Insulation and air sealing for Imperial homes: attics, crawl spaces, rim joists and walls, starting with a free assessment of the R-value you actually have. Imperial enforces the 2015 IECC, which sets R-49 for a new attic.
Imperial runs to about 6.0 square miles and roughly 4,407 people. It sits about 20 miles south of downtown St. Louis. That is roughly 1,960 housing units. We cover ZIP code 63052.
Our job history shows nothing in Imperial so far. Plenty of sites will show you a number here anyway.
The typical home in Imperial dates to around the early-1990s. Houses of this vintage usually got batts or blown fiber at whatever the standard of the day was, which is well short of what is recommended now. Most are one top-up away from being right.
Imperial CDP was originally known as West Kimmswick and today surrounds (but does not include) the separately incorporated city of Kimmswick; its eastern edge is the Mississippi River / Illinois state line.
The Census Bureau estimates 1,960 homes in Imperial. 83 of them (4%) went up before 1940 — 24th of 44 places on this site for pre-1940 housing. The 2000s were the busiest decade, adding 389 of today's homes (20%); 30% predate 1980 and 35% were built in 2000 or later. For Jefferson County as a whole the pre-1940 share is 3%, so Imperial sits above it.
Of 1,835 occupied homes, 27% heat with utility gas and 62% with electricity; another 6% burn propane or other tank gas. Electric heat here is more common than across the county (58%), and ranks 3rd of 44 on this site. Whoever comes out will ask about the furnace or heat pump first, since the heating fuel and the utility named on the bill settle which program money is on the table.
93% of occupied homes are owner-occupied and 86% of all homes are single-family detached houses, with 146 mobile homes in the count. With houses like these, the conversations we expect most are about air sealing on newer houses that already have depth and an energy assessment before deciding what to fix first.
| Built | Homes | Share | |
|---|---|---|---|
| Before 1940 | 83 | 4% | |
| 1940s | 11 | 1% | |
| 1950s | 143 | 7% | |
| 1960s | 173 | 9% | |
| 1970s | 174 | 9% | |
| 1980s | 387 | 20% | |
| 1990s | 301 | 15% | |
| 2000s | 389 | 20% | |
| 2010s | 109 | 6% | |
| 2020 or later | 190 | 10% |
1,960 homes, Census ACS 2020–2024 (B25034, B25040, B25003); 1,835 occupied.
688 of Imperial's 1,960 homes (35%) were built in the 1980s and 1990s. The gaps in houses of that age are the parts nobody sealed: batts stuffed into the rim joist, bare spots over cathedral and tray ceilings, soffit vents buried with no baffles, can lights punched through the ceiling plane. A top-up plus a day of sealing usually covers it.
Imperial enforces the 2015 IECC. Imperial is unincorporated Jefferson County, so Jefferson County's code applies. Chapter 500, Article VII of the Jefferson County code is titled International Energy Conservation Code 2015 - Amendments and adopts the 2015 IECC under Ord. No. 11-0248 Section 1, Article VII Section 1, of 8-9-2011, as amended by Ord. No. 18-0499 of 12-10-2018. The county's Chapter 500 also carries the 2015 IBC in Article II, the 2015 IRC in Article III, the 2015 IFC, IFGC, IMC, IPC and ISPSC, the 2014 NEC and a Jefferson County Electrical Code 2017.
For new work, the attic number under that edition is R-49, with walls at R-20 or R-13 + R-5 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.
Table R402.1.2 of the 2015 IECC, climate zone 4 except Marine, as reprinted in the U.S. Department of Energy Building Energy Codes Program summary of 2015 IECC residential requirements. Jefferson County's Article VII amendments do not change this table.
There is no published answer for Imperial. Neither the permit-required list nor the exemption list mentions insulation or air sealing at all. Chapter 500 Article I says the county regulates the erection, construction, alteration, addition, repair, removal, demolition, use, location, occupancy and maintenance of all buildings and structures and their electrical, plumbing, drain-laying and mechanical systems, and names permits for building construction and alterations, electrical, plumbing, mechanical and sewage systems, decks, pools, signs, retaining walls and alternative energy installations. That silence is not permission and it is not a prohibition. We settle it with a phone call before the crew is scheduled.
Jefferson County licenses named trades only. Chapter 500 Article I states that no contractor shall perform the work or advertise as available to perform it unless licensed under that section, and the licensed trades listed are plumbing, electrical, mechanical, on-site sewer system installation, sprinkler fitting, lawn irrigation installation and communications. Insulation is not a licensed trade in the county code.
The published number is 636-797-5555. The department page is here.
Permitting is on us, not on you.
Most Imperial addresses are Ameren Missouri electric customers, and Ameren Missouri pays toward insulation through Pay As You Save: $0.20 per square foot on the attic and $0.06 per square foot on air sealing in the 2026 program year, with the rest of the cost recovered through the electric 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 Jefferson-Franklin Community Action Corp. (JFCAC) (636-789-2686) for free weatherization instead. The Jefferson County page and the rebate guide carry the full rules.
Every layer of an insulated attic, explained
Imperial borders Arnold, Barnhart and Kimmswick. These are the ones we also cover, each with its own energy code and permit rule:
Elsewhere in Jefferson County we also cover:
Also on this site, in neighboring St. Louis County:
Missouri sets none of this at state level. Across the 3 places in this table there are 2 different adopted editions (2015 IECC and 2021 IECC), and none of the 3 publishes a permit rule for insulation.
| City | Energy code | Attic R required | Permit to insulate | Building dept. |
|---|---|---|---|---|
| Imperial | 2015 IECC | R-49 | Not published | 636-797-5555 |
| Arnold | 2021 IECC | — | Not published | 636-282-2378 |
| Festus | Not published | — | Not published | 636-937-6646 |
All 3 Jefferson County jurisdictions side by side →
Imperial enforces the 2015 IECC, which sets R-49 for an attic in new work. It applies to new work only, so on a retrofit it is a benchmark rather than a rule.
Imperial has not published a rule for it; the building department at 636-797-5555 is called before the job starts.
For most Ameren Missouri customers, Pay As You Save: $0.20 per square foot on an attic starting at R-20 or lower and $0.06 per square foot on air sealing in 2026, the rest repaid on the bill. The federal 25C credit ended for work placed in service after December 31, 2025.
The typical home in Imperial dates to around the early-1990s; the Census Bureau's 2020-2024 median year built is 1990. Of its 1,960 homes, 4% went up before 1940 and 35% in 2000 or later. Half the homes here are older than that and half newer; yours may sit at either end.
Code and permit facts checked September 10, 2026, rebates October 24, 2026; housing: Census ACS 2020–2024. Sources: ecode360.com (2, 3, 4) · jeffcomo.gov (2) · energycodes.gov · en.wikipedia.org · bestplaces.net · ameren.com (2, 3, 4) · energystar.gov · data.census.gov. These change; confirm with the building department at 636-797-5555 or your electric utility first.
Free assessment, a measured R-value, and photos you keep either way.
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