Brentwood enforces its own energy code edition, which sets its own attic number. Here is that number, whether the work needs a permit, which utility programme pays toward it, and what a house of this vintage usually turns up.
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, and the great majority of them are heated and cooled through a ceiling nobody has ever sealed. 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 fibreglass 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 postwar housing in Brentwood is the metro's biggest and most consistent insulation opportunity. The pattern is remarkably repeatable: three or four inches of fibreglass laid between the ceiling joists, nothing over the top plates, an uninsulated attic hatch, and a bathroom fan venting into the attic instead of through the roof. Ranches and split-levels of this era also give away heat at the garage ceiling and the cantilevered floor over a porch. None of that is a defect — it was normal practice, built to a standard that did not yet exist. It just means the house is running at a fraction of what is recommended for this climate zone now, and the fix is usually a day's work rather than 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.
Under that edition the required attic value for new work here is R-49, and walls R-30, or R-20 plus R-5 continuous, or R-13 plus R-10 continuous, or R-0 plus R-20 continuous. For comparison, the Department of Energy recommends R60 for an uninsulated attic in this climate zone and R49 where there are already a few inches up there.
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. That is the normal state of affairs across this metro — only a handful of the 45 jurisdictions on this site say anything about it at all. 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, which for most addresses means Ameren Missouri — and Ameren Missouri does not hand out a straight per-square-foot insulation rebate the way its Illinois sister utility does. What it runs instead is Pay As You Save: a free home energy assessment, then the work installed by a programme partner and paid back through a fixed monthly charge on the electric bill, which cannot exceed 80% of the estimated monthly saving, so the bill still comes down while it is being repaid. No loan and no credit check.
Published incentives inside that programme for the 2026 programme year are $0.20 per square foot on ceiling and attic insulation, $0.06 per square foot on air sealing, and 50% of costs up to $250 per home on duct sealing. Each one has a condition attached, and they matter:
Ameren Missouri also runs CommunitySavers, which installs attic insulation at no charge for income-eligible households. The program operates through December 31, 2026; incentives are dependent on available funds.
Spire, the gas utility on this side, lists furnace, water heater and thermostat rebates on its Missouri rebate page rather than a standalone insulation one. Its published route to attic insulation and air sealing is the same on-bill Pay As You Save programme, which it co-delivers, plus income-based weatherization. If you are a Spire customer it is worth ringing them to ask what is open this year, because that page moves.
If the household income qualifies, the work can be free rather than discounted. St. Louis County is served by Community Action Agency of St. Louis County (CAASTLC) under the Missouri low-income weatherization program — 314-863-0015, details here.
One more, by its absence: the federal 25C credit, which covered 30% of insulation and air sealing up to $1,200 a year, ended for anything placed in service after 31 December 2025. Work finished on or before that date is still claimed on that year's return; nothing done in 2026 is. It should not be in your 2026 price, whoever tells you otherwise — the rebate guide has the detail.
Brentwood sits in all eight counties are iecc 2021 climate zone 4, mixed-humid, which is the zone that has to be defended in both directions: 4,433 heating degree days and 1,713 cooling degree days a year at Lambert. That is what every R-value on this page is sized for. The energy code and rebate guide works through the rest of the figures.
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, so the number that was right one municipality over is not automatically right here.
| 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 |
| 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 |
Free assessment, measured at the hatch, with the photographs and the number in writing.
The code edition Brentwood enforces sets R-49 for new work. The Department of Energy separately recommends R60 for an uninsulated attic in this climate zone, and R49 where a few inches are already there.
Nobody can tell you from a website, including this one. Brentwood lists neither insulation nor air sealing as permit work, and does not exempt it either. We ring the department, get an answer for your specific job, and pull anything it needs.
For most addresses here the route is Ameren Missouri's Pay As You Save programme, which publishes $0.20 per square foot on ceiling and attic insulation and $0.06 per square foot on air sealing for the 2026 programme year. Both carry conditions: the attic has to start at R-20 or below and reach at least R-38, and the air sealing has to cut leakage by at least 20 percent. The incentives sit inside tier 4 of the programme and need you to have lived in the home for the past twelve months, and they are recovered through a monthly charge on the electric bill rather than paid as a cheque. Income-eligible households can get attic insulation at no charge through CommunitySavers instead. The federal 25C credit ended for work placed in service after 31 December 2025.
The typical home in Brentwood dates to around the mid-1950s. Postwar building here often meant three or four inches of fibreglass and no attempt at air sealing. If nobody has touched it since, that is what is still up there. That figure is an ACS-derived median republished by housing-data services, not a survey of individual houses.
Not yet. We have no completed job logged in Brentwood, and we would rather say so than put a number on this page that is not real.
Neither state licenses insulation contractors as a trade. In Missouri there is no statewide residential code at all, and registration is imposed city by city — several metro municipalities require a contractor to be registered with them before a permit is pulled. What matters more in practice is utility programme enrolment, because that is what decides whether your rebate is real.
Energy code, permit and department details for Brentwood come from the jurisdiction's own published pages and codified ordinances. Rebate figures come from the utility's own published incentive tables and carry the programme year they were verified in. Housing-age figures are ACS-derived medians republished by housing-data services, so treat them as approximate. Sources: ecode360.com · brentwoodmo.org · brentwoodmo.org · brentwoodmo.org · cdb.illinois.gov · nahb.org · data.mo.gov · ecode360.com · ecode360.com · en.wikipedia.org · censusreporter.org · point2homes.com · ameren.com · ameren.com · ameren.com · ameren.com · energy.gov. Adopted code editions, department phone numbers and utility rebate amounts all change — confirm with the jurisdiction or the utility before relying on anything here.