Attic insulation, air sealing, crawl spaces and walls for homes in Des Peres — starting with a free assessment that measures the R-value you actually have. Des Peres enforces the 2018 IRC ch. 11, which sets R-49 for a new attic.
Des Peres runs to about 4.3 square miles and roughly 9,170 people. It sits about 14 miles west of downtown St. Louis. That is roughly 3,331 housing units. The community dates back to 1934. We cover ZIP code 63131.
Our job history shows nothing in Des Peres so far. Plenty of sites will show you a number here anyway.
The typical home in Des Peres dates to around the mid-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.
Mostly built in the 1970s (nearly 30% of homes).
That includes Dougherty Lake. Housing age and construction shift across Des Peres, sometimes by decades within a few streets, which is why we look in the attic before quoting rather than after.
Des Peres was incorporated as a town in 1934. Dougherty Lake was one of its original residential subdivisions, and its City Hall predates incorporation, having originally been built by a neighboring Lutheran church as an orphanage.
The Census Bureau estimates 3,331 homes in Des Peres. 12 of them (0%) went up before 1940 — one of the five lowest pre-1940 shares among the 44 places on this site. The 1970s were the busiest decade, adding 990 of today's homes (30%); 61% predate 1980 and 13% were built in 2000 or later. For St. Louis County as a whole the pre-1940 share is 10%, so Des Peres sits below it.
Of 3,195 occupied homes, 84% heat with utility gas and 15% with electricity. Electric heat here is less common than across the county (23%), and ranks 43rd of 44 on this site. Which utility program can contribute depends on the heating fuel and on who sends the bill, so that is the first thing an assessment pins down.
96% of occupied homes are owner-occupied and 98% of all homes are single-family detached houses. On a housing mix like this, the likely starting points are an attic top-up over postwar fiberglass.
| Built | Homes | Share | |
|---|---|---|---|
| Before 1940 | 12 | 0% | |
| 1940s | 17 | 1% | |
| 1950s | 643 | 19% | |
| 1960s | 386 | 12% | |
| 1970s | 990 | 30% | |
| 1980s | 631 | 19% | |
| 1990s | 223 | 7% | |
| 2000s | 206 | 6% | |
| 2010s | 210 | 6% | |
| 2020 or later | 13 | 0% |
3,331 homes, Census ACS 2020–2024 (B25034, B25040, B25003); 3,195 occupied.
854 of Des Peres' 3,331 homes (26%) 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.
Des Peres enforces the 2018 IRC Chapter 11 (Energy Efficiency). Ordinance 2873, the city's 2018 code adoption, adopts the 2018 International Building Code, the 2018 International Residential Code, the 2018 International Swimming Pool and Spa Code, the 2018 International Existing Building Code, the 2018 International Fire Code and the 2018 International Property Maintenance Code. It does not adopt an International Energy Conservation Code of any edition. The ordinance's amendments touch Sections 112.4, 302.4, 304.14, 602.3 and 602.4 and state that no other sections are altered, so Chapter 11, Energy Efficiency, of the 2018 IRC is in force as written. The Missouri state code database likewise lists Des Peres with the 2018 IRC and 2018 IBC and no separate energy code.
Under that edition the required attic value for new work here is R-49, and walls R-20, or R-13 plus R-5 continuous. For comparison, the Department of Energy recommends R60 for an uninsulated attic in climate zone 4A, where Des Peres sits, and R49 where there are already a few inches up there.
Chapter 11 of the 2018 IRC carries the same envelope requirements as Table R402.1.2 of the 2018 IECC. For climate zone 4 except marine that is ceiling R-49 and wood frame wall R-20 or R-13+5, per the PNNL Building America Solution Center IECC and IRC insulation table and NAIMA's 2018 IECC climate zone 4 summary.
There is no published answer for Des Peres. Neither the permit-required list nor the exemption list mentions insulation or air sealing at all. The Permit Requirements page lists residential building, pool, fence and demolition permits, commercial building, sign and occupancy permits, and grading, land disturbance and subdivision permits. Insulation, air sealing and weatherization are not named on any of those lists, and the city directs specific questions to the Public Works Department. That silence is not permission and it is not a prohibition. We settle it with a phone call before the crew is scheduled.
Neither the Building Division page nor the permit requirements page states a contractor registration or licensing requirement.
The published number is 314-835-6130. The department page is here.
Permitting is on us, not on you.
Most Des Peres 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. It counts only when the attic is at R-20 or below beforehand and R-38 or more afterward, when air sealing cuts measured leakage by 20 percent, and when the household has lived there for the past year; for income-eligible households, CommunitySavers can include attic insulation at no charge. Income-qualified households can apply to Community Action Agency of St. Louis County (CAASTLC) (314-863-0015) for free weatherization instead. The St. Louis County page and the rebate guide carry the full rules.
Every layer of an insulated attic, explained
Elsewhere in St. Louis County we also cover:
Missouri sets none of this at state level. Across the 7 places in this table there are 4 different adopted editions (2015 IECC, 2018 IRC ch. 11, 2021 IECC and 2024 IECC), and 1 of the 7 publishes a permit rule for insulation.
| City | Energy code | Attic R required | Permit to insulate | Building dept. |
|---|---|---|---|---|
| Des Peres | 2018 IRC ch. 11 | R-49 | Not published | 314-835-6130 |
| 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 |
All 21 St. Louis County jurisdictions side by side →
Des Peres enforces the 2018 IRC ch. 11, which sets R-49 for an attic in new work. Whether it reaches a retrofit of an existing house is not published.
Des Peres has not published a rule for it; the building department at 314-835-6130 is called before the job starts.
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 Des Peres dates to around the mid-1970s; the Census Bureau's 2020-2024 median year built is 1976. Of its 3,331 homes, 0% went up before 1940 and 13% in 2000 or later. It is a median for the place, not a survey of individual houses.
Code and permit facts checked September 10, 2026, rebates October 24, 2026; housing: Census ACS 2020–2024. Sources: desperesmo.org (2, 3, 4, 5, 6) · data.mo.gov · basc.pnnl.gov · insulationinstitute.org · 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 314-835-6130 or your electric utility first.
Free assessment, a measured R-value, and photos you keep either way.
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