True divided lite means each pane is genuinely separate. Simulated divided lite applies bars to both glass surfaces with a spacer between the panes. Grilles between the glass sit inside the sealed unit. Historic boards generally accept the first two and reject the third.
Grilles are the bars that divide a window into smaller panes, and they are the single most visible difference between a window that looks right on an old house and one that does not.
There are three ways to do it and they are not interchangeable, particularly if you are in a historic district.
The three types
| Type | How it works | Added cost per window | Historic approval |
|---|---|---|---|
| True divided lite | Each pane genuinely separate, real muntins | $300 to $800 | Always acceptable |
| Simulated divided lite with spacer | Bars bonded to both glass faces, spacer bar between panes | $150 to $400 | Usually acceptable |
| Simulated divided lite, no spacer | Bars on both faces only | $100 to $250 | Sometimes acceptable |
| Grilles between the glass | Bars inside the sealed unit | $60 to $150 | Usually rejected |
| Removable interior grille | Clips into the sash on the room side | $50 to $120 | Usually rejected |
Why review boards care
The difference is the shadow line. On a true divided lite window, each muntin is a physical piece of wood or clad wood that projects from the glass surface, casting a shadow and creating depth. Simulated divided lite with an internal spacer bar recreates this convincingly: the exterior bar casts a real shadow, the interior bar matches it, and the spacer between the panes lines up so the window does not read as a single sheet of glass with stripes on it. Grilles between the glass have no exterior relief at all. From the street on a sunny day, a window with grilles between the glass reads as flat, and from an angle the bars appear to float. That is what a review board is looking at, and it is why the internal spacer is usually the item that decides an approval.
Common patterns and what they suit
- Six over six, meaning six panes in each sash. Standard on Federal, Greek Revival and Colonial homes through roughly 1850.
- Two over two. Common from the 1860s through the 1890s as larger glass became affordable, and typical of Troy and Cohoes mill-era housing.
- One over one, meaning no divisions at all. Standard from roughly 1900 onward and correct on most early 1900s homes.
- Nine over one or six over one. A Craftsman and Colonial Revival pattern from roughly 1900 to 1930, common in Delmar, Woodlawn and Pine Hills.
- Prairie pattern, with a border of small panes around a large central pane. Arts and Crafts era.
- Diamond or leaded patterns, typical in stair landings and entry sidelights in Victorian and Tudor Revival homes.
Practical considerations
Grilles have costs beyond money. They reduce visible glass area and therefore daylight, modestly but measurably. They add cleaning work on true divided lite, where each small pane has to be cleaned individually on both sides. They slightly reduce the thermal performance of the unit, because the spacer bar and the muntins create small thermal bridges. And they are effectively permanent on true and simulated divided lite, because the pattern is built into the sash. Removable interior grilles are the one reversible option, which is why they are popular with people who are not sure, though they are also the least convincing from outside.
Ranges reflect typical Capital Region projects and are for planning only. Every Sundog quote is written, itemized, and free.
Frequently asked questions
What is the difference between grilles and muntins?
Muntins are the real structural bars that separate individual panes of glass in a true divided lite window. Grilles are the decorative bars that simulate that appearance on a modern insulated unit. In everyday use the terms get mixed, but on a quote the distinction matters because the cost difference is large.
Are grilles between the glass acceptable in a historic district?
Usually not, because they create no exterior shadow line and the window reads as flat from the street. Simulated divided lite with an internal spacer bar is the option that most often gets approved, because it recreates the shadow and depth of real muntins convincingly at a fraction of true divided lite cost.
How much do grilles add to the cost of a window?
Between the glass runs $60 to $150 per window. Simulated divided lite runs $100 to $400 depending on whether an internal spacer bar is included. True divided lite runs $300 to $800, because each pane is genuinely separate and the sash construction is entirely different.
Do grilles reduce energy efficiency?
Slightly. Grilles between the glass and simulated divided lite spacer bars create small thermal bridges within the sealed unit, and true divided lite windows have more frame area and less glass area. The effect is modest and it is rarely the deciding factor, but it is real and it is why very high performance windows often skip grilles entirely.
What grille pattern is right for my house?
Match the original where you can see evidence of it, either in surviving windows elsewhere on the house or in old photographs. As a rough guide: six over six for pre-1850, two over two for 1860 to 1890, one over one from 1900 onward, and six over one or nine over one for Craftsman and Colonial Revival homes from roughly 1900 to 1930.
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