Windows and siding in St. Clair County
4 places we cover, and the rules that apply in each.
Every place in St. Clair County enforces the same residential energy code, and that is not a coincidence or a courtesy — it is state law. The Illinois Energy Conservation Code sets the standard for the whole state, and no unit of local government, home rule or not, may regulate residential energy standards in a way that is either weaker or stronger than it. The Capital Development Board adopted the 2024 edition, in force since 30 November 2025.
What still changes city to city here is permits and contractor requirements, and those change a great deal. One village in this metro exempts siding and window replacement outright; a city ten minutes away deleted its entire exemption list.
55.3% of the housing in St. Clair County was built before 1980, and 13.4% before 1940 (15,436 of 115,348 units). That is the number that decides whether the federal lead rule is on your job, and on both of these trades it very often is: window replacement is never exempt from it at any size, and a whole-house re-side clears the exterior threshold immediately.
| Place | Permit to re-side? | Permit for a like-for-like window? | Adopted energy code | Window must meet |
|---|---|---|---|---|
| Belleville | Yes | Yes | 2024 IECC, as amended by the Capital Development Board (Illinois Energy Conservation Code) - statewide, effective 11/30/2025 | — |
| Fairview Heights | Yes | Yes | 2024 IECC, as amended by the Capital Development Board (Illinois Energy Conservation Code) - statewide, effective 11/30/2025 | — |
| O'Fallon | Not published | Not published | Illinois Energy Conservation Code (statewide) | — |
| Swansea | No | No | 2024 IECC, as amended by the Capital Development Board (Illinois Energy Conservation Code) - statewide, effective 11/30/2025 | — |
Things worth knowing before you sign anything
Belleville
No published exempt-work list of any kind, so nothing is carved out for re-siding, re-roofing or windows. Doubled fee for work started without a permit. Contractor registration is a bare filing with the Building Official - no fee, bond or insurance published, which is weaker than a typical Illinois bonded-registration scheme.
Fairview Heights
Neither publishes adopted code editions, a fee schedule, or contractor requirements. Published exemption of note: 'no permit is required for fencing.' Accessory-structure threshold is 200 square feet (compare Waterloo's 50 sq ft).
Swansea
Swansea is the only jurisdiction in this metro that expressly exempts replacement of windows, siding, shingles and roof decking from any building permit - no permit, no fee, no inspection for a straight re-side or same-opening window job. The exemption dates to Ord. 1465 (2006) and was carried forward by Ord. 1830 (7-2-2018). Swansea also runs the oldest residential code in this metro (2006 IRC, Sec. 150.023 as revised by Ord. 1887, 8-17-2020), tied with Waterloo. The Residential page hedges generally - 'Remodeling existing residences is generally allowed but may need a building permit' - which reads as contradicting the categorical Sec. 150.025(D) exemption; the codified ordinance is the authority and the web page is the looser text.
Windows or siding in St. Clair County?
We will tell you what your particular city requires before we quote anything.
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