Replacing windows in St. Louis is a different job than replacing them almost anywhere else, because of what the houses are made of. More than half of the City's homes were built before 1940, most of them in brick, and eighteen City neighborhoods sit under a historic review whose approved window list contains no vinyl product and whose district standards — every one we have read — keep vinyl off the street side. Cross into St. Charles County and the house is probably from the 1990s, the wall is siding over frame, and the county wants a permit once you replace four windows. The glass you need is the same in both places — this is a true mixed climate — but the frame, the install method, the paperwork and the price are not. This guide walks the whole purchase in the order the decisions actually come up.
What does your house era decide before you pick a window?
The year your house was built sets three things at once: the wall your window sits in, whether lead-safe work rules apply, and whether a historic review has a say. In St. Louis those three line up with geography more tightly than in most metros, so start with the era and let it narrow the choices.
| Where | Units | Built before 1940 | Built before 1980 | Median year | What that means for windows |
|---|---|---|---|---|---|
| St. Louis City | 174,111 | 57.9% | 86.2% | 1938 | Brick masonry openings, original wood sash, lead-safe rules on nearly every job, 18 historic districts |
| St. Louis County | 446,192 | 9.7% | 68.6% | 1969 | Inner ring is pre-war wood and brick; the middle ring is 1950s–60s ranches with steel or aluminum sash |
| St. Charles County | 167,163 | 2.2% | 24.8% | 1994 | Frame walls, first-generation builder vinyl that is now 25–35 years old |
| Jefferson County | 93,955 | 3.5% | 40.6% | 1987 | Mixed; mostly frame |
| Madison County, IL | 119,168 | 14.6% | 61.0% | 1971 | Older river towns plus 1960s–70s subdivisions |
| St. Clair County, IL | 115,630 | 13.5% | 54.9% | 1975 | Belleville's pre-war core, Shiloh/O'Fallon new |
Source: U.S. Census Bureau, ACS 2020–2024 5-year, tables B25034 and B25035.
Three rules of thumb fall out of that table:
- Pre-1940, City or inner ring: assume a masonry opening and original weight-and-pulley wood sash. Insert replacement is possible but not always right; see the brick guide.
- 1950–1975, North County and South County: assume steel or aluminum sash in a frame or brick-veneer wall. These usually want full-frame replacement because the old frames are thin and conduct cold. See insert vs. full-frame.
- 1985 and newer, St. Charles County and West County: assume builder-grade vinyl with failed seals. These are the simplest replacements in the metro, and the cheapest.
Is your house in a City historic district?
If your house is inside one of the City of St. Louis's eighteen local historic districts, the Cultural Resources Office must approve your replacement windows before a building permit can be issued, and its approved list contains no vinyl window. This is the single most common surprise for St. Louis buyers, and it is the reason a national window company's standard quote does not work in Soulard, Lafayette Square, Benton Park, Shaw, the Central West End, Skinker DeBaliviere, Compton Hill, Hyde Park, Fox Park, McKinley Heights, Cherokee-Lemp, Kingsbury-Washington Terrace, North I-44, The Ville, Union Station, Visitation Park or the Hyde Park Extension. (Tower Grove East is a district too, but its adopted standards cover new construction and additions only.)
The City's own permit page says it plainly: in a historic district, approval "is usually required by the Cultural Resources Office even though it is not required by the Building Code." The office reviews roughly 2,000 exterior-alteration permits a year and offers a free preliminary review before you buy anything.
What the districts allow, in short:
- Street-facing façades: wood, clad wood, composite, or color-finished aluminum, replicating the original sash in configuration and profile. Soulard, Benton Park, Shaw and Hyde Park say "wood or finished aluminum"; the Central West End says "wood, clad wood, or a composite material"; Lafayette Square's primary façades are all-wood or composite-clad wood with metal-clad specifically prohibited.
- Side and rear façades: looser, district by district. Central West End rear elevations may be "any material." Soulard and Benton Park do not regulate material on private façades at all.
- Opening size: Benton Park and the Central West End prohibit altering a street-facing opening's size; most districts treat it the same way.
Tower Grove South, Old North St. Louis and the "Compton Heights" name are not local historic districts; being on the National Register alone does not trigger CRO review for privately funded work. The full district-by-district table, with the approved product list, is in the historic district window rules guide, and the service that handles the review is historic district windows.
Do lead-safe rules apply to your window job?
If your home was built before 1978, federal Renovation, Repair and Painting rules apply to window replacement, and window replacement is specifically written out of the small-job exemption. The rule's minor-repair exception covers disturbances of six square feet per room inside or twenty outside — "where the work does not involve window replacement." That phrase is in the regulation itself (40 CFR 745.83). So on a pre-1978 house, every window replacement is an RRP job: a certified firm, a certified renovator on site, containment, cleaning verification and records.
In St. Louis that is most of the work. By the Census proxy (pre-1980), it is 86% of the City, 69% of the County, 61% of Madison County and 55% of St. Clair County. Missouri and Illinois both leave the program to the EPA rather than running their own, so the certification you ask to see is the EPA Lead-Safe Certified Firm certificate. What that changes about the day, and what to ask any installer, is in lead-safe window replacement.
