For AI agents: read the machine-readable documentation index at /llms.txt or the single-file full reference at /llms-full.txt.
Form a Business

EXISTING BUILDINGS

Municipal Code of Chicago tit. 14N, pt. I, ch. 14N-C5
in effect

Municipal Code of Chicago § 14N-C5-C501 General.

14N-C5-C501 General. The provisions of Section C501 of IECC-CE are adopted by reference with the following modifications: 1. Revise Sections C501.1 and C501.1.1 to read: "C501.1 Scope. The provisions of this chapter shall control additions, alterations, repairs, and changes of occupancy to and relocation of existing buildings. C501.1.1 Existing buildings. Except as specified in this chapter, this code shall not be used to require the removal, alteration or abandonment of, nor prevent the continued use and maintenance of, an existing building or building system lawfully in existence at the time of adoption of this code." 2. Revise Section C501.2 to read: "C501.2 Compliance. Additions, alterations, repairs, and changes of occupancy to or relocation of existing buildings shall comply with Sections C502, C503, C504 and C505 of this code, as applicable, and with the provisions for alterations, repairs, additions and changes of occupancy or relocation, respectively, in the other Chicago Construction Codes. Alterations where unconditioned or low-energy space is changed to conditioned space shall comply with Section C502. Exception: Additions, alterations, repairs or changes of occupancy complying with ANSI/ASHRAE/IESNA 90.1." 3. Revise Section C501.3 to read: "Devices and systems required by this code shall be maintained in conformance to the code edition under which they were installed. The requirements of this chapter shall not provide the basis for removal or abrogation of energy conservation, fire protection or safety systems and devices in existing buildings." 4. Revise Section C501.4 by replacing each "permitted" with "allowed." 5. Revise Section C501.5 to read: "Provisions of this code relating to the repair, alteration, relocation and change of occupancy of existing buildings shall not be mandatory for historic buildings provided that a report has been submitted to the building official and signed by a registered design professional demonstrating that compliance with that provision would threaten, degrade or destroy the historic form, fabric or function of the historic building."

Municipal Code of Chicago § 14N-C5-C502 Additions.

14N-C5-C502 Additions. The provisions of Section C502 of IECC-CE are adopted by reference with the following modifications: 1. Revise Section C502.1 to read: "Additions to an existing building shall conform to the provisions of this code as those provisions relate to new construction without requiring the unaltered portion of the existing building to comply with this code. Additions shall not create an unsafe or hazardous condition or overload existing building systems. An addition shall be deemed to comply with this code if the addition alone complies, if the existing building and addition comply with this code as a single building or if the building with the addition will use no more energy than the existing building." 2. Revise Section C502.2 by replacing "nonconditioned" with "unconditioned." 3. Revise exception 2 to Section C502.2 to read: "Where the total building performance option in Section C407 is used to comply with this section, the annual energy cost of the proposed design shall be not greater than 110 percent of the annual energy cost otherwise allowed by Section C407.2." 4. Revise Section C502.3.1 to read: "Additions shall comply with the following: 1. Where an addition has vertical fenestration that results in a total building vertical fenestration area less than or equal to that allowed by Section C402.4.1, the addition shall comply with Section C402.1.5, C402.4.3 or C407. 2. Where an addition has vertical fenestration that results in a total building vertical fenestration area greater than that allowed by Section C402.4.1, the vertical fenestration shall comply with Section C402.4.1.1 for the addition only. 3. Where an addition has a vertical fenestration area greater than that allowed by Section C402.4.1, the vertical fenestration shall comply with Section C402.4.1.1 for the addition only. 4. Where an addition has vertical fenestration that results in a total building vertical fenestration area exceeding that allowed by Section C402.4.1.1, the addition shall comply with Section C402.1.5 or C407." 5. Revise Section C502.3.2 to read: "C502.3.2 Skylight area. Additions shall comply with the following: 1. Where an addition has a skylight fenestration area that results in a total building skylight fenestration area less than or equal to that allowed by Section C402.4.1, the addition shall comply with Section C402.1.5 or C407. 2. Where an addition has a skylight fenestration area that results in a total building skylight fenestration area greater than allowed by Section C402.4.1, the skylights shall comply with Section C402.4.1.2 for the addition only. 3. Where an addition has a skylight fenestration area greater than that allowed by Section C402.4.1, the skylights shall comply with Section C402.4.1.2 for the addition only. 4. Where an addition has a skylight fenestration area that results in a total building skylight fenestration area exceeding that allowed by Section C402.4.1.2, the addition shall comply with Section C402.1.5 or C407." 6. Revise Section C502.3.3 by replacing "building" with "existing building’s."

Municipal Code of Chicago § 14N-C5-C503 Alterations.

