Attic insulation, air sealing, crawl spaces and walls for homes in Alton — starting with a free assessment that measures the R-value you actually have. The typical home here dates to the early-1950s, and 28% of its 12,551 homes went up before 1940.
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. 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 fiberglass 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 Census Bureau estimates 12,551 homes in Alton. 3,459 of them (28%) went up before 1940 — 6th of 44 places on this site for pre-1940 housing. More of today's homes date from before 1940 than from any single decade since, and 85% predate 1980. For Madison County as a whole the pre-1940 share is 15%, so Alton sits above it.
Of 10,714 occupied homes, 62% heat with utility gas and 36% with electricity. Electric heat here is more common than across the county (32%), and ranks 17th of 44 on this site. Whoever comes out will ask about the furnace or heat pump first, since the heating fuel and the utility named on the bill settle which program money is on the table.
60% of occupied homes are owner-occupied and 75% of all homes are single-family detached houses, with 356 mobile homes in the count. With houses like these, the conversations we expect most are about wall insulation for walls built empty, a vermiculite check before anything is disturbed, an attic top-up over postwar fiberglass and an energy assessment before deciding what to fix first.
| Built | Homes | Share | |
|---|---|---|---|
| Before 1940 | 3,459 | 28% | |
| 1940s | 2,057 | 16% | |
| 1950s | 2,585 | 21% | |
| 1960s | 1,103 | 9% | |
| 1970s | 1,420 | 11% | |
| 1980s | 446 | 4% | |
| 1990s | 480 | 4% | |
| 2000s | 706 | 6% | |
| 2010s | 236 | 2% | |
| 2020 or later | 59 | 0% |
12,551 homes, Census ACS 2020–2024 (B25034, B25040, B25003); 10,714 occupied.
5,108 of Alton's 12,551 homes (41%) date from 1950 through 1979. The leaks in houses of that era repeat: nothing over the top plates, wire and pipe holes left open, an unsealed hatch, a bath fan venting into the attic, and in ranches and split-levels, heat lost at the garage ceiling and over cantilevered floors. Sealing the plates, holes and fans comes before any more fiber, and it is usually a day's work, not 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 climate zone 4A, where Alton sits, 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. 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.
Ameren Illinois serves most Alton addresses, and its 2026 discount table pays $1.10 per square foot for attic or wall insulation, $2.50 per linear foot for rim joist, $3.75 per linear foot for crawl space wall and $0.70 per cubic foot per minute (CFM) of air leakage reduced for air sealing, taken off the invoice. The discount comes off a registered Ameren Illinois Program Ally's price, once the program's home energy assessment confirms the house is eligible. Income-qualified households can apply to Madison County Community Development (618-692-8940) for free weatherization instead. The full program rules are on the Madison County page and in the rebate guide.
Every layer of an insulated attic, explained
Alton borders West Alton, Missouri and Grafton.
Elsewhere in Madison County we also cover:
Illinois sets the residential energy code from Springfield, so the attic figure is R-49 wherever it is published here; what changes is the permit desk, and none of the 5 publishes a permit rule for insulation.
| City | Energy code | Attic R required | Permit to insulate | Building dept. |
|---|---|---|---|---|
| Alton | Illinois state code | R-49 | Not published | 618-463-3500 |
| 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 |
All 5 Madison County jurisdictions side by side →
Alton enforces the Illinois state code, which sets R-49 for an attic in new work. That code also reaches work on existing houses, not only new ones.
Alton has not published a rule for it; the building department at 618-463-3500 is called before the job starts.
Ameren Illinois' 2026 table: $1.10 per square foot for attic insulation and $0.70 per cubic foot per minute (CFM) of air leakage reduced for air sealing, taken off the invoice by a registered Program Ally following a home energy assessment. The federal 25C credit ended for work placed in service after December 31, 2025.
The typical home in Alton dates to around the early-1950s; the Census Bureau's 2020-2024 median year built is 1953. Of its 12,551 homes, 28% went up before 1940 and 8% in 2000 or later. It is a median for the place, not a survey of individual houses.
Code and permit facts checked September 10, 2026, rebates October 24, 2026; housing: Census ACS 2020–2024. Sources: cityofaltonil.gov (2) · codelibrary.amlegal.com (2) · en.wikipedia.org · censusreporter.org · point2homes.com · ameren.com (2, 3, 4) · energystar.gov · data.census.gov. These change; confirm with the building department at 618-463-3500 or your electric utility first.
Free assessment, measured at the hatch, with the photographs and the number in writing.
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