Which wall are the windows in — and does it change the install?
Brick changes the install more than any other variable, because a masonry opening has no nailing fin, no sheathing and no siding to tuck a flange under. The window sits inside the opening against brickmould or a rabbet, on a stone or rowlock-brick sill, under a steel or stone lintel. There are two honest ways to replace it:
| Method | What happens | When it is right | Cost (relative) |
|---|---|---|---|
| Insert (pocket) replacement | Old sash and stops come out; the new unit is set inside the existing wood frame | Frame is sound, square and dry; you want to keep interior trim | Base |
| Full-frame replacement | Entire old frame comes out to the masonry; new unit is set, flashed and sealed to the opening | Rot, out-of-square frames, weight pockets you want insulated, steel sash, any time you are changing size | Typically 25–60% more per opening |
On a 1920s brick two-story the pockets where the sash weights hang are uninsulated voids; a full-frame job fills them. On a 1960s brick-veneer ranch with steel casements there is no wood frame to insert into at all. On a 1995 St. Charles County frame house with a nailing-fin vinyl window, an insert is usually fine and a full-frame job is an upgrade, not a necessity. The method is the biggest swing in the price after the window count, so get it settled before comparing quotes. Details: replacing windows in a brick house and insert vs. full-frame.
Do you need a permit, and who do you ask?
It depends on which side of which line you live on, and the answers are not the same. The St. Louis region has one independent city, two large counties, a third across the river in Illinois, and nearly ninety municipalities inside St. Louis County alone. Three verified cases:
| Jurisdiction | Same-size replacement | Enlarging or adding an opening | Code | Source |
|---|---|---|---|---|
| City of St. Louis | No permit: "replacement or repair of existing windows and frames, whenever no modification is made to the opening" | Permit required (structural change) | 2018 IRC | City residential permit criteria |
| City of St. Louis, historic district | CRO approval required before any permit, regardless of the building code | Same, and most districts prohibit it on street façades | — | CRO permit review page |
| St. Charles County (unincorporated) | No permit for three or fewer windows in the same opening; four or more need a permit | Permit required | 2021 IRC | County Code §500.150, R105.2 |
For St. Louis County unincorporated and for each municipality — Kirkwood, Webster Groves, University City, Florissant, Chesterfield, Ballwin and the rest — the rule has to be confirmed with that building department before the job starts; we do that as part of the measure visit, and the permits guide lists what we could and could not verify as of this update. Metro East is Illinois: Edwardsville, Belleville, Collinsville and Granite City each run their own permit desk. Contractor licensing differs too: the City requires a construction-contractor business licence, and Ballwin will not let a contractor pull a permit without a Ballwin licence and an active St. Louis County trade licence.
What should the glass be for a St. Louis climate?
St. Louis is a mixed climate — 4,433 heating degree days and 1,713 cooling degree days a year at Lambert — so the right glass has a low U-factor for January and a moderate solar heat gain coefficient for July, not the extreme of either. The July normal high is 89.6°F with a dew point normal of 66.8°F; the January normal low is 23.8°F. That is why EPA's ENERGY STAR map places this region in the North-Central zone, whose Version 7.0 thresholds are a U-factor of 0.25 or lower and an SHGC of 0.40 or lower. Northern-zone windows (U ≤ 0.22, built to let the winter sun in) and Southern-zone windows (SHGC ≤ 0.23, built to block it) both exist on the market and both are sold here by national companies.
Practical reading of a label:
- U-factor 0.25–0.28 is the sweet spot for double-pane low-e argon units here. Going to triple-pane for 0.20 buys comfort on north-facing glass and noise reduction on busy streets; it rarely buys a payback.
- SHGC 0.25–0.40, lower on west-facing glass in a house with no shade, higher on a south façade with a porch roof.
- Air leakage ≤ 0.3 cfm/ft², and ask how the sash meeting rail seals — that is where old double-hungs lose the battle.
The longer explanation, including when to spend on the frame instead of the glass, is in window performance ratings for St. Louis.
What happened to the window tax credit?
There is no federal tax credit for windows installed in 2026. The Energy Efficient Home Improvement Credit (Section 25C), which paid up to $600 on ENERGY STAR Most Efficient windows, ended for property placed in service after December 31, 2025 under Public Law 119-21. The IRS says so on its own page. Ameren Missouri's residential rebate chart has no window line; neither does Ameren Illinois or Spire. Residential PACE financing through the Missouri Clean Energy District is suspended. The weatherization assistance programs on both sides of the river are income-qualified and audit-driven, and windows are rarely the measure they fund. If a quote in 2026 still leans on "the tax credit," that is a reason to read the rest of it carefully. The full picture is in tax credits and rebates in 2026.
What do replacement windows cost in St. Louis?
Expect a typical St. Louis whole-house replacement to land between roughly $7,000 and $26,000 installed, and a single opening between about $550 and $2,800 depending on frame material, install method and what the wall is made of. The widely cited aggregator figure for the metro is an average of about $6,278 per project with a typical range of $3,100 to $9,500 (Angi, St. Louis page, October 2026) — but that figure mixes partial jobs, unit-only purchases and everything from vinyl inserts to clad-wood full-frame work in brick. Our published bands are in the cost guide and in the instant estimate, and they break out the three things that move a St. Louis price that national guides ignore:
- Masonry openings add labor and flashing work over a frame wall.
