Windows are a very impactful design feature of a building. They have the ability to greatly affect its appearance, they provide openings for natural daylight and air to enter a building, and moreover, they improve building occupants’ health and wellbeing by providing a visual connection to nature. Choosing the right windows for a home or commercial building is an important decision, but other than considering window size, most people don’t realize how many other decisions need to be made when purchasing windows. Having to choose the style, color, frame material, type of glass, number of panes, type of mullions (or not!), and manufacturer is a lot of information to process, and all of these decisions will greatly impact the aesthetics and thermal performance, as well as the material cost. Choosing windows is one of the biggest decisions to be made when designing a home or any other building.

Since there is so much to learn about windows, we decided to publish a blog miniseries. Breaking the pertinent information into smaller chunks will allow us to address all the major window options and details more manageably, and hopefully the information will feel less overwhelming if it’s coming out in smaller chunks. For this first post, we are mostly going to focus on window types and how they operate, but we’ll also touch on a couple of other window “types” that get their names based on location rather than how they open. As you’ll see, there are a lot of window types out there, some of which you already know, and then there are others that are probably less familiar. In this post we will cover most of the most common window types one might find on a residential or multi-family project.

An overview of the most common types of windows on the market. Every major window manufacturer should have these options available in multiple sizes and materials.

Fixed Windows (aka Picture Windows)

These windows, as the name implies, do not open. Fixed windows allow natural light to enter the space and provide views to the outdoors, but since there are no operable parts, there is no need for hardware or insect screens.

Single & Double Hung Windows

Hung windows are probably the most common residential window type. They come in either a single hung or double hung style. A single hung window has a fixed top half, while the bottom half can raise and lower. A double hung window can open on both the top and bottom halves.

Casement & French Casement Windows

A casement window has a hinge along one of its vertical edges and opens similarly to the way a door swings. A crank operates the window, swinging the window either inward or outward (most typically outward), depending on the window selected. A French casement has two operable sashes that open like a pair of doors.

Casements may be a good option because they are generally easier to operate than hung windows, and they also provide a tighter seal than hung windows, resulting in less heat loss. However, not everyone appreciates the look of casement windows or the fact that the window protrudes out from the wall when open.

Awning & Hopper Windows

An awning window has a hinge along the top edge of the window and opens from the bottom. The window creates an awning overhang as it opens out. A hopper window opens the opposite way, from the top.

Sliding Windows

A sliding window opens from side to side instead of up and down like a hung window. Think of the way sliding doors work and that’s the way sliding windows work as well. Sliding windows may be a good choice when a kitchen is adjacent to a patio, and having pass-through access makes sense.

Bay Windows

A bay window is a set of several windows that often extends beyond the main building to create an extra nook in a room. Bay windows were a very common architectural feature in living areas of houses from the middle of the Twentieth Century.


Skylights are windows that are installed in the roof of a building instead of in the wall, and they may be fixed or operable. Skylights can bring additional light and ventilation to a room, provide views of the sky, and may be a way to provide a hallway or bathroom with natural light and air if there isn’t an opportunity for a window.

Specialty Shape Windows

Specialty windows are typically fixed windows that come in unique sizes or shapes and provide an architectural accent. Some of the more common specialty window types are round, octagonal, arched, and oval.

Clerestory Windows

Clerestory windows get their name because of where they’re located, not because of the way they operate. Clerestory windows can be either a single window or series of smaller windows installed towards the top of the wall, typically near the roofline, and they can be either fixed or operable. These kinds of windows provide light and ventilation (when operable), but because of their height above eye level maintain privacy for those inside the building.

Transoms & Sidelights

Like clerestory windows, transoms and sidelights get their name based on their location and not their method of operation. A transom is the name for a window installed directly above a door or another window. It allows additional light to enter the interior space without making the main window so tall or heavy that it’s difficult to operate. A sidelight is a fixed window typically found alongside a door that allows additional light to enter the interior space without having to install a very wide door.

So. Many. Window. Types.

There is a time and place for all of these window types, and in fact most buildings will have a combination of them to serve different purposes. However, cohesiveness is important to ensure a building is well designed and beautiful, and this is where an architect can help guide the decision-making process. A good designer will be able to optimize style, quantity, size, and location while balancing the functional needs of the building occupants.

In the next post we’ll cover window materials and types of glass.