Insulation in Cottleville, Missouri

Insulation and air sealing in Cottleville

Cottleville runs to about 4.7 square miles and roughly 5,937 people. It sits about 27 miles west of downtown St. Louis. Around 2,275 housing units sit inside those boundaries. We cover ZIP code 63304.

No completed job in Cottleville is logged in our records yet, and this page will say so until one is.

The housing stock in Cottleville

The typical home in Cottleville dates to around the early-2010s. Houses this new were built to an energy code, so the attic usually started at something close to the required depth. What goes wrong here is settlement, gaps at the eaves, and a ceiling plane nobody ever sealed.

Overwhelmingly new construction -- more than half of all homes (about 52%) were built in the 2010s.

That includes Old Town Cottleville. Housing age and construction shift across Cottleville, sometimes by decades within a few streets, which is why we look in the attic before quoting rather than after.

First settled in 1798 under a Spanish land grant and platted as a town in 1839, modern Cottleville has been one of Missouri's fastest-growing cities (population grew nearly 1,500% between 1980 and 1990). Its median housing construction year of 2012 makes it by far the newest-built town in this set outside its small historic Old Town core.

Cottleville homes in the Census numbers

The Census Bureau estimates 2,275 homes in Cottleville. 32 of them (1%) went up before 1940 — one of the five lowest pre-1940 shares among the 44 places on this site. The 2010s were the busiest decade, adding 1,171 of today's homes (51%); 2% predate 1980 and 81% were built in 2000 or later. For St. Charles County as a whole the pre-1940 share is 2%, so Cottleville sits below it.

Of 2,206 occupied homes, 67% heat with utility gas and 28% with electricity; another 2% burn propane or other tank gas. Electric heat here is less common than across the county (30%), and ranks 29th 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.

81% of occupied homes are owner-occupied and 72% of all homes are single-family detached houses. Read together, those numbers point toward air sealing on newer houses that already have depth and an energy assessment before deciding what to fix first.

2,275 homes, Census ACS 2020–2024 (B25034, B25040, B25003); 2,206 occupied.

Sealing comes first in Cottleville

1,834 of Cottleville's 2,275 homes (81%) were built in 2000 or later. Depth is rarely what is missing in houses this new; air paths are: attached garages, bonus rooms over them, the chase around a high-efficiency flue, and the thin edge where blown fiber meets the wall plate. They usually earn their money back on sealing rather than on more fiber.

What the energy code requires in Cottleville

Cottleville enforces the 2021 IRC Chapter 11 (Energy Efficiency), as amended. Chapter 500, Article X, Section 500.130 adopts the International Residential Code, One- and Two-Family Dwellings, 2021 Edition, with Appendices A, B, C, E, F, G, H, J, M, N and P, by Ordinance No. 2157 of 6-26-2024. Chapter 11, Energy Efficiency, is kept and amended in more than twenty places rather than deleted. Article I, Section 500.010 separately adopts the 2021 International Building Code with Appendices C, E, F, G, I, J and K under Ord. No. 1750 of 2-20-2019 and Ord. No. 2157 of 6-26-2024. No standalone International Energy Conservation Code is adopted.

For new work, the attic number under that edition is R-38, with walls at R-13. 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 N1102.1.3, cross-referenced as R402.1.3, as amended in Chapter 500 Article X, row for climate zone 4 except Marine.

Do you need a permit to insulate here?

Nothing Cottleville publishes settles this. Its permit lists name the work types it cares about, and insulation is not among them in either direction. Section 500.030 requires a building permit with the exception of ordinary repairs and the exceptions in IBC Section 105.2. The city building permit application lists the work types New Construction, Addition, Alteration, Replacement, Repair, Interior Finish, Occupancy, Demolition, Fence and wireless support structures. Insulation is not a listed work type. So we ask the department directly before the first day on site, and whatever comes back, pulling it is our job rather than yours.

Not published for insulation contractors. The building permit application asks for a St. Charles County License number for electrical, plumbing and mechanical contractors only, and notes that any new business must also submit a business license. There is no insulation trade registration.

Permits and inspections in Cottleville

The published number is 636-498-6565. The department page is here.

Permitting is on us, not on you.

Rebates a Cottleville homeowner can actually use

Cottleville 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 North East Community Action Corp. (NECAC) (573-324-2231) for free weatherization instead. The St. Charles County page and the rebate guide carry the full rules.

Nearby

Elsewhere in St. Charles County we also cover:

How Cottleville compares with its neighbors

Missouri sets none of this at state level. Across the 6 places in this table there are 3 different adopted editions (2015 IECC, 2021 IECC and 2021 IRC ch. 11), and none of the 6 publishes a permit rule for insulation.

All 6 St. Charles County jurisdictions side by side →

Common questions about insulation in Cottleville

Code and permit facts checked September 10, 2026, rebates October 24, 2026; housing: Census ACS 2020–2024. Sources: ecode360.com (2) · cityofcottleville.com (2, 3, 4) · 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 636-498-6565 or your electric utility first.