- Historic-district product — wood, clad or composite from the approved list — costs two to three times a vinyl unit.
- Lead-safe setup on pre-1978 houses adds containment time per opening.
Sales tax is worth knowing about: in Missouri the contractor is the final consumer of the materials and pays tax on them when buying; the materials tax is inside the material cost, and a separate sales-tax line applied to labor is something to ask about.
Should you buy a window that is only on sale today?
No. A price that expires when the salesperson leaves is a pressure tactic, not a discount. The St. Louis market is unusually heavy on in-home selling: as of October 2026 every major window company we checked requires an in-home appointment to give a price, and several print that their promotion is "valid only at the initial in-home estimate." Published financing in this market runs from 6.99% to 29.49% APR depending on the company and promotion. The way to protect yourself is to compare written quotes on the same scope — same count, same install method, same glass package, same lead-safe and disposal line items — which is what the quote comparison guide and its worksheet are for.
Was the window damaged by the storm, or was it already failing?
After the March 14, 2024 hail and the May 16, 2025 tornado, a lot of St. Louis windows are being replaced on insurance, and the adjuster's question is always whether the damage is storm-caused or pre-existing. The 2025 tornado was an EF-3 with a path 3,168 yards wide — the widest recorded in the St. Louis forecast area since 1950 — running from Clayton through the City into Madison County, Illinois. By May 2026 Missouri insurers had paid more than $475 million on over 10,000 claims from that one storm, about 90% of it residential. Fogged glass, worn balances and rotted sills are not storm damage; cracked or broken glass, bent frames, failed seals with a matching impact mark, and water intrusion that started with the storm are. The storm damage window replacement page covers documentation, matching versus upgrading, and what to do while the metro's crews are booked out.
How does buying windows online actually work here?
You see a budget range first, without handing over an email; you shortlist styles, materials and glass on your own time; then one measure visit confirms sizes and conditions, and you approve a written quote before anything is ordered. That is the whole model, and the only step that cannot happen online is the measure, because a replacement window is made to the sixteenth of an inch for your opening. We will never ask you to measure for the order yourself; we will ask for rough sizes and a photo of the worst window so the estimate is honest. How it works walks the five steps, and measuring and photos for an online estimate shows exactly what to send.
Repair, or replace?
Original wood sash in a pre-war St. Louis house are usually repairable, and in a historic district repair is what the standards prefer. A broken sash cord, a rotted sill nosing, a painted-shut window, a cracked pane — these are repairs. Fogged insulated glass in a 1990s vinyl window is a glass-unit replacement, not a window replacement. What is not repairable is a frame that is rotted through, a steel casement that has rusted at the hinge, or a window whose opening has settled out of square. Repair or replace gives the decision tree, and window repair is the service.
Frequently asked questions
Can I put vinyl windows in a St. Louis historic district? Not on a street-facing façade in any of the eighteen City Historic Districts whose standards we have read, and no vinyl product appears on the Cultural Resources Office's approved replacement window list. Some districts allow vinyl on rear elevations or oblique side elevations; the Central West End does. Check the district's standard, or let us check it in the free preliminary review.
Do I need a permit to replace windows in St. Louis? In the City, not for same-size replacement, unless you are in a historic district, where CRO approval is required before a permit. In unincorporated St. Charles County, four or more windows need a permit even at the same size. In St. Louis County municipalities, confirm with the city's building department; rules vary.
How long does window replacement take? A crew replaces roughly eight to twelve insert windows a day in a frame house; brick full-frame work and lead-safe containment slow that to four to eight. Lead time from order to installation is typically four to eight weeks for stock vinyl and eight to fourteen weeks for clad-wood or historic-replica units.
What time of year is best? Any month. Installers remove and set one opening at a time, so the house is never open for long. Spring and fall are busiest; winter installs are common and are often priced more keenly.
Is triple-pane worth it in St. Louis? For comfort on north glass and for noise, sometimes. For energy payback alone, rarely — the climate is mixed, not northern.
Is there still a tax credit for windows in 2026? No. The federal 25C credit ended for anything placed in service after December 31, 2025.
Do you have to come to my house? Once, to measure and confirm conditions, after you have already seen a budget range and shortlisted online.
Ready to get a quote?
Pick the page that matches your house and start there — every one of them leads to the same written quote.
- Window replacement — the standard job: insert or full-frame replacement in any St. Louis home.
- Full-frame replacement — when the old frame has to come out: rot, steel sash, masonry openings.
- Historic district windows — windows from the CRO approved list, with the review handled.
- Energy-efficient windows — the right glass package for a mixed climate, without the tax-credit sales pitch.
- Storm damage window replacement — hail and tornado claims, documentation and matching.
- Window repair — glass, sash and balance repair when replacement is not the honest answer.
Or go straight to the instant estimate and see a range in under a minute.