Attic insulation, air sealing and crawl space work across St. Louis County. We cover 21 jurisdictions here, each with its own page: the energy code that applies, the attic R-value it requires, the permit position and the building department's number. Of the county's 446,192 homes, 10% were built before 1940, and 23% of occupied homes heat with electricity.
Click a city for its full code, permit and rebate detail.
| City | Energy code | Attic R required | Permit to insulate | Building dept. |
|---|---|---|---|---|
| Affton | 2015 IECC | R-49 | Not for an attic top-up | 314-615-5184 |
| Ballwin | Not published | — | Not published | 636-227-2129 |
| Brentwood | 2024 IECC | R-49 | Not published | 314-963-8602 |
| Chesterfield | Not published | — | Not published | 636-537-4000 |
| Clayton | 2021 IECC | R-60 | Not published | 314-290-8463 |
| Creve Coeur | 2015 IECC | R-49 | Not published | 314-872-2500 |
| Des Peres | 2018 IRC ch. 11 | R-49 | Not published | 314-835-6130 |
| Ellisville | 2015 IRC ch. 11 | R-49 | Not published | 636-227-9660 |
| Eureka | 2018 IRC ch. 11 | R-49 | Not published | 636-938-5233 |
| Florissant | 2021 IECC | R-60 | Not published | 314-839-7648 |
| Kirkwood | 2021 IECC | R-60 | Not published | 314-822-5823 |
| Manchester | Not published | — | Not published | 314-615-5184 |
| Maryland Heights | 2015 IECC | R-49 | Not published | 314-291-6550 |
| Mehlville | Not published | — | Not for an attic top-up | 314-615-5184 |
| Oakville | 2015 IECC | R-49 | Not for an attic top-up | 314-615-5184 |
| Richmond Heights | 2024 IECC | R-49 | Not published | 314-646-7658 |
| Unincorporated St. Louis County | 2015 IECC | R-49 | Not for an attic top-up | 314-615-5184 |
| Town and Country | 2018 IRC ch. 11 | R-49 | Not published | 314-587-2820 |
| University City | 2018 IECC | R-49 | Not published | — |
| Webster Groves | Not published | — | Not published | 314-963-5300 |
| Wildwood | Not published | — | Not for an attic top-up | 636-458-0440 |
15 of the 21 publish an energy code edition we could name and 15 of the 21 a required R-value we could read; a blank in this table means the jurisdiction publishes nothing, not that we guessed.
Missouri sets no statewide residential energy code, so across St. Louis County the code is whatever each jurisdiction adopted on its own: the 2015 IECC in Affton, Creve Coeur, Maryland Heights, Oakville and Unincorporated St. Louis County; the 2021 IECC in Clayton, Florissant and Kirkwood; the 2018 IRC ch. 11 in Des Peres, Eureka and Town and Country; the 2024 IECC in Brentwood and Richmond Heights; the 2015 IRC ch. 11 in Ellisville; the 2018 IECC in University City; no published edition in Ballwin, Chesterfield, Manchester, Mehlville, Webster Groves and Wildwood.
The attic figures that follow from those editions, for new work: R-49 in Affton, Brentwood, Creve Coeur, Des Peres, Ellisville, Eureka, Maryland Heights and Oakville; R-60 in Clayton, Florissant and Kirkwood. A specification that was right one town over is not automatically right here, which is why each place has its own page.
The 20 places here with their own Census row hold 210,664 of St. Louis County's 446,192 homes (47%); the rest are in other municipalities or unincorporated areas.
St. Louis County has 446,192 homes in the Census count, with a median year built of 1969. 69% were built before 1980 and 11% in 2000 or later; the single biggest decade was the 1960s, with 82,127 homes (18%). Of 413,849 occupied homes, 75% heat with utility gas and 23% with electricity.
Across the 20 places we cover here, Richmond Heights has the oldest housing (43% before 1940) and Eureka the newest (47% built in 2000 or later). Florissant is the largest, at 23,064 homes, and Brentwood has the most electric heat (49%).
