Every city and county we cover, each with the energy code that actually applies there, the attic R-value it requires, the permit position and the department's own number. Missouri has no statewide code, so on this side of the river that genuinely changes from one side of a street to the other.
Missouri has no statewide residential building or energy code. What insulation a house here has to have is decided entirely by whatever code the city, village or county has adopted by local ordinance, and by whether that jurisdiction runs a permit and inspection programme at all. In unincorporated areas the county's code applies; inside a city the municipal ordinance does, and a municipality may contract its permitting back to the county. There is no state floor and no state pre-emption.
Illinois does the opposite. The Capital Development Board's Illinois Energy Conservation Code page states that the 2024 edition of the IECC as amended went into effect on 11/30/25 for both commercial and residential buildings. The 2021 edition applied to permit applications filed on or after 1/1/2024, and the 2018 edition took effect 7/1/2019. And under 20 ILCS 3125 that state code is both the floor and the ceiling for houses: a municipality may not set residential energy standards either less or more stringent than it. So on the Illinois side of this metro, every town on this site answers the R-value question the same way, while on the Missouri side the answer changes town by town — and in a couple of places there is no answer at all, because the jurisdiction deleted the energy chapter.
These pages exist so you can check your own address before anyone quotes you. Every figure on them comes from the jurisdiction's own published page, its codified ordinance, the state code, or the utility's own published incentive table, and every page says where it came from. Where a city does not publish something, we leave it blank rather than filling it in.
Free assessment, a measured R-value, and photos you keep either way.
Municipal and county research 2026-09-09; energy code, R-value and rebate research 2026-09-10. Arch City Insulation is a service-area business serving greater St. Louis.