One of the main reasons to add a dormer to a house is to bring light into the attic or living space that's tucked under the roof. This is why dormers always feature one or more windows.
Peeking out from a slate roof, this dormer features two double-hung windows, a style named for the fact that the top and bottom sections each move up and down. Double-hung windows are popular where houses don't have air conditioning because they can be opened part way at the top and at the bottom. That creates a draft, which helps push hot air out through the top as cooler air flows in at the bottom.
Multiple small panes of glass add to the appeal of a pair of double-hung dormer windows. Small panes were once a necessity because of how glass was manufactured. Once larger pieces became available, small-pane windows fell out of favor among some people because they are more difficult to clean. Today, however, many people treasure the warm, historical look that small panes create.
Because eyebrow dormers are curved on top, their windows usually are, too. The three double-hung windows in this eyebrow dormer play up this special shape with especially small panes along the very top, where the windows curve.
Instead of moving up and down, as many windows do, these casement windows swing in and out. When casement windows are open, the entire space is available for ventilation; it's not half-covered with glass, as it is in a double-hung window. Casement windows are also simpler to build, so they evoke more of a cottage look.
Protected by a storm window, this old dormer window consists of small, triangular panes of glass held in place with strips of lead. You can buy a similar window today, but it's likely to have two layers of glass separated by an air chamber. That eliminates the need for storm windows, a feature that's especially helpful for dormer windows because they are so hard to reach from a ladder.
Besides using strips of lead to hold small panes in place, window makers have two other ways to create dormer windows that have diamond-shape panes.
Option 1: Build the windows with a lattice of thin wooden frames, known as mullions or muntins, depending on where you live.
Option 2: Make a large-pane window and cover the glass with a wooden, metal or plastic grill.
Palladian-style windows are a natural fit in arched top dormers where windows curve in line with the roof. This style of window came to the United States in the 1700s from England, where the published designs of Italian architect Andrea Palladio had caught on. Palladian windows have a shape that fit with a general desire in the late 1800s for architecture rooted in ancient European traditions.
Palladian windows are rooted in the classical architecture of Greece and Rome, so they look particularly good on dormers with molding that creates the look of columns that are holding up a pediment (the triangular wall under a gable roof). Palladian windows originated in the 1700s, but these are clearly later because the large panes weren't possible to make with the technology of that era.
This dormer's half-round window uses some of the same stylistic details characteristic of Palladian windows, which often sit in arched top dormers. This dormer, though, is the eyebrow type because it lacks side walls. Many eyebrow dormers have roofs that flip up on the ends, but this is not an essential detail. Eyebrow windows can also be half-elliptical—or half-round like this one.
Windows in arched top dormers do not always curve on top. These have rectangular windows. The windows appear to be fixed, perhaps because the dormers are purely decorative or serve only to channel light into a room with a vaulted ceiling.