14N-C5-C503 Alterations. The provisions of Section C503 of IECC-CE are adopted by reference with the following modifications: 1. Revise Section C503.1 to read: "C503.1 General. Alterations to any existing building shall comply with the requirements of Section C503. Alterations shall be such that the existing building is not less conforming to the provisions of this code than the existing building was prior to the alteration. Alterations to an existing building, building system or portion thereof shall conform to the provisions of this code as those provisions relate to new construction without requiring the unaltered portions of the existing building or building system to comply with this code. Alterations shall not create an unsafe or hazardous condition or overload existing building systems. Exception: The following alterations need not comply with the requirements for new construction, provided that the energy use of the building is not increased: 1. Storm windows installed over existing fenestration. 2. Surface-applied window film installed on existing fenestration assemblies reducing solar heat gain, provided that the code does not require the glazing or fenestration to be replaced. 3. Existing ceiling, wall or floor cavities exposed during construction, provided that these cavities are filled with insulation with a thermal resistance of at least R-3 per inch. Insulation shall not be required to be added to existing wall cavities for masonry above-grade walls where a registered design professional indicates in the construction documents that insulation would block air circulation in the cavity and create moisture problems that would potentially lead to differential expansion and contraction. 4. Construction where the existing roof, wall or floor cavity is not exposed. 5. Roof recover. 6. Air barriers shall not be required for roof recover and roof replacement where the scope of work does not include alterations or repairs to the remainder of the building envelope." 2. Revise the exception to Section C503.2 to read: "Exception: Where the existing building exceeds the fenestration area limitations of Section C402.4.1 prior to alteration, the building is exempt from Section C402.4.1 provided that there is not an increase in fenestration area." 3. Revise Section C503.2.1 to read: "Roof replacements shall comply with Section C402.1.3, C402.1.4, C402.1.5 or C407 where the existing roof assembly is part of the building thermal envelope and contains insulation entirely above the roof deck. In no case shall the thermal resistance (R-value) of the roof insulation be reduced or the thermal transmittance (U-factor) of the roof assembly be increased as part of the roof replacement. For low-sloped roofs, where the required R- value cannot be provided due to flashing height limitations presented by existing rooftop conditions that are not being altered, such as HVAC equipment, door or window sill height, parapet height, weep holes, and roof flashing heights not meeting the manufacturer’s specifications if reduced, the maximum thickness of insulation compatible with the available space and existing conditions shall be installed. New insulation shall have a minimum R-value of R-5 per inch. In no case shall a roof replacement reduce the R-value of the roof assembly." 4. Revise Section C503.2.2 to read: "The addition of vertical fenestration that results in a total building fenestration area less than or equal to that specified in Section C402.4.1 shall comply with Section C402.1.5, C402.4.3 or C407. The addition of vertical fenestration that results in a total building fenestration area greater than Section C402.4.1 shall comply with Section C402.4.1.1 for the space adjacent to the new fenestration only. Alterations that result in a total building vertical fenestration area exceeding that specified in Section C402.4.1.1 shall comply with Section C402.1.5 or C407. Provided that the vertical fenestration area is not changed, using the same vertical fenestration area in the standard reference design as the building prior to alteration shall be an alternative to using the vertical fenestration area specified in Table C407.4.1(1)." 5. Revise the exception to Section C503.2.2.1 by replacing "permitted" with "allowed." 6. Revise Section C503.2.3 to read: "C503.2.3 Skylight fenestration area. New skylight fenestration area that results in a total building skylight fenestration area less than or equal to that specified in Section C402.4.1 shall comply with Section C402.1.5, C402.4 or C407. The addition of skylight fenestration area that results in a total building skylight fenestration area greater than Section C402.4.1 shall comply with Section C402.4.1.2 for the space adjacent to the new skylights. Alterations that result in a total building skylight fenestration area exceeding that specified in Section C402.4.1.2 shall comply with Section C402.1.5 or C407. Provided that the skylight fenestration area is not changed, using the same skylight fenestration area in the standard reference design as the building prior to alteration shall be an alternative to using the skylight fenestration area specified in Table C407.4.1(1)." 7. Revise Section C503.3 by replacing "duct systems" with "duct systems."

Municipal Code of Chicago § 14N-C5-C504 Repairs.

14N-C5-C504 Repairs. The provisions of Section C504 of IECC-CE are adopted by reference with the following modifications: 1. Revise Section C504.1 to read: "Existing buildings shall be repaired in compliance with Section C501.3 and this section. Work on nondamaged components that is necessary for the required repair of damaged components shall be considered to be part of the repair and shall not be subject to the requirements for alterations in this chapter. Routine maintenance required by Section C501.3, repairs exempt from permit and abatement of wear due to normal service conditions shall not be subject to the requirements for repairs in this section. Where a building was constructed to comply with ANSI/ASHRAE/IESNA 90.1, repairs shall comply with the standard and need not comply with Sections C402, C403, C404 and C405." 2. Revise Section C504.2, item 3 to read: "Air barriers shall not be required to be added as part of roof repair where the scope of work does not include alterations to the remainder of the building envelope."

Municipal Code of Chicago § 14N-C5-C505 Change in use.

14N-C5-C505 Change in use. The provisions of Section C505 of IECC-CE are not adopted. The following is adopted as Section C505: "C505 CHANGE IN USE C505.1 General. Spaces undergoing a change in use that will result in an increase in demand for either fossil fuel or electrical energy and that requires a building permit shall comply with this code. Where the use of a space changes from one use in Table C405.3.2(1) or C405.3.2(2) to another use in Table C405.3.2(1) or C405.3.2(2), the installed lighting wattage shall comply with Section C405.3. Where the space undergoing a change in use is in a building with a fenestration area that exceeds the limitations of Section C402.4.1, the space is exempt from Section C402.4.1 provided that there is not an increase in fenestration area. Exceptions: 1. Where the component performance alternative in Section C402.1.5 is used to comply with this section, the proposed UA shall not be greater than 110 percent of the target UA. 2. Where the total building performance option in Section C407 is used to comply with this section, the annual energy cost of the proposed design shall not be greater than 110 percent of the annual energy cost otherwise allowed by Section C407.3."
Source: City of Chicago, Municipal Code of Chicago (American Legal Publishing, codelibrary.amlegal.com)URL: https://codelibrary.amlegal.com/codes/chicago/latest/chicago_il/0-0-0-2698671Fetched: 10/24/2026

Starting a business in Illinois? Illinois LLC guide: costs and requirements