Attic insulation, air sealing, crawl spaces and walls for homes in Waterloo — starting with a free assessment that measures the R-value you actually have. The typical home here dates to the early-1990s, and 11% of its 4,818 homes went up before 1940.
Waterloo runs to about 8.2 square miles and roughly 11,013 people. It sits about 24 miles south of downtown St. Louis. Around 4,818 housing units sit inside those boundaries. The community dates back to 1889. We cover ZIP code 62298.
No completed job in Waterloo is logged in our records yet, and this page will say so until one is.
The typical home in Waterloo dates to around the early-1990s. Houses of this vintage usually got batts or blown fiber at whatever the standard of the day was, which is well short of what is recommended now. Most are one top-up away from being right.
Downtown retains a 19th-century core recognized as the Waterloo Historic District (NRHP-listed December 1, 1978), reflecting the town's 1818 founding as a merger of two rival settlements, Bellefontaine and Peterstown.
That includes Bellefontaine and Peterstown. Housing age and construction shift across Waterloo, sometimes by decades within a few streets, which is why we look in the attic before quoting rather than after.
Waterloo formed in 1818 from the unification of two rival communities, Bellefontaine (south) and Peterstown (north); it is the Monroe County seat.
The Census Bureau estimates 4,818 homes in Waterloo. 507 of them (11%) went up before 1940 — 14th of 44 places on this site for pre-1940 housing. The 2000s were the busiest decade, adding 908 of today's homes (19%); 44% predate 1980 and 34% were built in 2000 or later. For Monroe County as a whole the pre-1940 share is 10%, so Waterloo sits above it.
Of 4,491 occupied homes, 71% heat with utility gas and 24% with electricity; another 4% burn propane or other tank gas. Electric heat here is less common than across the county (30%), and ranks 37th of 44 on this site. Which utility program can contribute depends on the heating fuel and on who sends the bill, so that is the first thing an assessment pins down.
78% of occupied homes are owner-occupied and 78% of all homes are single-family detached houses. On a housing mix like this, the likely starting points are air sealing on newer houses that already have depth.
| Built | Homes | Share | |
|---|---|---|---|
| Before 1940 | 507 | 11% | |
| 1940s | 187 | 4% | |
| 1950s | 433 | 9% | |
| 1960s | 537 | 11% | |
| 1970s | 439 | 9% | |
| 1980s | 248 | 5% | |
| 1990s | 811 | 17% | |
| 2000s | 908 | 19% | |
| 2010s | 729 | 15% | |
| 2020 or later | 19 | 0% |
4,818 homes, Census ACS 2020–2024 (B25034, B25040, B25003); 4,491 occupied.
1,059 of Waterloo's 4,818 homes (22%) were built in the 1980s and 1990s. The gaps in houses of that age are the parts nobody sealed: batts stuffed into the rim joist, bare spots over cathedral and tray ceilings, soffit vents buried with no baffles, can lights punched through the ceiling plane. A top-up plus a day of sealing usually covers it.
Waterloo enforces the Illinois Energy Conservation Code (2024 IECC with Illinois amendments), by state law. The city's building permits page lists its adopted codes as the 2012 International Building Code, the 2006 International Residential Code, the 2012 International Mechanical Code, the National Electrical Code, the National Fuel Gas Code and the Illinois State Plumbing Code. The Illinois Energy Conservation Code governs residential energy work by statute.
That edition sets R-49 for the attic in new work, and R-20 + R-5 continuous, or R-13 + R-10 continuous for walls. The Department of Energy's recommendation for this climate zone runs higher: R60 for an attic with nothing in it, R49 where a few inches are already down.
Table R402.1.3 of the 2024 IECC as amended for Illinois, climate zone 4. Monroe County is in climate zone 4 per the NAIMA IECC compliance guide for Illinois homes.
Nothing Waterloo publishes settles this. Its permit lists name the work types it cares about, and insulation is not among them in either direction. The city publishes a list of what needs a permit: a principal building, accessory buildings such as sheds of 50 square feet and over, swimming pools, decks, and retaining walls over four feet high. Insulation is not on that list, but the list is not stated to be exhaustive, so this is not a published exemption. So we ask the department directly before the first day on site, and whatever comes back, pulling it is our job rather than yours.
The city states that it does not require business licenses, and publishes no contractor registration or licensing requirement.
The published number is 618-939-8600. The department page is here.
Permitting is on us, not on you.
Waterloo is on the Illinois side, where Ameren Illinois publishes discounts the contractor applies on the invoice: $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 on Ameren Illinois' 2026 discount table. 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 Western Egyptian Economic Opportunity Council (serves Monroe, Perry and Randolph counties) (618-965-3458) for free weatherization instead. The Monroe County page and the rebate guide carry the full rules.
Every layer of an insulated attic, explained
Elsewhere in Monroe County we also cover:
Also on this site, in neighboring St. Clair County:
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 neither publishes a permit rule for insulation.
| City | Energy code | Attic R required | Permit to insulate | Building dept. |
|---|---|---|---|---|
| Waterloo | Illinois state code | R-49 | Not published | 618-939-8600 |
| Columbia | Illinois state code | R-49 | Not published | 618-281-7144 |
Both Monroe County jurisdictions side by side →
Waterloo 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.
Not on paper: Waterloo names neither a permit nor an exemption for insulation, so one call to the department at 618-939-8600 settles it first.
First check whose name is on your electric bill: Waterloo has a municipal electric utility, and the Ameren programs are open only to Ameren customers. 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 for 2026; only a registered Program Ally can apply it, once an assessment shows the house qualifies. The federal 25C credit ended for work placed in service after December 31, 2025.
The typical home in Waterloo dates to around the early-1990s; the Census Bureau's 2020-2024 median year built is 1991. Of its 4,818 homes, 11% went up before 1940 and 34% in 2000 or later. Half the homes here are older than that and half newer; yours may sit at either end.
Code and permit facts checked September 10, 2026, rebates October 24, 2026; housing: Census ACS 2020–2024. Sources: waterloo.il.us (2) · monroecountyil.gov · en.wikipedia.org · city-data.com · ameren.com (2, 3, 4) · energystar.gov · data.census.gov. These change; confirm with the building department at 618-939-8600 or your electric utility first.
Free assessment, a measured R-value, and photos you keep either way.
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