Insulation and air sealing for Brentwood homes: attics, crawl spaces, rim joists and walls, starting with a free assessment of the R-value you actually have. Brentwood enforces the 2024 IECC, which sets R-49 for a new attic.
Brentwood runs to about 2.0 square miles and roughly 8,144 people. It sits about 8 miles southwest of downtown St. Louis. There are around 4,442 housing units here. The community dates back to 1919. We cover ZIP code 63144.
We have not logged a completed job in Brentwood yet. We would rather say so than put a number on this page that is not real.
The typical home in Brentwood dates to around the mid-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.
Predominantly built during the 1950s postwar boom (about 36% of homes).
Originally called Maddenville, the area incorporated as a village in 1919 -- largely to avoid annexation by Maplewood -- and became a city in 1929; it is one of the most densely populated inner-ring suburbs in St. Louis County, with a median housing construction year of 1956.
The Census Bureau estimates 4,442 homes in Brentwood. 637 of them (14%) went up before 1940 — 13th of 44 places on this site for pre-1940 housing. The 1950s were the busiest decade, adding 1,612 of today's homes (36%); 78% predate 1980 and 13% were built in 2000 or later. For St. Louis County as a whole the pre-1940 share is 10%, so Brentwood sits above it.
Of 4,091 occupied homes, 51% heat with utility gas and 49% with electricity. Electric heat here is more common than across the county (23%), and ranks 5th of 44 on this site. That is why the assessment asks how the house is heated: the fuel and the name on the utility bill decide which program, if any, can pay toward the work.
63% of occupied homes are owner-occupied and 49% of all homes are single-family detached houses, with 86 mobile homes in the count. Read together, those numbers point toward an attic top-up over postwar fiberglass and an energy assessment before deciding what to fix first.
| Built | Homes | Share | |
|---|---|---|---|
| Before 1940 | 637 | 14% | |
| 1940s | 656 | 15% | |
| 1950s | 1,612 | 36% | |
| 1960s | 368 | 8% | |
| 1970s | 176 | 4% | |
| 1980s | 171 | 4% | |
| 1990s | 237 | 5% | |
| 2000s | 327 | 7% | |
| 2010s | 258 | 6% | |
| 2020 or later | 0 | 0% |
4,442 homes, Census ACS 2020–2024 (B25034, B25040, B25003); 4,091 occupied.
2,156 of Brentwood's 4,442 homes (49%) 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.
Brentwood enforces the 2024 IECC. The city's Energy Conservation Code article adopts the International Energy Conservation Code, 2024 Edition, by Ordinance No. 5204 dated 12-15-2025. The city's Planning and Development page lists the same 2024 edition alongside the 2024 IBC, 2024 IRC, 2024 IMC, 2024 IPC, 2024 IEBC, 2024 IFGC, 2024 IPMC, 2024 IFC and the 2023 National Electrical Code, all under Ordinance 5204. The amendments retitle Section C101.1, change the penalty reference in C110.4, delete Section C405.13 on energy monitoring, and add electric vehicle charging requirements and EV definitions in the residential provisions at Section R404.2.
For new work, the attic number under that edition is R-49, with walls at R-30, or R-20 plus R-5 continuous, or R-13 plus R-10 continuous, or R-0 plus R-20 continuous. Set that against the Department of Energy, which recommends R60 for an uninsulated attic in this climate zone and R49 for one that already has a few inches.
2024 IECC residential R-value alternative table, climate zone 4. The Illinois Capital Development Board's cost-effectiveness study of the 2024 IECC residential provisions states that ceiling insulation in Table R402.1.3 was reduced from R-60 to R-49 in climate zones 4 through 8; NAHB's summary of significant changes from the 2018 to the 2024 IECC gives the climate zone 4 and 5 wood frame wall requirement as 'R-20&5ci, R-13&10ci, 30, or 0&20ci'.
Brentwood publishes no answer either way. Insulation and air sealing appear on neither the permit-required list nor the exempt list. The Building and Occupancy Permits page says examples of projects requiring a permit include fences, driveways, garages, pools and interior and exterior remodeling. Insulation, air sealing and weatherization are not named anywhere on either page. We confirm it with the department before we start and pull whatever is needed. We would rather write that here than guess on your behalf.
The published number is 314-963-8602. The department page is here.
Permitting is on us, not on you.
Brentwood 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 St. Louis County page and the rebate guide carry the full rules.
Every layer of an insulated attic, explained
Brentwood borders Richmond Heights. These are the ones we also cover, each with its own energy code and permit rule:
Elsewhere in St. Louis County we also cover:
Missouri sets none of this at state level. Across the 7 places in this table there are 3 different adopted editions (2015 IECC, 2021 IECC and 2024 IECC), and 1 of the 7 publishes a permit rule for insulation.
| City | Energy code | Attic R required | Permit to insulate | Building dept. |
|---|---|---|---|---|
| Brentwood | 2024 IECC | R-49 | Not published | 314-963-8602 |
| Richmond Heights | 2024 IECC | R-49 | Not published | 314-646-7658 |
| Affton | 2015 IECC | R-49 | Not for an attic top-up | 314-615-5184 |
| Ballwin | Not published | — | Not published | 636-227-2129 |
| 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 |
All 21 St. Louis County jurisdictions side by side →
Brentwood enforces the 2024 IECC, which sets R-49 for an attic in new work. That code also reaches work on existing houses, not only new ones.
Brentwood publishes no rule either way, so we ask its building department at 314-963-8602 before the job is scheduled.
Ameren Missouri's Pay As You Save: $0.20 per square foot for an attic starting at R-20 or below and $0.06 per square foot for air sealing in 2026, with the balance on the electric bill. The federal 25C credit ended for work placed in service after December 31, 2025.
The typical home in Brentwood dates to around the mid-1950s; the Census Bureau's 2020-2024 median year built is 1956. Of its 4,442 homes, 14% went up before 1940 and 13% 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: ecode360.com (2, 3) · brentwoodmo.org (2, 3) · cdb.illinois.gov · nahb.org · data.mo.gov · 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 314-963-8602 or your electric utility first.
Free assessment, measured at the hatch, with the photographs and the number in writing.
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