What it actually takes to insulate a house in Union — what the city publishes about energy code and permits, what it does not, the rebate your address qualifies for, and how old the housing here really is.
Union runs to about 9.0 square miles and roughly 12,348 people. It sits about 50 miles southwest of downtown St. Louis. That is roughly 5,530 housing units, and the attic above almost all of them is the cheapest thing in the house left to fix. The community dates back to 1826. We cover ZIP code 63084.
Our job history shows nothing in Union so far. Plenty of sites will show you a number here anyway.
The typical home in Union dates to around the late-1990s. Houses of this vintage usually got batts or blown fibre 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.
, consistent with the city's fastest population-growth period of 2000-2010 — housing skews toward 1990s-2000s suburban construction.
Union is the Franklin County seat (designated 1827), sited on the Bourbeuse River; population grew from 402 in 1880 to 12,348 by 2020.
Housing from this stretch in Union generally got a real attempt at insulation — a real layer in the attic, batts in the walls — so the argument here is rarely about starting from nothing. It is about the gap between what was standard then and what is recommended now, and about the parts nobody insulated at all. Recurring finds: batts stuffed into the rim joist rather than sealed, insulation missing entirely above a cathedral or tray ceiling, soffit vents blocked solid by insulation blown over them with no baffles, and can lights punched straight through the ceiling plane. A house from this era is usually a top-up plus a day of sealing, not a rebuild.
Union does not publish the energy code edition it enforces anywhere we could verify, so this page does not name one. Chapter 500, Article I of the City of Union code adopts the 2021 International Building Code in Section 500.010(A) by Ordinance No. 4630 of 11-13-2023, the 2021 International Existing Building Code in Section 500.055(A) by Ordinance No. 4631 of 11-13-2023, and the 2021 International Residential Code in Section 500.060(A) by Ordinance No. 4636 of 11-13-2023, along with the 2020 NEC and 2021 plumbing, mechanical and fuel gas codes. Section 500.065(A)(49) deletes Chapter 11 Energy Efficiency from the adopted IRC, and the city also deletes IBC Section 101.4.6 Energy. No article adopting any edition of the International Energy Conservation Code exists in the codified chapter. The city's own Building Codes web page does list an International Energy Conservation Code among its 2021 codes, which contradicts the codified ordinance; the ordinance is the controlling source and this discrepancy should be confirmed with the city. 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 genuinely wide spread. Ask which one your contractor is building to.
There is no published answer for Union. Neither the permit-required list nor the exemption list mentions insulation or air sealing at all. That is the normal state of affairs across this metro — only a handful of the 45 jurisdictions on this site say anything about it at all. Union deleted items 1 and 2 of the IBC Section 105.2 permit exemption list, and the permits page says only that the department reviews plans and issues building permits for all residential and commercial construction and remodeling projects. Insulation, weatherization and air sealing are not named on either the permit list or the exemption list. That silence is not permission and it is not a prohibition. We settle it with a phone call before the crew is scheduled.
No contractor licensing or registration provision appears in Chapter 500 Article I, and the city's permits page does not mention one.
The published number is 636-583-1805. The department page is here.
Permitting is on us, not on you.
Union is on the Missouri side, which for most addresses means Ameren Missouri — and Ameren Missouri does not hand out a straight per-square-foot insulation rebate the way its Illinois sister utility does. What it runs instead is Pay As You Save: a free home energy assessment, then the work installed by a programme partner and paid back through a fixed monthly charge on the electric bill, which cannot exceed 80% of the estimated monthly saving, so the bill still comes down while it is being repaid. No loan and no credit check.
Published incentives inside that programme for the 2026 programme year are $0.20 per square foot on ceiling and attic insulation, $0.06 per square foot on air sealing, and 50% of costs up to $250 per home on duct sealing. Each one has a condition attached, and they matter:
Ameren Missouri also runs CommunitySavers, which installs attic insulation at no charge for income-eligible households. The program operates through December 31, 2026; incentives are dependent on available funds.
Spire, the gas utility on this side, lists furnace, water heater and thermostat rebates on its Missouri rebate page rather than a standalone insulation one. Its published route to attic insulation and air sealing is the same on-bill Pay As You Save programme, which it co-delivers, plus income-based weatherization. If you are a Spire customer it is worth ringing them to ask what is open this year, because that page moves.
If the household income qualifies, the work can be free rather than discounted. Franklin County is served by Jefferson-Franklin Community Action Corp. (JFCAC) under the Missouri low-income weatherization program — 636-789-2686, details here.
One more, by its absence: the federal 25C credit, which covered 30% of insulation and air sealing up to $1,200 a year, ended for anything placed in service after 31 December 2025. Work finished on or before that date is still claimed on that year's return; nothing done in 2026 is. It should not be in your 2026 price, whoever tells you otherwise — the rebate guide has the detail.
Union sits in all eight counties are iecc 2021 climate zone 4 on the same map the Department of Energy uses to write its recommendations, which is why the figure it recommends for an attic here is R60 rather than something borrowed from a national advert. Heating and cooling both matter at this latitude. The energy code and rebate guide sets out the numbers behind it.
Elsewhere in Franklin County we also cover:
Missouri sets none of this at state level, so the number that was right one municipality over is not automatically right here.
| City | Energy code | Attic R required | Permit to insulate | Building dept. |
|---|---|---|---|---|
| Pacific | None adopted | — | Not published | 636-271-0500 |
| Washington | Not published | — | Not for an attic top-up | 636-390-1000 |
Free assessment, a measured R-value, and photos you keep either way.
Union 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.
Union has not published a rule for it. In practice that means one call to the building department before the job starts, which is on us rather than on you.
For most addresses here the route is Ameren Missouri's Pay As You Save programme, which publishes $0.20 per square foot on ceiling and attic insulation and $0.06 per square foot on air sealing for the 2026 programme year. Both carry conditions: the attic has to start at R-20 or below and reach at least R-38, and the air sealing has to cut leakage by at least 20 percent. The incentives sit inside tier 4 of the programme and need you to have lived in the home for the past twelve months, and they are recovered through a monthly charge on the electric bill rather than paid as a cheque. Income-eligible households can get attic insulation at no charge through CommunitySavers instead. The federal 25C credit ended for work placed in service after 31 December 2025.
The typical home in Union dates to around the late-1990s. Houses of this vintage usually got batts or blown fibre 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. That figure is an ACS-derived median republished by housing-data services, not a survey of individual houses.
Not yet. We have no completed job logged in Union, and we would rather say so than put a number on this page that is not real.
Neither state licenses insulation contractors as a trade. In Missouri there is no statewide residential code at all, and registration is imposed city by city — several metro municipalities require a contractor to be registered with them before a permit is pulled. What matters more in practice is utility programme enrolment, because that is what decides whether your rebate is real.
Energy code, permit and department details for Union come from the jurisdiction's own published pages and codified ordinances. Rebate figures come from the utility's own published incentive tables and carry the programme year they were verified in. Housing-age figures are ACS-derived medians republished by housing-data services, so treat them as approximate. Sources: ecode360.com · unionmissouri.gov · unionmissouri.gov · cms4files.revize.com · en.wikipedia.org · city-data.com · ameren.com · ameren.com · ameren.com · ameren.com · energy.gov. Adopted code editions, department phone numbers and utility rebate amounts all change — confirm with the jurisdiction or the utility before relying on anything here.