Anatomy of a Window: Parts You Should Know If You’re Planning a Replacement

Kenneth Wilson

In a home, the window is the reflection of your exterior and interior parts of the room. The window is the soul of your house, and as time goes by, a replacement is a long-overdue chore! Replacing your old, leaky windows with efficient windows will help you save money on your energy costs while still improving the convenience of your favorite spaces. It does not only affect your home aesthetically but will give you a better function for your rooms.

The anatomy of a replacement window is determined by the type of window. Although the majority of the components are the same for all replacement windows, their positioning and functionality can vary significantly depending on the style. A double-glazed picture window, for example, shares many of the same features as a double-glazed casement window.

Here is a helpful guide in regards to parts of the window that will help you to be guided in window replacement. One note, always consult a window professional for an optimum result!

The Window and Frame

Frames are available in a number of materials, including vinyl, wood, brass, and fiberglass. The material used to build the frame has a significant impact on the window's durability. Some fabrics are vulnerable to warping or rotting over time, and since the frame protects the entire window, its structural stability would be jeopardized if it lacks its strength or rigidity.

The Windowsill

This part extends horizontally around the bottom of the window.

The Jambs

The frame's side bits extend vertically from the windowsill to the head.

The Head

It's also known as the head jamb which functions as the frame's upper section that extends horizontally over the top.


The architrave is a decorative molding that forms the window's wall opening.


This part is seen as an upper and lower rail, as well as stiles on either side that encloses a casement window portion. It could also be divided into several bits. A casement can be fixed or hinged, and it can open from the top, bottom, or foot.


A horizontal divider is known as a transom. It's typically used to allow the upper portion of a window to open independently of the lower section.

The Sash

The part of the window that gets the most use is the sash. It's the driving part, as well as the part that carries the bottle. The sashes of a double-hung window slip up and down to open and shut the window. When casement and awning windows are opened, the sash pivots outward like a door.

Rails and stiles are the elements that make up a window sash. The bottom rail runs horizontally along the bottom, the top rail runs horizontally along the top, and the stiles link the bottom rail to the top rail vertically, one on either side. The glazing device is fixed in place by these four elements of the sash.

The Glass A.K.A The Glazing

The glazing part refers to the glass in a window and is a scientific concept. Since modern replacement windows contain much more than just glass in their glazing schemes, it isn't merely referred to as "the glass." The pieces of glass are, of course, the core of the glazing method, but there are other factors that add to the window's total energy conservation and results.

The majority of the glass in new replacement windows is what's known as "low-emissivity" glass. This ensures that microscopic layers of metal, such as platinum, titanium oxide, and silicon dioxide, are added to the glass. UV rays from the sun are mirrored away from your house by these metal layers, which are designed to reflect heat rather than absorb it.


Any window frame fabrics inherently insulate better than others. Many window frames, on the other hand, have some kind of insulating material inside them. The hollow spaces within the frame of most new replacement windows are filled with polyurethane foam, which decreases heat flow into the frame and allows the window more energy efficient. Also, take note of Vinyl material because it is a better insulator of heat as compared to a metal component.

The Hardware

Hardware (locks and handles), window tints, and blinds between the glass are all elements that are arguably part of the anatomy of a window and should be used when constructing new windows. We're seeing this as sort like the "icing on the cake," so to say, since they're normally optional functions.

The Locks

The locking handle's aim is to keep the window open or closed.


Window stays have two goals: to make the window stay where it is while it is open so that it is not swept about by the breeze.


This part is a window-closing mechanism in which the central handle governs the vertical expansion of the bars above and below it. These bars match into catches on the window frame's top and bottom.

The Gas Fill

Another unseen yet vital part of new replacement windows is the gas fill, which is located between the panes of glass. An invisible gas is injected into the vacuum between the glass panes, acting as an insulator against heat transfer and sound waves. Argon or krypton are the most common gases used in this application.

Because argon and krypton are both denser than air, they effectively block air molecules from passing through them. They are excellent materials for keeping the interior chamber of replacement windows dry.

The Spacer System

A spacer mechanism keeps the glass panes squarely in place between these bits of ultra-durable, mind-bogglingly polished glass. Spacer devices, which are often made of stainless steel, ensure that the panes stay at the correct distance apart through temperature variations that allow molecules to shrink and expand. Desiccant beads are used in certain high-end spacer systems.

When to consult a professional for your window replacement?

Choosing the best windows for your home needs careful consideration and decision-making. However, the decision-making process should not stop until you've agreed on a window design and content. And if you buy a high-quality pane, if it isn't installed properly, the end result might be substandard.

We’re helping you to be guided with the essential parts of the window to make sure that you’re getting quality work and efficiency with the contractor’s service.

Kenneth Wilson
April 5, 2021
Window Replacement

Kenneth Wilson

Retired contractor. Currently residing in Southwest Florida. Now in semi-retirement, I write and manage this blog focused on helping home owners make savvy decisions when it comes to finding contractors and getting their projects done. I also operate remodeling design service for homeowners.

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