What are Window Sashes? An Easy to Understand Guide

You’ve had a contractor or two come over to your house to provide you a window replacement estimate, and they start using jargon that you don’t understand. One of those words is a “window sash.” What exactly is a window sash, and why are they important?

A sash is just a fancy name for the frame of the glass of your window that slides up and down. Sashes are a part of the window’s anatomy.

Any type of window that has a moving piece has a window sash.

It may be easy to confuse “window sash” with “sash windows.”

A window sash is a part of the window, whereas sash windows are a type of window.

Sash windows work by sliding one frame of glass (a sash) over or under the other one to open or close your window.

There are other types of windows such as a casement window. This type of frame opens up like a door does, with hinges on one side. The sash is the part that is moving.

Another type would be an awning window, which is just like a casement except the hinge is on the top.

Still confused? Don’t worry. We’ll talk more about the different parts of the window, window types, and why sashes are important in this article.

The Anatomy of a Window

photo of 2 sash windows from the outside of a house

A window sash is part of a window. Therefore, in order to really understand what the sash does, we need to look at all the surrounding pieces as well.

We’ll be using a double-hung window in our example because they are a very common type of window. If you’re looking for replacement windows, chances are that this is the type of window you’ll be wanting in your home.

A single-hung window has one sash that moves up and down, whereas a double-hung window has two pieces that moves. Each sash can slide up and down, and they can also rotate on their hinge to make cleaning easier as well.

basic anatomy of a window infographic

Window Frame

The first thing you see when looking at a window is the outer frame that encases everything. This is called the frame.

Inside the frame, you see two sashes. Each sash has glass panes inside it. A double pane window will have 2 glass panes with space in the middle filled with an inert gas to prevent the temperature outside from affecting the temperature inside your house too much.

Window Grilles

An optional part would be the grilles. If you want grids on your windows, then the grids would be placed in the middle of the 2 glass panes. A single pane window will have the grids on the outside, whereas a double pane window will have grids on the inside.

This can also be confusing because we’re talking about a double-hung window, but it can have single pane or double pane glass.

Sash Locks

window lock

There are also sash locks, which are the pull-out tabs that allow you to lock and unlock your windows. These are typically placed on the top of your inside sash.

There are many other complex and specific parts to a window, but these are the main ones that you’ll need to know to talk to your local contractors to communicate what you want out of your replacement windows.

A Quick Guide to Window Types and Styles

A window type typically refers to the way that it operates.

We have three main window types:

  • Sash windows (also known as hung windows)
  • Slider windows
  • Casement windows
  • Hopper windows
  • Awning windows
5 different types of windows

They differ in their look, the way they open and close, and their advantages and disadvantages.

Sash Windows

Sash windows are also called sliding windows because one sash will slide over the other one to open and close. Sash windows are primarily designed to maintain the internal temperature of your home. They are a great fit for places with very cold or very hot weather such as Texas. These windows slide vertically.

Sash windows do not take much space when opening and closing. It is also possible to put up a bug screen outside of your sash window.

Slider Windows

Another type would be a slider window. This is similar to a sash window in operation, except the sliding occurs horizontally, or left and right. These are great for large horizontal windows.

sliding window next to a sash window

Casement Windows

Casement windows open like a door, with a hinge on one side. Casement windows open outwards, so they may get in the way of a pathway or something outside your windows.

It is not possible to put a bug screen on your casement window because it opens outwards. However, the ventilation is great and not blocked by anything.

Awning Windows

Awning windows are just like casement windows, except the hinge is on the top of the window. It opens outwards. At times when it rains, awning windows are great to keep ventilation strong and keep the water out of your home as well.

Hopper Windows

Hopper windows are just like awning windows, except the hinge is at the bottom of the window. It opens inwards and should not be used in the rain. Typically, hopper windows are seen in basements.

Casement and awning windows are operated by crank, handle, or lever instead of sliding. These types of windows allow the window opening to fully ventilate instead of just half of the window.

Casement and awning windows are also more energy efficient than sash windows because there is only a single moving part. It is a rigid structure other than the hinged part.

Those are the most common window types, their benefits, and how they operate. All of these windows have window sashes.

Why are window sashes important?

photo of front of a house with sash windows on the left and picture window on the right

Without a sash, a window is just a frame of glass. There is no movement. It is merely something to look through. This is also commonly referred to as a picture window.

It offers no ventilation benefits. Picture windows are a great option to save money on windows that are located in places you’ll never reach or open.

Common places to see picture windows are the bathroom window, the windows over your door, or windows that serve merely to offer more light into your home that are in very high places.

The purpose of a sash and the reason you want to keep them in tip top shape is because they reduce the amount of energy waste from leaving your home.

Sashes are meant to keep an airtight seal between the frame and the window glass, keeping your air inside and the outside air outside.

When sashes are distorted, damaged, or gapping, moisture and air can enter your home. This can cause your house to deteriorate over time.

The material of a sash will determine whether you’ll have to worry much about distortion. Wooden sashes will swell over time with water. Vinyl sashes are resistant to water and temperature changes. Therefore, they are the most recommended when replacing your windows.

When do you replace a window sash?

Typically, window sashes will last a very long time. When you start to notice that the movement of the window isn’t as smooth or fluid as before, that is when you need to start contacting a professional.

Another reason is if you start to see water or air enter the home. Signs of this can be moisture on your window sills or rotting wood below your window.

Another reason, although uncommon, is if you see distortion on your window frame. Vinyl frames won’t see this, but other frames might such as old wooden windows or old aluminum windows.

Getting an inspection or a professional to come by and take a look at your windows is recommended if you do suspect your windows need to be replaced.

What do I need to do to maintain my window sashes?

Window sashes do not require regular maintenance, since they’re made to last a couple of decades. By a really long time, I mean about 30 years on the upper end. It depends on where you live, the age of your windows, and the type of your windows as well.

Should I replace my single-pane windows?

If you currently have old single-pane windows in your home, a window replacement will save you energy because new windows are air-tight, have double-pane glass with gas in between, and are designed with better window technology than single-pane windows.


A window sash is a fancy word for the moving frame of glass in a window.

Many different types of windows have a sash such as hung windows, sliding windows, awning windows, casement windows, and hopper windows.

Window sashes are important to maintain the airtight seal between the inside of your home and the outside. They don’t need much maintenance, and last many decades.

Window sashes let you open up your windows to allow more airflow rather than just being a piece of glass you can look through.

If you’re looking for replacement windows, contact a local professional who can come to your house and give you a free estimate as well as consult you on the different options you have with window replacements. I hope this guide helped you understand window sashes more, and that you feel more confident talking to your local contractors about a potential window replacement.

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