Insulating a house in Alton 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.
Alton runs to about 16 square miles and roughly 25,279 people. It sits about 20 miles north of downtown St. Louis. That is roughly 12,551 housing units, and the attic above almost all of them is the cheapest thing in the house left to fix. The community dates back to 1837. We cover ZIP code 62002.
Our job history shows nothing in Alton so far. Plenty of sites will show you a number here anyway.
The typical home in Alton dates to around the early-1950s. 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 Victorian-era housing (about 28% of homes) and a large 1950s postwar wave (about 21%).
That includes Upper Alton. Housing age and construction shift across Alton, sometimes by decades within a few streets, which is why we look in the attic before quoting rather than after.
Many blocks of Alton were built in Victorian Queen Anne style during its 19th-century steamboat-era prosperity, and the city retains an unusually high number of brick-paved streets; the Great Flood of 1993 cut off Alton's water supply for weeks and inundated the historic downtown.
The postwar housing in Alton 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.
Alton enforces the Illinois Energy Conservation Code (2024 IECC with Illinois amendments), by state law. Alton City Code section 9-1-3, which sets out amendments to the codes adopted in 9-1-1, shows the city on the 2021 International Building Code, 2021 International Residential Code, 2021 International Property Maintenance Code, 2021 International Fire Code with appendices B, C, D, I and K, and the 2015 NFPA Life Safety Code. The ordinance is silent on an energy code; it names no IECC edition and does not state that the IRC adoption includes Chapter 11. The Illinois Energy Conservation Code governs residential energy work by statute regardless.
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. Madison County is in climate zone 4 per the NAIMA IECC compliance guide for Illinois homes.
There is no published answer for Alton. Neither the permit-required list nor the exemption list mentions insulation or air sealing at all. 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. City Code 9-1-2 requires a permit for the erection, construction, alteration, repair or removal of any wall, fence, building or structure or part thereof, and its fee schedule itemises signs, demolition, electrical, plumbing and fences. Insulation is not named in either the ordinance text or the department's list of permit types, which covers building, demolition, electrical, plumbing, signage, occupancy, agent authorization and restoration of services. That silence is not permission and it is not a prohibition. We settle it with a phone call before the crew is scheduled.
No contractor registration or licensing requirement for insulation contractors is published on the Code Enforcement page or in the building permit section of the city code that was read.
The published number is 618-463-3500. The department page is here.
Permitting is on us, not on you.
Alton 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. Madison County is served by Madison County Community Development under the Illinois low-income weatherization program — 618-692-8940, 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.
Alton sits in all eight counties are iecc 2021 climate zone 4 on the same map the Department of Energy uses to write its recommendations, which is why the figure it recommends for an attic here is R60 rather than something borrowed from a national advert. Heating and cooling both matter at this latitude. The energy code and rebate guide sets out the numbers behind it.
Alton borders West Alton, Missouri and Grafton.
Elsewhere in Madison 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. |
|---|---|---|---|---|
| Collinsville | Illinois state code | R-49 | Not published | 618-346-5200 |
| Edwardsville | Illinois state code | R-49 | Not published | 618-692-7535 |
| Glen Carbon | Illinois state code | R-49 | Not published | 618-288-2615 |
| Granite City | Illinois state code | R-49 | Not published | 618-452-6218 |
Free assessment, measured at the hatch, with the photographs and the number in writing.
The code edition Alton 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.
Alton has not published a rule for it. In practice that means one call to the building department before the job starts, which is on us rather than on you.
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 Alton dates to around the early-1950s. 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 Alton, 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 Alton 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: cityofaltonil.gov · codelibrary.amlegal.com · codelibrary.amlegal.com · cityofaltonil.gov · 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.