Window Terminology: What Are the Parts of Windows?

Windows come in all shapes and sizes, yet many of them are made of the same parts. Window terminology may seem confusing, but once you know the basics, you can find the exact window part you’re looking for.

  • Frame
  • Jamb
  • Apron
  • Casing
  • Sash
  • Stiles
  • Rails
  • Mullion

We wouldn’t be Glass Doctor if we didn’t know each and every part of our patients. Learn all about window terminology and how each part contributes to the final design, from our experts.

What Are the Parts of Windows?

Window Frame

The sill, head and jamb all make up the window frame. The window frame is usually made out of wood or vinyl. Sizes vary and are usually available in standard dimensions or can be special-ordered for custom fits.

  • Sill – The lowest part of the window frame.
  • Head – The highest part of the window frame.
  • Jamb – The vertical sides of the window frame.
  • Apron – A piece of decorative trim installed beneath the railing or sill.

Casing and Trim

The terms window casing and trim are used interchangeably to describe the decorative wood that surrounds the perimeter of the window to cover the space between the wall and jamb.

Window Glass

The window glass is held together by a variety of components, depending on the type of window and glass.

  • Pane – A single sheet of glass.
  • Sash – The vertical and horizonal moveable parts of the window that contain the glass.
  • Mullion – A horizonal or vertical structural element that combines two or more windows together.
  • Grilles or Muntins – Strips of material that divide the glass to give the visual appearance of multiple panes of glass.
  • Check Rail – Where the bottom sash of the top window and top sash of the lower window meet on double-hung windows.

Ancillary Parts

Many windows wouldn’t be complete without these important parts.

  • Weep Hole – The weep hole provides an escape route for water and condensation.
  • Weather Stripping – No window is complete without weather stripping for a weathertight seal. Many windows use a combination of rubber, vinyl, felt and metal weather stripping for the best seal.
  • Balance – Some single- and double-hung windows use a counterbalance weight to keep the windows open.
  • Screen – This familiar part is fine mesh made from fiberglass or aluminum to keep out insects.
  • Window Film – Window film can be applied to window glass to reflect UV light or increase thermal efficiency.

Unique Window Parts

Many windows share the same basic parts. However, some parts are unique to certain types of windows.

Insulated Glass Windows

Also known as double-pane windows, they have special components to make them more energy efficient.

  • Argon – Inert and non-toxic gas used to fill the void between double-pane windows to increase thermal efficiently. Manufacturers also use Krypton or a combination of both gases.
  • Spacers – These are special strips between panes filled with desiccant to absorb moisture and prevent fogging.

Casement Windows

Casement and awning windows or skylights have special hardware to allow them to open and close with a hand crank.

  • Lock Handle – This is the lock located on the jamb to allow the window to be locked.
  • Operator – This is the crank handle used to open and close the window

Window Glass

Many manufacturers use different types of glass for specific window applications.

  • Laminated Glass – This type of window glass fuses a layer of polyvinyl butyral to make a very strong sheet of glass that won’t break into shards, if broken at all.
  • Tempered Glass – This type of glass is very similar to laminated glass, except it is significantly stronger.
  • Low-E Glass – Low-emissivity glass is specifically coated to reflect thermal radiation.

Professional Window Installation

When shopping for windows, it helps to know certain terminology so you can find what you’re looking for. Whatever you need, Glass Doctor can help you find it. Give us a call at (833) 365-2927, or schedule an appointment online. We’ll help you find the windows you’re looking for – and we’ll install them for you!

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