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Replacement Window Shopping: Getting to Know The Parts of a Window

Parts of a window and their terminology

If you’re shopping for replacement windows, the first thing you should do is get to know the parts of a window. That way, when you set out on your journey meeting different window contractors in Houston, you won’t get stifled by wonky window wordiness that may leave you slightly offended: “Single-hung? Double-hung? How inappropriate!”

But all those words really mean is how many movable sashes there are. “Wait, but what are sashes?” Great question! By doing a little studying on the different parts of a window, it’ll help make replacement window shopping a whole lot easier for you.

What are the Parts of a Window I Should Know About

Although it depends on what style of replacement window you’re thinking of buying, there are basic parts to every window that you should know about:


What is a Window Apron?

An apron is decorative trim installed against the wall immediately beneath the stool of a window. It accentuates the look of the window inside the house; almost a like a piece of moulding.

What is a Balance?

A balance is a device in single- and double-hung windows that uses a spring mechanism to help you with the weight of the sash as you open and close your window. Balances sit inside the window frame so they are somewhat hidden.

What is Interior Window Casing? What is Exterior Window Casing?

Casing is a type of moulding used as trim for the perimeter of windows and doors. Just as their names state, interior window casing is installed on the interior walls of a house to frame the window on the inside for aesthetic purposes, and exterior window casing is the trim or molding that frames the window on the exterior of the house.

What is a Window Frame?

The framework that surrounds and supports the entire window system – comprised of the head, jamb and sill. It is what makes up the perimeter of the window.

What is a Grid?

A grid is the framework of spaced bars that form a pattern in a window.

What is Hardware?

Window hardware is all the devices, fittings, or assemblies that are used to operate a window. Window hardware may include catches, cords, fasteners, hinges, handles, locks, pivots, pulls, pulleys, and sash weights.

What is Insulated Glass?

Two or more pieces of glass with a space between them that are hermetically sealed to provide insulating characteristics.

What is a Jamb?

Jambs are the main vertical components that form the sides of a window. A head or head jamb is the vertical component that sits at the very top of the window frame. The window sash seats against it.

What is a Jamb Liner?

A jamb liner is a strip which goes on the sides of a window frame that provides a snug fit for the window sash.

What is a Lift?

A lift is a handle on a single- or double-hung window that is attached to the the bottom of the lower sash to help open and shut the window. Not all windows have a lift.

What are Muntins for Windows?

Muntins are the actual bars that create a grid pattern in windows. They are permanently stuck to the interior and exterior of the window.

What is a Sash? Lower and Upper Sash?

A sash is the part of the window unit inside yet separate from the frame. It is the part of the window you open and shut or it can also remain stationary. On a typical single-hung window, the lower or bottom sash is the one that can be opened or shut while the upper sash on a single-hung window doesn’t move. On a double hung window, you can have two sashes that are functional. The sash consists of the stiles, rails, bars, and muntins.

What is a Window Pane?

A window pane is the plate of glass that fills the sash. When you hear the terms single-pane, double-pane, triple-pane, or even quadruple-pane, it refers to how many plates of glass are built into the window for added insulation. You will also hear these terms interchanged with double-glazed, triple-glazed, or quadruple-glazed. Just know those terms mean the same thing.

What is a Rail?

A rail is the horizontal component that runs at the bottom of the lower sash and the top of the upper sash.

What is a Sash Lock?

A sash lock is the locking device which interacts with the sash to keep the window from rattling. In a double-hung window, it fixes both sashes to a locked position.

What is a Window Sill?

A window sill is the horizontal component forming the bottom of a window frame in the interior of the house or building.

What is a Stile?

While rails are the components that run horizontally at the top and bottom of a sash, stiles are the components that run vertically on the sides of a sash.

What is a Stool?

The window stool is the part of the window commonly called the window sill. However, a stool and a sill are two different things. The sill of the window is the bottom horizontal portion of the window. The stool is the more visible piece of wood, metal or stone attached to the window sill that you might sit your plants on.

What is Weather Stripping?

Weather stripping is a strip of resilient material designed to seal the sash and frame members in order to reduce air and water infiltration.

Take Part in Knowing Your Window Parts

As you can see, there’s a lot to learn about before you have replacement windows installed or if you decide to do it yourself. Most top window contractors in Houston will typically take the time to ensure you understand how a window functions and the benefits that come along with it. But you may come across a replacement window company or two that assumes you know what they’re talking about. They’ll zip right through a presentation filled with wacky wordy window terminology that leaves you in the dark. Don’t get caught like a deer in a headlights.

Start by knowing your window parts so you can confidently make a decision on the right windows to meet your needs. And while you’re at it, read up on the latest replacement window advancements like Low-E and Warm Edge technology. We guarantee you’ll come across these terms while replacement window shopping.