms designated for living and dining IN ADDITION TO the multi-purpose room that is exempt.

The multi-purpose room must meet ALL of these requirements to be considered exempt of the natural light and vent requirements.