Insulating a house in Belleville runs on one state energy code, not a local one — here is the R-value it sets, what the city does and does not ask a permit for, the Ameren Illinois discount your address qualifies for, and how old the housing here really is.
Belleville runs to about 23 square miles and roughly 41,370 people. It sits about 14 miles southeast of downtown St. Louis. There are around 20,212 housing units here, and the great majority of them are heated and cooled through a ceiling nobody has ever sealed. The community dates back to 1819. We cover ZIP codes 62220, 62221, 62222, 62223, 62225 and 62226.
We have not logged a completed job in Belleville yet. We would rather say so than put a number on this page that is not real.
The typical home in Belleville dates to around the early-1960s. Postwar building here often meant three or four inches of fibreglass and no attempt at air sealing. If nobody has touched it since, that is what is still up there.
A mix of pre-1940 housing (about 26% of homes, including German-built row houses) and mid-20th-century construction.
Founded in 1814 and incorporated as a village in 1819, Belleville was heavily settled by German immigrants (an estimated 90% of the population was German-born or of German descent by 1870); their legacy includes 'German street house' row homes alongside later American Foursquare, Queen Anne and other Victorian-era construction concentrated in its historic districts.
The postwar housing in Belleville is the metro's biggest and most consistent insulation opportunity. The pattern is remarkably repeatable: three or four inches of fibreglass laid between the ceiling joists, nothing over the top plates, an uninsulated attic hatch, and a bathroom fan venting into the attic instead of through the roof. Ranches and split-levels of this era also give away heat at the garage ceiling and the cantilevered floor over a porch. None of that is a defect — it was normal practice, built to a standard that did not yet exist. It just means the house is running at a fraction of what is recommended for this climate zone now, and the fix is usually a day's work rather than a renovation.
Belleville enforces the Illinois Energy Conservation Code (2024 IECC with Illinois amendments), by state law. Belleville City Code § 150.01 adopts the 2006 International Building Code, the 2006 International Residential Code for One- and Two-Family Dwellings, and the International Energy Conservation Code. The ordinance names the International Energy Conservation Code without stating an edition. Because 20 ILCS 3125 makes the Illinois Energy Conservation Code both the floor and the ceiling for residential energy standards, the edition that governs a Belleville house is the state edition, currently the 2024 IECC as amended, effective 11/30/2025.
Under that edition the required attic value for new work here is R-49, and walls R-20 + R-5 continuous, or R-13 + R-10 continuous. For comparison, the Department of Energy recommends R60 for an uninsulated attic in this climate zone and R49 where there are already a few inches up there.
Table R402.1.3 of the 2024 IECC as amended for Illinois, climate zone 4. St. Clair County is in climate zone 4 per the NAIMA IECC compliance guide for Illinois homes.
Belleville publishes no answer either way. Insulation and air sealing appear on neither the permit-required list nor the exempt list. That is the normal state of affairs across this metro — only a handful of the 45 jurisdictions on this site say anything about it at all. The city says any improvements to private property within the corporate city limits require appropriate permits obtained through the Health, Housing & Building Department, but that is a general statement. Neither the department page nor the building permit application form names insulation, weatherization or attic work as a permit type. We confirm it with the department before we start and pull whatever is needed. We would rather write that here than guess on your behalf.
The city building permit application asks for a contractor name and a contractor ID number, which implies a city contractor file, but no published city page states a registration requirement or fee for insulation contractors. The department does maintain a list of approved electrical contractors.
The published number is 618-233-6817. The department page is here.
Permitting is on us, not on you.
Belleville is on the Illinois side, and the Illinois programme is the more generous of the two by a wide margin. Ameren Illinois publishes flat per-unit discounts applied by the contractor rather than mailed to you as a cheque. On Ameren Illinois' 2026 discount table: $1.10 per square foot for attic insulation and the same for wall insulation, $2.00 per linear foot for rim joist, $3.00 per linear foot for crawl space wall, and $0.70 per cubic foot per minute (CFM) of air leakage reduced for air sealing.
