Clayton 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.
Clayton runs to about 2.5 square miles and roughly 17,380 people. It sits about 8 miles west of downtown St. Louis. Around 6,934 housing units sit inside those boundaries, most of them built before anyone measured a house for air leakage. The community dates back to 1913. We cover ZIP code 63105.
No completed job in Clayton is logged in our records yet, and this page will say so until one is.
The typical home in Clayton 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.
A mix of pre-1940 construction (about 35% of homes) and mid-20th-century mid-rise/high-rise development.
We work across Clayton rather than one corner of it — Claverach Park, Clayshire, DeMun, Downtown Clayton, The Moorlands, North Clayton, Brentmoor Park, Carrswold, Forest Ridge and Hillcrest included. Construction and vintage change between them, sometimes by thirty years and a whole different framing method, which decides whether a wall can be dense-packed at all.
Settled in 1877 and incorporated in 1913 on land donated by Ralph Clayton, the St. Louis County seat's housing stock ranges from pre-war brick walkups, apartment buildings and mansions to mid-century-modern low- and high-rise towers downtown.
The postwar housing in Clayton 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.
Clayton enforces the 2021 IECC. Section 500.010 of the Clayton city code adopts the 2021 International Energy Conservation Code as Part VI of its building code, alongside the 2021 International Building, Mechanical, Plumbing, Residential, Fuel Gas, Existing Building and Swimming Pool and Spa Codes, by Ordinance No. 6780, effective November 8, 2022. The Building Division states the 2021 code family took effect January 1, 2023. Section 500.020(F) carries amended violation penalties and stop work order procedures. Electrical work follows the St. Louis County Electrical Code as amended through County Ordinance 24,439, adopted by City Ordinance No. 6131 effective December 14, 2010, and the property maintenance code is the 2015 International Property Maintenance Code.
Under that edition the required attic value for new work here is R-60, and walls R-30, or R-20 cavity plus R-5 continuous, or R-13 cavity plus R-10 continuous, or 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.
2021 IECC Table R402.1.3, climate zone 4 (except marine), as reproduced in the U.S. Department of Energy / PNNL Building America Solution Center comparison of 2009-2021 IECC and IRC minimum insulation requirements.
Nothing Clayton publishes settles this. Its permit lists name the work types it cares about, and insulation is not among them in either direction. 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. Clayton publishes a short list of work that does not require a permit: painting, carpeting, trim work, installing cabinets where there is no relocation, layout change or electrical work, and flooring. Insulation, air sealing and weatherization appear neither on that list nor on the list of work that requires a permit. So we ask the department directly before the first day on site, and whatever comes back, pulling it is our job rather than yours.
The Building Division requires a Master Plumber licensed through both St. Louis County and the City of Clayton to pull and perform plumbing work, but publishes no general contractor registration requirement and says nothing about insulation contractors.
The published number is 314-290-8463. The department page is here.
Permitting is on us, not on you.
Clayton 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.
NOAA's 1991–2020 normals put 84.9 nights a year at or below freezing here, and only 19.3 days that never climb back above it. Most freezes in Clayton thaw the same day, and that daily cycling is what drives moisture into a cold attic. The energy code and rebate guide has the full climate figures.
Clayton borders City of St. Louis, University City and Ladue. 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 |
| Brentwood | 2024 IECC | R-49 | Not published | 314-963-8602 |
| Chesterfield | Not published | — | Not published | 636-537-4000 |
| 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 Clayton enforces sets R-60 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.
Unresolved on paper. Clayton names the work types it wants permits for and insulation is not one of them, but nor is it on the exemption list. It gets settled by phone before we schedule, at our end.
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 Clayton 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 Clayton, 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 Clayton 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 · claytonmo.gov · claytonmo.gov · onestl.org · basc.pnnl.gov · 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.