We cover 2 jurisdictions in Monroe County. Each one below has its own page with the energy code that applies there, the attic R-value it requires, the permit position and the building department's number.
Click a city for its full code, permit and rebate detail.
| City | Energy code | Attic R required | Permit to insulate | Building dept. |
|---|---|---|---|---|
| Columbia | Illinois state code | R-49 | Not published | 618-281-7144 |
| Waterloo | Illinois state code | R-49 | Not published | 618-939-8600 |
We name an energy code edition only where the jurisdiction or the state publishes one — 2 of 2 here do. We print a required R-value only where the adopted edition and its local amendments are readable — 2 of 2 here. Everything else is left blank on purpose, and no page on this site fills a blank with a guess.
For residential buildings the state code is both a floor and a ceiling. The Illinois amendment section R102.1.1 carried in the state code text reads that units of local government may not regulate residential energy conservation standards either less or more stringent than the Illinois Energy Conservation Code.
So the R-value argument is settled before anyone knocks on your door here, and what actually varies between these towns is the permit desk, the contractor registration and how quickly an inspection can be had.
Monroe County 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. Monroe County is served by Western Egyptian Economic Opportunity Council (serves Monroe, Perry and Randolph counties) under the Illinois low-income weatherization program — 618-965-3458, details here. That is a different queue from ours, and we will point you at it rather than sell you something you could get for nothing.
| Figure | Number | What it drives |
|---|---|---|
| Climate zone | All eight counties are IECC 2021 Climate Zone 4 | Every R-value in the code table, on both sides of the river |
| Heating degree days | 4,433 | How hard the furnace works. Base 65°F, 1991–2020 normals at St. Louis Lambert International Airport |
| Cooling degree days | 1,713 | Why an under-insulated attic costs you in July as well as January |
| Nights at or below freezing | 84.9 | Condensation on the cold side of the insulation |
| Days that never rise above freezing | 19.3 | Most St. Louis freezes thaw the same day — the cycling is the problem, not the cold |
The full explanation is in our St. Louis energy code and rebate guide.
Free assessment, a measured R-value, and photos you keep either way.