Attic insulation, air sealing, crawl spaces and walls for homes in Washington — starting with a free assessment that measures the R-value you actually have. The typical home here dates to the late-1970s, and 17% of its 6,889 homes went up before 1940.
Washington runs to about 9.7 square miles and roughly 15,075 people. It sits about 50 miles west of downtown St. Louis. That is roughly 6,889 housing units. The community dates back to 1827. We cover ZIP code 63090.
Our job history shows nothing in Washington so far. Plenty of sites will show you a number here anyway.
The typical home in Washington dates to around the late-1970s. Postwar building here often meant three or four inches of fiberglass and no attempt at air sealing. If nobody has touched it since, that is what is still up there.
Settled during Spanish colonial rule as St. John Meyer's Settlement, later Washington Landing (1814); the largest city in Franklin County and sited on the south bank of the Missouri River.
The Census Bureau estimates 6,889 homes in Washington. 1,174 of them (17%) went up before 1940 — 10th of 44 places on this site for pre-1940 housing. More of today's homes date from before 1940 than from any single decade since, and 53% predate 1980. For Franklin County as a whole the pre-1940 share is 10%, so Washington sits above it.
Of 6,702 occupied homes, 29% heat with utility gas and 66% with electricity; another 2% burn propane or other tank gas. Electric heat here is less common than across the county (68%), and ranks 2nd of 44 on this site. That is why the assessment asks how the house is heated: the fuel and the name on the utility bill decide which program, if any, can pay toward the work.
74% of occupied homes are owner-occupied and 73% of all homes are single-family detached houses, with 83 mobile homes in the count. On a housing mix like this, the likely starting points are an energy assessment before deciding what to fix first.
| Built | Homes | Share | |
|---|---|---|---|
| Before 1940 | 1,174 | 17% | |
| 1940s | 429 | 6% | |
| 1950s | 495 | 7% | |
| 1960s | 586 | 9% | |
| 1970s | 988 | 14% | |
| 1980s | 746 | 11% | |
| 1990s | 684 | 10% | |
| 2000s | 1,107 | 16% | |
| 2010s | 552 | 8% | |
| 2020 or later | 128 | 2% |
6,889 homes, Census ACS 2020–2024 (B25034, B25040, B25003); 6,702 occupied.
1,430 of Washington's 6,889 homes (21%) 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.
Washington does not publish the energy code edition it enforces, so this page does not name one. Section 500.010(A) of the City of Washington code, Ordinance No. 23-13877 effective 12-4-2023, adopts by reference the 2021 editions of the International Residential Code, International Property Maintenance Code, International Existing Building Code, International Building Code, International Fire Code, International Plumbing Code, International Fuel Gas Code, International Mechanical Code and International Swimming Pool and Spa Code, plus the 2020 National Electrical Code, each as amended. No International Energy Conservation Code is named. Section 500.010(B) says the codes are amended as set forth on Exhibit A, a separate PDF attachment. Across this metro the adopted editions run from the 2015 IECC to the 2024 IECC, and several jurisdictions have no energy code at all, which is a wide spread. Ask which one your contractor is building to.
Chapter 500 states: Residential remodel that does not involve structural, electrical or plumbing changes and/or cost less than one thousand dollars ($1,000.00) shall not require a building permit. Retrofit attic insulation and air sealing involve no structural, electrical or plumbing change.
The published number is 636-390-1000. The department page is here.
Permitting is on us, not on you.
Most Washington 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 full program rules are on the Franklin County page and in the rebate guide.
Every layer of an insulated attic, explained
Elsewhere in Franklin 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 none of them publishes an energy code edition, and 1 of the 3 publishes a permit rule for insulation.
| City | Energy code | Attic R required | Permit to insulate | Building dept. |
|---|---|---|---|---|
| Washington | Not published | — | Not for an attic top-up | 636-390-1000 |
| Pacific | None adopted | — | Not published | 636-271-0500 |
| Union | Not published | — | Not published | 636-583-1805 |
All 3 Franklin County jurisdictions side by side →
Washington does not publish the energy code edition it enforces, so we do not state a required figure here. The Department of Energy recommends R60 for an uninsulated attic in this climate zone and R49 where there are already a few inches.
Chapter 500 states: Residential remodel that does not involve structural, electrical or plumbing changes and/or cost less than one thousand dollars ($1,000.00) shall not require a building permit. Retrofit attic insulation and air sealing involve no structural, electrical or plumbing change.
Ameren Missouri's Pay As You Save: $0.20 per square foot for an attic starting at R-20 or below and $0.06 per square foot for air sealing in 2026, with the balance on the electric bill. The federal 25C credit ended for work placed in service after December 31, 2025.
The typical home in Washington dates to around the late-1970s; the Census Bureau's 2020-2024 median year built is 1978. Of its 6,889 homes, 17% went up before 1940 and 26% 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) · washmo.gov (2, 3) · ci-washington-mo.smartgovcommunity.com · en.wikipedia.org (2, 3) · city-data.com · ameren.com (2, 3, 4) · energystar.gov · data.census.gov. These change; confirm with the building department at 636-390-1000 or your electric utility first.
Free assessment, a measured R-value, and photos you keep either way.
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