Attic insulation, air sealing and crawl space work across Franklin County. We cover 3 jurisdictions here, each with its own page: the energy code that applies, the attic R-value it requires, the permit position and the building department's number. Of the county's 46,312 homes, 10% were built before 1940, and 68% of occupied homes heat with electricity.
Click a city for its full code, permit and rebate detail.
| City | Energy code | Attic R required | Permit to insulate | Building dept. |
|---|---|---|---|---|
| Pacific | None adopted | — | Not published | 636-271-0500 |
| Union | Not published | — | Not published | 636-583-1805 |
| Washington | Not published | — | Not for an attic top-up | 636-390-1000 |
None publish an energy code edition we could name and none a required R-value we could read; a blank in this table means the jurisdiction publishes nothing, not that we guessed.
Missouri sets no statewide residential energy code, so across Franklin County the code is whatever each jurisdiction adopted on its own: no published edition in Union and Washington; no energy code at all in Pacific.
None of them publishes an attic figure we could read, which is why each place has its own page and the Department of Energy's recommendation does the work instead.
The 3 places here with their own Census row hold 15,506 of Franklin County's 46,312 homes (33%); the rest are in other municipalities or unincorporated areas.
One detail worth knowing before a job in each of them:
Franklin County has 46,312 homes in the Census count, with a median year built of 1984. 44% were built before 1980 and 27% in 2000 or later; the single biggest decade was the 2000s, with 7,478 homes (16%). Of 43,036 occupied homes, 15% heat with utility gas and 68% with electricity.
Across the 3 places we cover here, Washington has the oldest housing (17% before 1940) and Union the newest (44% built in 2000 or later). Washington is the largest, at 6,889 homes, and Union has the most electric heat (85%).
| Place | Homes | Before 1940 | Median built | Electric heat | Owner-occupied |
|---|---|---|---|---|---|
| Washington | 6,889 | 17% | 1978 | 66% | 74% |
| Union | 5,399 | 8% | 1996 | 85% | 61% |
| Pacific | 3,218 | 5% | 1985 | 61% | 65% |
Against the eight-county metro on this site (1,177,290 homes), Franklin County's pre-1940 share of 10% compares with 16%, and its electric-heat share of 68% with 32%. 4,667 occupied homes (11%) burn propane or other tank gas and 1,766 (4%) heat with wood, which matters because neither fuel comes with a gas utility's program attached. 77% of occupied homes are owner-occupied and 76% of all homes are single-family detached houses.
In Franklin County that adds up to 13,874 homes from the 1950s to the 1970s, the usual candidates for an attic top-up; 12,622 built since 2000, where air sealing tends to matter more than extra depth.
| Built | Homes | Share | |
|---|---|---|---|
| Before 1940 | 4,583 | 10% | |
| 1940s | 1,948 | 4% | |
| 1950s | 3,177 | 7% | |
| 1960s | 3,645 | 8% | |
| 1970s | 7,052 | 15% | |
| 1980s | 6,138 | 13% | |
| 1990s | 7,147 | 15% | |
| 2000s | 7,478 | 16% | |
| 2010s | 4,439 | 10% | |
| 2020 or later | 705 | 2% |
Figures: U.S. Census Bureau, American Community Survey 2020–2024 5-year estimates (tables B25001, B25003, B25024, B25034, B25035, B25040). Survey estimates carry margins of error, widest in the smallest places. Census table.
Franklin County 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 Jefferson-Franklin Community Action Corp. (JFCAC) (636-789-2686) for free weatherization instead. The rebate guide carries the full rules.
It depends on the city, not the county. Across Franklin County, 1 publish that an attic top-up needs none (Washington); the other 2 publish no rule either way. Each town page says which applies and gives the building department's number.
None of the 3 jurisdictions we cover in Franklin County publishes an attic figure we could read, so the useful benchmark is the Department of Energy's: R60 for an uninsulated attic in this climate zone.
The Census Bureau's 2020–2024 estimates put 10% of Franklin County's 46,312 homes before 1940 and 44% before 1980, with a median year built of 1984.
For most addresses across Franklin County the electric utility is Ameren Missouri, whose 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, with the rest of the cost repaid through the bill, and only where the attic starts at R-20 or below. For income-eligible households, CommunitySavers can include attic insulation at no charge.
Yes, through the Missouri low-income weatherization program, which Jefferson-Franklin Community Action Corp. (JFCAC) runs for Franklin County (636-789-2686). If the household income qualifies, the work can be free rather than discounted.
Free assessment, a measured R-value, and photos you keep either way.
Book my free assessment →