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A guide to popular window types

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It’s all about the true divided light


Welcome back to Period Dramas, a weekly column that alternates between rounding up historic homes on the market and answering questions we’ve always had about older structures.

There are many different types of windows out there—double-hung, fanlight, and Palladian, just to name a few—but most designs are based on a few common styles. Master these fenestration types, and you’ll have people believing you’re a window expert in no time.


One of the most common types on residential architecture is a sash window. There are two main parts of the window, and each part is called a sash. The sashes slide up and down along a rail to open or close the window. The origins of the window are disputed, but they first saw widespread popularity in 18th-century England.

An example of a double-sash, six-over-six window.
Illustration by Sunny Eckerle

Double-sash windows are the most common. A double-sash—or double-hung—window is made up of two sashes. These sashes can either have single sheets of plate glass or many separate panes of glass divided by muntins. These dividers are typically made of wood in older houses, but can theoretically be made of almost any material.

The number of panes of glass in each sash can further organize the window into a specific type. A term like “six-over-six window” means that there are six panes of glass on the upper sash, and six panes of glass on the lower sash. The number of panes of glass in each sash can modify the taxonomy: “eight-over-eight,” “twelve-over-twelve,” and so forth.

The term “true divided light” may also come into play here. That’s when the panes of glass are actually divided into discrete pieces by the muntins. In modern construction, what’s often found are sashes made up of sheet glass that has a muntin pattern overlaid onto the glass to give the look of divided light, when in reality the window isn’t truly divided into separate panes.


A “fanlight” is a semi-circular window generally found over an exterior doorway. Fanlights were also quite popular in Georgian England, because they let light into dark entry hallways. Stateside, they can be found in Federal and Colonial Revival architecture, among other building styles.

Fanlights can be quite intricately designed, with muntins made of lead or wood, separating the panes into sunburst or other patterns that appear to spread like a fan outwards.


A Palladian window is a symmetrical, three-part window that has a semi-circular fanlight placed atop the central portion of the window. The style takes shape from a form used by the 16th-century Italian architect Andrea Palladio.

Similar to fanlights, Palladian windows were popular with Georgian architecture in England, when rigorous symmetry was a guiding characteristic of the architectural style. Stateside, the window type found a lot of use when Federal architecture and, later, Colonial Revival architecture were in vogue.


Used frequently in the 19th century, “eyebrow windows” are squat windows used to illuminate the second floor of a house.

Sometimes, eyebrow windows are rectangular and located just below the eaves of a roof. The regular presence of eyebrow windows across the second floor of a house will classify the house as an “eyebrow colonial.

Other times, the eyebrow window will be semi-round and extend above the roofline. The line of the window resembles an arched eyebrow. The rounded eyebrow window became popular in the later 19th century with the Shingle Style of architecture.


Casement windows are one of the earliest types of windows that can open. Unlike sash windows, which slide vertically along a track to open and close, casement windows are hinged so they swing outward like a door to open.

Sometimes, they are separated by metal muntins

In France, casement windows would often swing inward. “French doors” in America aped on the style of French casement windows. After all, they are essentially floor-length windows that often swing inward.

A casement window swings instead of slides.
Illustration by Sunny Eckerle.