In most of the country the frame material question is vinyl versus fiberglass versus wood on cost and looks. In St. Louis there is a fourth axis: whether the house is in one of the City's eighteen historic districts, where the Cultural Resources Office's approved list — which has no vinyl product — decides the street-facing product. So this guide starts with the house, not the catalog.
Materials compared
| Material | Installed cost (vinyl = 1.0) | U-factor range (low-e argon) | Lifespan | Maintenance | Looks | Historic district street façade? |
|---|---|---|---|---|---|---|
| Vinyl | 1.0 | 0.26–0.30 | 20–35 yrs; cheaper lines warp and weld-crack sooner | None | Wider frames, limited colors, white dominant | No |
| Fiberglass | 1.3–1.5 | 0.25–0.29 | 40+ yrs; dimensionally stable in St. Louis's 65°F annual swing | Paintable | Narrower frames, closer to wood | Case by case; Lafayette Square allows on secondary façades |
| Composite | 1.4–1.6 | 0.25–0.29 | 40+ yrs | Low | Wood-like profiles | Yes where listed (Andersen Renewal double-hung is on the CRO list) |
| Aluminum-clad wood | 2.0–2.4 | 0.26–0.30 | 40+ yrs with the cladding intact | Interior wood needs finish | Traditional profiles and colors | Yes for listed lines (Marvin Ultimate, Andersen E-Series, Pella Architect, Kolbe, Sierra Pacific, etc.); Lafayette Square primary façades prohibit metal-clad |
| All-wood | 2.0–3.0 | 0.27–0.32 | Indefinite if painted; the originals are 100+ years old | Paint every 7–10 yrs | The original | Yes — the top of the approved list |
| Color-finished aluminum (historic replica) | 1.9–2.3 | 0.30–0.40 (thermally broken) | 40+ yrs | Low | Thin profiles matching old steel or wood sash | Yes for listed products (Crown M-1400, Quaker H650, EFCO Historic); mill-finish aluminum prohibited in every standard we have read |
Three notes on that table:
- Vinyl is a fine window in a frame house. It is the floor on price and performs well. Its problems are aesthetic (frame width) and, on cheap lines, long-term (warping on a west elevation, cracking welds). Buy a multi-chamber, welded, mid-grade or better line.
- Fiberglass earns its premium in St. Louis because the climate moves — a 23.8°F January low normal, an 89.6°F July high normal — and fiberglass expands and contracts at close to the rate of glass, so seals last.
- In a historic district the table collapses to the right-hand column. See the district rules.
Styles, and which St. Louis house they belong to
| Style | How it works | Where it belongs in St. Louis |
|---|---|---|
| Double-hung | Two sash slide vertically; both tilt in for cleaning on modern units | The default in every era: 1890s flats, 1920s bungalows, 1950s ranches, 1990s two-stories. In a historic district the configuration (one-over-one, two-over-two, cottage) must match the original |
| Single-hung | Only the lower sash moves | Soulard's standard allows double-hung to become single-hung; otherwise a budget choice |
| Casement | Hinged at the side, cranks out; compression seal is the tightest of the common types | 1920s–30s Tudor-style houses in University City, Webster Groves, the Central West End; 1950s–60s ranches where steel casements were original |
| Awning | Hinged at the top, opens out; can stay open in rain | Basements, bathrooms, over kitchen sinks; paired under picture windows on mid-century ranches |
| Slider | Sash slide horizontally | 1960s–70s ranches and split-levels in North and South County; rarely right on a pre-war house |
| Picture / fixed | Does not open | The 1950s–60s ranch front window, usually flanked by double-hungs or casements |
| Bay / bow | Three or more units projecting from the wall | 1970s–90s houses in West County and St. Charles County; occasionally added to older houses; quoted after measure because the roof and support vary |
| Hopper | Hinged at the bottom, opens in | Basement windows in every era |
| Egress | A casement or slider sized to the escape-opening rule | Basement bedrooms; the opening is new and permitted |
Grids and glass
- Grids between the glass (GBG) are easy to clean and cheap; they read flat from the street.
- Simulated divided lights (SDL) have bars applied to the glass surface, inside and out, often with a spacer between the panes; they read like true divided lights. In a historic district, exterior-applied muntins matching the original pattern are what Skinker DeBaliviere's standard describes; a new muntin pattern is not permitted there.
- Colors. Vinyl is white, tan and a few laminated exteriors; fiberglass and clad wood come in a full palette. Hyde Park's standard specifies a color code of white, dark green, gray or wood tones. Black exterior frames are fashionable on new construction and look wrong on most pre-war St. Louis brick.
- Glass. Low-e argon double-pane is the baseline; see performance ratings.
Matching the house: three worked examples
1905 brick flat, Benton Park, two-over-two wood double-hungs, street side. Street façade must be wood or finished aluminum replicating the original; a wood sash kit if the frames are sound, a clad or finished-aluminum replica full-frame if not. Alley side: material unregulated — composite or fiberglass. Lead-safe throughout.
1962 brick-veneer ranch, Florissant, steel casements and a picture window. Full-frame, no choice. Fiberglass or vinyl casements to keep the look, or double-hungs if the owner prefers; picture window replaced in kind. No historic constraint. Lead-safe (pre-1978).
1996 two-story, O'Fallon, builder vinyl double-hungs with fogged seals. Vinyl or fiberglass inserts; keep or change the grid pattern; check the HOA's color and grid rules; St. Charles County permit if four or more and unincorporated. No lead-safe requirement.
Frequently asked questions
What is the best window material for St. Louis? For a frame house with no historic constraint and a long horizon, fiberglass. For budget, a good mid-grade vinyl. For a historic district street façade, whatever is on the CRO list — usually clad wood, composite or finished aluminum.
Are black windows allowed in a historic district? Color is regulated in some districts (Hyde Park's code is white, dark green, gray or wood tones); elsewhere it is a matching-the-original question. Ask at the free preliminary review.
Do I have to match my old grid pattern? In a historic district, yes. Elsewhere, no — but the house usually looks better when you do.
Vinyl or fiberglass in a 1950s ranch? Either; fiberglass if you expect to be there twenty years.
Next step
Window replacement for most houses; historic district windows if you are in one. Related: the brick guide · the complete St. Louis guide.