Two conditions decide whether any of that reaches you. Air sealing has to be pre-approved before the work starts — do it first and ask afterwards and the money is gone. And only a registered Ameren Illinois Program Ally can apply the discount at all: a contractor who is not on that list cannot get it for you, whatever they say on the doorstep. Ask which they are before you sign.
Compare that with the Missouri side of the metro, where the same attic gets an on-bill programme paying $0.20 per square foot instead, and only if the attic started at R-20 or below. Same weather, same houses, different utility regulator.
If the household income qualifies, the work can be free rather than discounted. St. Clair County is served by St. Clair County Community Action Agency under the Illinois low-income weatherization program — 618-277-6790, details here.
One more, by its absence: the federal 25C credit, which covered 30% of insulation and air sealing up to $1,200 a year, ended for anything placed in service after 31 December 2025. Work finished on or before that date is still claimed on that year's return; nothing done in 2026 is. It should not be in your 2026 price, whoever tells you otherwise — the rebate guide has the detail.
Belleville sits in all eight counties are iecc 2021 climate zone 4, mixed-humid, which is the zone that has to be defended in both directions: 4,433 heating degree days and 1,713 cooling degree days a year at Lambert. That is what every R-value on this page is sized for. The energy code and rebate guide works through the rest of the figures.
Elsewhere in St. Clair County we also cover:
Illinois sets the residential energy code from Springfield, so these figures agree across the county — what changes here is the permit desk, not the R-value.
| City | Energy code | Attic R required | Permit to insulate | Building dept. |
|---|---|---|---|---|
| Fairview Heights | Illinois state code | R-49 | Not published | 618-489-2060 |
| O'Fallon | Illinois state code | R-49 | Not published | 618-624-4500 |
| Swansea | Illinois state code | R-49 | Not published | 618-234-0044 |
Free assessment, measured at the hatch, with the photographs and the number in writing.
The code edition Belleville enforces sets R-49 for new work. The Department of Energy separately recommends R60 for an uninsulated attic in this climate zone, and R49 where a few inches are already there.
Nobody can tell you from a website, including this one. Belleville lists neither insulation nor air sealing as permit work, and does not exempt it either. We ring the department, get an answer for your specific job, and pull anything it needs.
Ameren Illinois publishes $1.10 per square foot for attic insulation and $0.70 per cubic foot per minute (CFM) of air leakage reduced for air sealing on its 2026 discount table, applied by the contractor rather than paid to you directly. Two conditions decide whether it reaches you: air sealing has to be pre-approved before the work starts, and only a registered Ameren Illinois Program Ally can apply the discount at all. The federal 25C credit ended for work placed in service after 31 December 2025.
The typical home in Belleville dates to around the early-1960s. Postwar building here often meant three or four inches of fibreglass and no attempt at air sealing. If nobody has touched it since, that is what is still up there. That figure is an ACS-derived median republished by housing-data services, not a survey of individual houses.
Not yet. We have no completed job logged in Belleville, and we would rather say so than put a number on this page that is not real.
Illinois does not license insulation contractors as a trade, though it does run the residential energy code from Springfield rather than leaving it to each city. Municipal registration varies — some Metro East cities require a business licence, others require none at all. What matters more in practice is whether the contractor is a registered Ameren Illinois Program Ally, because only an Ally can apply the rebate.
Energy code, permit and department details for Belleville come from the jurisdiction's own published pages and codified ordinances. Rebate figures come from the utility's own published incentive tables and carry the programme year they were verified in. Housing-age figures are ACS-derived medians republished by housing-data services, so treat them as approximate. Sources: belleville.net · belleville.net · codelibrary.amlegal.com · jaspector.com · belleville.net · belleville.net · codelibrary.amlegal.com · en.wikipedia.org · censusreporter.org · point2homes.com · ameren.com · ameren.com · ameren.com · ameren.com · energy.gov. Adopted code editions, department phone numbers and utility rebate amounts all change — confirm with the jurisdiction or the utility before relying on anything here.