What it actually takes to insulate a house in Florissant: the energy code the city enforces and the attic R-value that comes with it, the permit position, the rebate your address qualifies for, and the vintage of the housing here.
Florissant runs to about 13 square miles and roughly 52,533 people. It sits about 14 miles north of downtown St. Louis. That is roughly 22,710 housing units, and the attic above almost all of them is the cheapest thing in the house left to fix. The community dates back to 1785. We cover ZIP codes 63031, 63032, 63033 and 63034.
Our job history shows nothing in Florissant so far. Plenty of sites will show you a number here anyway.
The typical home in Florissant dates to around the early-1970s. 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.
Around 18,000 houses were built in Florissant between 1947 and 1980 as the city's population surged toward a mid-1970s peak near 76,000 -- making its housing stock overwhelmingly postwar/mid-century, aside from the older Old Town core.
That includes Old Town. Housing age and construction shift across Florissant, sometimes by decades within a few streets, which is why we look in the attic before quoting rather than after.
Florissant has a city Landmarks and Historic Districts Commission and a large historic core (Old Town / St. Ferdinand) with properties dating to the 1790s, surrounded by a huge ring of 1947-1980 postwar housing.
The postwar housing in Florissant 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.
Florissant enforces the 2021 IECC. Chapter 500, Article IX, Section 500.220 of the Florissant city code adopts the International Energy Conservation Code, 2021 Edition, as published by the International Code Council, by Ordinance No. 8748 dated November 22, 2021, which repealed and replaced the city's former Chapter 500. The same ordinance adopted the rest of the 2021 code family, including the building, residential, mechanical, plumbing, fire, fuel gas, swimming pool and spa, private sewage disposal, property maintenance and existing building codes. The listed local amendments name the Planning and Zoning Commission as the board of appeals, set penalties under Section 100.080, delete Sections C106 and R106 (Notice of Approval), and add electric-vehicle-ready parking requirements for commercial and multi-family projects.
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.
There is no published answer for Florissant. Neither the permit-required list nor the exemption list mentions insulation or air sealing at all. 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 city's permits page lists construction permits for plumbing, electrical, mechanical and building work, container permits, occupancy inspections and certificates, rental licenses, excavation permits, contractor bonding and insurance filings and business licenses. Insulation, air sealing and weatherization are not named, and the city publishes no exemption list. That silence is not permission and it is not a prohibition. We settle it with a phone call before the crew is scheduled.
The permits page shows contractor bonding and insurance filings handled by the Engineering Department and business licenses handled by the Finance Department, but it does not state that a contractor, or an insulation contractor specifically, must register with the city before doing work.
The published number is 314-839-7648. The department page is here.
Permitting is on us, not on you.
Florissant 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.
Florissant sits in all eight counties are iecc 2021 climate zone 4 on the same map the Department of Energy uses to write its recommendations, which is why the figure it recommends for an attic here is R60 rather than something borrowed from a national advert. Heating and cooling both matter at this latitude. The energy code and rebate guide sets out the numbers behind it.
Florissant borders Hazelwood, Ferguson, Black Jack and Old Jamestown.
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 |
| 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 |
| 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 Florissant 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.
Florissant has not published a rule for it. In practice that means one call to the building department before the job starts, which is on us rather than on you.
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 Florissant dates to around the early-1970s. 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 Florissant, 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 Florissant 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 · ecode360.com · florissantmo.com · florissantmo.com · basc.pnnl.gov · ecode360.com · en.wikipedia.org · florissantmo.com · bestplaces.net · 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.