| Place | Homes | Before 1940 | Median built | Electric heat | Owner-occupied |
|---|---|---|---|---|---|
| Florissant | 23,064 | 2% | 1963 | 15% | 67% |
| Chesterfield | 21,603 | 1% | 1982 | 25% | 78% |
| University City | 17,841 | 38% | 1949 | 19% | 56% |
| Oakville | 14,242 | 2% | 1982 | 24% | 86% |
| Mehlville | 13,994 | 1% | 1969 | 37% | 66% |
| Wildwood | 13,391 | 2% | 1992 | 31% | 92% |
| Maryland Heights | 13,108 | 1% | 1975 | 38% | 57% |
| Kirkwood | 12,978 | 17% | 1962 | 22% | 77% |
| Ballwin | 12,563 | 0% | 1976 | 14% | 84% |
| Webster Groves | 9,921 | 35% | 1952 | 20% | 76% |
| Affton | 9,092 | 9% | 1958 | 16% | 81% |
| Creve Coeur | 8,821 | 1% | 1980 | 44% | 61% |
| Manchester | 7,423 | 1% | 1977 | 26% | 75% |
| Clayton | 6,934 | 35% | 1954 | 36% | 55% |
| Eureka | 4,805 | 3% | 1999 | 35% | 79% |
| Richmond Heights | 4,599 | 43% | 1947 | 24% | 54% |
| Brentwood | 4,442 | 14% | 1956 | 49% | 63% |
| Ellisville | 4,349 | 0% | 1983 | 35% | 75% |
| Town and Country | 4,163 | 3% | 1983 | 27% | 86% |
| Des Peres | 3,331 | 0% | 1976 | 15% | 96% |
Against the eight-county metro on this site (1,177,290 homes), St. Louis County's pre-1940 share of 10% compares with 16%, and its electric-heat share of 23% with 32%. 5,764 occupied homes (1%) burn propane or other tank gas and 401 (0%) heat with wood, which matters because neither fuel comes with a gas utility's program attached. 69% of occupied homes are owner-occupied and 72% of all homes are single-family detached houses.
In St. Louis County that adds up to 234,387 homes from the 1950s to the 1970s, the usual candidates for an attic top-up; 46,854 built since 2000, where air sealing tends to matter more than extra depth.
| Built | Homes | Share | |
|---|---|---|---|
| Before 1940 | 43,354 | 10% | |
| 1940s | 28,196 | 6% | |
| 1950s | 81,063 | 18% | |
| 1960s | 82,127 | 18% | |
| 1970s | 71,197 | 16% | |
| 1980s | 53,584 | 12% | |
| 1990s | 39,817 | 9% | |
| 2000s | 27,989 | 6% | |
| 2010s | 15,700 | 4% | |
| 2020 or later | 3,165 | 1% |
Figures: U.S. Census Bureau, American Community Survey 2020–2024 5-year estimates (tables B25001, B25003, B25024, B25034, B25035, B25040). Survey estimates carry margins of error, widest in the smallest places. Census table.
St. Louis County is on the Missouri side, where most addresses buy their electricity from Ameren Missouri. Its Pay As You Save program publishes $0.20 per square foot on ceiling and attic insulation and $0.06 per square foot on air sealing for the 2026 program year; the incentive comes off the cost and the rest is repaid through a monthly charge on the bill. The conditions: an attic going from R-20 or below to at least R-38, air sealing that cuts measured leakage by 20 percent, and twelve months in the home. CommunitySavers can include attic insulation at no charge for income-eligible households. Income-qualified households can apply to Community Action Agency of St. Louis County (CAASTLC) (314-863-0015) for free weatherization instead. The full program rules are in the rebate guide.
It depends on the city, not the county. Across St. Louis County, 5 publish that an attic top-up needs none (Affton, Mehlville, Oakville, Unincorporated St. Louis County, Wildwood); the other 16 publish no rule either way. Each town page says which applies and gives the building department's number.
For new work, the published attic figures across St. Louis County are R-49 in Affton, Brentwood, Creve Coeur, Des Peres, Ellisville, Eureka, Maryland Heights, Oakville; R-60 in Clayton, Florissant, Kirkwood. 6 of the 21 jurisdictions publish no figure we could read. The Department of Energy recommends R60 for an uninsulated attic in this climate zone.
The Census Bureau's 2020–2024 estimates put 10% of St. Louis County's 446,192 homes before 1940 and 69% before 1980, with a median year built of 1969.
For most addresses across St. Louis County the electric utility is Ameren Missouri, whose Pay As You Save program publishes $0.20 per square foot on ceiling and attic insulation and $0.06 per square foot on air sealing for the 2026 program year, with the rest of the cost repaid through the bill, and only where the attic starts at R-20 or below. For income-eligible households, CommunitySavers can include attic insulation at no charge.
Yes, through the Missouri low-income weatherization program, which Community Action Agency of St. Louis County (CAASTLC) runs for St. Louis County (314-863-0015). If the household income qualifies, the work can be free rather than discounted.
Free assessment, a measured R-value, and photos you keep either way.
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